Charged particle beam device

Abstract

In the charged particle beam device according to the present disclosure, in order to reduce the field of view offset when the stage is rotated in the direction of the θx, θy, θz axes about an arbitrary rotation center, (i) the motor thrust in the translation direction and the rotation direction of the stage device is used to control the arbitrary rotation center, (ii) during the rotation operation, based on the 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, the respective rotation angles of the θx-axis, θy-axis, θz-axis, the offset from the field of view center of the observation image or the trajectory of the offset is calculated, (iii) when the stage device is moved, the offset or the trajectory of the offset is added to the position information of the stage device, thereby correcting the offset from the field of view center of the observation image (see Fig. 4).

Description

Technical Field

[0001] This disclosure relates to charged particle beam devices. Background Technology

[0002] In recent years, with the miniaturization of semiconductor devices, the requirements for semiconductor manufacturing and inspection equipment have also increased to correspond with this miniaturization. Typically, scanning electron microscopes (hereinafter referred to as SEMs) are used to evaluate patterns formed on semiconductor wafers or to inspect defects in the formed wafers. In particular, length-measuring SEMs are used to evaluate the shape and size of patterns.

[0003] Dimensioning SEM is a device that uses an electron beam to illuminate a wafer, processes the resulting secondary electron signal to determine the edge of the pattern based on changes in brightness, and measures and analyzes the size of the pattern formed on the wafer. In recent years, with the increasing functionality of semiconductor devices and the growing complexity of mounting methods, it has become necessary to irradiate semiconductor wafers with electron beams at various angles to obtain cross-sectional images for dimensional measurement.

[0004] To accurately position semiconductor devices such as semiconductor wafers, a sample stage is used. The sample stage can be driven, for example, by a rotary motor and ball screw, or by a linear motor. As for the driving direction of the stage, sometimes a 6-axis drive stage is used, which can move not only along the X, Y, and Z axes, but also in rotational directions around the X, Y, and Z axes (θx, θy, θz axes). In particular, in recent years, to achieve ultra-precision positioning, non-contact floating stages utilizing hydrostatic bearings or electromagnetically based bearings are widely used.

[0005] One method involves controlling the deflection of the electron beam to change the tilt angle of the electron beam irradiating the semiconductor device when obtaining the cross-sectional image of the semiconductor wafer. However, in this case, the electron beam irradiation trajectory of the electron optical system changes, resulting in changes in the appearance of the pattern and image blurring due to the change in the characteristics of the electron beam, leading to a deterioration in the accuracy of pattern size measurement.

[0006] To address this issue, by controlling the tilt angle (rotation along the θx-axis or θy-axis) of the sample stage while maintaining a constant tilt angle of the electron beam, the irradiation angle of the electron beam onto the semiconductor device can be controlled without reducing the accuracy of dimensional measurements. However, when the rotation center of the stage is not aligned with the field of view center of the image, a field of view shift occurs when the stage is rotated, causing the pattern to be measured to deviate from the image's field of view, which becomes a problem.

[0007] In this regard, for example, Patent Document 1 proposes a technique related to the observation method of a scanning charged particle beam device as follows: when rotating the rotating stage, the XY stage is moved according to the distance and rotation angle between the center position of the observed image and the mechanical rotation center, and the moving speed of the XY stage is controlled according to the length of the distance, so that the image always rotates at the center of the observed image through mechanical rotation.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2001-35433 Summary of the Invention

[0011] The problem that the invention aims to solve

[0012] However, the technology disclosed in Patent Document 1 only handles rotation in the XY plane, i.e., rotation along the θz axis. Furthermore, Patent Document 1 does not consider changing the rotation center of the stage. When the X, Y, and Z axis coordinates of the stage rotation center are changed according to factors such as the cross-sectional height of the semiconductor device to be observed, the field of view offset of the image changes, thus reducing the effectiveness of field of view offset correction. Therefore, in order to achieve high-precision inspection corresponding to various semiconductor device mounting methods, reducing the field of view offset even when the stage is rotated along the θx, θy, and θz axes from any rotation center has become a challenge.

[0013] In view of this situation, this disclosure proposes a technique for reducing the field of view offset when the stage rotates along the θx, θy, and θz axes at any stage rotation center in a charged particle beam device.

