Charged particle beam device

Abstract

The present disclosure proposes a charged particle beam device, wherein, in order to reduce a field-of-view deviation amount when stage rotation is performed in each of θx, θy, and θz axial directions with respect to a discretionary stage rotation center: (i) the discretionary rotation center is controlled using motor thrust in a translation direction and a rotation direction of a stage device; (ii) a deviation amount from the center of the field of view in an observation image, or the trajectory of the deviation amount, is obtained on the basis of position information indicating the distance in at least one of an X-axis direction, a Y-axis direction, and a Z-axis direction between rotation center coordinates of the stage device and sample observation coordinates, and on the basis of the rotation angles of a θx axis, a θy axis, and a θz axis, during the rotation operation; and (iii) the deviation amount, or the trajectory of the deviation amount, is added to the position information pertaining to the stage when the stage device is moved, whereby the deviation amount from the center of the field of view in the observation image is corrected (see fig. 4).

Description

charged particle beam equipment

[0001] The present disclosure relates to a charged particle beam device.

[0002] In recent years, with the miniaturization of semiconductor devices, semiconductor manufacturing equipment and inspection equipment are required to be highly accurate to accommodate this miniaturization. Scanning electron microscopes (hereinafter referred to as SEMs) are typically used to evaluate patterns formed on semiconductor wafers and to inspect the formed wafers for defects. In particular, critical dimension SEMs are used to evaluate the shape and dimensions of patterns.

[0003] A CD-SEM is a device that irradiates a wafer with an electron beam, processes the resulting secondary electron signals, and measures and analyzes the dimensions of the patterns formed on the wafer by identifying the edges of the patterns from changes in brightness. In recent years, with the increasing sophistication of semiconductor devices and the increasing complexity of packaging methods, it has become necessary to irradiate semiconductor wafers with an electron beam at various angles to obtain cross-sectional images and perform dimensional measurements.

[0004] Sample stages are used to accurately position semiconductor devices such as semiconductor wafers. Sample stages can be driven, for example, by a rotary motor and ball screw or a linear motor. In addition to movement along the X, Y, and Z axes, six-axis drive stages are sometimes used, capable of rotating around the X, Y, and Z axes (θx, θy, and θz axes). In particular, non-contact levitation stages using hydrostatic bearings or electromagnetic bearings are often used in recent years to achieve ultra-precise positioning.

[0005] When acquiring the cross-sectional image of the semiconductor wafer mentioned above, one method is to change the tilt angle of the electron beam irradiating the semiconductor device by controlling the amount of deflection of the electron beam. However, this method changes the electron beam irradiation trajectory of the electron optical system, which changes the characteristics of the electron beam, causing changes in the appearance of the pattern and image blurring, leading to a deterioration in the accuracy of pattern dimension measurement.

[0006] To address this issue, by controlling the tilt angle of the sample stage (rotation along the θx or θy axis) while keeping the inclination angle of the electron beam constant, it becomes possible to control the irradiation angle of the electron beam on the semiconductor device without reducing the accuracy of dimensional measurement. However, if the center of rotation of the stage does not coincide with the center of the field of view of the image, a field shift occurs when the stage is rotated, and the pattern to be measured falls outside the field of view of the image, which is a problem.

[0007] In this regard, for example, Patent Document 1 proposes a technique for an observation method of a scanning charged particle beam device in which, when rotating the rotation stage, the X-Y stage is moved according to the distance and rotation angle between the center position of the observation image and the mechanical center of rotation, and the movement speed of the X-Y stage is controlled according to the length of the distance, so that the image always rotates at the center of the observation screen due to mechanical rotation.

[0008] Japanese Patent Application Laid-Open No. 2001-35433

[0009] However, the technology disclosed in Patent Document 1 only deals with rotation on the X-Y plane, i.e., rotation along the θz axis. Furthermore, Patent Document 1 does not consider changing the stage's center of rotation. Changing the X-, Y-, or Z-axis coordinates of the stage's center of rotation depending on the cross-sectional height of the semiconductor device to be observed changes the amount of field of view shift of the image, resulting in a decrease in the effectiveness of field of view shift correction. Therefore, in order to achieve high-precision inspection compatible with various semiconductor device mounting methods, it is necessary to reduce the amount of field of view shift even when the stage is rotated along the θx, θy, or θz axes around an arbitrary stage center of rotation.

[0010] In view of such circumstances, the present disclosure proposes a technique for reducing the amount of field of view deviation when a stage rotates in the θx, θy, and θz axis directions around an arbitrary stage rotation center in a charged particle beam device.

