Stage Movement Control Apparatus and Charged Particle Beam System
20220148845 · 2022-05-12
Inventors
- Hironori OGAWA (Tokyo, JP)
- Shuichi NAKAGAWA (Tokyo, JP)
- Masaki MIZUOCHI (Tokyo, JP)
- Takanori Kato (Tokyo, JP)
- Naruo WATANABE (Tokyo, JP)
- Motohiro TAKAHASHI (Tokyo, JP)
Cpc classification
H01J37/147
ELECTRICITY
H01J37/1471
ELECTRICITY
H01J37/20
ELECTRICITY
International classification
H01J37/20
ELECTRICITY
H01J37/147
ELECTRICITY
Abstract
In order to improve the accuracy of stage movement in a charged particle beam apparatus, this stage movement control apparatus is characterized by comprising: a storage device in which overshoot amount data in which the movement distance of a stage and the overshoot amount of the stage are associated is stored; a movement target position setting unit which sets the movement target position of the stage; a stage movement amount calculation unit which calculates a stage movement amount that is an amount by which the stage moves to the movement target position in future; an overshoot estimation unit which, on the basis of the calculated stage movement amount and the overshoot amount data, estimates an overshoot amount corresponding to the stage movement amount; a movement target position correction unit which sets a corrected movement target position obtained by correcting the movement target position closer than the movement target position by the calculated overshoot amount; and a stage movement control unit which moves the stage to the corrected movement target position.
Claims
1. A stage movement control apparatus, comprising: a storage unit that stores overshoot amount data in which a movement distance of a stage in a charged particle beam device and an overshoot amount of the stage are associated; a movement target position setting unit that sets a movement target position of the stage; a stage movement amount calculation unit that calculates a stage movement amount, which is an amount by which the stage moves in future toward the movement target position; an overshoot estimation unit that estimates the overshoot amount corresponding to the stage movement amount based on the stage movement amount having been calculated and the overshoot amount data; a movement target position correction unit that sets a correction movement target position in which the movement target position is corrected from the movement target position to a near side by the overshoot amount having been calculated; and a stage movement control unit that moves the stage with respect to the correction movement target position.
2. The stage movement control apparatus according to claim 1, further comprising: an overshoot amount update unit that updates overshoot amount data by acquiring the overshoot amount generated when the stage is actually moved by the stage movement control unit and reflecting the acquired overshoot amount on the overshoot amount data.
3. The stage movement control apparatus according to claim 1, further comprising: a stage stabilization range setting unit that sets a stage stabilization range that is a permissible range of deviation of an arrival point, in which all measurement points exist in a range of beam shift of the charged particle beam device when the arrival point of the stage is deviated from the movement target position in movement of the stage.
4. The stage movement control apparatus according to claim 3, further comprising: a maximum beam shift amount setting unit that sets a maximum value of a beam shift amount in the charged particle beam device; and a permissible beam shift range setting unit that sets a permissible beam shift range that is a permissible range of the beam shift based on a maximum value of the beam shift amount, wherein the stage stabilization range setting unit sets a measurement point distribution range that is a range including all measurement points existing in the permissible beam shift range, and sets, as the stage stabilization range, a region having a width of a range obtained by subtracting the measurement point distribution range from the permissible beam shift range with the movement target position as a center.
5. The stage movement control apparatus according to claim 3, further comprising: a maximum beam shift amount setting unit that sets a maximum value of a beam shift amount in the charged particle beam device; and a permissible beam shift range setting unit that sets a permissible beam shift range that is a permissible range of the beam shift based on a maximum value of the beam shift amount, wherein the stage stabilization range setting unit designates the permissible beam shift range to be the stage stabilization range.
6. The stage movement control apparatus according to claim 3, wherein the stage movement control unit generates a command trajectory that is a trajectory for the stage is to move when performing movement of the stage, and performs movement of the stage based on the command trajectory, generates the command trajectory toward the correction movement target position until the stage enters the stage stabilization range from a movement start point of the stage, and changes the command trajectory when the stage enters the stage stabilization range so that an arrival point of the stage becomes any location in the stage stabilization range.
