Automatic calibration method and apparatus for position of wafer, and charged particle beam apparatus
By acquiring edge contour data of the wafer and ring electrode during sample stage movement, the wafer position is automatically calibrated, solving the problem of long processing time in traditional methods and improving the throughput and efficiency of scanning electron microscope stages.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- ANGSTROM PRECISION INSTRUMENTS CORP
- Filing Date
- 2025-11-10
- Publication Date
- 2026-06-18
AI Technical Summary
Traditional wafer positioning calibration processes are time-consuming, resulting in low throughput and low efficiency for scanning electron microscopes.
An automatic calibration method is adopted. By acquiring edge contour data of the wafer and ring electrode during the sample stage movement, calibration parameters are calculated, and the movement trajectory of the sample stage is adjusted so that the area to be observed on the wafer is moved into the observable range of the observation instrument.
It shortened the position calibration time, improved the machine throughput and observation efficiency, made full use of the sample stage movement time, and reduced the overall process time.
Smart Images
Figure CN2025133792_18062026_PF_FP_ABST
Abstract
Description
An automatic wafer positioning calibration method and apparatus, and a charged particle beam device. Technical Field
[0001] This invention relates to the field of semiconductor observation, and more particularly to an automatic calibration method and apparatus for wafer position and a charged particle beam device. Background Technology
[0002] Before measuring or observing an object using a scanning electron microscope (SEM), the object's position needs to be determined to accurately move the area to be measured under the SEM. The traditional calibration process involves sequential alignment of the optical microscope (OM) and the SEM.
[0003] However, the traditional calibration process requires waiting until the object under test is moved to the observation position, and the alignment of the optical microscope takes a long time, usually around 5 seconds. This results in low throughput of the SEM machine and reduced efficiency. Summary of the Invention
[0004] The purpose of this invention is to provide an automatic wafer position calibration method and apparatus, and a charged particle beam device, which can quickly complete wafer position calibration, reduce the position calibration time before observation, increase the throughput of the equipment, and improve observation efficiency.
[0005] To achieve the above objectives, the present invention provides an automatic wafer position calibration method for automatically calibrating the position of a wafer on a sample stage. The sample stage is provided with a wafer carrier disk for supporting the wafer and an annular electrode arranged around the wafer carrier disk. The sample stage can move along a moving trajectory from a wafer loading position to a wafer observation position. An observation instrument is provided at the wafer observation position. The automatic calibration method includes:
[0006] Before the sample stage is moved to the wafer observation position, edge contour data of the wafer and the ring electrode are acquired;
[0007] The calibration parameters for the wafer position are obtained based on the edge contour data;
[0008] Adjust the movement trajectory of the sample stage according to the calibration parameters so that the area to be observed on the wafer is moved into the observable range of the observation instrument.
[0009] Optionally, in some embodiments, obtaining calibration parameters for the wafer position based on the edge contour data includes: obtaining relative position information between the wafer and the annular electrode based on the edge contour data; and obtaining the coordinates of the wafer in the sample stage coordinate system based on the relative position information.
[0010] Optionally, in some embodiments, a scanning device is disposed above the moving trajectory to acquire edge contour data of the wafer and the ring electrode, including: controlling the sample stage to carry the wafer and the ring electrode past the scanner; controlling the scanner to scan a portion of the edge contour of the wafer and the ring electrode to obtain edge contour data.
[0011] Optionally, in some embodiments, when the scanning instrument scans the wafer, the scanning area at least covers the positioning marks on the edge of the wafer.
[0012] Optionally, in some embodiments, the scanning instrument includes a line scan camera or a line scan sensor.
[0013] Optionally, in some embodiments, an imaging instrument is disposed above the wafer loading position or movement trajectory; acquiring edge contour data of the wafer and the ring electrode includes: controlling the sample stage to move the wafer and the ring electrode below the imaging instrument and stay there for a first preset time; controlling the imaging instrument to photograph part of the edge contour of the wafer and the ring electrode to obtain edge contour data.
[0014] Optionally, in some embodiments, the number of imaging instruments is at least two, to capture at least two edge profiles of the wafer and two edge profiles of the annular electrode.
[0015] Optionally, in some embodiments, when the camera captures the edge contour of the wafer, the capture area includes at least the positioning marks on the wafer edge.
[0016] Optionally, in some embodiments, the imaging instrument includes an optical microscope or a camera.
[0017] Optionally, in some embodiments, obtaining the relative positional information between the wafer and the ring electrode based on edge contour data includes:
[0018] The center coordinates of the wafer are calculated based on the edge contour data of the wafer.
[0019] The coordinates of the center of the annular electrode are calculated based on the edge contour data of the annular electrode.