[0011] As one aspect for achieving the above object, the present disclosure proposes a charged particle beam device that irradiates a sample with a charged particle beam and acquires an observation image of the sample, the charged particle beam device comprising: a mirror body including a charged particle beam source and a lens; a stage device; and a control device that controls the operation of the stage device, wherein the control device (i) controls an arbitrary center of rotation using motor thrust in the translational and rotational directions of the stage device; (ii) during rotation operation, calculates the amount of deviation of the observation image from the center of the field of view or the trajectory of the deviation based on position information indicating the distance in at least one of the X-axis, Y-axis, and Z-axis directions between the rotation center coordinate of the stage device and the sample observation coordinate, and the rotation angles of the θx-axis, θy-axis, and θz-axis; and (iii) when moving the stage device, corrects the amount of deviation of the observation image from the center of the field of view by adding the amount of deviation or the trajectory of the deviation to the position information of the stage device.

[0012] Further features related to the present disclosure will become apparent from the description of this specification and the accompanying drawings. Also, aspects of the present disclosure are achieved and realized by the elements and combinations of various elements and the aspects of the following detailed description and the appended claims. The description of this specification is merely exemplary and does not limit the scope or application of the claims of the present disclosure in any way.

[0013] According to the technology of the present disclosure, it is possible to reduce the amount of field of view deviation when the stage rotates in the θx-axis, θy-axis, and θz-axis directions around an arbitrary stage rotation center.

[0014] 1 is a diagram showing how an electron beam is irradiated onto a wafer and observed; FIG. 1 is a diagram showing an example of a case where the stage is rotated with the field of view center and the stage rotation center coinciding; FIG. 2 is a diagram showing an example of a case where the stage is rotated with the field of view center and the stage rotation center not coinciding; FIG. 3 is a diagram showing a state of pattern observation when the sample stage 205 is not rotated; FIG. 4 is a diagram showing a state when the sample stage 205 is rotated in the θx-axis direction; FIG. 5 is a diagram showing an example of the arrangement of a levitation stage and a motor; FIG. 6 is a diagram showing the state of the levitation stage 301 as viewed from the XZ plane; FIG. 7 is a diagram showing the state of the levitation stage 301 when the magnitude of the Z-axis thrust is changed; FIG. 8 is a diagram for explaining a control system for the rotation center of the levitation stage; FIG. 9 is a diagram showing an example of the configuration of a stage control system that corrects field of view deviation; FIG. 10 is a diagram showing stage position information that corrects the field of view deviation amount; FIG. 11 is a diagram showing an example when field of view deviation amount correction processing is not applied; FIG. 12 is a diagram showing an example when field of view deviation amount correction processing is applied; FIG. 13 is a diagram showing a change in the height of the wafer surface; FIG. 14 is a diagram showing a GUI (Graphical User Interface) 901 for a user to input a rotation center and a rotation angle using a UI; and FIG. 15 is a diagram showing how an electron beam is irradiated onto a sample at a certain angle of incidence. 1 is a diagram for explaining the principle of determining the incident angle of the electron beam 102 by changing the height of the levitation stage 301. FIG. 2 is a diagram showing how the incident angle of the electron beam with respect to the sample is changed by rotating the stage.

[0015] This embodiment discloses a technique for reducing the field of view shift of an SEM image that occurs during stage rotation in a charged particle beam device (e.g., a critical dimension SEM). More specifically, this embodiment proposes calculating the amount of deviation of an observed image from the center of the field of view or the trajectory of the deviation based on position information indicating the distance between the stage rotation center coordinates and the sample observation coordinates and the stage rotation angle, and correcting the amount of deviation of the observed image from the center of the field of view by adding (reflecting) the amount of deviation or the trajectory of the deviation to the stage position information when moving the stage.

[0016] Hereinafter, embodiments and examples of the present disclosure will be described with reference to the accompanying drawings. In the accompanying drawings, functionally identical elements may be designated by the same numerals. Note that the accompanying drawings show specific embodiments and implementation examples in accordance with the principles of the present disclosure, but these are intended to aid in understanding the present disclosure and are by no means to be used to interpret the present disclosure in a limiting manner.

[0017] Although the present embodiment has been described in sufficient detail to enable those skilled in the art to practice the present disclosure, it should be understood that other implementations and forms are possible, and that changes in configuration and structure and substitutions of various elements are possible without departing from the scope and spirit of the technical ideas of the present disclosure. Therefore, the following description should not be interpreted as being limited thereto.

[0018] <Changes in Visual Field Misalignment> Changes in visual field misalignment depending on whether the center of rotation and the center of the visual field coincide with each other will be described with reference to FIGS. 1A to 1C.

