Exposure method, exposure apparatus, and device manufacturing method

Abstract

Correction information is acquired for compensating for a measurement error of a second encoder system that occurs due to a displacement between four sections of a scale member of the second encoder system, based on measurement information of the second encoder system obtained in a fifth area in which four heads of the second encoder system that are provided on a second stage, which holds a substrate, respectively face the four sections of the scale member.

Claims

1. An exposure apparatus that exposes a substrate with an illumination light via a projection optical system, the apparatus comprising: a stage that is disposed below the projection optical system and holds the substrate; a drive system having a planar motor to drive the stage; an encoder system that has a plurality of heads and measures positional information of the stage, the plurality of heads being provided at the stage and irradiating a scale member disposed above the stage with a measurement beam from below the scale member; and a controller coupled to the drive system and the encoder system, wherein the scale member has four sections in each of which a reflective grating is formed and an opening substantially surrounded by the four sections, and the scale member is disposed substantially parallel to a predetermined plane so that the projection optical system is located in the opening, the predetermined plane being orthogonal to an optical axis of the projection optical system, wherein the plurality of heads have four heads that irradiate the four sections, respectively, with the measurement beams in a part of an exposure operation of the substrate, of the four heads, a first head and a second head being disposed at a spacing wider than a width of the opening in a first direction within the predetermined plane, the first head and a third head being disposed at a spacing wider than a width of the opening in a second direction orthogonal to the first direction within the predetermined plane, the third head and a fourth head being disposed at a spacing wider than the width of the opening in the first direction, and the second head and the fourth head being disposed at a spacing wider than the width of the opening in the second direction, and wherein a movement area where the stage is moved in the exposure operation includes a first area, a second area, a third area, a fourth area and a fifth area, in the first area, the second, the third and the fourth heads of the four heads excluding the first head respectively irradiating a second section, a third section and a fourth section of the four sections excluding a first section, with the measurement beams, in the second area, the first, the third and the fourth heads of the four heads excluding the second head respectively irradiating the first, the third and the fourth sections of the four sections excluding the second section, with the measurement beams, in the third area, the first, the second and the fourth heads of the four heads excluding the third head respectively irradiating the first, the second and the fourth sections of the four sections excluding the third section, with the measurement beams, in the fourth area, the first, the second and the third heads of the four heads excluding the fourth head respectively irradiating the first, the second and the third sections of the four sections excluding the fourth section, with the measurement beams, and in the fifth area, the first, the second, the third and the fourth heads respectively irradiating the first, the second, the third and the fourth sections, with the measurement beams, and wherein the controller acquires correction information for compensating for a measurement error of the encoder system that occurs due to a displacement between the four sections within the predetermined plane, based on outputs of the four heads that respectively irradiate the four sections with the measurement beams in the fifth area, and the controller uses the correction information in another part of the exposure operation different from the part of the exposure operation, in the another part the stage being moved in the first area, the second area, the third area or the fourth area.

2. The exposure apparatus according to claim 1, wherein the encoder system measures the positional information of the stage in directions of six degrees of freedom with at least three of the four heads, the directions of six degrees of freedom including the first and the second directions and a third direction orthogonal to the predetermined plane, and the correction information includes information for compensating for the measurement error of the encoder system that occurs due to a displacement in at least one of height and inclination of the four sections.

3. The exposure apparatus according to claim 2, wherein the reflective grating is a two-dimensional grating that is periodic in two directions orthogonal to each other within the predetermined plane, each of the four heads has a measurement direction in one of the two directions and in the third directions, and the two directions are set to be rotated at 45 degrees with respect to the first and the second directions within the predetermined plane.

4. The exposure apparatus according to claim 3, wherein each of the four sections has an L-shaped area in which the two-dimensional grating is formed, and the scale member has a non-effective area on an outer periphery of the four sections.

5. The exposure apparatus according to claim 4, wherein the plurality of heads have at least one head that is different from the four heads and is disposed in proximity to each of the four heads.

6. The exposure apparatus according to claim 1, wherein in the exposure operation, the controller controls the drive system so that the stage is moved from one area of the first, the second, the third and the fourth areas to another area of the first, the second, the third and the fourth areas via the fifth area, the another area being different from the one area, and in order to measure the positional information of the stage in the another area, instead of one head of three heads used in the one area, another head different from the three heads of the four heads is used.

7. The exposure apparatus according to claim 6, wherein in the another area, three heads including two remaining heads and the another head face three sections of the four sections, the two remaining heads excluding the one head of the three heads used in the one area, and the three sections excluding one section to which the one head faces in the one area.

8. The exposure apparatus according to claim 7, wherein in the another area, the one head does not face the one section to which the one head faces in the one area, of the four sections, and in the one area, the another head does not face one of the three sections to which the another head faces in the another area, of the four sections.

9. The exposure apparatus according to claim 8, wherein switching information for controlling drive of the stage using the another head instead of the one head in the another area is acquired, based on the positional information obtained from the three heads used in the one area.

10. The exposure apparatus according to claim 9, wherein the switching information is acquired while the stage is in the fifth area.

11. The exposure apparatus according to claim 1, further comprising: a detection system disposed, spaced apart from the projection optical system, wherein in a detection operation of the substrate by the detection system, the positional information of the stage is measured by the encoder system that irradiates another scale member different from the scale member with a measurement beam from below the another scale member, and the another scale member has four sections different from the four sections of the scale member and another opening substantially surrounded by the four sections of the another scale member and different from the opening, and the another scale member is disposed substantially parallel to the predetermined plane so that the detection system is located in the another opening, in each of the four sections of the another scale member a reflective grating being formed.

12. The exposure apparatus according to claim 11, further comprising: a metrology frame that supports the projection optical system, wherein the scale member and the another scale member are supported in a suspended manner by the metrology frame so that the two scale members are substantially disposed in a same plane.

13. The exposure apparatus according to claim 12, wherein the controller acquires another correction information for compensating for the measurement error of the encoder system that occurs due to a displacement between the four sections of the another scale member, based on the positional information obtained from the four heads that respectively irradiate the four sections of the another scale member with the measurement beams, the another correction information being different from the correction information.

14. A device manufacturing method, comprising: exposing a wafer using the exposure apparatus according to claim 1; and developing the wafer that has been exposed.

15. The device manufacturing method according to claim 14, wherein the exposure apparatus is of a liquid immersion type.

16. An exposure method of exposing a substrate with an illumination light via a projection optical system, the method comprising: holding the substrate with a stage that is disposed below the projection optical system, the stage being moved by a planar motor; measuring positional information of the stage with an encoder system that has a plurality of heads provided at the stage, the encoder system irradiating a scale member with a measurement beam from below the scale member via each of the plurality of heads; and moving the stage based on measurement information of the encoder system in an exposure operation of the substrate, wherein the scale member has four sections in each of which a reflective grating is formed and an opening substantially surrounded by the four sections, and the scale member is disposed substantially parallel to a predetermined plane so that the projection optical system is located in the opening, the predetermined plane being orthogonal to an optical axis of the projection optical system, wherein the plurality of heads have four heads that irradiate the four sections, respectively, with the measurement beams in a part of an exposure operation of the substrate, of the four heads, a first head and a second head being disposed at a spacing wider than a width of the opening in a first direction within the predetermined plane, the first head and a third head being disposed at a spacing wider than a width of the opening in a second direction orthogonal to the first direction within the predetermined plane, the third head and a fourth head being disposed at a spacing wider than the width of the opening in the first direction, and the second head and the fourth head being disposed at a spacing wider than the width of the opening in the second direction, and wherein a movement area where the stage is moved in the exposure operation includes a first area, a second area, a third area, a fourth area and a fifth area, in the first area, the second, the third and the fourth heads of the four heads excluding the first head respectively irradiating a second section, a third section and a fourth section of the four sections excluding a first section, with the measurement beams, in the second area, the first, the third and the fourth heads of the four heads excluding the second head respectively irradiating the first, the third and the fourth sections of the four sections excluding the second section, with the measurement beams, in the third area, the first, the second and the fourth heads of the four heads excluding the third head respectively irradiating the first, the second and the fourth sections of the four sections excluding the third section, with the measurement beams, in the fourth area, the first, the second and the third heads of the four heads excluding the fourth head respectively irradiating the first, the second and the third sections of the four sections excluding the fourth section, with the measurement beams, and in the fifth area, the first, the second, the third and the fourth heads respectively irradiating the first, the second, the third and the fourth sections, with the measurement beams, and wherein correction information for compensating for a measurement error of the encoder system that occurs due to a displacement between the four sections within the predetermined plane is acquired, based on outputs of the four heads that respectively irradiate the four sections with the measurement beams in the fifth area, and the correction information is used in another part of the exposure operation different from the part of the exposure operation, in the another part the stage being moved in the first area, the second area, the third area or the fourth area.

17. The exposure method according to claim 16, wherein the positional information of the stage is measured in directions of six degrees of freedom with at least three of the four heads, the directions of six degrees of freedom including the first and the second directions and a third direction orthogonal to the predetermined plane, and the correction information includes information for compensating for the measurement error of the encoder system that occurs due to a displacement in at least one of height and inclination of the four sections.

18. The exposure method according to claim 16, wherein in the exposure operation, the stage is moved from one area of the first, the second, the third and the fourth areas to another area of the first, the second, the third and the fourth areas via the fifth area, the another area being different from the one area, and in order to measure the positional information of the stage in the another area, instead of one head of three heads used in the one area, another head different from the three heads of the four heads is used.

19. The exposure method according to claim 18, wherein in the another area, three heads including two remaining heads and the another head face three sections of the four sections, the two remaining heads excluding the one head of the three heads used in the one area, and the three sections excluding one section to which the one head faces in the one area.

20. The exposure method according to claim 19, wherein in the another area, the one head does not face the one section to which the one head faces in the one area, of the four sections, and in the one area, the another head does not face one of the three sections to which the another head faces in the another area, of the four sections.

21. The exposure method according to claim 20, wherein switching information for controlling movement of the stage using the another head instead of the one head in the another area is acquired, based on the positional information obtained from the three heads used in the one area.

22. The exposure method according to claim 16, wherein the substrate is detected by a detection system disposed, spaced apart from the projection optical system, in a detection operation of the substrate, the positional information of the stage is measured by the encoder system that irradiates another scale member different from the scale member with a measurement beam from below the another scale member, the another scale member having four sections different from the four sections of the scale member and another opening substantially surrounded by the four sections of the another scale member and different from the opening, and the another scale member being disposed substantially parallel to the predetermined plane so that the detection system is located in the another opening, and another correction information for compensating for the measurement error of the encoder system that occurs due to a displacement between the four sections of the another scale member is acquired, based on the positional information obtained from the four heads that respectively irradiate the four sections of the another scale member with the measurement beams, the another correction information being different from the correction information.

23. A device manufacturing method, comprising: exposing a wafer using the exposure method according to claim 16; and developing the wafer that has been exposed.