[0014] Methods for solving problems

[0015] As a means to achieve the above objectives, this disclosure proposes a charged particle beam device for irradiating a sample with a charged particle beam to obtain an observation image of the sample. The charged particle beam device includes: a mirror body comprising a charged particle beam source and a lens; a stage device; and a control device for controlling the movement of the stage device. The control device (i) controls an arbitrary rotation center using motor thrust in the translational and rotational directions of the stage device; (ii) during rotation, it calculates an offset or trajectory of the offset from the field of view of the observation image based on position information representing the distance between the rotation center coordinates of the stage device and the observation coordinates of the sample in at least one of the X-axis, Y-axis, and Z-axis directions, and rotation angles of the θx-axis, θy-axis, and θz-axis; and (iii) when moving the stage device, it corrects the offset from the field of view of the observation image by adding the offset or trajectory of the offset to the position information of the stage device.

[0016] Further features relating to this disclosure will become clear from the description and drawings in this specification. Furthermore, this disclosure is achieved and implemented by means of elements and combinations thereof, as well as the detailed description thereafter and the appended scope of the claimed patent protection.

[0017] The description in this specification is merely a typical example and does not limit the scope of the patent protection sought or the application of this disclosure in any sense.

[0018] Invention Effects

[0019] According to the technology disclosed herein, it is possible to reduce the field of view offset when the stage is rotated along the θx-axis, θy-axis, and θz-axis directions at any stage rotation center. Attached Figure Description

[0020] Figure 1A This diagram illustrates the process of irradiating a wafer with an electron beam and observing it.

[0021] Figure 1B This diagram illustrates an example of rotating the stage while aligning the center of the field of view with the rotation center of the stage.

[0022] Figure 1C This diagram illustrates an example of rotating the stage when the center of the field of view is not aligned with the rotation center of the stage.

[0023] Figure 2A This is a diagram showing the state of pattern observation without rotating the sample stage 205.

[0024] Figure 2B This is a diagram showing the state when the sample stage 205 rotates in the θx axis direction.

[0025] Figure 3A This is a diagram showing an example of the configuration of the floating platform and the electric motor.

[0026] Figure 3B This is a diagram showing the state of the floating platform 301 as viewed from the XZ plane.

[0027] Figure 3C This is a diagram showing the state of the floating platform 301 when the magnitude of the Z-axis thrust changes.

[0028] Figure 4 This is a diagram illustrating the control system of the rotation center of the floating platform.

[0029] Figure 5 This is a diagram illustrating a structural example of a stage control system for correcting field of view offset.

[0030] Figure 6 This is a diagram showing the stage position information for correcting the field of view offset.

[0031] Figure 7A This is a diagram illustrating an example of a case where field offset correction was not applied.

[0032] Figure 7B This is a diagram illustrating an example of applying field-of-view offset correction.

[0033] Figure 8 This is a diagram showing the height variation of the wafer facets.

[0034] Figure 9 This is a diagram representing the GUI (Graphical User Interface) 901 where the user inputs the rotation center and rotation angle using the UI.

[0035] Figure 10A This is a diagram showing the situation where an electron beam irradiates a sample at a certain incident angle.

[0036] Figure 10B This diagram illustrates the principle of determining the incident angle of the electron beam 102 by changing the height of the floating stage 301.

[0037] Figure 10C This diagram illustrates how rotating the stage changes the incident angle of the electron beam relative to the sample. Detailed Implementation

[0038] This embodiment discloses a technique for reducing the field-of-view offset of SEM images generated during stage rotation in charged particle beam apparatus (e.g., length measurement SEM). More specifically, this embodiment proposes a scheme in which, based on positional information representing the distance between the stage rotation center coordinates and the sample observation coordinates and the stage rotation angle, the offset or trajectory of the offset from the field-of-view center of the observed image is calculated. When the stage is moved, the offset or trajectory of the offset is added to (reflected) in the aforementioned stage positional information, thereby correcting the offset from the field-of-view center of the observed image.

[0039] Hereinafter, embodiments and various examples of the present disclosure will be described with reference to the accompanying drawings. In the drawings, functionally identical elements are sometimes shown with the same numbers. Furthermore, the drawings illustrate specific embodiments and installation examples that follow the principles of the present disclosure, but these are for the purpose of understanding the present disclosure and are in no way intended to limit the interpretation of the present disclosure.

[0040] In this embodiment, the description has been provided in sufficient detail to enable those skilled in the art to implement the present disclosure. However, other installations and methods are also possible, and it should be understood that structural and constructional changes and various element substitutions can be made without departing from the scope and spirit of the technical concept of the present disclosure. Therefore, the following description is not intended to be limited thereto.