[0019] 1A is a diagram showing how an electron beam is irradiated onto a wafer and observed. An electron beam 102 emitted from an electron optical system 101 is irradiated onto a wafer 103 mounted on a stage 104, and an observed image including a center of view 105 is obtained.

[0020] 1B is a diagram showing an example of a case where the stage is rotated with the center of the field of view and the center of stage rotation coinciding. In this case, the stage is rotated around the center of the field of view 105 as the rotation center 106, so no misalignment of the field of view occurs.

[0021] 1C is a diagram showing an example of a case where the stage is rotated in a state where the center of the field of view and the center of rotation of the stage do not coincide with each other. In this case, the center of rotation 106 of the stage does not coincide with the center of the field of view, resulting in a field of view deviation 108.

[0022] 2A and 2B, a description will be given of the field of view shift that occurs when the sample stage 205 rotates. A method for calculating the amount of field of view shift will also be shown based on FIGS. 2A and 2B.

[0023] 2A is a diagram showing a state during pattern observation without rotating the sample stage 205. A bar mirror 204 is installed on the sample stage 205, and the position of the sample stage 205 is measured using a laser interferometer (not shown). When measuring the position of the sample stage 205, displacements in the X-axis, Y-axis, Z-axis, θx-axis, θy-axis, and θz-axis may be measured using multiple laser interferometers.

[0024] The sample stage 205 is equipped with a motor (not shown). The motor can be used to control the position and attitude of the sample stage 205. Furthermore, by arranging multiple motors, it is possible to control the displacement of the sample stage 205 in the X-axis, Y-axis, Z-axis, θx-axis, θy-axis, and θz-axis. Furthermore, a chuck 203 is mounted on the sample stage 205. The chuck 203 holds the wafer 103 using electrostatic force or the like. Then, by irradiating the wafer 103 with an electron beam 102, it is possible to observe a pattern at an observation coordinate 201.

[0025] 2B is a diagram showing the state when the sample stage 205 is rotated in the θx-axis direction. Here, if the distance 206 from the stage rotation center 207 to the observation coordinate is Lz and the rotation angle 208 of the sample stage 205 is θx, the field of view deviation 209 (Δ) in the Y-axis direction can be calculated by equation (1). Note that the counterclockwise direction with respect to the axis is defined as the positive rotation direction.

[0026] Δ=-Lzθx... (1)

[0027] Furthermore, when the sample stage is rotated by stage rotation angles θx, θy, and θz about the θx, θy, and θz axes, respectively, and the distances from the observation coordinate to the rotation center coordinate in the X-, Y-, and Z-axis directions are Lx, Ly, and Lz, respectively, the field of view shift amounts (ΔX, ΔY, ΔZ) in the X-, Y-, and Z-axis directions can be calculated by the following equation (2).

[0028] ΔX=Lzθy−Lyθz ΔY=−Lzθx+Lxθz (2) ΔZ=Lyθx−Lxθy Here, ΔZ corresponds to the focus deviation.

[0029] <Control of Rotation Center of Levitation Stage: Overview> With reference to FIG. 3, the following describes how the rotation center of the levitation stage 301 can be varied by moment control.

[0030] FIG. 3A is a diagram showing an example of the arrangement of the levitation stage 301 and motors. In this example, the levitation stage 301 is supported non-contact with respect to the base unit 302 by electromagnetic bearings, hydrostatic bearings, and the like. By arranging an X-axis motor 304, a Z-axis motor 303, and a Y-axis motor (not shown) on the levitation stage 301, it becomes possible to move in six axial directions: the X-axis, Y-axis, Z-axis, θx-axis, θy-axis, and θz-axis. Here, the motors (X-axis motor 304, Z-axis motor 303, and Y-axis motor) can be voice coil motors or linear motors. Furthermore, the stators and movers of the motors can be arranged on either the levitation stage 301 side or the base unit 302 side. The position of the levitation stage 301 can be measured using the laser or scale described above.

[0031] 3B is a diagram showing the state of levitation stage 301 as viewed from the XZ plane. Using thrusts 306 and 307 of the Z-axis motor makes it possible to control the rotation angle of levitation stage 301. Furthermore, by making thrusts 306 and 307 approximately equal in magnitude, it is possible to control levitation stage 301 with the coordinates of its center of gravity as the center of rotation 305.

[0032] 3C is a diagram showing the state of levitation stage 301 when the magnitude of the Z-axis thrust is changed. In this case, too, by changing the magnitude of thrusts 306 and 307 of the Z-axis motor, it is possible to change the stage rotation center 305 to any position. In other words, by controlling the motor thrust, the semiconductor device can be rotated around any rotation center, allowing the pattern to be observed from various angles.