[0020] Based on the coordinates of the wafer's center and the center of the ring electrode, the difference between the wafer's center and the ring electrode's center in the X direction, ΔX0, and the difference in the Y direction, ΔY0, are calculated.
[0021] Optionally, in some embodiments, obtaining the relative positional information between the wafer and the ring electrode based on edge contour data further includes:
[0022] The center coordinates of the wafer are calculated based on the edge contour data of the wafer.
[0023] The coordinates of the positioning marks are obtained based on the edge contour data of the wafer;
[0024] The rotation angle of the wafer is calculated based on the coordinates of the positioning mark and the center coordinates of the wafer.
[0025] Optionally, in some embodiments, obtaining the relative position information between the wafer and the ring electrode based on the edge contour data further includes: calculating the expansion coefficient of the wafer based on the edge contour data of the wafer.
[0026] Optionally, in some embodiments, before acquiring the edge contour data of the wafer and the ring electrode, a pre-calibration step is included: acquiring the coordinates of the ring electrode in the sample stage coordinate system.
[0027] Optionally, in some embodiments, a photographic instrument is positioned above the movement trajectory to acquire the coordinates of the annular electrode in the sample stage coordinate system, including:
[0028] The sample stage is controlled to move the ring electrode to below the imaging instrument and remain there for a second preset time.
[0029] The camera is controlled to scan part of the edge contour of the ring electrode to obtain the edge contour data of the ring electrode.
[0030] The coordinates of the annular electrode in the sample stage coordinate system are determined based on the edge contour data.
[0031] Optionally, in some embodiments, a scanning instrument is disposed above the movement trajectory to acquire the coordinates of the annular electrode in the sample stage coordinate system, including:
[0032] The sample stage, carrying the ring electrode, passes beneath the scanning instrument.
[0033] The scanning instrument is controlled to scan a portion of the edge contour of the annular electrode and a portion of the edge contour of the sample stage to obtain edge contour data of the annular electrode and the sample stage.
[0034] The coordinates of the annular electrode in the sample stage coordinate system are determined based on the edge contour data.
[0035] Optionally, in some embodiments, both the wafer loading position and the wafer observation position are located in the main chamber. Adjusting the movement trajectory of the sample stage according to the calibration parameters includes: obtaining the position information of the wafer in the main chamber based on the coordinates of the wafer in the sample stage coordinate system; and adjusting the movement trajectory of the sample stage based on the position information of the wafer in the main chamber so that when the sample stage reaches the wafer observation position, the area to be observed on the wafer is within the observable range of the observation instrument.
[0036] Optionally, in some embodiments, the calibration parameters adjust the movement trajectory of the sample stage, including: obtaining a position compensation amount for the wafer based on the relative position information between the wafer and the annular electrode; and after the sample stage reaches the wafer observation position along the movement trajectory, moving the sample stage according to the wafer position compensation amount so that the area to be observed on the wafer moves into the observable range of the observation instrument.
[0037] Optionally, in some embodiments, the observation instrument includes an electron microscope.
[0038] Optionally, in some embodiments, after the area to be observed on the wafer is moved into the observable range of the observation instrument, the method further includes: performing an electron microscope alignment step.
[0039] An automatic wafer positioning calibration device, comprising:
[0040] The sample stage is capable of moving along a first moving trajectory from the wafer loading position to the wafer observation position.
[0041] A wafer carrier disk is used to hold wafers and is located on a sample stage;
[0042] A ring electrode is arranged around the wafer carrier disk;
[0043] The inspection instrument is positioned above or to the side of the wafer loading position, or above or to the side of the movement trajectory. The inspection instrument is capable of measuring the edge contour data of the wafer and the ring electrode.
[0044] The processor is connected to the detection instrument and the sample stage. The processor acquires the edge contour data from the detection instrument, acquires the calibration parameters of the wafer position based on the edge contour data, and adjusts the movement trajectory of the sample stage based on the calibration parameters so that the area to be observed on the wafer is moved into the observable range of the observation instrument.
[0045] Optionally, in some embodiments, the detection instrument includes at least one of a line scan camera, a line scan sensor, an optical microscope, or a camera.
[0046] Optionally, in some embodiments, the detection instrument includes at least two optical microscopes or at least two cameras.
[0047] Optionally, in some embodiments, the annular electrode includes a circular base plate and an annular sidewall disposed on the circular base plate, and a wafer carrier disk is disposed on the circular base plate and surrounded by the annular sidewall; wherein the diameter of the wafer carrier disk is smaller than the diameter of the circular base plate.
[0048] A charged particle beam device, characterized in that it comprises:
[0049] The main chamber includes the wafer loading position and the wafer observation position;
[0050] The particle beam irradiation device is located in the main chamber and above the wafer observation position;
[0051] Automatic wafer positioning calibration device in any of the above embodiments;
[0052] The sample stage, wafer carrier disk, ring electrode, and detection instruments are located in the main chamber.