7. A charged particle beam system, comprising: a charged particle beam device having an electron gun for generating a charged particle beam, a column equipped with a deflector capable of deflecting the charged particle beam generated from the electron gun to a desired position, a stage configured to be moveable in which a sample irradiated with the charged particle beam generated from the electron gun is placed, a drive unit that drives the stage, and a position detection unit that detects a position of the stage; and a stage movement control apparatus that controls movement of the stage, wherein the stage movement control apparatus includes a storage unit that stores overshoot amount data in which a movement distance of the stage in the charged particle beam device and an overshoot amount of the stage are associated, a movement target position setting unit that sets a movement target position of the stage, a stage movement amount calculation unit that calculates a stage movement amount, which is an amount by which the stage moves in future toward the movement target position, an overshoot estimation unit that estimates the overshoot amount corresponding to the stage movement amount based on the stage movement amount having been calculated and the overshoot amount data, a movement target position correction unit that sets a correction movement target position in which the movement target position is corrected from the movement target position to a near side by the overshoot amount having been calculated, and a stage movement control unit that moves the stage with respect to the correction movement target position.
8. The charged particle beam system according to claim 7, further comprising: an overshoot amount update unit that updates overshoot amount data by acquiring the overshoot amount generated when the stage is actually moved by the stage movement control unit and reflecting the acquired overshoot amount on the overshoot amount data.
9. The charged particle beam system according to claim 7, further comprising: a stage stabilization range setting unit that sets a stage stabilization range that is a permissible range of deviation of an arrival point, in which all measurement points exist in a range of beam shift of the charged particle beam device when the arrival point of the stage is deviated from the movement target position in movement of the stage.
10. The charged particle beam system according to claim 9, further comprising: a maximum beam shift amount setting unit that sets a maximum value of a beam shift amount in the charged particle beam device; and a permissible beam shift range setting unit that sets a permissible beam shift range that is a permissible range of the beam shift based on a maximum value of the beam shift amount, wherein the stage stabilization range setting unit sets a measurement point distribution range that is a range including all measurement points existing in the permissible beam shift range, and sets, as the stage stabilization range, a region having a width of a range obtained by subtracting the measurement point distribution range from the permissible beam shift range with the movement target position as a center.
11. The charged particle beam system according to claim 9, further comprising: a maximum beam shift amount setting unit that sets a maximum value of a beam shift amount in the charged particle beam device; and a permissible beam shift range setting unit that sets a permissible beam shift range that is a permissible range of the beam shift based on a maximum value of the beam shift amount, wherein the stage stabilization range setting unit designates the permissible beam shift range to be the stage stabilization range.
12. The charged particle beam system of claim 9, further comprising: a maximum beam shift amount setting unit that sets a maximum value of a beam shift amount in the charged particle beam device, wherein the maximum beam shift amount setting unit associates an imaging state of the charged particle beam device with a maximum value of the beam shift amount, and displays, on a display unit, a screen for selecting a maximum value of the beam shift amount via an input unit.
13. The charged particle beam system of claim 9, further comprising: a maximum beam shift amount setting unit that sets a maximum value of a beam shift amount in the charged particle beam device, wherein the maximum beam shift amount setting unit sets a maximum value of the beam shift amount based on at least one of a state of an imaging target and an imaging condition.
14. The charged particle beam system according to claim 9, wherein the stage movement control unit generates a command trajectory that is a trajectory for the stage is to move when performing movement of the stage, and performs movement of the stage based on the command trajectory, generates the command trajectory toward the correction movement target position until the stage enters the stage stabilization range from a movement start point of the stage, and changes the command trajectory when the stage enters the stage stabilization range so that an arrival point of the stage becomes any location in the stage stabilization range.
15. The charged particle beam system according to claim 7, wherein the overshoot amount data is stored for each drive parameter for moving the stage.
Description
BRIEF DESCRIPTION OF DRAWINGS
[0017]
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[0020]
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DESCRIPTION OF EMBODIMENTS
[0034] Next, an embodiment for carrying out the present invention (referred to as an “embodiment”) will be described in detail with reference to the drawings as appropriate. The present embodiment is to measure a semiconductor wafer (wafer), and the structure of the wafer to be measured shall be known in advance by design data or the like. The coordinate of a measurement point shall be determined in advance by a recipe (recipe information) based on the design data. Here, the measurement indicates measurement of the configuration on the wafer by a length measurement SEM, and the measurement point means a point at which measurement is performed on the wafer.