[0033] <Control of the Rotation Center of the Levitation Stage: Control System> (i) FIG. 4 is a diagram illustrating a control system for the rotation center of the levitation stage. In FIG. 4, a levitation stage 301 is mounted in a vacuum chamber 401. The sample on the levitation stage 301 can be observed by irradiating an electron beam 102 from an electron optical system 101 onto the sample. The levitation stage 301 is supported in a non-contact manner by a base 407 and is controlled using multiple motors 403. The levitation stage 301 may also employ a planar levitation system or a system capable of long-distance movement in a single axis direction. Note that a coarse / fine adjustment stage may be disposed in place of the base 407.

[0034] The control device 404 uses signals from a position measuring device (not shown) that measures the position of the levitation stage to measure six-axis displacement of the levitation stage 301—the X-axis, Y-axis, Z-axis, θx-axis, θy-axis, and θz-axis—to configure a feedback control system for controlling the six-axis displacement. As described above, for example, a laser interferometer can be used as the position measuring device. A reflecting mirror (not shown) is placed on the levitation stage 301 to measure the position of the levitation stage 301 through interference between laser light and reflected light. Position measurement using a laser interferometer makes it possible to measure the height position near an object such as a semiconductor wafer, enabling high-precision position measurement with minimal Abbe error. Furthermore, the laser interferometer has a resolution on the order of picometers, enabling accurate positioning. Note that an optical scale or a magnetic scale may be used instead of a laser interferometer.

[0035] When configuring a feedback control system, information from multiple position measuring devices may be coordinate-converted to measure six-axis displacement. Furthermore, thrust 402 for multiple motors 403 may be calculated by performing coordinate conversion on the feedback controller output. For coordinate conversion, a conversion formula may be applied to the six axes, or a matrix operation may be used instead of the conversion formula. Furthermore, coefficient parameters used in coordinate conversion may be optimized using an evaluation function J (quadratic form) such as in equation (3).

[0036] J=X ＴQX (3) where X is a vector storing coefficient parameters used for coordinate transformation, and Q is a matrix relating to the weight of the evaluation function and the evaluation items of the control characteristics.

[0037] When rotating the levitation stage 301, the control device 404 calculates the amount of field of view deviation using stage rotation angle information 405 and distance information 406 between the observation coordinates and the rotation center according to the above-mentioned equation (2), and corrects the amount of field of view deviation. The control device 404, which performs coordinate conversion, control system calculations, and field of view deviation correction, can be configured using a microcomputer or FPGA (Field Programmable Gate Array). Because the levitation stage 301 is supported without contact, it is possible to arbitrarily change the stage rotation center 305 depending on the semiconductor wafer pattern mounting method and measurement method.

[0038] (ii) Figure 5 is a diagram showing an example of the configuration of a stage control system that corrects field of view deviation. The feedback control system is composed of a command generation unit 504, a command correction unit 505, a feedback control unit 502, and a control target 503. In this stage control system, by configuring the feedback control unit 502 for the control target 503 corresponding to the levitation stage 301, stable levitation operation and movement in the translational and rotational directions can be performed.

[0039] The feedback control unit 502 may use a control law such as PID control. Alternatively, switching control or other nonlinear control laws may be used. Furthermore, the feedforward control input 501 can speed up the movement operation by adding a control command to the drive command. Note that the feedforward control input 501 may use information such as position, velocity, acceleration (e.g., information on ideal acceleration), jerk, etc. Alternatively, a feedforward control input generated based on a learning control law such as iterative learning control may be used.

[0040] The command generation unit 504 generates commands for the levitation stage 301 using user input values ​​(information such as position, velocity, acceleration, and jerk). The command correction unit 505 updates the position information (generates a correction amount based on the field of view deviation) in response to changes in the stage rotation center and observation coordinates. Here, it is possible to specify from the UI whether or not to add the output result of the command correction unit 505 to the stage control command, thereby enabling selection of a mode in which the field of view deviation amount is not corrected. Even when the field of view deviation correction mode is selected, if no command for the rotation amount (θx, θy, θz) is input, ΔX, ΔY, and ΔZ are all 0 (no error), and therefore the command correction unit 505 does not update the position information (no field of view deviation correction amount is generated).

[0041] Position data measured by a laser interferometer (not shown) is fed back from the controlled object 503 (e.g., the levitation stage 301) to the feedback control unit 502 (feedback for controlling the position of the levitation stage 301 to a desired position).