[0053] Compared with the prior art, the technical solution of the present invention has at least the following beneficial effects:
[0054] The automatic wafer position calibration method provided by this invention can replace the commonly used OM alignment in traditional methods, and the time required can be controlled within 1 second, shortening the alignment time and improving the throughput of the equipment. Furthermore, the automatic wafer position calibration method of this invention occurs during the movement of the sample stage along the moving trajectory; that is, data measurement, data acquisition, and position calibration steps are performed during the sample stage movement, eliminating the need to wait until the sample stage reaches the wafer observation position before starting calibration. This fully utilizes the sample stage movement time, thereby shortening the overall process time and further improving throughput. Attached Figure Description
[0055] Figure 1 is a flowchart of an automatic wafer position calibration method according to an embodiment of the present invention.
[0056] Figure 2 is a schematic diagram of the structure of an automatic wafer position calibration device in one embodiment of the present invention.
[0057] Figure 3 is a schematic diagram of the structure of a charged particle beam device in one embodiment of the present invention.
[0058] Figure 4 is a schematic diagram showing the relative positions of the scanning instrument, wafer, and ring electrode in one embodiment of the present invention.
[0059] Figure 5 is a schematic diagram of the area covered by the camera in one embodiment of the present invention.
[0060] Figure 6 is a schematic diagram of using a photographic instrument to pre-calibrate the ring electrode in one embodiment of the present invention.
[0061] Figure 7 is a schematic diagram of using a scanning instrument to pre-calibrate a ring electrode in one embodiment of the present invention.
[0062] Explanation of icon numbers:
[0063] 10-Sample stage; 20-Wafer carrier disk; 30-Ring electrode; 40-Detection instrument; 50-Wafer; 51-Positioning mark; 60-Processor; 70-Airlock chamber; 80-Main chamber; 81-Wafer loading position; 82-Wafer observation position; 90-Particle beam irradiation device. Detailed Implementation
[0064] The technical solutions, structural features, achieved objectives, and effects of the present invention will be described in detail below with reference to Figures 1 to 5 in the embodiments of the present invention.
[0065] It should be noted that the accompanying drawings are in a very simplified form and use non-precise proportions. They are only used to facilitate and clarify the purpose of illustrating the embodiments of the present invention, and are not intended to limit the implementation conditions of the present invention. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportional relationship, or adjustments to the size should still fall within the scope of the technical content disclosed in the present invention, provided that they do not affect the effects and objectives that the present invention can produce.
[0066] It should be noted that, in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only the expressly listed elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.
[0067] When observing wafers using a scanning electron microscope (SEM), the wafer needs to be placed on a wafer carrier tray on the sample stage (with a placement accuracy of approximately 100 micrometers). The sample stage then moves the wafer to the bottom of the SEM. Due to mechanical errors, slight positional shifts and rotations may occur during wafer placement, making it impossible to guarantee that the wafer will always be precisely centered on the wafer carrier tray. This means that when the sample stage moves the wafer from the wafer loading position to the wafer observation position, it cannot accurately move the area to be observed on the wafer into the observable range of the SEM (field of view from 10 to 30 micrometers). Such positional errors are unacceptable for high-precision SEM observations. Therefore, wafer positioning calibration is necessary before formal observation.
[0068] As described in the background section, the traditional calibration process involves waiting until the sample under test is moved to the wafer observation position, then using an optical microscope positioned at that position to perform optical microscope alignment (OM alignment) on the wafer, followed by SEM alignment. The optical microscope has a field of view of approximately 1000 micrometers, allowing alignment marks to be covered within its field of view for OM alignment. In this calibration process, the time spent moving the sample stage is not fully utilized, and the lengthy optical microscope alignment process results in low throughput for the SEM equipment, reducing efficiency.
[0069] To address this technical problem, this invention provides an automatic wafer position calibration method for automatically calibrating the position of a wafer on a sample stage. The sample stage is equipped with a wafer carrier disk for supporting the wafer and an annular electrode surrounding the wafer carrier disk. The sample stage can move along a trajectory from a wafer loading position to a wafer observation position, where an observation instrument is located. As shown in Figure 1, the automatic wafer position calibration method includes:
[0070] S10: Before the sample stage is moved to the wafer observation position, acquire edge contour data of the wafer and the ring electrode;
[0071] S20: Obtain the calibration parameters for the wafer position based on the edge contour data;
[0072] S30: Adjust the movement trajectory of the sample stage according to the calibration parameters so that the area to be observed on the wafer is moved into the observable range of the observation instrument.