[0035] [Charged Particle Beam System G]
[0036]
[0037] The charged particle beam system G has a charged particle beam device 200, which is a length measurement SEM, and a control apparatus (stage control apparatus) 100 that controls the charged particle beam device 200.
[0038] In the charged particle beam device 200, a Y stage (stage) 210 is arranged on a base 203 fixed in a sample chamber 201. The Y stage 210 can freely move in the Y direction (depth direction in the drawing) via two Y linear guides 211 and 212. A Y linear motor (drive unit) 213 is arranged between the base 203 and the Y stage 210 so as to generate thrust relatively in the Y direction. On the Y stage 210, an X stage (stage) 220 that can freely move in the X direction via two X linear guides 221 (one is not illustrated) is arranged. The X linear motor (drive unit) 223 is arranged between the Y stage 210 and the X stage 220 so as to generate thrust in the X direction. This enables the X stage 220 to freely move in the XY direction with respect to the base 203 and the sample chamber 201. Hereinafter, the Y stage 210 and the X stage 220 are collectively referred to as a stage 230 as appropriate.
[0039] A wafer 202 as a sample is placed on the X stage 220. A wafer retention mechanism (not illustrated) including a retention force such as a mechanical restraint force or an electrostatic force is used for arranging the wafer 202. A top plate 204 and a column 251 are placed in the sample chamber 201. The column 251 includes an electron optical system for generating a secondary electron image by an electron beam. The electron optical system includes an electron gun 252 that generates an electron beam (charged particle beam) and a deflector 253 that can deflect the electron beam generated from the electron gun 252 to a desired position.
[0040] The X stage 220 is provided with an X mirror (position detection unit) 242. On the side surface of the sample chamber 201, an X laser interferometer (position detection unit) 241 is placed. The X laser interferometer 241 irradiates the X mirror 242 with a laser light (broken line arrow in
[0041] Although the present embodiment assumes an example in which a linear guide is used as the drive mechanism of the stage 230, another drive mechanism (e.g., fluid bearing, magnetic bearing, or the like) can be used. Although a linear motor is used as the drive mechanism, an actuator that can be used in a vacuum such as a ball screw and a piezoelectric actuator can also be used. In the present embodiment, a laser interferometer is used for position detection of the stage 230, but another position detection method such as a linear scale, a two-dimensional scale, and a capacitance sensor may be used.
[0042] Although a length measurement SEM is assumed as the charged particle beam device 200 in the present embodiment, another charged particle beam device 200 such as a review SEM may be applied. However, in the present embodiment, as described above, it is premised that information on a portion to be imaged in advance by design data or the like is available.
[0043] [Control Apparatus 100]
[0044]
[0045] As illustrated in
[0046] The control apparatus 100 has a memory 130, a central processing unit (CPU) 140, and a storage device (storage unit) 150 such as a hard disk (HD). The control apparatus 100 further has an input device (input unit) 161 such as a keyboard and a mouse, a display device (display unit) 162 such as a display, and a communication device 163 such as a network card.
[0047] The storage device 150 stores overshoot amount data 151, a minimum stage stabilization range T0, beam shift amount data 152, and the like.
[0048] The overshoot amount data 151 stores an overshoot amount collected in the past and the like, and is used for estimating the overshoot amount caused by the stage movement.
[0049] The minimum stage stabilization range T0 is a minimum value of a stage stabilization range T (see
[0050] The beam shift amount data 152 is used when the setting of a permissible beam shift amount is automatically set as described later.
[0051] In the memory 130, a program stored in the storage device 150 is loaded. When executed by the CPU 140, the loaded program implements a processing unit 110, a permissible beam shift amount setting unit (maximum beam shift amount setting unit) 111 constituting the processing unit 110, an imaging range setting unit (permissible beam shift range setting unit) 112, a movement target position setting unit 113, a stage stabilization range setting unit 114, a stage movement amount calculation unit 115, an overshoot amount estimation unit 116, a movement target position correction unit 117, a stage movement control unit 118, an overshoot amount update unit 119, and an imaging control unit 120.