24. A making method of an exposure apparatus that exposes a substrate with an illumination light via a projection optical system, the method comprising: providing a stage that is disposed below the projection optical system and holds the substrate; providing a drive system having a planar motor to drive the stage; providing an encoder system that has a plurality of heads and measures positional information of the stage, the plurality of heads being provided at the stage and irradiating a scale member disposed above the stage with a measurement beam from below the scale member; and providing a controller coupled to the drive system and the encoder system, wherein the scale member has four sections in each of which a reflective grating is formed and an opening substantially surrounded by the four sections, and the scale member is disposed substantially parallel to a predetermined plane so that the projection optical system is located in the opening, the predetermined plane being orthogonal to an optical axis of the projection optical system, wherein the plurality of heads have four heads that irradiate the four sections, respectively, with the measurement beams in a part of an exposure operation of the substrate, of the four heads, a first head and a second head being disposed at a spacing wider than a width of the opening in a first direction within the predetermined plane, the first head and a third head being disposed at a spacing wider than a width of the opening in a second direction orthogonal to the first direction within the predetermined plane, the third head and a fourth head being disposed at a spacing wider than the width of the opening in the first direction, and the second head and the fourth head being disposed at a spacing wider than the width of the opening in the second direction, and wherein a movement area where the stage is moved in the exposure operation includes a first area, a second area, a third area, a fourth area and a fifth area, in the first area, the second, the third and the fourth heads of the four heads excluding the first head respectively irradiating a second section, a third section and a fourth section of the four sections excluding a first section, with the measurement beams, in the second area, the first, the third and the fourth heads of the four heads excluding the second head respectively irradiating the first, the third and the fourth sections of the four sections excluding the second section, with the measurement beams, in the third area, the first, the second and the fourth heads of the four heads excluding the third head respectively irradiating the first, the second and the fourth sections of the four sections excluding the third section, with the measurement beams, in the fourth area, the first, the second and the third heads of the four heads excluding the fourth head respectively irradiating the first, the second and the third sections of the four sections excluding the fourth section, with the measurement beams, and in the fifth area, the first, the second, the third and the fourth heads respectively irradiating the first, the second, the third and the fourth sections, with the measurement beams, and wherein the controller acquires correction information for compensating for a measurement error of the encoder system that occurs due to a displacement between the four sections within the predetermined plane, based on outputs of the four heads that respectively irradiate the four sections with the measurement beams in the fifth area, and the controller uses the correction information in another part of the exposure operation different from the part of the exposure operation, in the another part the stage being moved in the first area, the second area, the third area or the fourth area.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the accompanying drawings;

(2) FIG. 1 is a view schematically showing the configuration of an exposure apparatus related to an embodiment;

(3) FIG. 2 is a view showing a configuration of an encoder system placed in the periphery of a projection optical system;

(4) FIG. 3 is a view showing a configuration of an encoder system placed in the periphery of an alignment system;

(5) FIG. 4 is an enlarged view of a wafer stage partially fractured;

(6) FIG. 5 is a view showing a placement of encoder heads on the wafer stage;

(7) FIG. 6 is a block diagram showing the main configuration of the control system related with the stage control in the exposure apparatus in FIG. 1;

(8) FIG. 7A is a view showing a relation between a placement of encoder heads and a scale plate and a measurement area of the encoder system, FIG. 7B is a view showing four stage coordinate systems which are set corresponding to four sets of encoder heads facing the scale plate, and FIG. 7C is a view showing a case when there is a displacement reciprocally in the four sections of the scale plate;

(9) FIGS. 8A, 8C, and 8E are views (Nos. 1, 2, and 3) showing a movement of the wafer stage in stage position measurement to calibrate a stage coordinate, and FIGS. 8B, 8D, and 8F are views (Nos. 1, 2, and 3) used to explain calibration of the four stage coordinate systems (the one or two and 3);

(10) FIGS. 9A and 9B are views used to explain an origin, rotation, and measurement of scaling of combined stage coordinate system C.sub.E; and

(11) FIGS. 10A and 10B are views used to explain an origin, rotation, and measurement of scaling of combined stage coordinate system C.sub.A.

DESCRIPTION OF THE EMBODIMENTS

(12) An embodiment of the present invention will be described below, with reference to FIGS. 1 to 10B.

(13) FIG. 1 schematically shows the configuration of an exposure apparatus 100 related to the present embodiment. Exposure apparatus 100 is a projection exposure apparatus of the step-and-scan method, namely the so-called scanner. As it will be described later, a projection optical system PL is arranged in the embodiment, and in the description below, a direction parallel to an optical axis AX of projection optical system PL will be described as the Z-axis direction, a direction within a plane orthogonal to the Z-axis direction in which a reticle and a wafer are relatively scanned will be described as the Y-axis direction, a direction orthogonal to the Z-axis and the Y-axis will be described as the X-axis direction, and rotational (inclination) directions around the X-axis, the Y-axis, and the Z-axis will be described as θ x, θ y, and θ z directions, respectively.

(14) Exposure apparatus 100 is equipped with an illumination system 10, a reticle stage RST holding reticle R, a projection unit PU, a wafer stage device 50 including wafer stages WST1 and WST2 on which a wafer W is mounted, a control system for these parts and the like.

(15) Illumination system 10 includes a light source, an illuminance uniformity optical system, which includes an optical integrator and the like, and an illumination optical system that has a reticle blind and the like (none of which are shown), as is disclosed in, for example, U.S. Patent Application Publication No. 2003/0025890 and the like. Illumination system 10 illuminates a slit-shaped illumination area IAR, which is set on reticle R with a reticle blind (a masking system), by an illumination light (exposure light) IL with a substantially uniform illuminance. Here, as one example, ArF excimer laser light (with a wavelength of 193 nm) is used as the illumination light IL.

(16) On reticle stage RST, reticle R on which a circuit pattern or the like is formed on its pattern surface (the lower surface in FIG. 1) is fixed, for example, by vacuum chucking. Reticle stage RST is finely drivable within an XY plane, for example, by a reticle stage drive section 11 (not shown in FIG. 1, refer to FIG. 6) that includes a linear motor or the like, and reticle stage RST is also drivable in a scanning direction (in this case, the Y-axis direction, which is the lateral direction of the page surface in FIG. 1) at a predetermined scanning speed.

(17) The positional information (including position information in the θz direction (θz rotation quantity)) of reticle stage RST in the XY plane (movement plane) is constantly detected, for example, at a resolution of around 0.25 nm by a reticle laser interferometer (hereinafter referred to as a “reticle interferometer”) 16, which irradiates a measurement beam on a movable mirror 15 (the mirrors actually arranged are a Y movable mirror (or a retro reflector) that has a reflection surface which is orthogonal to the Y-axis direction and an X movable mirror that has a reflection surface orthogonal to the X-axis direction) shown in FIG. 1. Incidentally, to measure the positional information of reticle R at least in directions of three degrees of freedom, instead of, or together with reticle interferometer 16, the encoder system which is disclosed in, for example, U.S. Patent Application Publication No. 2007/0288121 and the like can be used.

(18) Projection unit PU is placed below (−Z side) reticle stage RST in FIG. 1, and is held by a main frame (not shown) (metrology frame) which configures a part of a body. Projection unit PU has a barrel 40, and a projection optical system PL consisting of a plurality of optical elements held by barrel 40. As projection optical system PL, for example, a dioptric system is used, consisting of a plurality of lenses (lens elements) that has been disposed along optical axis AX, which is parallel to the Z-axis direction. Projection optical system PL is, for example, a both-side telecentric dioptric system that has a predetermined projection magnification (such as one-quarter, one-fifth, or one-eighth times). Therefore, when illumination light IL from illumination system 10 illuminates illumination area IAR, illumination light IL that has passed through reticle R which is placed so that its pattern surface substantially coincides with a first plane (an object plane) of projection optical system PL forms a reduced image of the circuit pattern (a reduced image of a part of the circuit pattern) of reticle R formed within illumination area IAR, via projection optical system PL, in an area (exposure area) IA conjugate to illumination area IAR on wafer W whose surface is coated with a resist (a sensitive agent) and is placed on a second plane (an image plane) side of projection optical system PL. And by reticle stage RST and wafer stages WST1 and WST2 being synchronously driven, reticle R is relatively moved in the scanning direction (the Y-axis direction) with respect to illumination area IAR (illumination light IL) while wafer W is relatively moved in the scanning direction (the Y-axis direction) with respect to exposure area IA (illumination light IL), thus scanning exposure of a shot area (divided area) on wafer W is performed, and the pattern of reticle R is transferred onto the shot area. That is, in the embodiment, the pattern of reticle R is generated on wafer W according to illumination system 10 and projection optical system PL, and then by the exposure of the sensitive layer (resist layer) on wafer W with illumination light IL, the pattern is formed on wafer W.

(19) Incidentally, the main frame can be one of a gate type frame which is conventionally used, and a hanging support type frame disclosed in, for example, U.S. Patent Application Publication No. 2008/0068568 and the like.

(20) In the periphery on the −Z side end of barrel 40, for example, a scale plate 21 is placed parallel to the XY plane, at a height substantially flush with a surface on the lower end of barrel 40. As shown in FIG. 2 in the embodiment, scale plate 21 is configured, for example, of four L-shaped sections (parts) 21.sub.1, 21.sub.2, 21.sub.3, and 21.sub.4, and the −Z end of barrel 40 is inserted, for example, inside a rectangular shaped opening 21a formed in the center. In this case, the width in the X-axis direction and the Y-axis direction of scale plate 21 is a and b, respectively, and the width of opening 21a in the X-axis direction and the Y-axis direction is a.sub.i and b.sub.i, respectively.

(21) At a position away from scale plate 21 in the +X direction is a scale plate 22, which is placed substantially flush with scale plate 21, as shown in FIG. 1. Scale plate 22 is also configured, for example, of four L-shaped sections (parts) 22.sub.1, 22.sub.2, 22.sub.3, and 22.sub.4 as is shown in FIG. 3, and the −Z end of an alignment system ALG which will be described later is inserted, for example, inside a rectangular shaped opening 22a formed in the center. The width in the X-axis direction and the Y-axis direction of scale plate 22 is a and b, respectively, and the width of opening 22a in the X-axis direction and the Y-axis direction is a.sub.i and b.sub.i, respectively. Incidentally, in the embodiment, while the width of scale plates 21 and 22, and the width of openings 21a and 22a in the X-axis and the Y-axis directions were the same, the width does not necessarily have to be the same, and the width may differ in at least one of the X-axis and the Y-axis directions.

(22) In the embodiment, scale plates 21 and 22 are supported by suspension from a main frame (not shown) (metrology frame) which supports projection unit PU and alignment system ALG. On the lower surface (a surface on the −Z side) of scale plates 21 and 22, a reflection type two-dimensional diffraction grating RG (refer to FIGS. 2, 3, and 4) is formed, consisting of a grating of a predetermined pitch, such as, for example, a grating of 1 μm whose periodic direction is in a direction of 45 degrees with the X-axis serving as a reference (a direction of −45 degrees when the Y-axis serves as a reference), and a grating of a predetermined pitch, such as, for example, a grating of 1 μm, whose periodic direction is in a direction of −45 degrees with the X-axis serving as a reference (−135 degrees when the Y-axis serves as a reference). However, due to the configuration of the two-dimensional grating RG and an encoder head which will be described later on, a non-effective area having a width t is included in each of the vicinity of the outer periphery of sections 21.sub.1 to 21.sub.4 and 22.sub.1 to 22.sub.4 configuring scale plates 21 and 22. The two-dimensional grating RG of scale plates 21 and 22 covers a movement range of wafer stages WST1 and WST2, respectively, at least at the time of exposure operation and alignment (measurement).

(23) Wafer stage device 50, as shown in FIG. 1, is equipped with a stage base 12 supported almost horizontally by a plurality of (for example, three or four) vibration isolation mechanisms (omitted in the drawings) on the floor surface, wafer stages WST1 and WST2 placed on stage base 12, a wafer stage drive system 27 (only a part of the system shown in FIG. 1, refer to FIG. 6) which drives wafer stages WST1 and WST2, and a measurement system which measures the position of wafer stages WST1 and WST2 and the like. The measurement system is equipped with encoder systems 70 and 71, and a wafer laser interferometer system (hereinafter simply described as a wafer interferometer system) 18 and the like shown in FIG. 6. Incidentally, encoder systems 70 and 71, and wafer interferometer system 18 will be further described later in the description. However, in the embodiment, wafer interferometer system 18 does not necessarily have to be provided.

(24) As shown in FIG. 1, stage base 12 is made of a

(25) As shown in FIG. 1, stage base 12 is made of a member having a tabular form, and the degree of flatness of the upper surface is extremely high and serves as a guide surface when wafer stages WST1 and WST2 move. Inside stage base 12, a coil unit is housed, including a plurality of coils 14a placed in the shape of a matrix with the XY two-dimensional direction serving as a row direction and a column direction.

(26) Incidentally, another base member to support the base by levitation can be provided separately from base 12, and stage base 12 can be made to function as a counter mass (reaction force canceller) which moves according to the law of conservation of momentum by the reaction force of the drive force of wafer stages WST1 and WST2.

