Method, measuring system and lithography apparatus

Abstract

A method for localizing an abnormality in a travel path of an optical component in or for a lithography apparatus includes: a) moving the optical component in at least one first degree of freedom; b) detecting a movement (R.sub.z) of the optical component and/or a force acting on the optical component in at least one second degree of freedom; and c) localizing the abnormality as a function of the movement detected in b) and/or the force detected in b).

Claims

1. A method, comprising: a) moving an optical component in a first degree of freedom; b) detecting a movement of the optical component in a second degree of freedom, and/or detecting a force acting on the optical component in the second degree of freedom; and c) localizing an abnormality in a travel path of the optical component based on the detected movement of the optical element in the second degree of freedom and/or the detected force of the optical element in the second degree of freedom.

2. The method of claim 1, wherein the first degree of freedom is a rotational degree of freedom, and the second degree of freedom is a translational degree of freedom.

3. The method of claim 1, wherein the first degree of freedom is a translational degree of freedom, and the second degree of freedom is a rotational degree of freedom.

4. The method of claim 3, further comprising using an end stop to limit the movement of the optical component in a).

5. The method of claim 1, wherein a) comprises moving the optical element in accordance with a predefined path or a predefined movement pattern.

6. The method of claim 5, wherein c) comprises localizing the abnormality in the travel path of the optical element based on at least one member selected from the group consisting of the predefined path, the predefined movement pattern, and an actuation force that moves the optical component in a).

7. The method of claim 6, wherein the first degree of freedom is a translational degree of freedom, and the second degree of freedom is a rotational degree of freedom.

8. The method of claim 5, wherein the first degree of freedom is a translational degree of freedom, and the second degree of freedom is a rotational degree of freedom.

9. The method of claim 1, wherein: a) comprises moving the optical element in accordance with a predefined movement pattern which comprises a plurality of translational movements of the optical component in a plane; and the translational movements proceed from a center point.

10. The method of claim 9, wherein c) comprises localizing the abnormality in the travel path of the optical element based on the predefined movement pattern.

11. The method of claim 10, wherein the first degree of freedom is a translational degree of freedom, and the second degree of freedom is a rotational degree of freedom.

12. The method of claim 9, wherein the first degree of freedom is a translational degree of freedom, and the second degree of freedom is a rotational degree of freedom.

13. The method of claim 1, a) further comprising detecting the movement of the optical element in the first degree of freedom, wherein c) further comprises localizing the abnormality based on the detected movement of the optical element in the first degree of freedom.

14. The method of claim 1, wherein c) comprises ascertaining that an end stop has the abnormality.

15. The method of claim 1, wherein an end stop comprises a peg which engages into a cutout of the optical component such that a ring gap is between the peg and the cutout.

16. The method of claim 15, wherein the abnormality comprises at least one member selected from the group consisting of a particle in the ring gap, a coating fault of the cutout, a coating fault of the peg, and an erroneous alignment of the peg relative to the cutout.

17. The method of claim 1, wherein the optical component comprises a member selected from the group consisting of a mirror, a lens element, an optical grating and a lambda plate.

18. The method of claim 1, wherein the optical element is an optical element in a lithography apparatus.

19. A measuring system configured to localize an abnormality in a travel path of an optical component, the measuring system comprising: an actuator configured to move the optical component in a first degree of freedom; a sensor unit configured to detect a movement of the optical component in a second degree of freedom and/or to detect a force acting on the optical component in the second degree of freedom; and a computer unit configured to localize the abnormality based on based on the detected movement of the optical element in the second degree of freedom and/or the detected force of the optical element in the second degree of freedom.

20. An apparatus comprising: an optical element; and a measuring system configured to localize an abnormality in a travel path of the optical component, the measuring system comprising: an actuator configured to move the optical component in a first degree of freedom; a sensor unit configured to detect a movement of the optical component in a second degree of freedom and/or to detect a force acting on the optical component in the second degree of freedom; and a computer unit configured to localize the abnormality based on based on the detected movement of the optical element in the second degree of freedom and/or the detected force of the optical element in the second degree of freedom, wherein the apparatus is a lithography apparatus.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Further configurations and aspects of the disclosure are the subject matter of the dependent claims and also of the exemplary embodiments of the disclosure described below. In the text that follows, the disclosure is explained in more detail on the basis of exemplary embodiments with reference to the accompanying figures, in which.