[0052] The permissible beam shift amount setting unit 111 sets a permissible beam shift amount (maximum value of the beam shift amount).
[0053] The imaging range setting unit 112 sets an imaging range to be described later.
[0054] The movement target position setting unit 113 sets a measurement point B (see
[0055] The stage stabilization range setting unit 114 performs setting of the stage stabilization range T (see
[0056] The stage movement amount calculation unit 115 calculates the movement amount of the stage 230.
[0057] The overshoot amount estimation unit 116 estimates the overshoot amount accompanying the movement of the stage 230. The estimation of the overshoot amount is performed based on the movement amount of the stage 230 calculated by the stage movement amount calculation unit 115 and the overshoot amount data 151 stored in the storage device 150.
[0058] The movement target position correction unit 117 corrects the movement target position of the stage 230 based on the overshoot amount estimated by the overshoot amount estimation unit 116.
[0059] The stage movement control unit 118 moves the stage 230 toward the movement target position (correction target position) corrected by the movement target position correction unit 117. Specifically, the stage movement control unit 118 drives the X linear motor 223 and the Y linear motor 213 of the charged particle beam device 200. These drives are performed via the linear motor drive amplifier 171. Thus, the X stage 220 and the Y stage 210 (i.e., the stage 230) move. As will be described later in detail, when the stage position reaches within the stage stabilization range T, the stage movement control unit 118 changes the movement target position to any point within the stage stabilization range T.
[0060] The overshoot amount update unit 119 acquires an actual overshoot amount caused by the stage movement, and updates the overshoot amount data 151 using this overshoot amount.
[0061] The imaging control unit 120 controls imaging of the measurement point B on the wafer 202 by the charged particle beam device 200.
[0062] The above configuration enables the control apparatus 100 to move the wafer 202 in the XY plane with respect to the sample chamber 201 and to generate a secondary electron image by the column 251.
[0063] [Flowchart]
[0064] Next, an imaging procedure of the wafer 202 performed in the present embodiment will be described with reference to
[0065]
[0066] The processing of
[0067] First, when an operator executes a recipe via the input device 161 or the like, the plurality of measurement points B (see
[0068] Then, the permissible beam shift amount setting unit 111 sets a permissible beam shift amount (S102). The permissible beam shift amount is the maximum value of the beam shift amount used for correction of deviation of the stage position and field of view movement, and is set, for example, within ±10 μm. As illustrated in
[0069] Then, the imaging range setting unit 112 sets the imaging range using the permissible beam shift amount and the minimum stage stabilization range T0 (S103).
[0070] The minimum stage stabilization range T0 is the minimum value of the stage stabilization range T (see
[0071] The minimum stage stabilization range T0 is set in advance, for example, is set within 0.1 μm. The stage stabilization range T will be described later.
[0072] In step S103, the imaging range setting unit 112 sets the imaging range at E=DR−T0. Here, E represents an imaging range, and DR represents a permissible beam shift range. The permissible beam shift range DR is the maximum range where the electron beam by the beam shift reaches. T0 represents the minimum stage stabilization range.
[0073] This imaging range will be described later with reference to
[0074] Next, the imaging range setting unit 112 determines whether or not the plurality of measurement points B exist in the imaging range (S104). In this processing, the imaging range setting unit 112 determines whether or not imaging of the plurality of measurement points B is possible after the next stage movement. Here, the order of the measurement points B on the wafer 202 is sometimes determined in advance, or sometimes only the coordinate of the measurement points B is determined and the order is not determined. As described above, in the present embodiment, since the structure of the wafer 202 to be measured is known by the design data or the like, it is possible to set the order of the measurement points B and the coordinate of the measurement points B in advance.
[0075] Here, if the order of the measurement points B is determined by the recipe information 181, the imaging range setting unit 112 sets the measurement points B that can be imaged in the imaging range.
[0076] If the order of the measurement points B is not determined by the recipe information 181, the imaging range setting unit 112 performs the following processing. That is, the imaging range setting unit 112 determines whether or not there is another measurement point B that can be imaged in the imaging range in the vicinity of the next measurement point B with respect to the unmeasured measurement point B on the wafer 202. When there is another measurement point B, the imaging range setting unit 112 decides the measurement order of the measurement points B in the imaging range. Here, the measurement order of the measurement points B is a so-called traveling salesman problem, and it may be decided by a known approximation algorithm or the like. Thus, the measurement point B to be measured next is set. The measurement order of the measurement points B is only required to be decided once in one imaging range.