(27) As shown in FIG. 1, wafer stage WST1 has a stage main section 91, and a wafer table WTB1 which is placed above stage main section 91 and is supported in a non-contact manner with respect to stage main section 91 by a Z tilt drive mechanism (not shown). In this case, wafer table WTB1 is supported in a non-contact manner by Z tilt drive mechanism by adjusting the balance of the upward force (repulsion) such as the electromagnetic force and the downward force (gravitation) including the self-weight at three points, and is also finely driven at least in directions of three degrees of freedom, which are the Z-axis direction, the θx direction, and the θy direction. At the bottom of stage main section 91, a slider section 91a is arranged. Slider section 91a has a magnetic unit made up of a plurality of magnets arranged two-dimensionally within the XY plane, a housing to house the magnetic unit, and a plurality of air bearings arranged in the periphery of the bottom surface of the housing. The magnet unit configures a planar motor 30 which uses the drive of an electromagnetic force (the Lorentz force) as disclosed in, for example, U.S. Pat. No. 5,196,745, along with the coil unit previously described. Incidentally, as planar motor 30, the drive method is not limited the Lorentz force drive method, and a planar motor by a variable reluctance drive system can also be used.

(28) Wafer stage WST1 is supported by levitation above stage base 12 by a predetermined clearance (clearance gap/distance/gap/spatial distance), such as around several μm, by the plurality of air bearings described above, and is driven in the X-axis direction, the Y-axis direction, and the θz direction by planar motor 30. Accordingly, wafer table WTB1 (wafer W) is drivable with respect to stage base 12 in directions of six degrees of freedom (hereinafter shortly described as the X-axis direction, the Y-axis direction, the Z-axis direction, the θx direction, the θy direction, and the θz direction (hereinafter shortly referred to as X, Y, Z, θx, θy, θz)).

(29) In the embodiment, a main controller 20 controls the magnitude and direction of current supplied each of the coils 14a configuring the coil unit. Wafer stage drive system 27 is configured, including planar motor 30 and the Z tilt drive mechanism previously described. Incidentally, planar motor 30 is not limited to a motor using a moving magnet method, and can be a motor using a moving coil method. Further, as planar motor 30, a magnetic levitation type planar motor can be used. In this case, the air bearing previously described does not have to be arranged. Further, wafer stage WST can be driven in directions of six degrees of freedom by planar motor 30. Further, wafer table WTB1 can be made finely movable in at least one of the X-axis direction, the Y-axis direction, and the θZ direction. More specifically, wafer stage WST1 can be configured by a rough/fine movement stage.

(30) On wafer table WTB1, wafer W is mounted via a wafer holder (not shown), and is fixed by a chuck mechanism (not shown), such as, for example, vacuum suction (or electrostatic adsorption). Further, on one of the diagonal lines on wafer table WTB1, a first fiducial mark plate FM1 and a second fiducial mark plate FM2 are provided, with the wafer holder in between (for example, refer to FIG. 2). On the upper surface of the first fiducial mark plate FM1 and the second fiducial mark plate FM2, a plurality of reference marks which are detected by a pair of reticle alignment systems 13A and 13B and alignment system ALG are formed, respectively. Incidentally, the positional relation between the plurality of reference marks on the first and second fiducial plates FM1 and FM2 are to be known.

(31) Wafer stage WST2 is also configured in a similar manner as wafer stage WST1.

(32) Encoder systems 70 and 71 obtain (measure) positional information of wafer stages WST1 and WST2, respectively, in directions of six degrees of freedom (X, Y, Z, θ x, θ y, θ z) in an exposure time movement area (in an area where the wafer stage moves when exposing a plurality of shot areas on wafer W) including an area right below projection optical system PL, and in an measurement time movement area including an area right below alignment system ALG. Now, a configuration and the like of encoder systems 70 and 71 will be described in detail. Incidentally, exposure time movement area (a first movement area) is an area in which the wafer stage moves during an exposure operation within the exposure station (a first area) where the exposure of the wafer is performed via projection optical system PL, and the exposure operation, for example, includes not only exposure of all of the shot areas on the wafer to which the pattern should be transferred, but also the preparatory operations (for example, detection of the fiducial marks previously described) for exposure. Measurement time movement area (a second movement area) is an area in which the wafer stage moves during a measurement operation within the measurement station (a second area) where the measurement of the positional information is performed by detection of alignment marks on the wafer by alignment system ALG, and the measurement operation, for example, includes not only detection of a plurality of alignment marks on the wafer, but also detection (furthermore, measurement of positional information (step information) of the wafer in the Z-axis direction) of fiducial marks by alignment system ALG.

(33) In wafer tables WTB1 and WTB2, as shown in an planar view in FIGS. 2 and 3, respectively, encoder heads (hereinafter appropriately referred to as a head) 60.sub.1 to 60.sub.4 are placed in each of the four corners on the upper surface. In this case, the separation distance in the X-axis direction between heads 60.sub.1 and 60.sub.2 and the separation distance in the X-axis direction between heads 60.sub.3 and 60.sub.4 are both equal to A. Further, the separation distance in the Y-axis direction between heads 60.sub.1 and 60.sub.4 and the separation distance in the Y-axis direction between heads 60.sub.2 and 60.sub.3 are both equal to B. These separation distances A and B are larger than width a.sub.i and b.sub.i of opening 21a of scale plate 21. Specifically, taking into consideration width t of the non-effective area previously described, A≥a.sub.i+2t, B≥b.sub.i+2t. Heads 60.sub.1 to 60.sub.4 are housed, respectively, inside holes of a predetermined depth in the Z-axis direction which have been formed in wafer tables WTB1 and WTB2 as shown in FIG. 4, with head 60.sub.1 taken up as a representative.

(34) As shown in FIG. 5, head 60.sub.1 is a two-dimensional head in a −135 degrees direction with the X-axis serving as a reference (in other words, a −45 degrees direction with the X-axis serving as a reference) and whose measurement direction is in the Z-axis direction. Similarly, heads 60.sub.2 to 60.sub.4 are two-dimensional heads that are in a 225 degrees direction with the X-axis serving as a reference (in other words, a 45 degrees direction with the X-axis serving as a reference) whose measurement direction is in the Z-axis direction, a 315 degrees direction with the X-axis serving as a reference (in other words, a −45 degrees direction with the X-axis serving as a reference) whose measurement direction is in the Z-axis direction, and a 45 degrees direction with the X-axis serving as a reference whose measurement direction is in the Z-axis direction, respectively. As is obvious from FIGS. 2 and 4, heads 60.sub.1 to 60.sub.4 irradiate a measurement beam on the two dimensional diffraction grating RG formed on the surface of sections 21.sub.1 to 21.sub.4 of scale plate 21 or sections 22.sub.1 to 22.sub.4 of scale plate 22 that face the heads, respectively, and by receiving the reflected/diffraction beams from two-dimensional grating RG, measure the position of wafer table WTB1 and WTB2 (wafer stages WST1 and WST2) for each of the measurement directions. Now, as each of the heads 60.sub.1 to 60.sub.4, a sensor head having a configuration similar to a sensor head for measuring variation as is disclosed in, for example, U.S. Pat. No. 7,561,280, can be used.

(35) In heads 60.sub.1 to 60.sub.4 configured in the manner described above, since the optical path lengths of the measurement beams in air are extremely short, the influence of air fluctuation can mostly be ignored. However, in the embodiment, the light source and a photodetector are arranged external to each head, or more specifically, inside (or outside) stage main section 91, and only the optical system is arranged inside of each head. And the light source, the photodetector, and the optical system are optically connected via an optical fiber (not shown). In order to improve the positioning precision of wafer table WTB (fine movement stage), air transmission of a laser beam and the like can be performed between stage main section 91 (rough movement stage) and wafer table WTB (fine movement stage) (hereinafter shortly referred to as a rough/fine movement stage), or a configuration can be employed where a head is provided in stage main section 91 (rough movement stage) so as to measure a position of stage main section 91 (rough movement stage) using the head and to measure relative displacement of the rough/fine movement stage with another sensor.

(36) When wafer stages WST1 and WST2 are located within the exposure time movement area previously described, head 60.sub.1 configures two-dimensional encoders 70.sub.1 and 71.sub.1 (refer to FIG. 6) which irradiate a measurement beam (measurement light) on (section 21.sub.1 of) scale plate 21, receive the diffraction beam from the grating whose periodical direction is in a 135 degrees direction with the X-axis serving as a reference, or in other words, in a −45 degrees direction (hereinafter simply referred to as a −45 degrees direction) with the X-axis serving as a reference, formed on the surface (lower surface) of scale plate 21, and measure the position of wafer tables WTB1 and WTB2 in the −45 degrees direction and in the Z-axis direction. Similarly, heads 60.sub.2 to 60.sub.4 each configure two-dimensional encoders 70.sub.2 to 70.sub.4 and 71.sub.2 to 71.sub.4 (refer to FIG. 6) which irradiate a measurement beam (measurement light) on (sections 21.sub.2 to 21.sub.4 of) scale plate 21, respectively, receive a diffraction beam from the grating whose periodical direction is in a 225 degrees direction, or in other words, in a +45 degrees direction (hereinafter simply referred to as a 45 degrees direction), a 315 degrees direction, or in other words, whose periodical direction is in a −45 degrees direction with the X-axis serving as a reference, and a 45 degrees direction with the X-axis serving as a reference, formed on the surface (lower surface) of scale plate 21, and measure the position in the 225 degrees (45 degrees) direction and in the Z-axis direction, the position in the 315 degrees (−45 degrees) direction and the Z-axis direction, and the position in the 45 degrees direction and the Z-axis direction of wafer tables WTB1 and WTB2.

(37) Further, when wafer stage WST1 and WST2 are located within the measurement time movement area previously described, head 60.sub.1 configures two-dimensional encoders 70.sub.1 and 71.sub.1 (refer to FIG. 6) which irradiate a measurement beam (measurement light) on (section 22.sub.1 of) scale plate 22, receive the diffraction beam from the grating whose periodical direction is in a 135 degrees direction (−45 degrees direction) with the X-axis serving as a reference formed on the surface (lower surface) of scale plate 22, and measure the position of wafer tables WTB1 and WTB2 in the −45 degrees direction and in the Z-axis direction. Similarly, heads 60.sub.2 to 60.sub.4 configure two-dimensional encoders 70.sub.2 to 70.sub.4 and 71.sub.2 to 71.sub.4 (refer to FIG. 6) which irradiate a measurement beam (measurement light) on (sections 22.sub.2 to 22.sub.4 of) scale plate 22, respectively, receive a diffraction beam from the grating whose periodical direction is in a 225 degrees direction (45 degrees direction), a 315 degrees direction (−45 degrees direction), and a 45 degrees direction with the X-axis serving as a reference, formed on the surface (lower surface) of scale plate 22, and measure the position in the 225 degrees direction (45 degrees direction) and in the Z-axis direction, the position in the 315 degrees direction (−45 degrees direction) and the Z-axis direction, and the position in the 45 degrees direction and the Z-axis direction of wafer tables WTB1 and WTB2.

(38) As it can be seen from the description above, in this embodiment, regardless of irradiating the measurement beam (measurement light) either on scale plate 21 or 22, or in other words, regardless of whether wafer stages WST1 and WST2 are located in the exposure time movement area or the measurement time movement area, heads 60.sub.1 to 60.sub.4 configure two-dimensional encoder 70.sub.1 to 70.sub.4 along with the scale plates on which the measurement beam (measurement light) is irradiated, and heads 60.sub.1 to 60.sub.4 on wafer stage WST2 are to configure two-dimensional encoders 71.sub.1 to 71.sub.4, along with the scale plates on which the measurement beams (measurement lights) are irradiated.