(2) FIG. 1A shows a schematic view of an embodiment of an EUV lithography apparatus;

(3) FIG. 1B shows a schematic view of an embodiment of a DUV lithography apparatus;

(4) FIG. 2A shows as an excerpt a measuring system in accordance with one embodiment, wherein for example a generalized optical component is illustrated;

(5) FIG. 2B shows six possible degrees of freedom of the optical component from FIG. 2A;

(6) FIG. 3 shows a section from FIG. 2A, wherein one of the pegs together with coating is illustrated partly in cut-away fashion;

(7) FIG. 4 schematically shows the measuring system from FIGS. 2 and 3 with further components;

(8) FIG. 5 shows the view from FIG. 2A in the fault situation;

(9) FIG. 6 shows an exemplary movement pattern applied to the optical component from FIG. 5, wherein for example the positions moved to for the normal situation and the positions moved to in the fault situation are illustrated in each case in the xy-plane and rotations about the z-axis are indicated;

(10) FIG. 7A shows a diagram showing the relationship of rotation or torque versus actual position for a spoke from FIG. 6;

(11) FIG. 7B shows the derivative of the rotation or torque with respect to the position with reference to FIG. 7A; and

(12) FIG. 8 shows a method in accordance with one embodiment in a flow diagram illustration.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

(13) Identical elements or elements having an identical function have been provided with the same reference signs in the figures, unless indicated to the contrary. It should also be noted that the illustrations in the figures are not necessarily true to scale.

(14) FIG. 1A shows a schematic view of an EUV lithography apparatus 100A, which includes a beam shaping and illumination system 102 and a projection system 104. In this case, EUV stands for “extreme ultraviolet” and refers to a wavelength of the working light of between 0.1 nm and 30 nm. The beam shaping and illumination system 102 and the projection system 104 are respectively provided in a vacuum housing (not shown), each vacuum housing being evacuated with the aid of an evacuation device (not shown). The vacuum housings are surrounded by a machine room (not shown), in which drive devices for mechanically moving or setting optical elements are provided. Moreover, electrical controllers and the like can also be provided in this machine room.

(15) The EUV lithography apparatus 100A includes an EUV light source 106A. A plasma source (or a synchrotron), which emits radiation 108A in the EUV range (extreme ultraviolet range), that is to say for example in the wavelength range of 5 nm to 20 nm, can for example be provided as the EUV light source 106A. In the beam shaping and illumination system 102, the EUV radiation 108A is focused and the desired operating wavelength is filtered out from the EUV radiation 108A. The EUV radiation 108A generated by the EUV light source 106A has a relatively low transmissivity through air, for which reason the beam guiding spaces in the beam shaping and illumination system 102 and in the projection system 104 are evacuated.

(16) The beam shaping and illumination system 102 illustrated in FIG. 1A has five mirrors 110, 112, 114, 116, 118. After passing through the beam shaping and illumination system 102, the EUV radiation 108A is guided onto a photomask (called a reticle) 120. The photomask 120 is likewise formed as a reflective optical element and can be arranged outside the systems 102, 104. Furthermore, the EUV radiation 108A can be directed onto the photomask 120 via a mirror 122. The photomask 120 has a structure which is imaged onto a wafer 124 or the like in a reduced fashion via the projection system 104.

(17) The projection system 104 (also referred to as projection lens) has six mirrors M1 to M6 for imaging the photomask 120 onto the wafer 124. In this case, individual mirrors M1 to M6 of the projection system 104 can be arranged symmetrically in relation to an optical axis 126 of the projection system 104. It should be noted that the number of mirrors M1 to M6 of the EUV lithography apparatus 100A is not restricted to the number represented. A greater or lesser number of mirrors M1 to M6 can also be provided. Furthermore, the mirrors M1 to M6 are generally curved on their front face for beam shaping.