[0041] <Regarding changes in field of view shift>

[0042] Reference Figures 1A to 1C The changes in field of view offset caused by whether or not the rotation center coincides with the field of view center are explained.

[0043] Figure 1A This diagram illustrates the process of irradiating a wafer with an electron beam and observing it. An electron beam 102, irradiated by the electron optical system 101, illuminates the wafer 103 mounted on the stage 104, and an observation image including the center of the field of view 105 is obtained.

[0044] Figure 1B This diagram illustrates an example of rotating the stage when the center of the field of view coincides with the rotation center of the stage. In this case, the stage rotates around the center of the field of view 105 as the rotation center 106, thus preventing field of view shift.

[0045] Figure 1C This diagram illustrates an example of rotating the stage when the center of the field of view is not aligned with the rotation center of the stage. In this case, the rotation center 106 of the stage is not aligned with the center of the field of view, thus causing a field of view offset 108.

[0046] <Regarding the field of view shift caused by stage rotation>

[0047] Reference Figure 2A and Figure 2B The field of view shift during the rotation of the sample stage 205 is explained. Furthermore, based on... Figure 2A and Figure 2B It also shows the method for calculating the field of view offset.

[0048] Figure 2A This diagram shows the pattern observation state without rotating the sample stage 205. A strip mirror 204 is provided on the sample stage 205, and a laser interferometer (not shown) is used to measure the position of the sample stage 205. Furthermore, multiple laser interferometers can be used to measure the displacement of the X, Y, Z axes, and θx, θy, and θz axes when measuring the position of the sample stage 205.

[0049] An electric motor (not shown) is mounted on the sample stage 205. This motor can be used to control the position and orientation of the sample stage 205. Alternatively, multiple motors can be configured to control the displacement of the sample stage 205 along the X, Y, Z axes, and θx, θy, and θz axes. Furthermore, a chuck 203 is mounted on the sample stage 205. The chuck 203 uses electrostatic force or the like to hold the wafer 103. Then, by irradiating the wafer 103 with an electron beam 102, a pattern can be observed at the observation coordinates 201.

[0050] Figure 2B This diagram shows the state when the sample stage 205 has been rotated in the θx-axis direction. Here, if the distance 206 from the rotation center 207 of the stage to the observation coordinate is set as Lz, and the rotation angle 208 of the sample stage 205 is set as θx, then the field of view offset 209 (Δ) in the Y-axis direction can be obtained by equation (1). In addition, the rotation direction is set as the counterclockwise direction relative to the axis.

[0051]

[0052] In addition, when the sample stage is rotated relative to the θx, θy, and θz axes by the rotation angles θx, θy, and θz of the stage, if the distances from the observation coordinates to the rotation center coordinates in the X, Y, and Z directions are set as Lx, Ly, and Lz, the field of view offsets (ΔX, ΔY, and ΔZ) in the X, Y, and Z directions can be calculated using the following equation (2).

[0053]

[0054] Here, ΔZ is equivalent to the focus offset.

[0055] <Control of the rotation center of the floating platform: Overview>

[0056] Reference Figures 3A-3C The case where the rotation center of the floating platform 301 can be changed through torque control will be explained.

[0057] Figure 3A This diagram illustrates an example configuration of the floating platform 301 and the electric motor. In this example, the floating platform 301 is supported on the base 302 in a non-contact manner using electromagnetic bearings and hydrostatic bearings. By arranging an X-axis motor 304, a Z-axis motor 303, and a Y-axis motor (not shown) on the floating platform 301, it can operate in six axial directions: X-axis, Y-axis, Z-axis, and θx-axis, θy-axis, and θz-axis. Here, voice coil motors and linear motors can be used as the electric motors (X-axis motor 304, Z-axis motor 303, and Y-axis motor). Furthermore, the stator and mover of the motor can be arranged on either the floating platform 301 side or the base 302 side. The position of the floating platform 301 can be measured using the aforementioned laser or scale.

[0058] Figure 3B This diagram shows the state of the floating platform 301 as viewed from the XZ plane. The rotation angle of the floating platform 301 can be controlled by using the thrusts 306 and 307 of the Z-axis motor. Furthermore, by making the magnitudes of thrusts 306 and 307 equal, the center of gravity coordinate of the floating platform 301 can be used as the rotation center 305 for control.

[0059] Figure 3C This diagram illustrates the state of the floating stage 301 when the magnitude of the Z-axis thrust is varied. In this case, by changing the magnitude of the thrust 306 and 307 of the Z-axis motor, the rotation center 305 of the stage can also be changed to any position. That is, by controlling the thrust of the motor, the semiconductor device can be rotated at any rotation center, allowing the pattern to be observed from various angles.