(39) The measurement values of each of the two-dimensional encoders (hereinafter shortly referred to as an encoder as appropriate) 70.sub.1 to 70.sub.4, and 71.sub.1 to 71.sub.4 are supplied to main controller 20 (refer to FIG. 6). Main controller 20 obtains the positional information of wafer table WTB1 and WTB2 within the exposure time movement area including the area right under projection optical system PL, based on the measurement values of at least three encoders (in other words, at least three encoders that output effective measurement values) which face the lower surface of (sections 21.sub.1 to 21.sub.4 configuring) scale plate 21 on which the two-dimensional diffraction grating RG is formed. Similarly, main controller 20 obtains the positional information of wafer table WTB1 and WTB2 within the measurement time movement area including the area right under alignment system ALG, based on the measurement values of at least three encoders (in other words, at least three encoders that output effective measurement values) which face the lower surface of (sections 22.sub.1 to 22.sub.4 configuring) scale plate 22 on which the two-dimensional diffraction grating RG is formed.

(40) Further, in exposure apparatus 100 of the embodiment, the position of wafer stages WST1 and WST2 (wafer tables WTB1 and WTB2) can be measured with wafer interferometer system 18 (refer to FIG. 6), independently from encoder systems 70 and 71. Measurement results of wafer interferometer system 18 are used secondarily such as when correcting (calibrating) a long-term fluctuation (for example, temporal deformation of the scale) of the measurement results of encoder systems 70 and 71, or as backup at the time of output abnormality in encoder systems 70 and 71. Incidentally, details on wafer interferometer system 18 will be omitted.

(41) Alignment system ALG is an alignment system of an off-axis method placed on the +X side of projection optical system PL away by a predetermined distance, as shown in FIG. 1. In the embodiment, as alignment system ALG, as an example, an FIA (Field Image Alignment) system is used which is a type of an alignment sensor by an image processing method that measures a mark position by illuminating a mark using a broadband (a wide band wavelength range) light such as a halogen lamp and performing image processing of the mark image. The imaging signals from alignment system ALG are supplied to main controller 20 (refer to FIG. 6), via an alignment signal processing system (not shown).

(42) Incidentally, alignment system ALG is not limited to the FIA system, and an alignment sensor, which irradiates a coherent detection light to a mark and detects a scattered light or a diffracted light generated from the mark or makes two diffracted lights (for example, diffracted lights of the same order or diffracted lights being diffracted in the same direction) generated from the mark interfere and detects an interference light, can naturally be used alone or in combination as needed. As alignment system ALG, an alignment system having a plurality of detection areas like the one disclosed in, for example, U.S. Patent Application Publication No. 2008/0088843 can be employed.

(43) Moreover, in exposure apparatus 100 of the embodiment, a multiple point focal point position detection system (hereinafter shortly referred to as a multipoint AF system) AF (not shown in FIG. 1, refer to FIG. 6) by the oblique incidence method having a similar configuration as the one disclosed in, for example, U.S. Pat. No. 5,448,332 and the like, is arranged at the measurement station together with alignment system ALG. At least a part of a measurement operation by the multipoint AF system AF is performed in parallel with the mark detection operation by alignment system ALG, and the positional information of the wafer table is also measured during the measurement operation by the encoder system previously described. Detection signals of multipoint AF system AF are supplied to main controller 20 (refer to FIG. 6) via an AF signal processing system (not shown). Main controller 20 detects positional information (step information/unevenness information) of the wafer W surface in the Z-axis direction based on the detection signals of multipoint AF system AF and the measurement information of the encoder system previously described, and in the exposure operation, performs a so-called focus leveling control of wafer W during the scanning exposure based on prior detection results and the measurement information (positional information in the Z-axis, the θx and θy directions) of the encoder system previously described. Incidentally, multipoint AF system can be arranged within the exposure station in the vicinity of projection unit PU, and at the time of exposure operation, the so-called focus leveling control of wafer W can be performed by driving the wafer table while measuring the surface position information (unevenness information) of the wafer surface.

(44) In exposure apparatus 100, furthermore, above reticle R, a pair of reticle alignment detection systems 13A and 13B (not shown in FIG. 1, refer to FIG. 6) of a TTR (Through The Reticle) method which uses light of the exposure wavelength, as is disclosed in, for example, U.S. Pat. No. 5,646,413 and the like, is arranged. Detection signals of reticle alignment systems 13A and 13B are supplied to main controller 20 via an alignment signal processing system (not shown). Incidentally, reticle alignment can be performed using an aerial image measuring instrument (not shown) provided on wafer stage WST, instead of the reticle alignment system.

(45) FIG. 6 is a block diagram showing a partially omitted control system related to stage control in exposure apparatus 100. This control system is mainly configured of main controller 20. Main controller 20 includes a so-called microcomputer (or workstation) consisting of a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory) and the like, and has overall control over the entire apparatus.

(46) In exposure apparatus 100 configured in the manner described above, when manufacturing a device, main controller 20 moves one of wafer stages WST1 and WST2 on which the wafer is loaded within the measurement station (measurement time movement area), and the measurement operation of the wafer by alignment system ALG and multipoint AF system is performed. More specifically, in the measurement time movement area on the wafer held by one of wafer stages WST1 and WST2, mark detection using alignment system ALG, or the so-called wafer alignment (such as Enhanced Global Alignment (EGA) disclosed in, for example, U.S. Pat. No. 4,780,617 and the like) and measurement of the surface position (step/unevenness information) of the wafer using the multipoint AF system are performed. On such alignment, encoder system 70 (encoders 70.sub.1 to 70.sub.4) or encoder system 71 (encoders 71.sub.1 to 71.sub.4) obtains (measures) the positional information of wafer stages WST1 and WST2 in directions of six degrees of freedom (X, Y, Z, θx, θy, and θz).

(47) After the measurement operation such as the wafer alignment and the like, one of the wafer stages (WST1 or WST2) is moved to exposure time movement area, and main controller 20 performs reticle alignment and the like in a procedure (a procedure disclosed in, for example, U.S. Pat. No. 5,646,413 and the like) similar to a normal scanning stepper, using reticle alignment systems 13A and 13B, fiducial mark plates (not shown) on the wafer table (WTB1 or WTB2) and the like.

(48) Then, main controller 20 performs an exposure operation by the step-and-scan method, based on the measurement results of the wafer alignment and the like, and a pattern of reticle R is transferred onto each of a plurality of shot areas on wafer W. The exposure operation by the step-and-scan method is performed by alternately repeating a scanning exposure operation where synchronous movement of reticle stage RST and wafer stage WST1 or WST2 is performed, and a movement (stepping) operation between shots where wafer stage WST1 or WST2 is moved to an acceleration starting position for exposure of the shot area. At the time of the exposure operation, encoder system 70 (encoders 70.sub.1 to 70.sub.4) or encoder system 71 (encoders 71.sub.1 to 71.sub.4) obtains (measures) the positional information of one of the wafer stages WST1 or WST2, in directions of six degrees of freedom (X, Y, Z, θx, θy, and θz).

(49) Further, exposure apparatus 100 of the embodiment is equipped with two wafer stages WST1 and WST2. Therefore, in parallel with performing an exposure by the step-and-scan method with respect to the wafer loaded on one of the wafer stages, such as, for example, wafer stage WST1, a parallel processing operation is performed in which wafer alignment and the like is performed on the wafer mounted on the other stage WST2.

(50) In exposure apparatus 100 of the embodiment, as is previously described, main controller 20 obtains (measures) the positional information of wafer stage WST1 in directions of six degrees of freedom (X, Y, Z, θx, θy, and θz) using encoder system 70 (refer to FIG. 6), within both the exposure time movement area and the measurement time movement area. Further, main controller 20 obtains (measures) the positional information of wafer stage WST2 in directions of six degrees of freedom (X, Y, Z, θx, θy, and θz) using encoder system 71 (refer to FIG. 6), within both the exposure time movement area and the measurement time movement area.

(51) Now, the principles of position measurement in directions of three degrees of freedom (also shortly referred to as the X-axis direction, the Y axis direction and the θz direction (X, Y, θ z)) within the XY plane by encoder systems 70 and 71 are further described. Here, measurement results or measurement values of encoder heads 60.sub.1 to 60.sub.4 or encoders 70.sub.1 to 70.sub.4 refer to measurement results of encoder heads 60.sub.1 to 60.sub.4 or encoders 70.sub.1 to 70.sub.4 in the measurement direction which is not in the Z-axis direction.

(52) In the embodiment, by employing a configuration and an arrangement of encoder heads 60.sub.1 to 60.sub.4 and scale plate 21 as is previously described, at least three of the encoders head 60.sub.1 to 60.sub.4 constantly face (corresponding sections 21.sub.1 to 21.sub.4 of) scale plate 21 within the exposure time movement area.

(53) FIG. 7 shows a relation between a placement of encoder heads 60.sub.1 to 60.sub.4 on wafer stage WST1 and each of the sections 21.sub.1 to 21.sub.4 of scale plate 21, and measurement areas A.sub.0 to A.sub.4 of encoder system 70. Incidentally, because the configuration of wafer stage WST2 is similar to wafer stage WST1, the description here will be made only on wafer stage WST1.

(54) When the center (coincides with the center of the wafer) of wafer stage WST1 is located in the exposure time movement area, and within a first area A.sub.1 which is an area on the +X and +Y sides with respect to exposure center (center of exposure area IA) P (an area within a first quadrant whose origin is exposure center P (except for area A.sub.0)), heads 60.sub.4, 60.sub.1, and 60.sub.2 on wafer stage WST1 face sections 21.sub.4, 21.sub.1, and 21.sub.2 of scale plate 21, respectively. In the first area A.sub.1, effective measurement values are sent to main controller 20 from these heads 60.sub.4, 60.sub.1, and 60.sub.2 (encoders 70.sub.4, 70.sub.1, and 70.sub.2). Incidentally, the position of wafer stages WST1 and WST2 in the description below, will refer to the position in the center of the wafer stages (coincides with the center of the wafer). In other words, instead of using the description of the position in the center of wafer stages WST1 and WST2, the description the position of wafer stages WST1 and WST2 will be used.

(55) Similarly, when wafer stage WST1 is located in the exposure time movement area, and also within a second area A.sub.2, which is an area (an area (except for area A.sub.0) within the second quadrant whose origin is exposure center P) on the −X side and also on the +Y side with respect to exposure center P, heads 60.sub.1, 60.sub.2, and 60.sub.3 face sections 21.sub.1, 21.sub.2, and 21.sub.3 of scale plate 21, respectively. When wafer stage WST1 is located in the exposure time movement area, and also within a third area A.sub.3, which is an area (an area (except for area A.sub.0) within the third quadrant whose origin is exposure center P) on the −X side and also on the −Y side with respect to exposure center P, heads 60.sub.2, 60.sub.3, and 60.sub.4 face sections 21.sub.2, 21.sub.3, and 21.sub.4 of scale plate 21, respectively. When wafer stage WST1 is located in the exposure time movement area, and also within a fourth area A.sub.4, which is an area (an area (except for area A.sub.0) within the fourth quadrant whose origin is exposure center P) on the +X side and also on the −Y side with respect to exposure center P, heads 60.sub.3, 60.sub.4, and 60.sub.1 face sections 21.sub.3, 21.sub.4, and 21.sub.1 of scale plate 21, respectively.

(56) In the embodiment, under a condition (A≥a.sub.i+2t B≥b.sub.i+2t) of the configuration and arrangement of encoder heads 60.sub.1 to 60.sub.4 and scale plate 21 previously described, as shown in FIG. 7A, in the case wafer stage WST1 is positioned within a cross-shaped area A.sub.0 (an area whose longitudinal direction is in the Y-axis direction and has a width A−a.sub.i−2t and an area an area whose longitudinal direction is in the X-axis direction and has a width B−b.sub.i−2t that pass through exposure center P (hereinafter referred to as a zeroth area)) in which exposure position P serves as the center, all of the heads 60.sub.1 to 60.sub.4 on wafer stage WST1 face scale plate 21 (sections 21.sub.1 to 21.sub.4 corresponding to the heads). Accordingly, within the zeroth area A.sub.0, effective measurement values from all of the heads 60.sub.1 to 60.sub.4 (encoders 70.sub.1 to 70.sub.4) are sent to main controller 20. Incidentally, in the embodiment, in addition to the conditions (A≥a.sub.i+2t, B≥b.sub.1+2t) described above, condition A≥a.sub.i+W+2t, B≥b.sub.i+L+2t may be added taking into consideration the size (W, L) of the shot area on the wafer in which the pattern is formed. In this case, W and L are the width of the shot area in the X-axis direction and the Y axis direction, respectively. W and L are equal to the distance of the scanning exposure section and the distance of stepping in the X-axis direction, respectively.