(18) FIG. 1B shows a schematic view of a DUV lithography apparatus 100B, which includes a beam shaping and illumination system 102 and a projection system 104. In this case, DUV stands for “deep ultraviolet” and refers to a wavelength of the working light of between 30 nm and 250 nm. As has already been described with reference to FIG. 1A, the beam shaping and illumination system 102 and the projection system 104 can be arranged in a vacuum housing and/or surrounded by a machine room with corresponding drive devices.

(19) The DUV lithography apparatus 100B has a DUV light source 106B. By way of example, an ArF excimer laser that emits radiation 108B in the DUV range at 193 nm, for example, can be provided as the DUV light source 106B.

(20) The beam shaping and illumination system 102 illustrated in FIG. 1B includes lens elements 127 and/or mirrors 131 (two of such elements are shown merely by way of example in FIG. 1B), which guide the DUV radiation 108B onto a photomask 120.

(21) The photomask 120 is embodied as a transmissive optical element and can be arranged outside the systems 102, 104. The photomask 120 has a structure which is imaged onto a wafer 124 or the like in a reduced fashion via the projection system 104.

(22) The projection system 104 has a plurality of lens elements 128 and/or mirrors 130 for imaging the photomask 120 onto the wafer 124. In this case, individual lens elements 128 and/or mirrors 130 of the projection system 104 can be arranged symmetrically in relation to an optical axis 126 of the projection system 104. It should be noted that the number of lens elements 128 and mirrors 130 of the DUV lithography apparatus 100B is not restricted to the number represented. A greater or lesser number of lens elements 128 and/or mirrors 130 can also be provided. Furthermore, the mirrors 130 are generally curved on their front face for beam shaping.

(23) An air gap between the last lens element 128 and the wafer 124 can be replaced by a liquid medium 132 which has a refractive index of >1. The liquid medium 132 can be highpurity water, for example. Such a construction is also referred to as immersion lithography and has an increased photolithographic resolution. The medium 132 can also be referred to as an immersion liquid.

(24) FIG. 2A shows, in a plan view, as an excerpt a measuring system 200 in accordance with one embodiment.

(25) The measuring system 200 includes an optical component 202. The optical component 202 is for example a mirror, a lens element, an optical grating or a lambda plate. For example, it can be one of the mirrors 110 to 118, M1 to M6, 130, 131 or one of the lens elements 127, 128 from the illumination system 102 or projection system 104 of the EUV or DUV lithography apparatus 100A, 100B from FIG. 1A or 1B, respectively.

(26) In accordance with the present exemplary embodiment, the optical component 202 is a mirror having an optically effective surface 204 (also referred to as “optical footprint”). The optically effective surface 204 reflects EUV light during operation.

(27) In principle, depending on the controlling actuator system, the optical component 202 can be moved in up to six degrees of freedom, specifically, as illustrated in FIG. 2B, in three translational degrees of freedom F.sub.x, F.sub.y, F.sub.z (that is to say a respective translation along the axes x, y, z in FIG. 2A) and three rotational degrees of freedom F.sub.Rx, F.sub.Ry, F.sub.Rz (that is to say a respective rotation about the axes x, y, z in FIG. 2A).

(28) Movements of the optical component 202 in the six degrees of freedom are described by corresponding translation vectors x, y, z (for better clarity, in the present case no distinction is drawn between the translation vectors x, y, z and axes x, y, z in the figures) and rotation vectors R.sub.x, R.sub.y, R.sub.z (only R.sub.z is illustrated in the figures). It should be noted that the rotation vectors are composed in each case of a unit vector and an angle. The unit vector is coaxial with the respective translation vectors (thus for example translation in x and rotation about x). The angle indicates the absolute value of the rotation about the unit vector.

(29) In accordance with the exemplary embodiment, the optical component 202 is moveable in two translational degrees of freedom F.sub.x, F.sub.y and in one rotational degree of freedom F.sub.Rz. However, any other combination of translational and rotational degrees of freedom is also conceivable.