[0073] In this embodiment, referring to Figure 2, both the wafer carrier 20 and the annular electrode 30 are fixedly assembled on the sample stage 10. Therefore, the relative positional relationship between the wafer carrier 20, the annular electrode 30, and the sample stage 10 is fixed. Furthermore, the relative positional relationship between the wafer carrier 20, the annular electrode 30, and the sample stage 10 can be obtained through measurement. Therefore, in this embodiment, the position of the annular electrode 30 relative to the sample stage 10 can be considered known; that is, the coordinates of the annular electrode 30 in the sample stage coordinate system are known. It should also be noted that the movement of the sample stage 10 within the main chamber of the instrument is controlled by the processor; therefore, the positional information of the sample stage 10 within the main chamber is also known. As an example, the wafer carrier 20 can be an electrostatic chuck.
[0074] Due to mechanical errors, the position of the wafer 50 placed on the wafer carrier 20 relative to the annular electrode 30 is different each time. If the relative positional relationship between the wafer 50 and the annular electrode 30 can be obtained each time, then the positional relationship of the wafer 50 relative to the sample stage 10 (i.e., the coordinates of the wafer 50 in the sample stage coordinate system) can be determined. Based on this positional relationship, the movement of the sample stage 10 in the main chamber 80 can be adjusted to calibrate the wafer position, moving the area to be observed on the wafer 50 into the observable range of the observation instrument. For example, the observation instrument could be a scanning electron microscope.
[0075] The above-mentioned automatic wafer position calibration method can replace the OM alignment (optical microscope alignment) commonly used in traditional methods. Furthermore, in this embodiment, the automatic wafer position calibration method occurs during the movement of the sample stage 10 along the moving trajectory. That is, the steps of data measurement, data acquisition, and position calibration are performed during the movement of the sample stage 10. It is not necessary to wait until the sample stage 10 reaches the wafer observation position 82 before starting the calibration. This can make full use of the time for the sample stage 10 to move, thereby shortening the overall process time and further improving the throughput.
[0076] In some embodiments, as shown in FIG3, a scanning device is disposed above the moving trajectory. Step S10 involves acquiring edge contour data of the wafer 50 and the annular electrode 30, specifically including the following steps:
[0077] The sample stage 10 carries the wafer 50 and the ring electrode 30 as it passes under the scanner.
[0078] The scanning instrument is controlled to scan a portion of the edge contours of the wafer 50 and the ring electrode 30 to obtain edge contour data.
[0079] It should be noted that the terms "above" and "below" used here are not limited to strictly above or below, but also include diagonally above and diagonally below, as long as the scanning instrument can scan the edge contours of the wafer 50 and the ring electrode 30. This application does not impose any restrictions on this. Specifically, please refer to Figures 3 and 4. The scanning instrument can be a line scan camera or a line scan sensor. When the sample stage 10 moves along the moving trajectory, it carries the wafer 50 and the ring electrode 30 past below the scanning instrument. The scanning area of the scanning instrument can cover part of the edge contours of the wafer 50 and the ring electrode 30, obtain edge contour data, and transmit it to the processor 60. The processor 60 can reconstruct a 2D image based on the edge contour data.
[0080] In some embodiments, when the scanning instrument scans the wafer 50, the scanning area at least covers the positioning marks 51 on the edge of the wafer 50.
[0081] The positioning mark 51 can be a positioning edge (Flat) or a notch. Taking a notch as an example, a notch is a small groove cut out directly below the wafer 50, usually in the shape of a V or U. The notch has two functions: one is to mark the crystal orientation of the wafer 50, and the other is to enable the wafer 50 to be correctly positioned and aligned in the semiconductor manufacturing equipment.
[0082] Preferably, the scanning area of the scanning instrument covers the positioning mark 51 on the edge of the wafer 50, thereby obtaining the coordinates of the positioning mark 51. Based on the coordinates of the positioning mark 51 and the center coordinates of the wafer 50, the rotation angle of the wafer 50 can be determined.
[0083] In some embodiments, obtaining calibration parameters for the wafer position based on edge contour data includes:
[0084] S21: Obtain the relative position information between the wafer and the annular electrode based on the edge contour data;
[0085] S22: Obtain the coordinates of the wafer in the sample stage coordinate system based on the relative position information.
[0086] Specifically, step S21 includes:
[0087] S211: Calculate the center coordinates of wafer 50 based on the edge contour data of wafer 50;
[0088] S212: The coordinates of the center of the annular electrode 30 are calculated based on the edge contour data of the annular electrode 30.
[0089] S213: The center coordinates of wafer 50 and the center coordinates of ring electrode 30 are used to calculate the difference ΔX0 in the X direction and the difference ΔY0 in the Y direction between the center of wafer 50 and the center of ring electrode 30.