(57) Main controller 20 computes the position (X, Y, θ z) of wafer stage WST1 in the XY plane, based on measurement results of heads 60.sub.1 to 60.sub.4 (encoders 70.sub.1 to 70.sub.4). In this case, measurement values (each described as C.sub.1 to C.sub.4) of encoders 70.sub.1 to 70.sub.4 depend upon the position (X, Y, θz) of wafer stage WST1 as in formulas (1) to (4) below.
C.sub.1=−(cos θz+sin θz)X/√2+(cos θz−sin θz)Y/√2+√2p sin θz  (1)
C.sub.2=−(cos θz−sin θz)X/√2−(cos θz+sin θz)Y/√2+√2p sin θz  (2)
C.sub.3=(cos θz+sin θz)X/√2−(cos θz−sin θz)Y/√2+√2p sin θz  (3)
C.sub.4=(cos θz−sin θz)X/√2+(cos θz+sin θz)Y/√2+√2p sin θz  (4)

(58) However, as shown in FIG. 5, p is the distance of the head in the X-axis and the Y-axis directions from the center of wafer table WTB1 (WTB2).

(59) Main controller 20 specifies three heads (encoders) facing scale plate 21 according to areas A.sub.0 to A.sub.4 where wafer stage WST1 is positioned and forms a simultaneous equation by choosing from the formulas (1) to (4) above the formula which the measurement values of the three heads follow, and by solving the simultaneous equation using the measurement values of the three heads (encoders), computes the position (X, Y, θz) of wafer sage WST1 in the XY plane. For example, when wafer stage WST1 is located in the first area A.sub.1, main controller 20 forms a simultaneous equation from formulas (1), (2) and (4) that measurement values of heads 60.sub.1, 60.sub.2, and 60.sub.4 (encoders 70.sub.1, 70.sub.2, and 70.sub.4) follow, and solves the simultaneous equation by substituting the measurement values of each of the heads into the left side of formulas (1), (2) and (4), respectively. The position (X, Y, θz) which is calculated is expressed as X.sub.1, Y.sub.1, and θz.sub.1. Similarly, in the case wafer stage WST1 is located in a k.sup.th area A.sub.k, main controller 20 forms a simultaneous equation from formulas (k−1), (k), and (k+1) that measurement values of heads head 60.sub.k−1, 60.sub.k, and 60.sub.0k+1 (encoders 70.sub.k−1, 70.sub.k, and 70.sub.k+1) follow, and solves the simultaneous equation by substituting the measurement values of each head into the left side of the formulas. By solving the equation, position (Xk, Yk, θz.sub.k) is computed. Here, the numbers from 1 to 4 which is periodically replaced is substituted into k−1, k and k+1.

(60) Incidentally, in the case wafer stage WST1 is located in the zeroth area A.sub.0, main controller 20 can randomly select three heads from heads 60.sub.1 to 60.sub.4 (encoders 70.sub.1 to 70.sub.4). For example, after the first wafer stage WST1 has moved from the first area to the zeroth area, heads 60.sub.1, 60.sub.2, and 60.sub.4 (encoders 70.sub.1, 70.sub.2, and 70.sub.4) corresponding to the first area are preferably selected.

(61) Main controller 20 drives (position control) wafer stage WST1 within the exposure time movement area, based on the computation results (X.sub.k, Y.sub.k, θz.sub.k) above.

(62) In the case wafer stage WST1 is located within measurement time movement area, main controller 20 measures the positional information in directions of three degrees of freedom (X, Y, θz), using encoder system 70. The measurement principle and the like, here, is the same as in the case when wafer stage WST1 is located within the measurement time movement area, except for the point where exposure center P is replaced with the detection center of alignment system ALG, and (sections 21.sub.1 to 21.sub.4 of) scale plate 21 is replaced with (sections 22.sub.1 to 22.sub.4 of) scale plate 22.

(63) Furthermore, main controller 20 switches and uses three heads that includes at least one different head, out of heads 60.sub.1 to 60.sub.4 that face scale plates 21 and 22, according to the position of wafer stages WST1 and WST2. In this case, when switching the encoder head, a linkage process to secure the continuity of the position measurement results of the wafer stage is performed, as is disclosed in, for example, U.S. Patent Application Publication No. 2008/0094592 and the like.

(64) As previously described, scale plates 21 and 22 in exposure apparatus 100 of the embodiment are configured of four sections, 21.sub.1 to 21.sub.4, and 22.sub.1 to 22.sub.4, respectively. When the four sections, or to be more exact, two-dimensional diffraction grating RG formed on the lower surface of the four sections, are displaced with one another, a measurement error occurs in encoder systems 70 and 71.

(65) FIGS. 7B and 7C typically shows a k.sup.th reference coordinate system C.sub.k (k=1-4) corresponding to the position (X.sub.k, Y.sub.k, θz.sub.k) of wafer stages WST1 or WST2 computed from effective measurement values of heads 60.sub.k−1, 60.sub.k, and 60.sub.k+1 (encoder 70.sub.k−1, 70.sub.k, and 70.sub.k+1 or encoders 71.sub.k−1, 71.sub.k, and 71.sub.k+1) within the k.sup.th area A.sub.k (k=1-4). The four reference coordinate systems C.sub.1 to C.sub.4 correspond to the placement of areas A.sub.1 to A.sub.4 (refer to FIG. 7A) and overlap one another in the vicinity of origin O, which serves as a center of a cross-shaped area C.sub.0 where adjacent reference coordinate systems overlap one another.

(66) When scale plate 21 is configured as designed, or in other words, in the case two-dimensional diffraction grating RG formed on the four sections 21.sub.1 to 21.sub.4 are not displaced with one another, origin O1 to O4 of the four reference coordinate systems C.sub.1 to C.sub.4 coincide with one another (shown using reference code O in the drawing) as shown in FIG. 7B, as well as rotation θz.sub.1 to θz.sub.4, and scaling Γx.sub.1 to Γx.sub.4 and Γy.sub.1 to Γy.sub.4. Accordingly, the four reference coordinate system can be combined into one coordinate system C.sub.E. In other words, the position of wafer stages WST1 and WST2 within exposure time movement areas A.sub.1 to A.sub.4 can be expressed using position coordinate X, Y, and θz in a combined coordinate system C.sub.E.

(67) However, when two-dimensional diffraction grating RG formed on the four sections 21.sub.1 to 21.sub.4 are displaced with one another, origin O.sub.1 to O.sub.4 of each of the four reference coordinate systems C.sub.1 to C.sub.4, rotation θz.sub.1 to θz.sub.4, and scaling Γx.sub.1 to Γx.sub.4 and Γy.sub.1 to Γy.sub.4 are displaced as shown in FIG. 7C, and measurement error occurs with such displacement. Therefore, the four reference coordinate systems cannot be combined to one coordinate system C.sub.E like the example shown in FIG. 7B.

(68) Similarly, when the four sections 22.sub.1 to 22.sub.4 configuring scale plate 22, or to be more exact, two-dimensional diffraction grating RG formed on the lower surface of the four sections 22.sub.1 to 22.sub.4, are displaced with each other, a measurement error occurs in encoder system 70 or 71.

(69) Therefore, in the embodiment, a calibration method is employed, so as to calibrate the four reference coordinate systems C.sub.1 to C.sub.4 which are displaced with one another due to displacement between sections 21.sub.1 to 21.sub.4, and 22.sub.1 to 22.sub.4 configuring scale plates 21 and 22. Now, details of a calibration method will be described, referring to scale plate 21 as an example.

(70) First of all, main controller 20 positions wafer stage WST1 (WST2) within area A.sub.0, as shown in FIG. 8A. In FIG. 8A, wafer stage WST1 is positioned in the center (right under projection optical system PL) of area A.sub.0. In area A.sub.0, all of the heads 60.sub.1 to 60.sub.4 installed on wafer stage WST1 faces (corresponding sections 21.sub.1 to 21.sub.4 of) scale plate 21, and sends effective measurement values to main controller 20. Main controller 20 obtains position (X.sub.k, Y.sub.k, θz.sub.k) of wafer stage WST1, using measurement values of heads 60.sub.k−1, 60.sub.k, and 60.sub.k+2 (referred to as a k.sup.th head group) which are used in the k (=1 to 4).sup.th area A.sub.k. Main controller 20 obtains a displacement of position (X.sub.k, Y.sub.k) computed from measurement values of the k(=2 to 4).sup.th head group with respect to position (X.sub.1, Y.sub.1) computed from measurement values of the first head group, or in other words, obtains an offset (O.sub.Xk=X.sub.k−X.sub.1, O.sub.Yk=Y.sub.k−Y.sub.1).

(71) Incidentally, with offset (O.sub.Xk, O.sub.Yk), an offset (O.sub.θzk=θz.sub.k−θz.sub.1) of rotation θz can also be obtained at the same time. In this case, computation of offset O.sub.θzk described below is to be omitted.

(72) The offset (O.sub.Xk, O.sub.Yk) obtained above is used to correct position (X.sub.k, Y.sub.k) computed from measurement values of the k (=2 to 4).sup.th head group to (X.sub.k−O.sub.Xk, Y.sub.k−O.sub.Yk). By this correction, origin O.sub.K of the k (=2 to 4).sup.th reference coordinate system C.sub.k coincides with origin O.sub.1 of the first reference coordinate system C.sub.1 as shown in FIG. 8B. In the figure, the origin coinciding with each other is indicated by reference code O.

(73) Next, as shown in FIG. 8C, main controller 20 drives wafer stage WST1 in area A.sub.0 in the direction of the arrow (the X-axis direction and the Y-axis direction), based on a stage position (X.sub.1, Y.sub.1, θz.sub.1) computed from the measurement values of the first head group serving as a reference on calibration, while setting a position by each predetermined pitch and obtaining four of position (X.sub.k, Y.sub.k (k=1 to 4)) of wafer stage WST1, using the measurement values of the four heads groups.

(74) Main controller 20 decides offset O.sub.θzk by a least-square calculation so that square error ε.sub.k=Σ((ξ.sub.k−X.sub.1).sup.2+(ζ.sub.k−Y.sub.1).sup.2) becomes minimal, using the four stage positions (X.sub.k, Y.sub.k (k=1 to 4)) obtained above. However, k=2 to 4. In this case, (ξ.sub.k, ξ.sub.k) is stage position (X.sub.k, Y.sub.k (k=2 to 4)), to which rotational transformation has been applied using formula (5) below. In this case, while the least-squares method is used as an example to obtain offset Oθzk, other computing methods can also be used.

(75) $\begin{array}{cc}\left(\begin{array}{c}{\xi }_k\\ {\zeta }_k\end{array}\right)=\left(\begin{array}{cc}\cos O_{\theta \mathrm{zk}}& -\sin O_{\theta \mathrm{zk}}\\ \sin O_{\theta \mathrm{zk}}& \cos O_{\theta \mathrm{zk}}\end{array}\right)\left(\begin{array}{c}{X}_k\\ Y_k\end{array}\right)& \left(5\right)\end{array}$

(76) Offset O.sub.θzk obtained above is used by to correct rotation θz.sub.k computed from measurement values of the k (=2 to 4).sup.th head group to θz.sub.k−O.sub.θzk. By this correction, the direction (rotation) of the k.sup.th reference coordinate system C.sub.k (=2 to 4) coincides with the direction (rotation) of the first reference coordinate system C.sub.1, as shown in FIG. 8D.

(77) Next, as shown in FIG. 8E, main controller 20 drives wafer stage WST1 in area A.sub.0 in the direction of the arrow (the X-axis direction and the Y-axis direction), based on a stage position (X.sub.1, Y.sub.1, θz.sub.1), while setting a position by each predetermined pitch and obtaining four of position (X.sub.k, Y.sub.k (k=1 to 4)) of wafer stage WST1, as in the earlier case.