[0060] <Control of the rotation center of the floating platform: Control system>

[0061] (i) Figure 4 This is a diagram illustrating the control system of the rotation center of the floating platform. Figure 4 Within the vacuum chamber 401, a floating stage 301 is mounted. The sample on the floating stage 301 can be observed by irradiating it with an electron beam 102 from the electron-optical system 101. The floating stage 301 is supported non-contactly on the base 407 and controlled by multiple motors 403. Alternatively, the floating stage 301 can be planar-floating, capable of long-distance movement in a single-axis direction. Furthermore, a coarse-fine motion stage can be used instead of the base 407.

[0062] The control device 404 uses signals from a position measuring device (not shown) that measures the position of the floating stage to measure the six-axis displacement of the floating stage 301 along the X, Y, Z axes and θx, θy, and θz axes, thus forming a feedback control system for controlling the six-axis displacement. As the position measuring device, for example, as described above, a laser interferometer can be used. A reflector (not shown) is placed on the floating stage 301, and the position of the floating stage 301 is measured by the interference of the laser and the reflected light. In position measurement using a laser interferometer, the height position near an object such as a semiconductor wafer can be measured, enabling high-precision position measurement with minimal Abbe error. Furthermore, since the laser interferometer has picometer-level resolution, accurate positioning is possible. Alternatively, an optical scale or a magnetic scale can be used instead of a laser interferometer.

[0063] When constructing a feedback control system, coordinate transformation can be performed on information from multiple position measuring devices to measure 6-axis displacement. Alternatively, the thrust 402 for multiple motors 403 can be calculated by performing coordinate transformation on the output of the feedback controller. In the coordinate transformation, a transformation formula can be applied to the 6 axes, or matrix operations can be used instead. Furthermore, an evaluation function J (quadratic form) like equation (3) can be used to optimize the coefficient parameters used for the coordinate transformation.

[0064]

[0065] Where X is a vector storing the coefficient parameters used for coordinate transformation, and Q is the matrix involved in the evaluation of the evaluation function weights and control characteristics evaluation items.

[0066] When the floating stage 301 rotates, the control device 404 calculates the field of view offset using the stage rotation angle information 405 and the distance information 406 between the observation coordinates and the rotation center, according to the above formula (2), and corrects the field of view offset. The control device 404, which performs coordinate transformation, system calculations, and field of view offset correction, can be constructed using a microcomputer or an FPGA (Field Programmable Gate Array). The floating stage 301 is supported in a non-contact manner, so the stage rotation center 305 can be arbitrarily changed according to the semiconductor wafer pattern mounting method and measurement method.

[0067] (ii) Figure 5This diagram illustrates a structural example of a stage control system for correcting field-of-view offset. The feedback control system comprises a command generation unit 504, a command correction unit 505, a feedback control unit 502, and a controlled object 503. In this stage control system, by configuring the feedback control unit 502 relative to the controlled object 503 corresponding to the floating stage 301, stable floating motion, translational movement, and rotational movement are possible.

[0068] As the feedback control unit 502, control rules such as PID control can also be used. Alternatively, switching control or other nonlinear control rules can be used. Furthermore, by adding control commands to the drive commands through the feedforward control input 501, the movement speed can be increased. In addition, information such as position, velocity, acceleration (e.g., ideal acceleration information), and jerk can be used as the feedforward control input 501. Alternatively, feedforward control inputs generated based on learning control rules such as iterative learning control can also be used.

[0069] The command generation unit 504 generates commands for the floating stage 301 using user input values ​​(position, velocity, acceleration, jerk, etc.). The command correction unit 505 updates the position information (generating a correction amount based on the field of view offset) as the stage's rotation center and observation coordinates change. Here, it can be specified on the UI whether the output of the command correction unit 505 is added to the stage control commands, and a mode without field of view offset correction can be selected. Furthermore, even when the field of view offset correction mode is selected, ΔX, ΔY, and ΔZ are all 0 (no error) when no commands regarding rotation (θx, θy, θz) are input, therefore no update of the position information based on the command correction unit 505 is performed (no field of view offset correction amount is generated).

[0070] Position data measured by a laser interferometer (not shown) is fed back from the controlled object 503 (e.g., the floating stage 301) to the feedback control unit 502 (for controlling the position of the floating stage 301 to the desired position).