[0042] (iii) FIG. 6 shows stage position information for correcting the amount of field of view deviation. Position information 602 in the θx-axis, θy-axis, and θz-axis directions is input to the command correction unit 505. The command correction unit 505 calculates ΔX, ΔY, and ΔZ based on the above-described formula (2) and adds these to position information 601 in the X-axis, Y-axis, and Z-axis directions to update the stage position information. In addition to updating the position information, information such as velocity, acceleration, and jerk may also be updated. Here, the position information 602 in the θx-axis, θy-axis, and θz-axis directions may be input as a single coordinate value of the rotation angle. Furthermore, a configuration may be adopted in which trajectory information from rotation angle A to rotation angle B (the trajectory at each time is determined from the temporal displacement) is input as the position information 602 in the θx-axis, θy-axis, and θz-axis directions to correct the amount of dynamic field of view deviation during stage rotation. This allows continuous acquisition of observation images while rotating the levitation stage 301.

[0043] <Change in Field of View Shift Amount> With reference to FIG. 7, a change in the field of view shift amount depending on whether or not the field of view shift amount correction process is applied will be described.

[0044] 7A is a diagram showing an example in which the field of view deviation correction process is not applied. When the floating stage 301 rotates around the rotation center 703, the observation coordinates 701 before the start of rotation on the wafer 103 move to the observation coordinates 702 after the rotation, causing a field of view deviation 704 in three dimensions along the X, Y, and Z axes.

[0045] 7B is a diagram showing an example in which the field of view shift amount correction process is applied. By applying the field of view shift amount correction process according to this embodiment, the observation coordinate 701 before the start of rotation is positioned at approximately the same position as the observation coordinate 702 after the rotation operation, thereby reducing the field of view shift amount.

[0046] By applying the field of view deviation correction process according to this embodiment, it is possible to correct the deviation of the observation coordinates in real time even during the stage rotation operation, which makes it possible to continuously observe and measure the sample pattern while rotating the floating stage 301.

[0047] Furthermore, if an error occurs between the observation coordinates 701 before the start of rotation and the observation coordinates 702 after the rotation operation, the residual error of the field of view may be corrected by learning a transfer characteristic in which angle information and distance information are input parameters and the field of view deviation error is output based on a learning rule such as machine learning. As an alternative to the learning rule, the error information may be stored as a map in a storage device (not shown), and a correction process in response to a command may be combined with the map.

[0048] <Field of view deviation amount correction taking into account height changes of the wafer surface> With reference to Figure 8, the field of view deviation correction process taking into account height changes of the wafer surface will be described. Figure 8 is a diagram showing height changes of the wafer surface. The wafer surface 801 is not flat due to warpage or irregularities of the wafer itself or tilt or warpage of the chuck, and has height changes. In this case, the field of view deviation correction amount will have an error corresponding to the height change, and the field of view deviation correction accuracy will decrease. Therefore, when there is a height change on the wafer surface, it is advisable to calculate the field of view deviation amounts ΔX', ΔY', and ΔZ' using equation (4) that adds the height change dz of each observation coordinate.

[0049] ΔX'=(Lz+dz)θy-Lyθz ΔY'=-(Lz+dz)θx+Lxθz... (4) ΔZ'=Lyθx-Lxθy

[0050] By using Equation (4) when calculating the field of view deviation, it is possible to perform field of view deviation correction that takes into account changes in wafer surface height. Here, the wafer surface height may be measured in advance using a height measuring device or the like installed in the semiconductor measurement device. Alternatively, the sample height may be measured using the focus amount by using an electronics focus function to focus on the sample. Alternatively, a map containing wafer surface height information may be created and stored in a storage device (not shown), and the field of view deviation (the deviation from the center of the field of view of the observed image or the trajectory of the deviation) may be calculated based on the information in the map. This enables field of view deviation correction regardless of the shape of changes in wafer surface height.

[0051] <GUI Configuration Example> A method in which a user specifies a rotation center and a rotation angle from a GUI (input to the command generation unit 504) will be described with reference to Fig. 9. Fig. 9 is a diagram showing a GUI (Graphical User Interface) 901 that allows a user to input a rotation center and a rotation angle using the UI.

[0052] A user (operator) 903 can specify rotation angles (values ​​desired by the user) for the θx axis, θy axis, and θz axis using the GUI 901. The GUI 901 can also be used to specify a height 904 from the sample observation height to the stage rotation center.