(30) The measuring system 200 includes by way of example three end stops 206A, 206B and 206C shown in FIG. 2A. For the sake of simplicity, explanations below relate to the end stop 206A, and are correspondingly applicable to the end stops 206B and 206C. Pegs 210 are secured to a section of the supporting frame which is shown by way of example in FIG. 3 and is provided there with the reference sign 300. The pegs 210 engage through cutouts 208 perpendicularly to the plane of the drawing in FIG. 2A. The cutouts 208 are introduced in the optical component 202. This is done for example by drilling a corresponding hole into the material of the mirror. Like the cutouts 208, the pegs 210 can have a circular-cylindrical cross section. This is also evident from FIG. 3, which shows a section III-III from FIG. 2A. In this case, there is a ring gap 212 between a respective cutout 208 and a respective peg 210.

(31) This results in a mobility of the optical component 202 along the translation vectors x and y oriented perpendicularly to one another. The translation vectors x and y are oriented in each case perpendicularly to corresponding centre axes 214 of the pegs 210. The rotation vector R.sub.z extends perpendicularly to the translation plane thus defined. The rotation vector denotes a rotation of the optical component 202 in the xy-plane.

(32) The end stops 206A, 206B, 206C limit the travel path x, y of the optical component 202 on account of a corresponding contact between the pegs 210 and the cutouts 208. In order to avoid damage to the optical component 202 on account of high acceleration, the peg 210 can be provided with a (soft) coating (for example composed of an elastomer, preferably fluoroelastomer). The coating is provided with the reference sign 216. By contrast, the inner wall of the cutout 208 is, for example, without a coating and thus embodied as comparatively hard.

(33) As can be seen in FIG. 3, the optical component 202 is adjustable in, depending on the embodiment, up to six degrees of freedom via—two illustrated by way of example—actuators 302, which engage on the optical component 202 in each case via corresponding pins 304. In accordance with the exemplary embodiment, the optical component 202 is adjustable in the translational degrees of freedom F.sub.x and F.sub.y and the rotational degree of freedom F.sub.Rz via the actuators 302.

(34) FIG. 4 shows the measuring system 200 as a block diagram, wherein the optical component 202 from FIGS. 2 and 3 together with end stops 206A, 206B, 206C and the (mechanical) properties determining them is illustrated as a block.

(35) The actuators 302 from FIG. 3 are also illustrated as a block in FIG. 4. The actuators generate a force and/or a torque FM, which has the effect that the optical component 202 moves in the degrees of freedom F.sub.x, F.sub.y, F.sub.Rz and in the process passes through actual positions, for example x.sub.actual, y.sub.actual, R.sub.z-actual. In this case, x.sub.actual denotes the position of the optical component 202 along the x-axis, y.sub.actual denotes the position along the y-axis, and R.sub.z-actual denotes the angle of rotation about the z-axis.

(36) The measuring system 200 furthermore includes a sensor unit 400, for example an optical sensor. The sensor unit 400 detects the actual positions x.sub.actual, y.sub.actual, R.sub.z-actual of the optical component 200.

(37) The measuring system 200 furthermore includes a computer unit 402. By way of example, in regulation (exposure) operation (this is in contrast to operation or a method—described in even greater detail below—for localizing an abnormality 500 in a travel path x, y of the optical component 202—referred to below as “localizing method”) of the lithography apparatus 100A, the computer unit determines the setpoint positions, for example x.sub.setpoint, y.sub.setpoint, R.sub.z-setpoint, of the optical component 202. The latter are determined according to the desired properties ultimately imposed by the structure to be imaged on the wafer 124 (see FIG. 1A).

(38) The setpoint positions x.sub.setpoint, y.sub.setpoint, R.sub.z-setpoint are buffer-stored for example on a storage unit 404 (for example hard disk or solid state drive) of the measuring system 200. A providing unit 406 (referred to as: setpoint generator) of the measuring system 200 finally provides the setpoint positions x.sub.setpoint, y.sub.setpoint, R.sub.z-setpoint both to a comparator unit 408 and to a feedforward control unit 410. The comparator unit 408 is connected to a regulator unit 412 of the measuring system 200 in terms of signalling.