[0071] (iii) Figure 6This is a diagram showing the stage position information for correcting the field of view offset. Position information 602 in the θx, θy, and θz axes is input to the command correction unit 505. The command correction unit 505 calculates ΔX, ΔY, and ΔZ based on the above equation (2), and adds them to the position information 601 in the X, Y, and Z axes to update the stage position information. In addition to updating the position information, information such as velocity, acceleration, and jerk can also be updated. Here, the position information 602 in the θx, θy, and θz axes can also be input as a coordinate value of the rotation angle. Moreover, it can also be configured such that the trajectory information from rotation angle A to rotation angle B (the trajectory at each moment is determined by the displacement over time) is input as the position information 602 in the θx, θy, and θz axes, thereby correcting the dynamic field of view offset during the stage rotation. As a result, it is possible to continuously acquire observation images while rotating the floating stage 301.

[0072] <Changes in field of view offset>

[0073] Reference Figure 7A , Figure 7B This section explains the changes in field of view offset caused by the application of field of view offset correction.

[0074] Figure 7A This diagram illustrates an example of a case where field-of-view offset correction is not applied. When the floating stage 301 rotates around the rotation center 703, the observation coordinates 701 before the start of the rotation of the wafer 103 move to the observation coordinates 702 after the rotation, resulting in a field-of-view offset 704 in the three dimensions of the X, Y, and Z axes.

[0075] on the other hand, Figure 7B This diagram illustrates an example of a case where field-of-view offset correction processing has been applied. By applying the field-of-view offset correction processing of this embodiment, the observation coordinate 701 before the rotation begins becomes approximately the same as the observation coordinate 702 after the rotation, thus reducing the field-of-view offset.

[0076] By applying the field-of-view offset correction processing of this embodiment, the offset of the observation coordinates can be corrected in real time even during the rotation of the stage. Therefore, it is possible to continuously observe and measure the sample pattern while the floating stage 301 is rotating.

[0077] In addition, when an error occurs between the observation coordinate 701 before the start of rotation and the observation coordinate 702 after the rotation operation, a learning rule such as machine learning can also be used to learn the transfer characteristics that take angle information and distance information as input parameters and the field of view shift error as an output, thereby correcting the residual of the field of view shift. In addition, as an alternative to the learning rule, the configuration may also be such that error information is stored as a map in a storage device (not shown), and correction processing in response to an instruction is combined with the map.

[0078] <Field of View Shift Correction Considering Height Variation of Wafer Surface>

[0079] With reference to Figure 8 , the field of view shift correction processing considering the height variation of the wafer surface will be described. Figure 8 is a diagram showing the height variation of the wafer surface. The wafer surface 801 is not flat due to warpage and unevenness of the wafer itself or tilt and warpage of the chuck, and has height variation. In this case, the field of view shift correction amount becomes an error according to the height variation amount, and the field of view shift correction accuracy decreases. Therefore, when there is height variation on the wafer surface, the field of view shift amounts ΔX', ΔY', ΔZ' can be obtained by adding the height variation dz of each observation coordinate using formula (4).

[0080]

[0081] By using formula (4) when obtaining the field of view shift amount, field of view shift correction considering the height variation of the wafer surface can be performed. Here, the height of the wafer surface may be measured in advance using a height gauge mounted on a semiconductor measuring device or the like. In addition, the focusing function of an electronic engineering system may also be used to focus on the sample, thereby measuring the sample height using the focusing amount. Furthermore, a map including the height information of the wafer surface may be created and stored in a storage device (not shown), and the field of view shift amount (the shift amount from the field of view center of the observation image or the track of the shift amount) may be calculated based on the information of the map. Thereby, field of view shift correction can be performed regardless of the shape of the height variation of the wafer surface.

[0082] <Structural Example of GUI>

[0083] With reference to Figure 9 , the method for a user to specify the rotation center and rotation angle (input to the instruction generation unit 504) on the GUI will be described. Figure 9 is a diagram showing a GUI (Graphical User Interface) 901 used by a user to input a rotation center and a rotation angle via a UI.

[0084] User (operator) 903 can use GUI 901 to specify the rotation angles (user desired values) of the θx, θy, and θz axes. Additionally, GUI 901 can also be used to specify the height 904 from the specimen observation height to the stage rotation center.