[0053] When observing a deep hole pattern 902, it is important to measure the hole diameter dimensions at the bottom of the hole with high accuracy. Furthermore, the detailed structure of a sample pattern such as the deep hole pattern 902 includes information that is known only to the semiconductor manufacturer. Therefore, it is desirable for a user 903 of the semiconductor inspection device to be able to arbitrarily specify the distance and rotation angle from the UI 901. The distance information and rotation angle information (input values ​​to the command generation unit 504: the user can enter them according to the design information) input by the user 903 are used as input parameters for the command correction unit 505, and the amount of field shift is corrected. The rotation angle information may be configured so that the rotation direction (clockwise or counterclockwise) can be specified by specifying a plus or minus sign.

[0054] Alternatively, the height of the deep hole may be measured from the stage rotation angle and the amount of field shift by rotating the stage with the field shift correction function by the command correction unit 505 turned OFF (an ON / OFF selection display for the correction function is provided on the GUI 901). The height of the deep hole measured by focusing the electron beam contains errors due to the influence of changes in the magnetic field caused by the magnetic material inside the sample chamber and the charging of the wafer, so rotating the stage enables accurate height measurement that is not influenced by the magnetic field or the charging of the wafer.

[0055] Furthermore, although the input method for the GUI 901 has been described here using a deep hole pattern as an example, the scope of application of this technology is not limited to specific patterns such as the deep hole pattern 902 .

[0056] <Changing the Incident Angle of the Electron Beam> A method for changing the incident angle of the electron beam with respect to the sample by rotating the stage will be described with reference to FIGS. 10A and 10B.

[0057] 10A is a diagram showing how an electron beam is irradiated onto a sample at a certain angle of incidence. In this example, the electron beam 102 is irradiated onto a wafer 103 on a levitation stage 301 at an angle of incidence θ. In this case, the appearance of the SEM image changes depending on the angle of incidence θ, resulting in image distortion and changes in the accuracy of the measured dimensions.

[0058] 10B is a diagram for explaining the principle of determining the angle of incidence of the electron beam 102 by changing the height of the levitation stage 301. When the levitation stage 301 is moved in the Z-axis direction by ΔZ, the center of the field of view of the SEM image shifts by ΔX in accordance with the change in the height at which the electron beam 102 irradiates the wafer 103. Therefore, by using the relationship between ΔZ and ΔX, the angle of incidence θ of the electron beam 102 with respect to the wafer 103 can be determined.

[0059] FIG. 10C illustrates how the stage is rotated to change the incident angle of the electron beam relative to the sample. By rotating the levitation stage 301 according to the incident angle θ calculated using the relationship between ΔZ and ΔX, the incident angle of the electron beam 102 relative to the wafer 103 can be kept perpendicular. At this time, the rotation center 703 of the levitation stage 301 may be changed depending on the irradiation position of the electron beam 102 relative to the wafer 103. Alternatively, the stage rotation angle (the stage rotation angle corresponding to the displacement of the incident angle and the stage coordinate) within the wafer 103 plane may be measured in advance while changing the incident angle of the electron beam 102 and the stage coordinate, and a map may be created. The levitation stage 301 may then be rotated based on this map. Furthermore, if the chuck is tilted, the levitation stage 301 may be rotated to correct the tilt on the chuck side, thereby adjusting the incident angle of the electron beam 102.

[0060] As described above, when the angle of incidence is adjusted by tilting the levitation stage 301 instead of the electron beam 102, the angle of incidence of the electron beam 102 with respect to the sample can be changed while keeping the irradiation trajectory of the electron beam 102 inside the electron optical system constant, which has the advantage of not causing a decrease in the accuracy of dimension measurement.

[0061] Although a charged particle beam device that performs inspection using an electron beam 102 has been described in detail as an example of a device that uses the stage device of this embodiment, the field of view deviation correction process of this embodiment can also be applied to optical inspection devices that inspect objects using light.

[0062] The above describes in detail an embodiment of the present disclosure using the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like may be made within the scope that does not deviate from the gist of the technology of the present disclosure.

[0063] <Summary> (i) According to this embodiment, in the charged particle beam device, the control device 404 (e.g., a computer, which may include a display device) controls an arbitrary rotation center of the stage device (e.g., the levitation stage 301) using motor thrust in the translation direction (including at least one of the X-axis, Y-axis, or Z-axis) and rotation direction (including at least one of the θx-axis, θy-axis, or θz-axis). During rotation of the stage device, the control device 404 calculates the amount of deviation or the trajectory of the deviation from the center of the field of view of the observation image based on position information indicating the distance between the rotation center coordinate and the sample observation coordinate in at least one of the X-axis, Y-axis, or Z-axis directions, and the rotation angles of the θx-axis, θy-axis, and θz-axis. Then, when moving the stage device, the control device 404 corrects the amount of deviation or the trajectory of the deviation from the center of the field of view of the observation image by adding the amount of deviation or the trajectory of the deviation to the position information of the stage device. In addition to the position information, at least one of the velocity information, acceleration information, and jerk information of the stage device may be changed. By doing so, the rotation center of the stage device can be aligned with the center of the field of view of the observation image, so that it is possible to reduce the amount of field of view deviation when the stage device is opened.