[0077] As a result of step S104, if the plurality of measurement points B exist in the imaging range (Yes in step S104), the movement target position setting unit 113 decides a movement target position Pt (see
[0078] Next, the stage stabilization range setting unit 114 sets the stage stabilization range T in the next stage movement (S112).
[0079] That is, as illustrated in
[0080] In
[0081] For example, if the permissible beam shift range DR is ±10 μm and the coordinates of the measurement point B are distributed in a range (measurement point distribution range BR) of ±6 μm from the movement target position Pt, the stage stabilization range T is a square having a value of ±4 μm on one side centered on the movement target position Pt. Here, since the coordinates of the measurement point B have different distributions in the XY direction, the stage stabilization range T can have different values from each other in the XY direction.
[0082] The stage stabilization range T will be described specifically.
[0083]
[0084] The minimum stage stabilization range T0 used in step S103 is the minimum value of the stage stabilization range T. The imaging range set in step S103 corresponds to the measurement point distribution range BR in a case where the stage stabilization range T is the minimum stage stabilization range T0. However, the imaging range in step S103 is different from the measurement point distribution range BR, and is for determining whether or not the plurality of measurement points B exist in the imaging range that is a range with a slight allowance from the permissible beam shift range DR.
[0085] Although it is possible to set the minimum stage stabilization range T0 to 0, if this is done, there is a possibility that the position of the measurement point B becomes close to the permissible beam shift range DR (see
[0086] The description returns to
[0087] After step S112, the processing unit 110 proceeds with the processing to step S131.
[0088] As a result of step S104, if only one measurement point B exists in the imaging range (No in step S104), the movement target position setting unit 113 sets the movement target position Pt in the next stage movement (step S121). Subsequently, the stage stabilization range setting unit 114 sets the stage stabilization range T (S122). Here, the imaging range setting unit 112 sets the movement target position Pt, which is the target position of stage movement, as the coordinate of the next measurement point B, and sets the stage stabilization range T so as to coincide with the permissible beam shift range DR. The next movement target position Pt is set based on the information of the measurement point B set in step S101.
[0089] The stage stabilization range T set in step S121 will be described with reference to
[0090] As illustrated in
[0091] As illustrated in
[0092] The description returns to
[0093] After step S122, the processing unit 110 proceeds with the processing to step S131.
[0094] In step S131, the stage movement amount calculation unit 115 calculates a necessary movement amount of the stage 230 from the movement target position Pt and the current coordinate of the stage 230. At this time, the stage movement amount calculation unit 115 also calculates the movement direction of the stage 230.
[0095] Subsequently, the overshoot amount estimation unit 116 calculates an estimated overshoot amount Δ (S132). Here, the estimated overshoot amount Δ is an amount by which the position response of the stage 230 is estimated in advance from the movement target position at the time of positioning of the stage 230. Based on a drive parameter 182, the overshoot amount estimation unit 116 calculates the estimated overshoot amount based on the estimation processing described later. The drive parameter 182 is at least one of the speed, acceleration, and jerk of the stage 230 set in the recipe information 181, for example. Parameters other than the speed, acceleration, and jerk of the stage 230 may be used as the drive parameter 182. The overshoot amount data 151 is used for estimation of the overshoot amount. The overshoot amount data 151 is generated based on an actual overshoot amount that has occurred in the past as described later. Since the overshoot amount data is generated based on the actual overshoot amount that has occurred in the past, the overshoot amount data 151 includes a tendency of machine difference and error for each charged particle beam device 200. Since the stage movement amount to the next movement target position Pt is different in each of XY directions, the estimated overshoot amount Δ has different values in each of XY directions.