(78) Main controller 20 decides scaling (Γ.sub.Xk, Γ.sub.Yk) by a least-square calculation so that square error εk=Σ((ξ.sub.k′−X.sub.1).sup.2+(ζ.sub.k′−Y.sub.1).sup.2) becomes minimal, using the four stage positions (X.sub.k, Y.sub.k (k=1-4)) obtained above. However, k=2 to 4. In this case, (ξ.sub.5′, ξ.sub.k′) is stage position (X.sub.k, Y.sub.k (k=2-4)), to which scale transformation has been applied using formula (6) below.

(79) $\begin{array}{cc}\left(\begin{array}{c}{\xi }_k^{\prime }\\ {\zeta }_k^{\prime }\end{array}\right)=\left(\begin{array}{cc}1+{\Gamma }_{\mathrm{Xk}}& 0\\ 0& 1+{\Gamma }_{\mathrm{Yk}}\end{array}\right)\left(\begin{array}{c}{X}_k\\ Y_k\end{array}\right)& \left(6\right)\end{array}$

(80) Scaling (Γ.sub.Xk, Γ.sub.Yk) obtained above is used to correct position (X.sub.k, Y.sub.k) computed from measurement values of the k (=2 to 4).sup.th head group to (X.sub.k/(1+Γ.sub.Xk), Y.sub.k/(1+Γ.sub.Yk)). By this correction, the scaling of the k.sup.th reference coordinate system C.sub.k (=2 to 4) coincides with the scaling of the first reference coordinate system C.sub.1 as shown in FIG. 8F.

(81) The four reference coordinate systems C.sub.1 to C.sub.4 whose position, rotation, and scaling have been calibrated by the processing described above are combined into one coordinate system (a combined coordinate system) C.sub.E which covers exposure time movement area A.sub.0 to A.sub.4.

(82) Incidentally, instead of the processing described so far, the offset and scaling (O.sub.Xk, O.sub.Yk, O.sub.θzk, Γ.sub.Xk, Γ.sub.Yk (k=2-4)) can also be obtained by the following processing. In other words, as shown in FIGS. 8C and 8E, main controller 20 drives wafer stage WST1 in area A.sub.0 in the direction of the arrow (the X-axis direction and the Y-axis direction), based on a stage position (X.sub.1, Y.sub.1, θz.sub.1), while setting a position by each predetermined pitch and obtaining four of position (X.sub.k, Y.sub.k (k=1-4)) of wafer stage WST1. An offset and scaling (O.sub.Xk, O.sub.Yk, O.sub.θzk, Γ.sub.Xk, Γ.sub.Yk) are determined by least square operation so that main controller 20 uses four ways of bought stage location (X.sub.k, Y.sub.k (k=1-4)), and square error ε.sub.k=Σ((ξ″.sub.k−X.sub.1).sup.2+(ζ″.sub.k−Y.sub.1).sup.2) is minimized. However, k=2 to 4. In this case, (ξ″.sub.k, ζ″.sub.k) is stage position (X.sub.k, Y.sub.k (k=2-4)), to which transformation has been applied using formula (7) below.

(83) $\begin{array}{cc}\left(\begin{array}{c}{\xi }_k^{″}\\ {\zeta }_k^{″}\end{array}\right)=\left(\begin{array}{cc}1+{\Gamma }_{\mathrm{Xk}}& 0\\ 0& 1+{\Gamma }_{\mathrm{Yk}}\end{array}\right)\left(\begin{array}{cc}\cos O_{\theta \mathrm{zk}}& -\sin O_{\theta \mathrm{zk}}\\ \sin O_{\theta \mathrm{xzk}}& \cos O_{\theta \mathrm{zk}}\end{array}\right)\left(\begin{array}{c}{X}_k\\ Y_k\end{array}\right)+\left(\begin{array}{c}{O}_{\mathrm{Xk}}\\ O_{\mathrm{Yk}}\end{array}\right)& \left(7\right)\end{array}$

(84) Further, in the processing above, while the offset and scaling of the second to fourth reference coordinate systems C.sub.2 to C.sub.4 were obtained directly with the first reference coordinate system C.sub.1, the offset and scaling can also be obtained indirectly. For example, the offset and scaling (O.sub.X2, O.sub.Y2, O.sub.θz2, Γ.sub.X2, Γ.sub.Y2) is obtained for the second reference coordinate system C.sub.2 which uses the first reference coordinate system C.sub.1 as a reference according to the procedure described above. Similarly, the offset and scaling (O.sub.X32, O.sub.Y32, O.sub.θz32, Γ.sub.X32, Γ.sub.Y32) is obtained for the third reference coordinate system C.sub.3 which uses the second reference coordinate system C.sub.2 as a reference. From these results, an offset and scaling for the third reference coordinate system C.sub.3 using the first reference coordinate system C.sub.1 as a reference can be obtained (O.sub.X3=O.sub.X32+O.sub.X2, O.sub.Y3=O.sub.Y32+O.sub.Y2, O.sub.θz3=O.sub.θz32+O.sub.θz2, Γ.sub.X3=Γ.sub.X32.Math.Γ.sub.X2, Γ.sub.Y3=Γ.sub.Y32.Math.Γ.sub.Y2). Similarly, the offset and scaling of the fourth reference coordinate C.sub.4 using the third reference coordinate system C.sub.3 can be obtained, and the offset and scaling of the fourth reference coordinate C.sub.4 using the first reference coordinate system C.sub.1 as a reference can also be obtained using the results.

(85) Main controller 20 also calibrates the four reference coordinates with respect to scale plate 22 according to a similar procedure, and combines the four reference coordinate systems into one coordinate system (a combined coordinate system) C.sub.A (refer to FIG. 7B) which covers alignment time movement area.

(86) Finally, main controller 20 obtains the displacement of the position, rotation, and scaling between combined coordinate system C.sub.E which covers the exposure time movement areas A.sub.0 to A.sub.4 and combined coordinate system C.sub.A which covers the alignment time movement area. As shown in FIG. 9A, main controller 20 obtains (measures) the positional information of wafer stage WST1 using encoder system 70, and drives wafer stage WST1 based on the results and positions the first fiducial mark plate FM1 on wafer table WTB1 directly under (exposure center P of) projection optical system PL. Main controller 20 detects two (a pair of) reference marks formed on first fiducial mark plate FM1, using a pair of reticle alignment systems 13A and 13B. Then, main controller 20 drives wafer stage WST1 based on measurement results of encoder system 70, and positions the second fiducial mark plate FM2 on wafer table WTB1 directly under (exposure center P of) projection optical system PL, and detects a reference mark formed on second fiducial mark plate FM2 using one of the pair of reticle alignment systems 13A and 13B. Main controller 20 obtains the position of the origin, rotation, and scaling of combined coordinate system C.sub.E from the detection results (in other words, the two-dimensional position coordinates of the three reference marks) of the three reference marks.

(87) Main controller 20 moves wafer stage WST1 to the measurement time movement area. Here, main controller 20 measures the positional information of wafer stage WST1, using wafer interferometer system 18 in the area between exposure time movement area A.sub.0 to A.sub.4 and the measurement time movement area and encoder system 70 in the measurement time movement area, and drives (controls the position of) wafer stage WST1 based on the results. After the movement, as shown in FIGS. 10A and 10B, main controller 20 detects the three reference marks as is previously described using alignment system ALG, and obtains the position of the origin, rotation and scaling of combined coordinate system C.sub.A from the detection results. Incidentally, while it is desirable for the three reference marks subject to detection of reticle alignment system 13A to be the same marks as the three reference marks subject to detection of alignment system ALG, when the same reference marks cannot be detected in reticle alignment systems 13A and 13B and alignment system ALG, different reference marks can be subject to detection in reticle alignment systems 13A and 13B and alignment system ALG since the positional relation between the reference marks is known.

(88) Incidentally, also in the case when the wafer stage is moved between the exposure time movement area and the measurement time movement area, position control of the wafer stage can be performed using then encoder system. Further, a linkage process (a phase linkage and/or a coordinate linkage) is performed in each of the exposure time movement area and the measurement time movement area. Coordinate linkage, in this case, refers to a linkage process of setting a measurement value with respect to an encoder which will be used after the switching so that the position coordinate of wafer stage WST which is computed coincides completely before and after the switching of the encoder (head), and to re-set the phase offset on this setting. While the phase linkage method is basically similar to a coordinate linkage method, usage of the phase offset is different, and the phase linkage method refers to a linkage method in which the phase offset which is already set is continuously used without resetting the phase offset, and only the counter value is re-set.

(89) Main controller 20 obtains the displacement of the origin, rotation, and scaling between combined coordinate systems C.sub.E and C.sub.A from the position of origin, rotation, and scaling of combined coordinate system C.sub.E and the position of origin, rotation, and scaling of combined coordinate system C.sub.A. Main controller 20 can use this displacement, for example, to convert results of wafer alignment measured on combined coordinate system C.sub.A, such as for example, to convert array coordinates (or a position coordinate of an alignment mark on the wafer) of a plurality of shot area on the wafer to an array coordinate of a plurality of shot areas on the wafer on combined coordinate system C.sub.E, and drives (controls the position of) wafer stage WST1 on combined coordinate system C.sub.E at the time of wafer exposure, based on the array coordinates which have been converted.

(90) Main controller 20 performs the calibration method described above each time exposure processing of a wafer (or each time exposure processing of a predetermined number of wafers) is performed. In other words, prior to wafer alignment using alignment system ALG, encoder systems 70 and 71 are calibrated on the usage of scale plate 22 as previously described (the four reference coordinate systems C.sub.1 to C.sub.4 are combined into combined coordinate system C.sub.A). Measurement operations such as wafer alignment to the wafer subject to exposure are performed, using encoder systems 70 and 71 which have been calibrated (on combined coordinate system C.sub.A). Successively, prior to the exposure processing of the wafer, encoder systems 70 and 71 are calibrated on the usage of scale plate 22 as previously described (the four reference coordinate systems C.sub.1 to C.sub.4 are combined into combined coordinate system C.sub.E). Further, displacement (relative position, relative rotation, and relative scaling) of the position, rotation, and scaling between combined coordinate systems C.sub.A and C.sub.E is obtained. Results (for example, array coordinates of a plurality of shot areas on the wafer) of wafer alignment measured on combined coordinate system C.sub.A using these results are converted into array coordinates of a plurality of shot areas on the wafer on combined coordinate system C.sub.E, and exposure processing on the wafer is performed by driving (controlling the position of) wafer stages WST1 and WST2 holding the wafer on combined coordinate system C.sub.E, based on the array coordinates after the conversion.

(91) Incidentally, as the calibration process (calibration method), while the measurement values of the encoder system can be corrected, other processing can also be employed. For example, other methods can also be applied, such as driving (performing position control of) the wafer stage while adding an offset to the current position or the target position of the wafer stage with the measurement errors serving as an offset, or correcting the reticle position only by the measurement error.

(92) Next, the principle of position measurement in directions of three degrees of freedom (Z, θx, θy) by encoder systems 70 and 71 will be further described. Here, measurement results or measurement values of encoder heads 60.sub.1 to 60.sub.4 or encoders 701 to 704 refer to measurement results of encoder heads 60.sub.1 to 60.sub.4 or encoders 701 to 704 in the Z-axis direction.

(93) In the embodiment, by employing a configuration and an arrangement of encoder heads 60.sub.1 to 60.sub.4 and scale plate 21 as is previously described, at least three of the encoders head 60.sub.1 to 60.sub.4 face (corresponding sections 21.sub.1 to 21.sub.4 of) scale plate 21 according to area A.sub.0 to A.sub.4 where wafer stage WST1 (or WST2) is located within the exposure time movement area. Effective measurement values are sent to main controller 20 from the heads (encoders) facing scale plate 21.