(39) The regulator unit 412 regulates a first part of a manipulated variable SG.sub.1 (for a respective degree of freedom) as a function of the setpoint positions x.sub.setpoint, y.sub.setpoint, R.sub.z-setpoint and the actual positions x.sub.actual, y.sub.actual, R.sub.z-actual. For this purpose, the setpoint and actual positions are compared with one another in the comparator unit 408 and a comparison value is provided to the regulator unit 412.

(40) The regulator unit 412 is followed by an adding unit 414. The adding unit 414 adds the first part of the manipulated variable SG.sub.1 and a second part of the manipulated variable SG.sub.2 to form the manipulated variable SG.

(41) The feedforward control unit 410, depending on the setpoint positions x.sub.setpoint, y.sub.setpoint, R.sub.z-setpoint, provides the second manipulated variable SG.sub.2 at the adding unit 414. For this purpose, by way of example, the following equation is stored on the feedforward control unit 414:
SG.sub.2=c*x.sub.setpoint,
wherein c is a constant. Corresponding equations can be stored for y.sub.setpoint, R.sub.z-setpoint.

(42) In other words, the feedforward control unit 410 supplies a value SG.sub.2 for the force/torque FM to be generated by the actuators 302, which value can be calculated simply and therefore rapidly. The value SG.sub.2 is corrected by the value SG.sub.1 with the aid of the regulator unit 412 in order thus to move precisely to the desired position x.sub.setpoint, y.sub.setpoint, R.sub.z-setpoint on the basis of the actual position x.sub.actual, y.sub.actual, R.sub.z-actual.

(43) It is pointed out that the control and/or regulation of the movement of the optical component 202 can also have any other expedient set-up. In other words, a control and/or regulation of the movement of the optical component 202 can be implemented via the units 404, 406, 408, 412, 414 or else in some other way. The set-up illustrated here corresponds for example to that which is expedient in embodiments in which the measuring system 200 is integrated immediately into a lithography apparatus, for example into the lithography apparatus 100A or 100B. In this case, parts of the measuring system 200, such as e.g. the feedforward control unit 410 and the regulator unit, also serve for regulation (exposure) operation.

(44) In an embodiment in which the measuring system 200 is embodied as a stand-alone solution (not integrated in lithography apparatuses), provision can be made for the optical component 200 together with the end stops 206A, 206B, 206C and also a corresponding section of the supporting frame 300 to be inserted as a module into the measuring system 200.

(45) The computer unit 402, specifically independently of whether a stand-alone solution or integration into a lithography apparatus is implemented, is configured to detect and localize an abnormality, for example a particle 500 (see FIG. 5), in one or more of the ring gaps 212 of the end stops 206A, 206B, 206C.

(46) The localizing method (as described below) can be followed—by the isolated measuring system 200 or a lithography apparatus 100A, 100B including such a system—if it is ascertained that the entire setpoint travel path of the optical component 200 is not available (first variant) or the setpoint travel path can be taken only with a force or torque FM, wherein the force or the torque FM exceeds a predefined threshold value (second variant). This ascertainment can be effected by the computer unit 402. For this purpose, the computer unit 402 is connected to the sensor unit 400 in the case of the first variant, and to the adding unit 414 in the case of the second variant, in order to detect the actuating signal SG provided for the actuators 302. Both variants are indicated in FIG. 4.

(47) The localization of the abnormality 500 is carried out at least as a function of the detected actual rotation R.sub.z-actual. Alternatively or additionally, in one embodiment, the sensor unit 400 can also be configured for detecting a torque M.sub.z-actual (for better clarity not shown in FIG. 4, but shown in FIGS. 7A and 7B) about the z-axis. In this case, as an alternative or in addition to the rotation about R.sub.z, the computer unit 402 can use the detected torque M.sub.z about the z-axis to localize the abnormality 500 as a function thereof. Instead of the torque M.sub.z, a force can also be sensed and taken into account by the computer unit 402 in the localization. This is not illustrated in greater detail, however.