[0090] In step S211, the processor 60 acquires edge contour data of the wafer 50 from the scanning device, and selects at least three points to substitute into the standard equation of a circle to calculate the center coordinates and diameter of the wafer 50. Similarly, in step S212, the processor 60 acquires edge contour data of the annular electrode 30 from the scanning device, and selects at least three points to substitute into the standard equation of a circle to calculate the center coordinates and diameter of the annular electrode 30. In step S213, the processor 60, based on the center coordinates of the wafer 50 and the annular electrode 30, can obtain the difference ΔX0 in the X direction and the difference ΔY0 in the Y direction between the center of the wafer 50 and the center of the annular electrode 30.
[0091] In some embodiments, the relative position information further includes the rotation angle α of the wafer 50. The rotation angle α of the wafer 50 can be calculated based on the edge contour data of the wafer 50, and the specific steps include:
[0092] S211': The center coordinates of wafer 50 are calculated based on the edge contour data of wafer 50;
[0093] S212': Obtain the coordinates of the positioning mark 51 based on the edge contour data of wafer 50;
[0094] S213': The rotation angle α of wafer 50 is calculated based on the coordinates of the positioning mark 51 and the center coordinates of wafer 50.
[0095] Step S211' is the same as step S211, and will not be repeated here. In step S212', since the scanning area of the scanning instrument covers the positioning mark 51, the coordinates of the positioning mark 51 can be directly obtained from the edge contour data. In step S213', a straight line can be obtained based on the center coordinates of the wafer 50 and the coordinates of the positioning mark 51. The angle between this straight line and the Y-axis is the rotation angle α of the wafer 50.
[0096] In some embodiments, the relative position information also includes the coefficient of thermal expansion M of the wafer 50. The dimensions of the wafer 50 may change slightly due to temperature variations and / or process effects, and the parameter used to measure this change is the coefficient of thermal expansion of the wafer 50. Obtaining the relative position information between the wafer 50 and the ring electrode 30 based on edge contour data further includes:
[0097] S214: The expansion coefficient of wafer 50 is calculated based on the edge contour data of wafer 50.
[0098] Specifically, the diameter of wafer 50 has been calculated in step S211. This diameter can be compared with the diameter of a standard wafer 50 of the same size to obtain the coefficient of thermal expansion M of wafer 50.
[0099] In step S22, the coordinates of wafer 50 in the sample stage coordinate system are obtained based on the relative position information. Specifically, as mentioned above, the coordinates of the ring electrode 30 in the sample stage coordinate system are known. The relative position information between wafer 50 and ring electrode 30 is obtained in step S21, such as the difference ΔX0, difference ΔY0, rotation angle α, and expansion coefficient M. Therefore, given the known coordinates of ring electrode 30 in the sample stage coordinate system, the center coordinates of wafer 50 in the sample stage coordinate system can be determined based on ΔX0 and ΔY0 in the relative position information, and the rotation angle and expansion coefficient of wafer 50 in the sample stage coordinate system can be obtained based on α and M.
[0100] In step S30, the movement trajectory of the sample stage 10 is adjusted according to the calibration parameters so that the area to be observed on the wafer 50 is moved into the observable range of the observation instrument.
[0101] For example, after the sample stage 10 passes under the scanning instrument, the scanning instrument acquires edge contour data and transmits it to the processor 60 for processing to obtain the coordinates of the wafer 50 in the sample stage coordinate system. During this process, the sample stage 10 continuously moves towards the wafer observation position 82. The movement trajectory of the sample stage 10 can be divided into two segments: before passing under the scanning instrument, the sample stage 10 moves along a fixed movement trajectory; after passing under the scanning instrument, the sample stage 10 can adjust the preset movement trajectory according to the adjustment instructions issued by the processor 60.
[0102] It should be clarified that this embodiment involves not only the sample stage coordinate system but also another coordinate system, namely the main chamber coordinate system. The processor 60 controls the movement of the sample stage 10 within the main chamber 80; therefore, the processor 60 stores the coordinates of the sample stage 10 in the main chamber coordinate system. Combining the coordinates of the sample stage 10 in the main chamber coordinate system with the position of the wafer 50 in the sample stage coordinate system, the processor 60 can obtain the coordinates of the wafer 50 in the main chamber coordinate system and adjust the movement trajectory of the sample stage 10 accordingly. This ensures that after the sample stage 10 reaches the wafer observation position 82, the area to be observed on the wafer 50 is within the observable range of the scanning electron microscope.
[0103] In some embodiments, a photographic instrument is disposed above the wafer loading position 81 or the moving trajectory, which can be used to collect edge contour data of the wafer 50 and the ring electrode 30. Specific steps include:
[0104] The sample stage 10 is controlled to move the wafer 50 and the ring electrode 30 to below the imaging instrument and stay there for a first preset time.