[0085] In observing the deep hole pattern 902, it is important to accurately measure the diameter of the hole bottom. Furthermore, the detailed structure of the sample pattern, such as the deep hole pattern 902, includes information known only to the semiconductor manufacturer. Therefore, the user 903 of the semiconductor inspection device desires the ability to arbitrarily specify the distance and rotation angle from the UI 901. The distance and rotation angle information input by the user 903 (input values ​​to the instruction generation unit 504: the user can input according to design information) are used as input parameters to the instruction correction unit 505 to correct for the field of view offset. Additionally, the rotation angle information can also specify the rotation direction (clockwise or counterclockwise) by specifying a positive or negative sign.

[0086] Alternatively, with the field-of-view offset correction function of the command correction unit 505 turned off (the on / off selection of the correction function is displayed on the GUI901), the height of the deep hole can be measured by rotating the stage, based on the stage rotation angle and the field-of-view offset. The height of the deep hole measured by focusing the electron beam is subject to errors due to variations in the magnetic field caused by the magnetic material inside the sample chamber and the charge on the wafer. Therefore, by rotating the stage, accurate height measurement can be performed without being affected by the magnetic field or the charge on the wafer.

[0087] Furthermore, the input method of GUI901 is described here using deep hole pattern as an example, but the application scope of this technology is not limited to specific patterns such as deep hole pattern 902.

[0088] <Changes in the incident angle of the electron beam>

[0089] Reference Figure 10A and Figure 10B The method of changing the incident angle of the electron beam relative to the sample by rotating the stage is explained.

[0090] Figure 10A This diagram illustrates the situation where an electron beam is irradiated onto a sample at a certain incident angle. In this example, the electron beam 102 irradiates the wafer 103 on the floating stage 301 at an incident angle θ. In this case, the appearance of the SEM image varies depending on the incident angle θ, resulting in image distortion or changes in the accuracy of the measured dimensions.

[0091] Figure 10BThis diagram illustrates the principle of determining the incident angle of the electron beam 102 by changing the height of the floating stage 301. When the floating stage 301 is moved by ΔZ in the Z-axis direction, the center of the field of view of the SEM image shifts by ΔX as the height of the electron beam 102 irradiating the wafer 103 changes. Therefore, by using the relationship between ΔZ and ΔX, the incident angle θ of the electron beam 102 relative to the wafer 103 can be determined.

[0092] Figure 10C This diagram illustrates the case where rotating the stage changes the incident angle of the electron beam relative to the sample. By rotating the floating stage 301 according to the incident angle θ obtained using the aforementioned relationship between ΔZ and ΔX, the incident angle of the electron beam 102 relative to the wafer 103 can be maintained perpendicular. At this time, the rotation center 703 of the floating stage 301 can also be changed according to the irradiation position of the electron beam 102 relative to the wafer 103. Alternatively, a mapping can be created by pre-measuring the stage rotation angle (the stage rotation angle corresponding to the displacement of the incident angle and the stage coordinates) within the wafer 103 plane while changing the incident angle of the electron beam 102 and the stage coordinates, and the floating stage 301 can be rotated based on this mapping. Furthermore, if the chuck is tilted, the floating stage 301 can be rotated and the incident angle of the electron beam 102 adjusted to correct the tilt on the chuck side.

[0093] As described above, by tilting the floating stage 301 to adjust the incident angle without tilting the electron beam 102, the incident angle of the electron beam 102 relative to the sample can be changed while keeping the irradiation trajectory of the electron beam 102 inside the electron optical system constant. Therefore, it has the advantage of not causing a decrease in dimensional measurement accuracy.

[0094] Furthermore, as an example of the stage device equipped with this embodiment, a charged particle beam device that uses an electron beam 102 for inspection has been described in detail. However, the field of view offset correction processing of this embodiment can also be applied to optical inspection devices that use light to inspect objects.

[0095] The embodiments of this disclosure have been described in detail above with the aid of accompanying drawings. However, the specific structure is not limited to this embodiment, and there may be design changes that do not depart from the technical spirit of this disclosure.

[0096] Summary

[0097] (i) According to this embodiment, in the charged particle beam apparatus, the control device 404 (e.g., a computer capable of having a display device) controls an arbitrary rotation center using the motor thrust of the stage device (e.g., the levitation stage 301) in the translational direction (including at least one of the X-axis, Y-axis, or Z-axis) and rotational direction (including at least one of the θx-axis, θy-axis, or θz-axis). When the stage device rotates, the control device 404 calculates the offset or trajectory of the offset from the center of the field of view of the observed image based on position information representing the distance between the rotation center coordinates and the sample observation coordinates 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 offset from the center of the field of view of the observed image by adding the offset or trajectory of the offset to the position information of the stage device. In addition to position information, at least one of the velocity, acceleration, and jerk information of the stage device can be changed. This allows the rotation center of the stage device to be aligned with the field of view center of the observed image, thus reducing the field of view offset when the stage device is activated.