(48) Furthermore, the computer unit 402 can be connected to a storage unit 416 (for example hard disk or solid state drive) in terms of signalling. Predefined movement patterns BM are stored on the storage unit 416. The movement patterns BM describe for example setpoint positions x.sub.setpoint, y.sub.setpoint, R.sub.z-setpoint of the optical component 202 specifically for use in the localizing method. These values serve as input or predefined values for the feedforward control unit 410 and regulator unit 412 for controlling the actuators 302. The computer unit 404 can use the movement patterns BM in addition to the detected movement R.sub.z-actual and the detected torque M.sub.z-actual for localizing the abnormality 500.

(49) Finally, the spatial arrangement of the end stops 206A, 206B, 206C, of the actuators 302 or of the engagement points 306 thereof on the optical component 202 and also the direction of the forces which they apply to the optical component 202 can be stored on the storage unit 416. These further parameters, designated by WP, can be provided to the computer unit 404, which uses these data to localize the abnormality 500 as a function thereof.

(50) The further parameters WP can likewise include a so-called point of control (POC) of the optical component 202. This is the point of the optical component 202 to which is linked the coordinate system xyz to which all commanded and detected movements and forces/torques relate.

(51) FIG. 5 shows a particle 500 in the ring gap 212 of the end stop 206A. The particle 500 has the effect that a specified travel path of the optical component 202 cannot be taken via the actuators 302 in the xy-plane. This is because the particle 500 is not compressible or is only partly compressible and hence the coating 216 cannot completely compensate for the influence of the particle on the travel path and the force/torque FM of the actuators 302 is not sufficient for the desired compression.

(52) FIG. 6 shows a movement pattern BM as stored on the storage unit 416. Spokes 1 to 8 are shown in this case. The spokes each denote a (translational) travel path of the optical component 202 in the xy-plane. Furthermore, those positions which can be moved to by the optical component 202 in the normal situation (not fault situation) are designated in each case by N in FIG. 6.

(53) If there is an abnormality present, for example a particle 500, as shown in FIG. 5 (for example at the location therein), then the computer unit 402 will ascertain that the normal positions N on the spokes 5 and 6 cannot be moved to. Rather, the computing unit 402 ascertains a premature rise in the measured rotation R.sub.z-actual or the measured torque M.sub.z-actual. As shown in FIG. 7A for the spoke 5 (corresponds to actual positions of the optical component 202 in the-x-direction), this rise deviates significantly from the normal situation N in the fault situation F.

(54) For example, for this purpose it is possible to monitor the derivative (d/d-x.sub.actual) of the measured rotation R.sub.z-actual or of the measured torque M.sub.z-actual with respect to the actual position x.sub.actual, as shown in FIG. 7B. If the derivative exceeds a predefined threshold value, the computer unit 404 decides that a fault situation F is present.

(55) It is pointed out that FIGS. 7A and 7B each show only one curve for R.sub.z-actual and M.sub.z-actual. They are intended to illustrate the principle merely by way of example, which is why different curves for R.sub.z-actual and M.sub.z-actual are not shown. In FIGS. 7A and 7B, “/” should be understood as “or”.

(56) Returning then to FIG. 6, the latter also mentions the respective value for the monitored rotation R.sub.z on each spoke. For the spokes 1, 2, 3, 4, 7 and 8, the value from the exemplary embodiment according to FIG. 5 is in each case (ideally) 0, i.e. the respective end position N can be moved to, without a rotation occurring. The situation is different on the spokes 5 and 6. Here a negative rotation is sensed in each case (right hand rule).

(57) For the spoke 5, the computer unit 402 can deduce from the knowledge of the Point of Control (POC) and the actuating force vector F5 that the particle 500 cannot be present in the ring gap 212 of the end stop 206C.

(58) From the negative rotation for the spoke 6, the computer unit 404, once again taking account of the control force F6 can deduce for the spoke 6 that the particle 500 cannot be arranged in the ring gap of the end stop 206B.