[0105] The camera is controlled to capture partial edge contours of the wafer 50 and the ring electrode 30 to obtain edge contour data.
[0106] It should be noted that the terms "above" and "below" used here are not limited to strictly above or below, but also include diagonally above and diagonally below, as long as the imaging instrument can capture the edge contours of the wafer 50 and the ring electrode 30. This application does not impose any restrictions on this. As an example, the imaging instrument is positioned above the moving trajectory. When the sample stage 10 carrying the wafer 50 and the ring electrode 30 passes below the imaging instrument, the sample stage 10 remains below the imaging instrument for a first preset time to facilitate the imaging instrument's imaging action. This first preset time does not need to be very long, just enough for the imaging instrument to take a picture. For example, the first preset time can be 0.5s, 0.8s, or 1s. The sample stage 10 remains stationary for the first preset time, and the imaging instrument captures part of the edge contours of the wafer 50 and the ring electrode 30 to obtain edge contour data.
[0107] The processor 60 can acquire edge contour data from the imaging instrument and execute steps S20-S30 to achieve automatic calibration of the wafer position. The execution process of steps S20-S30 is similar to that described above and will not be repeated here.
[0108] In some embodiments, when the camera captures the edge contour of the wafer 50, the capture area includes at least the positioning mark 51 on the edge of the wafer 50.
[0109] After wafer 50 is placed on wafer carrier 20, it may rotate. To obtain this rotation angle, the imaging area of the imaging instrument needs to cover the positioning mark 51 on the edge of wafer 50 to facilitate the calculation of the rotation angle α. To ensure the imaging instrument can capture the positioning mark 51, it can be positioned above the movement path of the positioning mark 51. The wafer placement error range is approximately 100 micrometers, while the field of view of the imaging instrument can be 1000 micrometers (optical microscope) or greater (camera or other optical sensor). Therefore, by positioning the imaging instrument on the movement path of the positioning mark 51, the imaging area can cover the positioning mark 51 on the edge of wafer 50.
[0110] In some embodiments, at least two imaging instruments are used to capture images of at least two contours on the edge of the wafer 50 and at least two contours on the edge of the annular electrode 30, as shown in FIG5.
[0111] By increasing the number of cameras, the area covered by the camera can be increased, thereby increasing the amount of data collected. When the processor 60 reconstructs the 2D image based on the edge contour data, the more data there is, the higher the image fidelity. Furthermore, increasing the area covered by the camera also increases the probability of capturing the edge positioning mark 51 of the wafer 50.
[0112] In a preferred embodiment, the imaging instrument can be positioned at the wafer loading position 81. After the wafer 50 is placed on the wafer carrier 20, the imaging instrument immediately takes pictures of the wafer 50 and the ring electrode 30 on the sample stage 10, acquiring edge contour data of the wafer 50 and the ring electrode 30. Then, the sample stage 10 begins to move along its trajectory towards the wafer observation position 82. This configuration eliminates the need for the sample stage 10 to stop during movement, resulting in a smoother motion and improved efficiency.
[0113] In some embodiments, the photographing instrument includes an optical microscope, a camera, or an optical sensor.
[0114] It should be noted that the automatic wafer position calibration method described in the above embodiments may not be able to handle all situations. Therefore, users can choose whether to use this function in the machine's user interface (GUI). As an example, the option corresponding to the above automatic calibration method can be set to "on" by default in the machine, that is, this method is used by default to automatically calibrate the wafer position to improve throughput. When the wafer to be inspected is not suitable for this method, the option is set to "off". In this case, the traditional OM alignment method can be used to calibrate the wafer position.
[0115] In some embodiments, before acquiring the edge contour data of the wafer 50 and the annular electrode 30, the method further includes:
[0116] Pre-calibration step: Obtain the coordinates of the ring electrode 30 in the sample stage coordinate system.
[0117] It is important to note that the pre-calibration step does not need to be performed before every observation. It only needs to be performed after the equipment is assembled or after maintenance. For example, it is only necessary to perform the pre-calibration step when the ring electrode 30 or the sample stage 10 is being installed or removed after routine maintenance or repair. The purpose of pre-calibration is to obtain the coordinates of the ring electrode 30 in the sample stage coordinate system, that is, to obtain the relative positional relationship between the ring electrode 30 and the sample stage 10. By performing the pre-calibration step, the impact of the installation error of the ring electrode 30 on the observation process can be reduced or eliminated.
[0118] In some embodiments, an imaging instrument is positioned above the wafer loading position 81 or above the movement trajectory of the sample stage 10, and the pre-calibration step may include:
[0119] S1: Control the sample stage 10 to move the ring electrode 30 to below the imaging instrument and stay there for a second preset time;
[0120] S2: Control the camera to scan part of the edge contour of the ring electrode 30 to obtain the edge contour data of the ring electrode 30;
[0121] S3: Determine the coordinates of the annular electrode 30 in the sample stage coordinate system based on the edge contour data.