(94) Main controller 20 computes the position (Z, θx, θy) of wafer table WTB1 (or WTB2), based on measurement results of encoders 70.sub.1 to 70.sub.4 (or 71.sub.1 to 71.sub.4). Here, the measurement values (each expressed as D.sub.1 to D.sub.4, respectively, to distinguish the values from measurement values C.sub.1 to C.sub.4 in a measurement direction which is not in the Z-axis direction as is previously described, namely, in a uniaxial direction in the XY plane) of encoders 70.sub.1 to 70.sub.4 (or 71.sub.1 to 71.sub.4) in the Z-axis direction depend upon the position (Z, θx, θy) of wafer stage WST1 (or WST2) as in formulas (8) to (11) below.
D.sub.1=−p tan θy+p tan θx+Z  (8)
D.sub.2=p tan θy+p tan θx+Z  (9)
D.sub.3=p tan θy−p tan θx+Z  (10)
D.sub.4=−p tan θy−p tan θx+Z  (11)

(95) However, p is the distance (refer to FIG. 5) of the head in the X-axis and the Y-axis directions from the center of wafer table WTB1 (WTB2).

(96) Main controller 20 selects the formulas that the measurement values of the three heads (encoders) follow according to areas A.sub.0 to A.sub.4 where wafer stage WST1 (WST2) is positioned from formula (8) to (11) described above, and by substituting and solving the measurement values of the three heads (encoders) into the simultaneous equation built from the three formulas which were selected, the position (Z, θx, θy) of wafer table WTB1 (WTB2) is computed. For example, when wafer stage WST1 (WST2) is located in the first area A.sub.1, main controller 20 forms a simultaneous equation from formulas (8), (9) and (11) that measurement values of heads 60.sub.1, 60.sub.2, and 60.sub.4 (encoders 70.sub.1, 70.sub.2, and 70.sub.4) follow, and solves the simultaneous equation by substituting the measurement values into the left side of formulas (8), (9) and (11), respectively. The position (Z, θx, θy) which is calculated is expressed as Z.sub.1, θx.sub.1, and θy.sub.1. Similarly, in the case wafer stage WST1 is located in a k.sup.th area A.sub.k, main controller 20 forms a simultaneous equation from formulas ((k−1)+7), (k+7), and ((k+1)+7) that measurement values of heads head 60.sub.k−1, 60.sub.k, and 60.sub.k+1 (encoders 70.sub.k−1, 70.sub.k, and 70.sub.k+1) follow, and solves the simultaneous equation by substituting the measurement values of each head into the left side of formulas ((k−1)+7), (k+7), and ((k+1)+7). By solving the equation, position (Z.sub.k, θx.sub.k, θy.sub.k) is computed. Here, the numbers from 1 to 4 which is periodically replaced is substituted into k−1, k and k+1.

(97) Incidentally, in the case wafer stage WST1 (or WST2) is located in the 0.sup.th area A.sub.0, three heads from heads 60.sub.1 to 60.sub.4 (encoders 70.sub.1 to 70.sub.4 or 71.sub.1 to 71.sub.4) can be randomly selected, and a simultaneous equation made from the formulas that the measurement values of the selected three heads follow can be used.

(98) Based on the computation results (Z.sub.k, θx.sub.k, θy.sub.k) and step information (focus mapping data) previously described, main controller 20 performs a focus leveling control on wafer table WTB1 (WTB2) within the exposure time movement area.

(99) In the case wafer stage WST1 (or WST2) is located within measurement time movement area, main controller 20 measures the positional information in directions of three degrees of freedom (Z, θx, θy) of wafer table WTB1 (WTB2), using encoder system 70 or 71. The measurement principle and the like, here, is the same as in the case when wafer stage WST1 is located within the exposure time movement area previously described, except for the point where the exposure center is replaced with the detection center of alignment system ALG, and (sections 21.sub.1 to 21.sub.4 of) scale plate 21 is replaced with (sections 22.sub.1 to 22.sub.4 of) scale plate 22. Based on the measurement results of encoder system 70 or 71, main controller 20 performs a focus leveling control on wafer table WTB1 (WTB2). Incidentally, in the measurement time movement area (measurement station), focus leveling does not necessarily have to be performed. In other words, a mark position and the step information (focus mapping data) should be obtained in advance, and by deducting the Z tilt of the wafer stage at the time of obtaining the step information from the step information, the step information of the reference surface of the wafer stage, such as the step information with the upper surface serving as the reference surface, should be obtained. And, at the time of exposure, focus leveling becomes possible based on the positional information in directions of three degrees of freedom (Z, θx, θy) of this step information and (the reference surface of) the wafer surface.

(100) Furthermore, main controller 20 switches and uses three heads that include at least one different head out of heads 60.sub.1 to 60.sub.4 that face scale plates 21 and 22, according to the position of wafer stages WST1 and WST2. In this case, when an encoder head is switched, the linkage process is performed to secure the continuity of the measurement results of the position of wafer table WTB1 (or WTB2).

(101) As previously described, scale plates 21 and 22 in exposure apparatus 100 of the embodiment are configured of four sections, 21.sub.1 to 21.sub.4, and 22.sub.1 to 22.sub.4, respectively. When the height and tilt of the four sections are displaced with one another, a measurement error occurs in encoder systems 70 and 71. Therefore, the calibration method as is previously described is employed so as to calibrate the four reference coordinate system C.sub.1 to C.sub.4 which are displaced with one another due to displacement of height and tilt between sections 21.sub.1 to 21.sub.4, and 22.sub.1 to 22.sub.4.

(102) Now, an example of a calibration method will be described, with a case using encoder system 70 as an example.

(103) Main controller 20, as shown in FIGS. 8C and 8E, drives wafer stage WST1 in area A.sub.0 in the direction of the arrow (the X-axis direction and the Y-axis direction), based on measurement results (X.sub.1, Y.sub.1, θz.sub.1) of the position of wafer stage WST1 measured by encoder system 70, while setting a position by each predetermined pitch and obtaining four of position (Z.sub.k, θx.sub.k, θy.sub.k (k=1-4)) of wafer table WTB1, using the measurement values of the four heads groups. Using these results, main controller 20 obtains the displacement of position (Z.sub.k, θx.sub.k, θy.sub.k) computed from the measurement values of the k (=2-4).sup.th head group with respect to position (Z.sub.1, θx.sub.1, θy.sub.1) computed from the measurement values of the first head group, or in other words, obtains an offset (O.sub.zk=Z.sub.k−Z.sub.1, O.sub.θxk=θx.sub.k−θx.sub.1, O.sub.θyk=θy.sub.k−θy.sub.1). Furthermore, main controller 20 averages offset (O.sub.zk, O.sub.θxk, O.sub.θyk) which is obtained for each positioning.

(104) The offset (O.sub.zk, O.sub.θxk, O.sub.θyk) obtained above is used to correct position ((Z.sub.k, θx.sub.k, θy.sub.k) computed from measurement values of the k (=2-4)th head group to Z.sub.k−O.sub.zk, θx.sub.k−O.sub.θxk, and θy.sub.k−O.sub.θyk, respectively. By this correction, height Z and tilt θx and θy of the k.sup.th reference coordinate system Ck (k=2-4) coincides with height Z and tilt θx and θy of the reference coordinate system C.sub.1. In other words, the four reference coordinate systems C.sub.1 to C.sub.4 are combined into one coordinate system (a combined coordinate system) C.sub.E which covers exposure time movement area A.sub.0 to A.sub.4.

(105) Main controller 20 also calibrates the four reference coordinates with respect to encoder system 71 according to a similar procedure, and combines the four reference coordinate systems into one coordinate system (a combined coordinate system) C.sub.A which covers alignment time movement area.

(106) Main controller 20 performs the calibration method described above as previously described, each time exposure processing is performed on the wafer (or each time exposure processing is performed on a predetermined number of wafers). In other words, prior to wafer alignment using alignment system ALG, encoder system 70 or (71) on the usage of scale plate 22 is calibrated as previously described (the four reference coordinate systems C.sub.1 to C.sub.4 are combined into combined coordinate system C.sub.A). And, main controller 20 performs wafer alignment on the wafer subject to exposure, using encoder system 70 or (71) which has been calibrated (on combined coordinate system C.sub.A). Successively, prior to the exposure processing of a wafer, encoder system 70 (or 71) on the usage of scale plate 22 is calibrated as previously described (the four reference coordinate systems C.sub.1 to C.sub.4 are combined into combined coordinate system C.sub.E). Then, main controller 20 obtains (measures) the positional information of wafer table WTB1 (or WTB2) holding a wafer using encoder system 70 (or 71) (on combined coordinate system C.sub.E) which has been calibrated, and based on the measurement results and results of wafer alignment, drives (controls the position of) wafer table WTB1 (or WTB2) when exposing the wafer.

(107) As described in detail above, according to exposure apparatus 100 of the embodiment, within area A.sub.0 where of four heads 60.sub.1 to 60.sub.4 installed on wafer stages WST1 and WST2, heads included in the first head group and the second head group to which three heads each belong that include one head different from each other face the corresponding areas (sections 21.sub.1 to 21.sub.4 and 22.sub.1 to 22.sub.4) on scale plates 21 and 22, main controller 20 drives (controls the position of) wafer stages WST1 and WST2 based on positional information which is obtained using the first head group, as well as obtain the displacement (displacement of position, rotation, and scaling) between the first and second reference coordinate systems C.sub.1 and C.sub.2 corresponding to the first and second head groups using the positional information obtained using the first and second head groups. And by main controller 20 using the results and correcting measurement results obtained using the second head group, the displacement between the first and second reference coordinate systems C.sub.1 and C.sub.2 is calibrated, which makes it possible to correct the measurement errors that come with the displacement between areas on scale plates 21 and 22 where each of the four heads 60.sub.1 to 60.sub.4 face.

(108) Further, according to exposure apparatus 100 of the embodiment, because encoder systems 70 and 71 are calibrated using the calibration method described above and displacement of between the four reference coordinate systems C.sub.1 to C.sub.4 is corrected, it becomes possible to measure the positional information of wafer stages WST1 and WST2 using encoder systems 70 and 71 and to drive (control the position of) wafer stages WST1 and WST2 with high precision.

(109) Further, according to exposure apparatus 100 of the embodiment, by main controller 20 detecting the three reference marks provided on wafer stages WST1 and WST2 using reticle alignment systems 13A and 13B and alignment system ALG, relative position, relative rotation, and relative scaling of combined coordinate systems C.sub.E and C.sub.A corresponding to exposure time movement area and measurement time movement area, respectively, are obtained. Then, main controller 20 uses the results, which allows results of wafer alignment measured on combined coordinate system C.sub.A, such as for example, array coordinates of a plurality of shot areas on the wafer are converted into array coordinates of a plurality of shot areas on the wafer on combined coordinate system CE, and the wafer can be exposed by driving (controlling the position of) wafer stages WST1 and WST2 on combined coordinate system C.sub.E using the results.

(110) Incidentally, in the embodiment above, when wafer stage WST1 located within the zeroth area A.sub.0, all the heads 60.sub.1 to 60.sub.4 on wafer stage WST1 face scale plate 21 (corresponding sections 21.sub.1 to 21.sub.4). Accordingly, within the zeroth area A.sub.0, effective measurement values from all of the heads 60.sub.1 to 60.sub.4 (encoders 70.sub.1 to 70.sub.4) are sent to main controller 20. Accordingly, main controller 20 can drive (control the position of) wafer stages WST1 and WST2 within area A.sub.0 where of four heads 60.sub.1 to 60.sub.4, heads included in a k.sup.th head group (k=1 to 4) previously described to which three heads belong that include one head different from each other face the corresponding area (sections 21.sub.1 to 21.sub.4) on scale plate 21, based on positional information which is obtained using at least one head in the k.sup.th head group, such as for example, at least one of the first positional information which is obtained using the first head group and the second positional information which is obtained using the second head group. In such a case, even if the coordinate system (section of scale plate 21) corresponding to the first head group and the second head group is different, wafer stages WST1 and WST2 can be driven with high precision without being affected by this. The same is true also in the case of using scale plate 22.