[0064] In the charged particle beam device, the control device 404 may operate the stage device so as to continuously acquire observation images of the sample while rotating the stage device and correcting the amount of field of view shift, thereby making it possible to observe the sample from various angles without causing field of view shift.

[0065] The charged particle beam device may store, in a storage device, an error map that defines the deviation error corresponding to the deviation amount or deviation trajectory of the observed image from the center of the field of view. In this case, the control device 404 can acquire the deviation error from the error map and reflect the acquired error in the deviation amount or deviation trajectory. This makes it possible to more accurately correct the field of view deviation of the observed image.

[0066] In this embodiment, a stage control system (see FIG. 5) is employed. In this stage control system, coefficient parameters for determining six-axis displacement by coordinate transformation of position information (measured by a laser interferometer) may be determined using a quadratic evaluation function J (see equation (3)). By using the evaluation function J, it becomes possible to optimize the parameters for coordinate transformation.

[0067] The control device 404 may be configured to switch whether or not to add the deviation amount or deviation amount trajectory to the position information of the stage device in response to a mode command input externally (by the user) in the stage control system (see FIG. 5). Specifically, the GUI in FIG. 9 may be configured to display a selection button for a mode in which field of view deviation amount correction is performed. This allows the user to select a mode in which field of view deviation amount correction is performed and a mode in which it is not performed. This is to accommodate the fact that some users may not wish to perform field of view deviation amount correction.

[0068] In this embodiment, it is also possible to learn by machine learning the transfer characteristics between the distance in at least one of the X-axis, Y-axis, and Z-axis directions between the rotation center coordinate of the stage device and the sample observation coordinate, and the rotation angles (position information) of the θx-axis, θy-axis, and θz-axis, and the amount of deviation. This can be an alternative to using the error map described above.

[0069] (ii) This embodiment also accommodates cases where the wafer surface 801 has height variations. To accommodate height variations in the wafer surface 801 (caused by unevenness, warpage, chuck tilt, etc.), the control device 404 determines the amount of deviation or the trajectory of the deviation from the center of the field of view of the observation image based on height information about the sample surface (which may be measured in advance or measured during observation using the focus function). When measuring in advance, the height information about the wafer surface 801 may be stored as a map in a storage device. In this case, the control device 404 can read height information corresponding to wafer position information (e.g., coordinate values) from the map and reflect it in the amount of deviation or the trajectory of the deviation.

[0070] (iii) In this embodiment, the control device 404 displays a user interface (GUI; see FIG. 9 ) on the display screen, allowing the user (operator) to specify (input as commands) the stage rotation center, the stage rotation angles in each direction, and the rotation direction. The control device 404 then calculates the amount of deviation from the center of the field of view of the observed image or the trajectory of the deviation based on the rotation center, the rotation angles, and the rotation direction input as commands. This allows the user to easily input information such as the position, velocity, acceleration, and jerk of the stage device (floating stage 301) to be input to the command generator 504 as commands. For example, if the sample includes a deep hole pattern, specifying the center of rotation at the bottom of the deep hole when observing the deep hole pattern allows the deep hole pattern to be observed without causing any field of view deviation (minimizing the field of view deviation) and allowing accurate height measurement.

[0071] (iv) In this embodiment, as shown in Figures 10A to 10C, it is possible to execute an operation of rotating the stage device (levitation stage 301) to change the incident angle of the charged particle beam (electron beam 102) relative to the sample, depending on the incident angle θ of the charged particle beam. In this way, the incident angle of the charged particle beam relative to the sample can be changed without adjusting the irradiation of the charged particle beam (while keeping the irradiation trajectory constant), thereby ensuring the accuracy of the dimension measurement.