[0096] An example of a calculation method of the estimated overshoot amount will be described with reference to
[0097]
[0098] As illustrated in
[0099] Thus, by storing the overshoot amount estimation function 312 as an estimation parameter, the overshoot amount estimation unit 116 calculates the estimated overshoot amount Δ based on a movement amount M at the time of the stage movement, for example. Since the characteristics of the stage 230 are different in the XY directions, the overshoot amount estimation function 312 is desirably stored for each XY direction (
[0100] As described above, the overshoot amount of the stage 230 varies depending not only on the movement amount and movement direction of the stage 230 but also on the drive parameters 182 such as the speed, acceleration, and jerk, and the coordinate of the stage 230. The overshoot amount is likely to be affected by the structure of the stage 230, external air temperature, atmospheric pressure, and the like, and these characteristics generally have machine differences (variations) depending on each device within a range of mechanical and electrical tolerances.
[0101] In
[0102] When the input recipe information 181 uses a drive parameter 182 that is not included in the overshoot amount data 151, the closest drive parameter 182 may be used.
[0103] The overshoot amount data 151 is, as described above, data collected in advance by an experiment or the like, but is also updated by the actual operation of the charged particle beam device 200 as described later.
[0104] The description returns to
[0105] After step S132, the movement target position correction unit 117 calculates (step S133) a correction target position Pm (see
[0106] Then, the stage movement control unit 118 performs stage movement with respect to the correction target position Pm (S134). Here, the stage movement control unit 118 generates a command trajectory 401b (see
[0107] The stage movement will now be described with reference to
[0108]
[0109] In
[0110] Here, as illustrated in
[0111] The overshoot amount 403a increases a positioning time T1A until the response 402a falls within the range of the stage stabilization range T. As described above, by improving the control band of the servo control system, the overshoot amount 403a can be reduced, but the control band is often limited by the influence of the resonance of the structure in the stage 230. It is also possible to position the stage so as not to overshoot by adjusting the drive parameter 182 (e.g., reducing the acceleration). However, since the time required for the command trajectory 401a to reach the movement target position Pt increases, the positioning time is not shortened in many cases.
[0112]
[0113] In
[0114] Furthermore, as described above, the overshoot amount estimation unit 116 calculates the estimated overshoot amount Δ from the drive parameters 182 such as a predetermined speed, acceleration, and jerk (step S132 in
[0115] As described above, the stage movement control unit 118 performs the stage movement with respect to the correction target position Pm (step S134 in
[0116] The stage movement control unit 118 performs servo control so as to follow the generated command trajectory 401b. At this time, a response 402b is positioned after an overshoot 403b occurs with respect to the correction target position Pm. If the estimation of the estimated overshoot amount Δ is correct, the response 402b of the stage 230 approaches the command trajectory 401b (stage stabilization range T) after reaching the correction target position Pm. In a case where the stage 230 is positioned using the correction target position Pm, the position response of the stage 230 where the overshoot 403b occurs is stabilized near the movement target position Pt. Thus, the positioning accuracy of the stage 230 can be improved.
[0117] Here, the reason why the command trajectory 401b is switched from the correction target position Pm to coincide with the stage stabilization range T at the time T1B when the response 402b reaches the stage stabilization range T will be described. If the command trajectory 401b remains at the correction target position Pm even after the time T1B, the response 402b makes an attempt to follow the correction target position Pm by servo control. Therefore, at the time T1B when the response 402b reaches the stage stabilization range T, the command trajectory 401b is switched from the correction target position Pm to coincide with the stage stabilization range T. This is performed to prevent the response 402b from separating from the stage stabilization range T again. When detecting that the stage position has reached the stage stabilization range T, the stage movement control unit 118 changes the command trajectory 401b to the stage stabilization range T. Whether or not the stage position has reached the stage stabilization range T is determined based on the relative displacements of the stage 230 in the X direction and the Y direction by the X laser interferometer 241 and the Y laser interferometer.
[0118] If the estimation of the overshoot amount is deviated, it is conceivable a case where the response 402b does not reach the stage stabilization range T. Even in this case, for example, at a time point (time T1C) when the command trajectory 401b reaches the correction target position Pm, the command trajectory 401b is updated to the stage stabilization range T. This makes it possible to ensure that the response 402b falls within the stage stabilization range T. Whether or not the stage position has reached the correction target position Pm is also determined based on the relative displacements of the stage 230 in the X direction and Y direction by the X laser interferometer 241 and the Y laser interferometer.