(111) Incidentally, in the embodiment described above, in the calibration process of a displacement of the four reference coordinate systems C.sub.1 to C.sub.4 which occurs due to a displacement of sections 21.sub.1 to 21.sub.4 and 22.sub.1 to 22.sub.4 configuring scale plates 21 and 22, not all of position, rotation, and scaling require attention, and one or any two factors may be noted, or other factors (such as the orthogonal degree) may be added or substituted.

(112) Further, at least one auxiliary head can be provided in the vicinity of each of the heads on the four corners of the upper surface of the wafer table, and in the case a measurement abnormality occurs in the main heads, the measurement can be continued by switching to the auxiliary head nearby. In such a case, the placement condition previously described may also be applied to the auxiliary head.

(113) Incidentally, in the embodiment above, while the case where two-dimensional diffraction grating RG was formed on the lower surface of sections 21.sub.1 to 21.sub.4 of scale plate 21 and sections 22.sub.1 to 22.sub.4 of scale plate 22 was described as an example, besides this, the embodiment described above can also be applied in the case when a one-dimensional diffraction grating whose periodic direction is only in the measurement direction (in a uniaxial direction within the XY plane) of the corresponding encoder heads 60.sub.1 to 60.sub.4 is formed.

(114) Incidentally, in the embodiment above, while the case has been described where drive (position control) of wafer stages WST1 and WST2 is performed within area A.sub.0 where of the four heads 60.sub.1 to 60.sub.4 mounted on wafer stages WST1 and WST2, heads included in a first head group and a second head group to which three heads including one head different from each other belong face the corresponding area on scale plates 21 and 22, based on the positional information which is obtained using the first head group, and measurement errors which accompany the displacement occurring in the area above scale plates 21 and 22 where each of the four heads 60.sub.1 to 60.sub.4 faces are corrected, by obtaining the displacement (displacement of position, rotation, and scaling) between the first and second reference coordinate systems C.sub.1 and C.sub.2 corresponding to the first and second head groups using the positional information obtained using the first and second head groups, and by using the results, correcting the measurement results which can be obtained using the second head group, besides this, for example, the correction information of the positional information of the stage can be obtained by the encoder system, by moving the wafer stage within an area where the position can be measured for each of the plurality (a second number) of heads which is more than the plurality (a first number) of heads used for controlling the position of the wafer stage, or in other words, for example, the stage can move within a cross-shaped area A0 described in the embodiment above, and can obtain the correction information by using a redundancy head.

(115) In this case, while this correction information is used by main controller 20 to correct the encoder measurement value itself, the correction information can be used by other processing. For example, other methods can also be applied, such as driving (performing position control of) the wafer stage while adding an offset to the current position or the target position of the wafer stage with the measurement errors serving as an offset, or correcting the reticle position only by the measurement error.

(116) Further, in the embodiment above, while the case has been described where the displacement (displacement of position, rotation, and scaling) between the first and the second reference coordinate systems C.sub.1 and C.sub.2 corresponding to the first and second head groups was obtained using the positional information which was obtained using the first and the second head groups, besides this, for example, the exposure apparatus can be equipped with a position measurement system (for example, an encoder system) which obtains the positional information of the wafer stage based on an output of heads which irradiates a measurement beam on a measurement plane which is configured of a plurality of scale plates and is placed roughly parallel to the XY plane outside of the wafer stage in the vicinity of the exposure position of the wafer, of the plurality of heads provided on the wafer stage and a control system which drives the wafer stage based on the positional information obtained by the measurement system, and switches the heads used by the position measurement system to obtain the positional information from the plurality of heads according to the position of the wafer stage, and the control system can obtain the positional relation between the plurality scale plates corresponding to the plurality of heads within a first area within the first area of the movable body where the plurality of heads face the measurement plane. In this case, of the plurality of heads, the plurality of head groups to which a plurality of heads including at least one head different from each other can face the plurality of scale plates, respectively.

(117) In this case, the positional relation between the plurality of scale plates can be used not only to correct the encoder measurement values, but also in other processing as well. For example, other methods can also be applied, such as driving (performing position control of) the wafer stage while adding an offset to the current position or the target position of the wafer stage with the measurement errors serving as an offset, or correcting the reticle position only by the measurement error.

(118) Further, in the embodiment above, as each of the heads 60.sub.1 to 60.sub.4 (encoders 70.sub.1 to 70.sub.4), while the case has been described where a two-dimensional encoder whose measurement direction is in a uniaxial direction within the XY plane and in the Z-axis direction was employed as an example, besides this, a one-dimensional encoder whose measurement direction is in a uniaxial direction within the XY plane and a one-dimensional encoder (or a surface position sensor and the like of a non-encoder method) whose measurement direction is in the Z-axis direction can also be employed. Or, a two-dimensional encoder whose measurement direction is in two axial directions which are orthogonal to each other in the XY plane can be employed. Or, a two-dimensional encoder whose measurement direction is in two axial directions which are orthogonal to each other in the XY plane can be employed. Furthermore, a three-dimensional encoder (3 DOF sensor) whose measurement direction is in the X-axis, the Y-axis, and the Z-axis direction can also be employed.

(119) Incidentally, in each of the embodiments described above, while the case has been described where the exposure apparatus is a scanning stepper, the present invention is not limited to this, and the embodiment described above can also be applied to a static exposure apparatus such as a stepper. Even in the case of a stepper, by measuring the position of a stage (table) on which the object subject to exposure is mounted using an encoder, position measurement error caused by air fluctuation can substantially be nulled, which is different from when measuring the position of this stage (table) by an interferometer, and it becomes possible to position the stage (table) with high precision based on the measurement values of the encoder, which in turn makes it possible to transfer a reticle pattern on the wafer with high precision. Further, the embodiment described above can also be applied to a projection exposure apparatus by a step-and-stitch method that synthesizes a shot area and a shot area. Moreover, the embodiment described above can also be applied to a multi-stage type exposure apparatus equipped with a plurality of wafer stages, as is disclosed in, for example, U.S. Pat. Nos. 6,590,634, 5,969,441, 6,208,407 and the like. Further, the embodiment described above can also be applied to an exposure apparatus which is equipped with a measurement stage including a measurement member (for example, a reference mark, and/or a sensor and the like) separate from the wafer stage, as disclosed in, for example, U.S. Patent Application Publication No. 2007/0211235, and U.S. Patent Application Publication No. 2007/0127006 and the like.

(120) Further, the exposure apparatus in the embodiment above can be of a liquid immersion type, like the ones disclosed in, for example, PCT International Publication No. 99/49504, U.S. Patent Application Publication No. 2005/0259234 and the like.

(121) Further, the magnification of the projection optical system in the exposure apparatus of the embodiment above is not only a reduction system, but also may be either an equal magnifying system or a magnifying system, and projection optical system PL is not only a dioptric system, but also may be either a catoptric system or a catadioptric system, and in addition, the projected image may be either an inverted image or an upright image.

(122) In addition, the illumination light IL is not limited to ArF excimer laser light (with a wavelength of 193 nm), but may be ultraviolet light, such as KrF excimer laser light (with a wavelength of 248 nm), or vacuum ultraviolet light, such as F.sub.2 laser light (with a wavelength of 157 nm). As disclosed in, for example, U.S. Pat. No. 7,023,610, a harmonic wave, which is obtained by amplifying a single-wavelength laser beam in the infrared or visible range emitted by a DFB semiconductor laser or fiber laser as vacuum ultraviolet light, with a fiber amplifier doped with, for example, erbium (or both erbium and ytterbium), and by converting the wavelength into ultraviolet light using a nonlinear optical crystal, can also be used.

(123) Further, in the embodiment above, a transmissive type mask (reticle) is used, which is a transmissive substrate on which a predetermined light shielding pattern (or a phase pattern or a light attenuation pattern) is formed. Instead of this reticle, however, as is disclosed in, for example, U.S. Pat. No. 6,778,257 description, an electron mask (which is also called a variable shaped mask, an active mask or an image generator, and includes, for example, a DMD (Digital Micromirror Device) that is a type of a non-emission type image display device (spatial light modulator) or the like) on which a light-transmitting pattern, a reflection pattern, or an emission pattern is formed according to electronic data of the pattern that is to be exposed can also be used. In the case of using such a variable shaped mask, because the stage where a wafer, a glass plate or the like is mounted is scanned with respect to the variable shaped mask, an equivalent effect as the embodiment above can be obtained by measuring the position of the stage using an encoder.

(124) Further, as is disclosed in, for example, PCT International Publication No. 2001/035168, the embodiment above can also be applied to an exposure apparatus (lithography system) that forms line-and-space patterns on a wafer W by forming interference fringes on wafer W.

(125) Moreover, as disclosed in, for example, U.S. Pat. No. 6,611,316, the embodiment above can also be applied to an exposure apparatus that synthesizes two reticle patterns via a projection optical system and almost simultaneously performs double exposure of one shot area by one scanning exposure.

(126) Incidentally, an object on which a pattern is to be formed (an object subject to exposure to which an energy beam is irradiated) in the embodiment above is not limited to a wafer, but may be other objects such as a glass plate, a ceramic substrate, a film member, or a mask blank.

(127) The application of the exposure apparatus is not limited to an exposure apparatus for fabricating semiconductor devices, but can be widely adapted to, for example, an exposure apparatus for fabricating liquid crystal devices, wherein a liquid crystal display device pattern is transferred to a rectangular glass plate, as well as to exposure apparatuses for fabricating organic electroluminescent displays, thin film magnetic heads, image capturing devices (e.g., CCDs), micromachines, and DNA chips. Further, the embodiment described above can be applied not only to an exposure apparatus for producing microdevices such as semiconductor devices, but can also be applied to an exposure apparatus that transfers a circuit pattern onto a glass plate or silicon wafer to produce a mask or reticle used in a light exposure apparatus, an EUV exposure apparatus, an X-ray exposure apparatus, an electron-beam exposure apparatus, and the like.

(128) Incidentally, the disclosures of all publications, the Published PCT International Publications, the U.S. patent applications and the U.S. patents that are cited in the description so far related to exposure apparatuses and the like are each incorporated herein by reference.

(129) Electronic devices such as semiconductor devices are manufactured through the steps of; a step where the function/performance design of the device is performed, a step where a reticle based on the design step is manufactured, a step where a wafer is manufactured from silicon materials, a lithography step where the pattern formed on a mask is transferred onto an object such as the wafer by the exposure apparatus in the embodiment above, a development step where the wafer that has been exposed is developed, an etching step where an exposed member of an area other than the area where the resist remains is removed by etching, a resist removing step where the resist that is no longer necessary when etching has been completed is removed, a device assembly step (including a dicing process, a bonding process, the package process), inspection steps and the like. In this case, because the exposure apparatus and the exposure method in the embodiment above are used in the lithography step, devices having high integration can be produced with good yield.

(130) Further, the exposure apparatus (the pattern forming apparatus) of the embodiment above is manufactured by assembling various subsystems, which include the respective constituents that are recited in the claims of the present application, so as to keep predetermined mechanical accuracy, electrical accuracy and optical accuracy. In order to secure these various kinds of accuracy, before and after the assembly, adjustment to achieve the optical accuracy for various optical systems, adjustment to achieve the mechanical accuracy for various mechanical systems, and adjustment to achieve the electrical accuracy for various electric systems are performed. A process of assembling various subsystems into the exposure apparatus includes mechanical connection, wiring connection of electric circuits, piping connection of pressure circuits, and the like among various types of subsystems. Needless to say, an assembly process of individual subsystem is performed before the process of assembling the various subsystems into the exposure apparatus. When the process of assembling the various subsystems into the exposure apparatus is completed, a total adjustment is performed and various kinds of accuracy as the entire exposure apparatus are secured. Incidentally, the making of the exposure apparatus is preferably performed in a clean room where the temperature, the degree of cleanliness and the like are controlled.

(131) While the above-described embodiment of the present invention is the presently preferred embodiment thereof, those skilled in the art of lithography systems will readily recognize that numerous additions, modifications, and substitutions may be made to the above-described embodiment without departing from the spirit and scope thereof. It is intended that all such modifications, additions, and substitutions fall within the scope of the present invention, which is best defined by the claims appended below.