[0122] When the sample stage 10 is located below the imaging instrument, its position in the main chamber coordinate system is known. Further, the imaging instrument photographs a portion of the edge contour of the annular electrode 30 to obtain edge contour data. The coordinates of at least three points are extracted from this data and substituted into the standard equation of a circle by the processor 60 to calculate the position of the center of the annular electrode 30 in the main chamber coordinate system. Based on the coordinates of the center of the annular electrode 30 and the coordinates of the sample stage 10, the processor 60 can calculate the relative positional relationship between the annular electrode 30 and the sample stage 10, thus obtaining the coordinates of the annular electrode 30 in the sample stage coordinate system.
[0123] Optionally, as shown in Figure 6, the number of imaging devices can be two, forming imaging area 1 and imaging area 2, which can at least capture the two edge contours of the annular electrode 30. Optionally, the number of imaging devices can also be three or more.
[0124] In some embodiments, as shown in FIG7, a scanning instrument is disposed above the moving trajectory to acquire the coordinates of the annular electrode 30 in the sample stage coordinate system, including:
[0125] S1': Control the sample stage 10 to carry the ring electrode 30 as it passes under the scanning instrument;
[0126] S2': Control the scanning instrument to scan part of the edge contour of the annular electrode 30 and part of the edge contour of the sample stage 10 to obtain edge contour data of the annular electrode 30 and the sample stage 10.
[0127] S3': Determine the coordinates of the annular electrode 30 in the sample stage coordinate system based on the edge contour data.
[0128] When the scanning instrument scans the annular electrode 30, the annular electrode 30 moves continuously. The processor 60 processes the edge contour data obtained from the scan to obtain the relative positional relationship between the annular electrode 30 and the sample stage 10. Specifically, when the sample stage 10 moves the annular electrode 30 past the bottom of the scanning instrument, the scanning area of the scanning instrument will inevitably sweep across part of the edge of the sample stage 10 and part of the edge of the annular electrode 30, and transmit the measured edge contour data to the processor 60.
[0129] The processor 60 can reconstruct a 2D image of the annular electrode 30 and the sample stage 10 based on the edge contour data of the annular electrode 30 and the edge contour of the sample stage 10, and then obtain the coordinates of the annular electrode 30 in the sample stage coordinate system.
[0130] It should be noted that there are two scenarios for adjusting the movement trajectory of the sample stage 10 according to the calibration parameters. One is that the movement trajectory adjustment begins before the sample stage reaches the wafer observation position, and the other is that after the sample stage reaches the wafer observation position along the initially set movement trajectory, the position is finely adjusted according to the calibration parameters to achieve wafer position calibration. Details are as follows:
[0131] In one embodiment, both the wafer loading position 81 and the wafer observation position 82 are located in the main chamber 80. Adjusting the movement trajectory of the sample stage 10 according to calibration parameters includes:
[0132] The position information of wafer 50 in the main chamber is obtained based on the coordinates of wafer 50 in the sample stage coordinate system;
[0133] Based on the position information of wafer 50 in the main chamber 80, the movement trajectory of sample stage 10 is adjusted so that when sample stage 10 reaches wafer observation position 82, the area to be observed on wafer 50 is within the observable range of the observation instrument.
[0134] In another embodiment, adjusting the movement trajectory of the sample stage 10 according to calibration parameters includes:
[0135] Based on the relative position information between wafer 50 and ring electrode 30, the position compensation amount of wafer 50 is obtained;
[0136] After the sample stage 10 reaches the wafer observation position 82 along the moving trajectory, the sample stage 10 is moved according to the position compensation amount of the wafer 50 so that the area to be observed on the wafer 50 is moved into the observable range of the observation instrument.
[0137] In some embodiments, the observation instrument includes an electron microscope. Optionally, in other embodiments, the observation instrument may also include an ion microscope.
[0138] In some embodiments, after the area to be observed on the wafer 50 is moved into the observable range of the observation instrument, the method further includes: performing an electron microscope alignment step.
[0139] This embodiment implements an automatic wafer position calibration method, which allows for wafer position determination and calibration during the movement of the sample stage 10. Once the sample stage 10 reaches the wafer observation position 82, the area to be observed on the wafer 50 is within the observable range (observable area) of the instrument, allowing for direct execution of the next step: scanning electron microscope (SEM) alignment. This method eliminates the need to wait for the wafer 50 to reach the observation position 82 before performing OM alignment, saving process time and increasing the throughput of the SEM equipment.
[0140] As a second aspect of the present invention, an automatic wafer positioning calibration device is also disclosed.