[0119] At the time T1B, the command trajectory 401b is changed to not the movement target position Pt but the stage stabilization range T. This is because, if the command trajectory 401b is changed to the movement target position Pt, the degree of the change becomes large, and therefore, a fluctuation or the like occurs in the response 402b. Therefore, the command trajectory 401b is changed to the stage stabilization range T because imaging is possible and the change of the command trajectory 401b is minimized. At the time T1B, the command trajectory 401b may be changed to the movement target position Pt, or may be any point in the stage stabilization range T.
[0120] By performing the processing as illustrated in
[0121] As described above in
[0122] The description returns to
[0123] After step S134, the overshoot amount update unit 119 detects an overshoot amount that actually occurred in the stage movement, and updates the overshoot amount data 151 (step S141). Here, the overshoot amount is detected using the response deviation of the stage position with respect to the correction target position Pm, and is updated based on an update algorithm described later.
[0124] It is desirable to collect data on the overshoot amount before shipment of the charged particle beam device 200 with respect to stage movement conditions assumed in advance (such as a stage movement amount) and the drive parameter 182 (speed, acceleration, jerk, and the like). On the other hand, since the overshoot amount can be collected for each actual stage movement, the overshoot amount data 151 can be updated during operation of the charged particle beam device 200. Thus, during operation of the charged particle beam device 200, it is possible to collect data on the frequently used movement amount and the overshoot amount with respect to the coordinate. Thus, it is expected to improve the estimation accuracy of the overshoot with respect to the frequently used stage movement conditions.
[0125] Examples of the update algorithm of the overshoot amount data 151 include one described below. When a new overshoot amount Δnow is obtained by the stage movement, the overshoot amount update unit 119 calculates the new overshoot amount Δnew by calculating the following expression (1) using past data Δold.
Δnew=a×Δnow+(1−a)×Δold (1)
[0126] The overshoot amount update unit 119 updates the measurement data 311 and 321 of the overshoot amount of the corresponding drive parameters 182 in the overshoot amount data 151 illustrated in
[0127] This makes it possible to maintain the estimation accuracy of the overshoot amount even if the overshoot amount changes with time or the like. Here, a coefficient a in expression (1) is a parameter for determining how much weight to put to past data. A small coefficient a stabilizes the change in the estimated overshoot amount Δ. By setting the coefficient a to 0, it is possible to continue using the overshoot amount data 151 having already been set, without updating the overshoot amount data 151.
[0128] The description returns to
[0129] In step S142 of
[0130] Thereafter, the processing unit 110 determines whether or not imaging of all the measurement points B in the permissible beam shift range DR has been completed (S143).
[0131] As a result of step S143, if the imaging of all the measurement points B in the permissible beam shift range DR has not been completed (No in step S143), the processing unit 110 returns the processing to step S142. Then, the processing unit 110 repeats imaging of the SEM image without stage movement (i.e., by beam shift).
[0132] As a result of step S143, if the imaging of all the measurement points B in the permissible beam shift range DR has been completed (Yes in step S143), the processing unit 110 determines whether or not the imaging of all the measurement points B in the wafer 202 has been completed (step S144).
[0133] As a result of step S144, if the imaging of all the measurement points B in the wafer 202 has not been completed (No in step S144), the processing unit 110 returns the processing to the step S104.
[0134] As a result of step S144, if the imaging of all the measurement points B in the wafer 202 has been completed (Yes in step S144), the processing unit 110 ends the processing.
[0135] [Measurement Order]
[0136] Next, the measurement order will be described with reference to
[0137]
[0138] In the example of
[0139] When all the measurement points B1 to B4 in the permissible beam shift range DRa are imaged, stage movement (reference sign 511) is performed, and the stage 230 moves to the vicinity of a next movement target position Ptb. All of the measurement points B in the permissible beam shift range DRb including the movement target position Ptb are imaged by the field of view movement by the beam shift. When all the measurement points B in the permissible beam shift range DRb are imaged, stage movement (reference sign 512) is performed, and the stage 230 moves to the vicinity of a next movement target position Ptc. Then, each of the measurement points B in the permissible beam shift range DRc including the movement target position Ptc is imaged by the field of view movement by the beam shift.