[0098] In this charged particle beam device, the control device 404 can also rotate the stage while correcting the field of view offset, and simultaneously move the stage to continuously acquire observation images of the sample. Thus, the sample can be observed from various angles without causing a field of view offset.

[0099] The charged particle beam device can also maintain an error map in a storage device, which corresponds to the offset or trajectory of the offset from the center of the field of view of the observed image, specifying the error of the offset. In this case, the control device 404 can obtain the error of the offset from the error map and reflect the obtained error in the offset or trajectory of the offset. This allows for more accurate correction of the field of view offset of the observed image.

[0100] In this embodiment, a stage control system is used (see reference). Figure 5 In this stage control system, the quadratic evaluation function J (refer to equation (3)) can also be used to obtain the coefficient parameters when the position information (measured by a laser interferometer) is transformed into a coordinate system to obtain the 6-axis displacement. By using the evaluation function J, the parameters during coordinate transformation can be optimized.

[0101] Control device 404 can also be used in the stage control system (see reference). Figure 5 In response to mode commands input from external sources (by the user), it toggles whether to add the offset or the offset track to the position information of the stage device. Specifically, in Figure 9The GUI displays a selection button for the mode used to perform field-of-view offset correction. Therefore, users can choose between a mode that performs field-of-view offset correction and a mode that does not. This is to accommodate situations where, depending on the user, field-of-view offset correction may not be desired.

[0102] In this embodiment, machine learning can also be used to learn the distance in at least one of the X, Y, or Z axes between the rotation center coordinates of the stage device and the sample observation coordinates, the rotation angles (position information) of the θx, θy, and θz axes, and the propagation characteristics of the offset. This can serve as an alternative to the error mapping described above.

[0103] (ii) This embodiment also addresses the case where the wafer surface 801 has a height variation. To address the height variation of the wafer surface 801 (caused by unevenness, warping, chuck tilt, etc.), the control device 404 calculates the offset or offset trajectory from the center of the field of view of the observed image based on the height information of the sample surface (which may be pre-measured or measured during observation using the focusing function). Furthermore, in the case of pre-measurement, the height information of the wafer surface 801 may be stored as a mapping in a storage device. In this case, the control device 404 can read the height information corresponding to the wafer's position information (e.g., coordinate values) from this mapping and reflect it in the offset or offset trajectory.

[0104] (iii) In this embodiment, the control device 404 displays a user interface (GUI: see [reference]) on the display screen. Figure 9 The user interface is used by the user (operator) to specify (input as instructions) the rotation center of the stage, the rotation angles of the stage in each direction, and the rotation direction. Then, the control device 404 calculates the offset or trajectory of the offset from the center of the field of view of the observed image based on the rotation center, rotation angles, and rotation directions input as instructions. Thus, the user can easily input the position, speed, acceleration, jerk, and other information of the stage device (floating stage 301) to the instruction generation unit 504 as instructions. For example, when the sample contains a deep hole pattern, if the rotation is specified at the center of the bottom of the deep hole when observing the deep hole pattern, the deep hole pattern can be observed without generating a field of view offset when measuring the pattern (the field of view offset is suppressed to a minimum) to perform accurate height measurement.

[0105] (iv) In this embodiment, as Figures 10A to 10CAs shown, the stage device (floating stage 301) can be rotated according to the incident angle θ of the charged particle beam (electron beam 102) relative to the sample, thereby performing an action to change the incident angle of the charged particle beam. Therefore, the incident angle of the charged particle beam relative to the sample can be changed without adjusting the irradiation of the charged particle beam (keeping the irradiation track constant), thus ensuring the accuracy of dimensional measurements.

[0106] Symbol Explanation

[0107] 101 Electro-Optical System

[0108] 102 electron beam

[0109] 103 wafer

[0110] 104 Platform

[0111] 105 Field of View Center

[0112] 106 Rotation Center

[0113] 108 Field of View Shift

[0114] 201 Observation Coordinates

[0115] 202 Field of view offset

[0116] 203 chuck

[0117] 204 strip mirrors

[0118] 205 Sample Stage

[0119] 206 Distance from the center of rotation to the observation coordinates

[0120] 207 Platform Rotation Center

[0121] 208 Stage rotation angle

[0122] 301 Floating Platform

[0123] 302 base section

[0124] 303 Z-axis motor

[0125] 304 X-axis motor

[0126] 305 Rotation Center

[0127] 306 thrust

[0128] 307 thrust

[0129] 401 Vacuum Chamber

[0130] 402 thrust

[0131] 403 electric motor

[0132] 404 control device

[0133] 405 Stage Rotation Angle Information

[0134] 406 Observe the distance information between the coordinate system and the center of rotation.