[0072] 101 Electron optical system 102 Electron beam 103 Wafer 104 Stage 105 Field of view center 106 Rotation center 108 Field of view deviation 201 Observation coordinate 202 Field of view deviation 203 Chuck 204 Bar mirror 205 Sample stage 206 Distance from rotation center to observation coordinate 207 Stage rotation center 208 Stage rotation angle 301 Floating stage 302 Base unit 303 Z-axis motor 304 X-axis motor 305 Rotation center 306 Thrust 307 Thrust 401 Vacuum chamber 402 Thrust 403 Motor 404 Control device 405 Stage rotation angle information 406 Distance information between observation coordinate and rotation center 407 Base 501 Feedforward control input 502 Feedback control unit 503 Control target 504 Command generation unit 505 Command correction unit 601 Position information in the X-axis, Y-axis, and Z-axis directions 602 Position information in the θx-axis, θy-axis, and θz-axis directions 701 Observation coordinates before start of rotation 702 Observation coordinates after rotation operation 703 Rotation center 704 Field of view deviation 801 Wafer surface 901 GUI 902 Deep hole pattern 903 User 904 Height from sample observation height to stage rotation center

Claims

1. A charged particle beam device that irradiates a sample with a charged particle beam and acquires an observation image of the sample, comprising: a mirror body including a charged particle beam source and a lens; a stage device; and a control device that controls the operation of the stage device, wherein the control device controls an arbitrary center of rotation using motor thrust in the translational and rotational directions of the stage device, and during rotation, determines the amount of deviation of the observation image from the center of the field of view or the trajectory of the deviation based on position information indicating the distance in at least one of the X-axis, Y-axis, and Z-axis directions between the rotation center coordinates of the stage device and the sample observation coordinates, and the rotation angles of the θx-axis, θy-axis, and θz-axis, and when the stage device is moved, corrects the amount of deviation of the observation image from the center of the field of view by adding the amount of deviation or the trajectory of the deviation to the position information of the stage device.

2. A charged particle beam device according to claim 1, wherein the translation direction of the stage device includes at least one of the X-axis direction, the Y-axis direction, and the Z-axis direction, and the rotation direction of the stage device includes at least one of the θx-axis direction, the θy-axis direction, and the θz-axis direction.

3. A charged particle beam device according to claim 1, wherein the control device changes at least one of velocity information, acceleration information, and jerk information of the stage device based on the amount of deviation or the trajectory of the amount of deviation in addition to the position information.

4. A charged particle beam device according to claim 1, wherein the control device determines the amount of deviation or the trajectory of the amount of deviation from the center of the field of view of the observation image based on the distance in at least one direction of the X-axis, Y-axis, or Z-axis between the rotation center coordinate of the stage device and the sample observation coordinate, the rotation angle in at least one direction of the θx-axis, θy-axis, or θz-axis, and height information of the surface of the sample.

5. A charged particle beam device according to claim 4, wherein the height information from the surface of the sample is stored as a map in a storage device, and the control device acquires the height information from the map in the storage device when determining the amount of deviation or the trajectory of the amount of deviation.

6. A charged particle beam device according to claim 1, wherein the control device continuously acquires the observation images while rotating the stage device.

7. A charged particle beam device according to claim 1, wherein the control device displays on a display screen a user interface for specifying the rotation center, each of the rotation angles, and the rotation direction of the stage device, and calculates the amount of deviation of the observation image from the center of the field of view or the trajectory of the amount of deviation based on the specified rotation center, each of the rotation angles, and the rotation direction.

8. A charged particle beam device according to claim 7, wherein the sample includes a deep hole pattern, and when observing the deep hole pattern, the center of rotation is specified at the bottom of the deep hole.

9. A charged particle beam device according to claim 1, further comprising an error map stored in a storage device that defines an error in the amount of deviation corresponding to the amount of deviation or the trajectory of the amount of deviation, and wherein the control device acquires the error in the amount of deviation from the error map and reflects the acquired error in the amount of deviation or the trajectory of the amount of deviation.

10. A charged particle beam device according to claim 1, wherein the control device determines coefficient parameters relating to coordinate transformation when controlling the stage device by optimizing a quadratic evaluation function.

11. A charged particle beam device according to claim 1, wherein the control device switches whether or not to add the amount of deviation or the trajectory of the amount of deviation to the position information of the stage device in response to a mode command input from the outside.

12. A charged particle beam device according to claim 1, wherein the center of rotation of the stage device is the coordinates of the center of gravity of the stage device.

13. A charged particle beam device according to claim 1, wherein the control device learns, by machine learning, the distance in at least one of the X-axis, Y-axis, and Z-axis directions between the rotation center coordinate of the stage device and the sample observation coordinate, and the transfer characteristics between each of the rotation angles in the θx-axis, θy-axis, and θz-axis and the amount of deviation.

14. A charged particle beam device according to claim 1, wherein the control device rotates the stage device in accordance with the incident angle of the charged particle beam relative to the sample, thereby changing the incident angle of the charged particle beam.

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