[0140] In each of the permissible beam shift ranges DRa to DRc, since the distribution of the measurement points B to be imaged is different, a stage stabilization range T having a different size is set.
[0141]
[0142] The example of
[0143] [Variations]
[0144] (Overshoot Amount Data 151a)
[0145] In
[0146] As described above, when the new overshoot amount Δnow is obtained by the actual stage movement, the new overshoot amount Δnew is preferably updated by expression (1) or the like using the past data Δold (see step S141 in
[0147] The “positive direction” and the “negative direction” in
[0148] (Setting Example of Permissible Beam Shift Amount)
[0149]
[0150] The table presented in
[0151] In
[0152] In the “high accuracy” mode, the permissible beam shift amount becomes small, and it is hence desirable that one measurement point B is included in one permissible beam shift range DR as in
[0153] In
[0154] For example, as illustrated in
[0155] As illustrated in
[0156] Not that the permissible beam shift amount by the auto mode may be decided by a method other than that illustrated in
[0157] The setting of the permissible beam shift amount by the auto mode is effective particularly in a case where there are many measurement points B and a plurality of types of measurements are performed on one wafer 202.
[0158]
[0159] The table presented in
[0160] Display of such a reference image enables the operator to make a decision while confirming the affecting image deterioration when setting the mode. Here, the reference image to be displayed may be a previously obtained image, or an image in which the permissible beam shift amount is intentionally changed by using a semiconductor pattern that is an actual measurement object may be newly created and displayed. Alternatively, an image in which the permissible beam shift amount is changed based on the design data of the wafer 202 may be newly created and displayed. The estimated measurement time in
[0161] (Setting Example of Permissible Beam Shift Amount (Second Example))
[0162]
[0163]
[0164] The screen illustrated in
[0165] According to the present embodiment, it is possible to suppress the position deviation at the time of the stage movement due to overshoot. This makes it possible to shorten the stage movement time, and to reduce the permissible beam shift amount for correcting the deviation of the stage position. Along with this, it is possible to increase the beam shift amount used for field of view movement, and possible to enlarge the field of view movement by the beam shift. According to the present embodiment, the throughput can be improved by shortening of the stage movement time and enlargement of the field of view movement range by the beam shift.
[0166] Since the beam shift amount can be reduced, the beam tilt can be reduced. This makes it possible to improve the accuracy of an image imaged particularly in a deep hole or the like.
[0167] The present invention is not limited to the above-described embodiment, and includes various variations. For example, the above-described embodiment has been described in detail for the purpose of clearly explaining the present invention, and is not necessarily limited to one having all of the described configurations.
[0168] The above-described structures, functions, units 110 to 120, storage device 150, and the like may be implemented by hardware by designing some or all of them with an integrated circuit, for example. As illustrated in
[0169] In each embodiment, the control lines and the information lines that are considered to be necessary for explanation are illustrated, and not all the control lines and the information lines are necessarily illustrated on the product. In practice, almost all configurations may be considered to be interconnected.
REFERENCE SIGNS LIST
[0170] 100 control apparatus (stage movement control apparatus) [0171] 111 permissible beam shift amount setting unit (maximum beam shift amount setting unit) [0172] 112 imaging range setting unit (permissible beam shift range setting unit) [0173] 113 movement target position setting unit [0174] 114 stage stabilization range setting unit [0175] 115 stage movement amount calculation unit [0176] 116 overshoot amount estimation unit [0177] 117 movement target position correction unit [0178] 118 stage movement control unit [0179] 119 overshoot amount update unit [0180] 150 storage device (storage unit) [0181] 151 overshoot amount data [0182] 161 input device (input unit) [0183] 162 display device (display unit) [0184] 200 charged particle beam device [0185] 202 wafer (sample) [0186] 210 Y stage (stage) [0187] 213 Y linear motor (drive unit) [0188] 220 X stage (stage) [0189] 223 X linear motor (drive unit) [0190] 242 X mirror (position detection unit) [0191] 230 stage [0192] 241 X laser interferometer (position detection unit) [0193] 251 column [0194] 252 electron gun [0195] 253 deflector [0196] BR measurement point distribution range [0197] DR permissible beam shift range [0198] T stage stabilization range