(59) Consequently, the computer unit 402 ascertains that the abnormality 500 is caused by the end stop 206A. The localization of the abnormality 500, here the end stop 206A, can be output for example in the measuring system 200 on a screen 418 (see FIG. 4) or in some other way. By way of example, the fact that the end stop 206A has the abnormality 500 can be displayed on the screen 418.

(60) The logic according to which specific end stops, here 206B and 206C, can be excluded as fault sources (that is to say beset by an abnormality 500) results from the torques or rotational movements induced by a respective actuation force F5, F6. For elucidation, in this respect the axes along which these forces act are illustrated in a manner lengthened by dashed lines in FIG. 5.

(61) It should moreover be pointed out that, instead of the computer unit 402, a person, via intellectual activity, can carry out the steps performed by the computer unit 404.

(62) FIG. 8 generally shows the method for localizing an abnormality 500 in a travel path (xy-plane) of the optical component 202 in accordance with one embodiment.

(63) A step S1 involves moving the optical component 202 in the x- and y-directions. This corresponds to a movement in a first and second degree of freedom F.sub.x, F.sub.y, respectively.

(64) A step S2 involves detecting a movement R.sub.z of the optical component 202 and/or a torque M.sub.z acting on the optical component 202 in at least one second degree of freedom F.sub.Rz.

(65) A step S3 involves localizing the abnormality, for example in the form of a particle 500, as a function of the movement R.sub.z detected and/or the torque M.sub.z detected.

(66) Although the present disclosure has been described on the basis of exemplary embodiments, it is modifiable in diverse ways.

(67) The respective unit, e.g. the sensor unit 400, the comparative unit 408, the feedforward control unit 410, the regulator unit 412 and/or the adding unit 414, can be implemented in terms of hardware technology and/or software technology. In the case of an implementation in terms of hardware technology, the respective unit can be embodied as a device or as part of a device, e.g. as a computer or as a microprocessor. In the case of an implementation in terms of software technology, the respective unit can be embodied as a computer program or part thereof, as a function, as a routine or as an executable object.

(68) In the case of an implementation of the sensor unit 400 in terms of hardware technology, the sensor unit can be embodied for example as an optical, capacitive or inductive sensor.

LIST OF REFERENCE SIGNS

(69) 1 to 8 Spokes 100A EUV lithography apparatus 100B DUV lithography apparatus 102 Beam shaping and illumination system 104 Projection system 106A EUV light source 106B DUV light source 108A EUV radiation 108B DUV radiation 110 Mirror 112 Mirror 114 Mirror 116 Mirror 118 Mirror 120 Photomask 122 Mirror 124 Wafer 126 optical axis 127 Lens element 128 Lens element 130 Mirror 131 Mirror 132 Medium 200 Measuring system 202 Optical component 204 Optically effective surface 206A, 206B, 206C End stops 208 Cutout 210 Peg 212 Ring gap 214 Central axis 216 Coating 300 Supporting frame 302 Actuator 304 Peg 306 Point of Engagement 400 Sensor unit 402 Computer unit 404 Storage unit 406 Providing unit 408 Comparator unit 410 Feedforward control unit 412 Regulator unit 414 Adding unit 416 Storage unit 418 Screen BM Movement pattern F Fault situation FM Force or torque Fx translational degree of freedom in x Fy translational degree of freedom in y Fz translational degree of freedom in z F.sub.Rx rotational degree of freedom about x F.sub.Ry rotational degree of freedom about y F.sub.Rz rotational degree of freedom about z M1 Mirror M2 Mirror M3 Mirror M4 Mirror M5 Mirror M6 Mirror M.sub.z Torque M.sub.z-actual Actual torque N Normal situation R.sub.z Rotation vector R.sub.z-actual Actual position R.sub.z-setpoint Setpoint movement SG Manipulated variable SG.sub.1 first part of the manipulated variable SG.sub.2 second part of the manipulated variable WP further parameters x Translation vector or axis x.sub.actual Actual position y Translation vector or axis y.sub.actual Actual position z Translation vector or axis