[0135] 407 base

[0136] 501 Feedforward Control Input

[0137] 502 Feedback Control Department

[0138] 503 Control Object

[0139] 504 Instruction Generation Department

[0140] 505 Command Correction Department

[0141] 601 Position information in the X, Y, and Z axes

[0142] 602 Position information along the θx, θy, and θz axes

[0143] Observation coordinates before 701 rotation begins

[0144] Observation coordinates after 702 rotation

[0145] 703 Rotation Center

[0146] 704 Field Shift

[0147] 801 wafer surface

[0148] 901 GUI

[0149] 902 deep hole pattern

[0150] 903 users

[0151] 904 The height from the observation height of the sample to the center of rotation of the stage.

Claims

1. A charged particle beam device, which irradiates a sample with a charged particle beam to obtain an observation image of the sample, characterized in that, The charged particle beam device includes: The mirror body comprises a charged particle beam source and a lens; Stage device; and The control device controls the operation of the stage device. The control device performs the following controls: The arbitrary center of rotation can be controlled by the electric motor thrust in the translation and rotation directions of the stage device. During the rotation, based on positional information representing the distance between the rotation center coordinates of the stage device and the sample observation coordinates in at least one of the X-axis, Y-axis, and Z-axis directions, and the rotation angles of the θx-axis, θy-axis, and θz-axis, the offset from the field of view center of the observed image or the trajectory of the offset is calculated. as well as When the stage device is moved, the offset from the center of the field of view of the observed image is corrected by adding the offset or the trajectory of the offset to the position information of the stage device.

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

3. The charged particle beam device according to claim 1, characterized in that, In addition to the position information, the control device also changes at least one of the speed information, acceleration information, and jerk information of the platform device based on the offset or the trajectory of the offset.

4. The charged particle beam device according to claim 1, characterized in that, The control device calculates the offset or the trajectory of the offset from the center of the field of view of the observed image based on the distance between the rotation center coordinates of the stage device and the observation coordinates of the sample, the distance in at least one of the X-axis, Y-axis and Z-axis directions, the rotation angle of at least one of the θx-axis, θy-axis and θz-axis, and the height information of the sample surface.

5. The charged particle beam device according to claim 4, characterized in that, The height information from the surface of the sample is stored as a map in a storage device. When the control device determines the offset or the track of the offset, it obtains the height information from the mapping of the storage device.

6. The charged particle beam device according to claim 1, characterized in that, The control device rotates the stage while continuously acquiring the observation images.

7. The charged particle beam device according to claim 1, characterized in that, The control device performs the following controls: A user interface is displayed on the screen for specifying the rotation center, rotation angles, and rotation direction of the stage device; and Based on the specified rotation center, the rotation angles, and the rotation direction, the offset from the center of the field of view of the observed image or the trajectory of the offset is calculated.

8. The charged particle beam device according to claim 7, characterized in that, The sample contains a deep hole pattern. When observing the deep hole pattern, the rotation center is specified at the bottom of the deep hole.

9. The charged particle beam device according to claim 1, characterized in that, The charged particle beam device also stores an error map, which corresponds to the offset or the trajectory of the offset and specifies the error of the offset, in a storage device. The control device obtains the error of the offset from the error map, and reflects the obtained error in the offset or the trajectory of the offset.

10. The charged particle beam device according to claim 1, characterized in that, The control device calculates the coefficient parameters related to the coordinate transformation when controlling the stage device by optimizing a quadratic evaluation function.

11. The charged particle beam device according to claim 1, characterized in that, The control device responds to mode commands input from the outside and switches whether to add the offset or the track of the offset to the position information of the platform device.

12. The charged particle beam device according to claim 1, characterized in that, The rotation center of the stage device is the coordinate of the center of gravity of the stage device.

13. The charged particle beam device according to claim 1, characterized in that, The control device learns, through machine learning, 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, the rotation angles of the θx-axis, θy-axis, and θz-axis, and the transmission characteristics of the offset.

14. The charged particle beam device according to claim 1, characterized in that, The control device rotates the stage device according to the incident angle of the charged particle beam relative to the sample, thereby changing the incident angle of the charged particle beam.

Images