[0141] In some embodiments, referring to Figures 2 and 3, the automatic wafer position calibration device includes: a sample stage 10, which is capable of moving along a first movement trajectory from a wafer loading position 81 to a wafer observation position 82; a wafer carrier disk 20 for carrying a wafer 50, the wafer carrier disk 20 being located on the sample stage 10; an annular electrode 30, the annular electrode 30 being arranged around the wafer carrier disk 20; a detection instrument 40, disposed above or to the side of the wafer loading position 81, or above or to the side of the movement trajectory, the detection instrument 40 being capable of measuring edge contour data of the wafer 50 and the annular electrode 30; and a processor 60, connected to the detection instrument 40 and the sample stage 10, the processor 60 acquiring edge contour data from the detection instrument 40, acquiring calibration parameters for the wafer position based on the edge contour data, and adjusting the movement trajectory of the sample stage 10 based on the calibration parameters, so that the area to be observed on the wafer 50 is moved into the observable range of the observation instrument.
[0142] The automatic wafer position calibration device in this embodiment can execute the automatic calibration method in any of the above embodiments to optimize existing process steps, quickly complete the position calibration of wafer 50, reduce the position calibration time before observation, increase the throughput of the equipment, and improve observation efficiency.
[0143] It should be noted that the position of the detection instrument 40 is not limited to being above the moving trajectory or above the wafer loading position 81; it can also be positioned to the side of the moving trajectory or to the side of the wafer loading position 81. For example, when the detection instrument 40 is positioned to the side of the moving trajectory, if the top surface of the annular electrode 30 is lower than the top surface of the wafer 50, at least three detection instruments 40 are required. By measuring the distance between themselves and the edge of the wafer, the three detection instruments 40 can determine the coordinates of three points on the edge of the wafer. By substituting these coordinates into the standard equation of a circle, the coordinates of the center of the wafer 50 can be calculated, thereby obtaining the position of the wafer 50 in the sample stage coordinate system. If the top surface of the annular electrode 30 is higher than the top surface of the wafer 50, holes can be drilled in the sidewall of the annular electrode 30, with the hole positions corresponding to the positions of the detection instruments 40 (at least three). The wafer position information can then be obtained using the aforementioned principle.
[0144] In some embodiments, the detection instrument 40 includes at least one of a line scan camera, a line scan sensor, an optical microscope, a camera, or a rangefinder.
[0145] Specifically, the detection area of the detection instrument 40 needs to cover part of the edge contour of the wafer 50 and part of the edge contour of the ring electrode 30, and also cover the positioning mark 51 on the edge of the wafer 50.
[0146] When the detection instrument 40 is a line scan camera or a line scan sensor, only one detection instrument 40 needs to be used. When the detection instrument 40 is an optical microscope or a camera, in order to expand the coverage of the imaging area, the number of detection instruments 40 can be increased, for example, two cameras or two optical microscopes can be used.
[0147] In some embodiments, as shown in FIG2, the annular electrode 30 includes a circular base plate and an annular sidewall disposed on the circular base plate, and the wafer carrier disk 20 is disposed on the circular base plate and surrounded by the annular sidewall; wherein the diameter of the wafer carrier disk 20 is smaller than the diameter of the circular base plate.
[0148] The ring electrode 30 can be a voltage compensation electrode, used to apply a compensation voltage to the wafer 50 during the wafer 50 inspection process.
[0149] As a third aspect of the present invention, a charged particle beam device is also disclosed. As shown in FIG3, the charged particle beam device includes: a main chamber 80, the main chamber 80 including a wafer loading position 81 and a wafer observation position 82; a particle beam irradiation device 90, located in the main chamber 80 and above the wafer observation position 82; an automatic wafer position calibration device as described in any of the above embodiments; wherein, a sample stage 10, a wafer carrier disk 20, a ring electrode 30, and a detection instrument 40 are located in the main chamber 80.
[0150] Please refer to Figure 3. Wafer 50 enters the main chamber 80 from the loadlock chamber 70. Wafer loading position 81 is adjacent to the loadlock chamber 70.
[0151] The aforementioned charged particle beam device is equipped with an automatic wafer position calibration device, which can complete the wafer position calibration work more quickly before observing wafer 50, thereby improving the throughput of the equipment and increasing the observation efficiency.
[0152] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.
Claims
1. An automatic wafer position calibration method for automatically calibrating the position of a wafer on a sample stage, wherein the sample stage is provided with a wafer carrier disk for supporting the wafer and an annular electrode arranged around the wafer carrier disk, the sample stage is capable of moving along a movement trajectory from a wafer loading position to a wafer observation position, and an observation instrument is provided at the wafer observation position, characterized in that... The automatic calibration method includes: Before the sample stage moves to the wafer observation position, the edge contour data of the wafer and the annular electrode are acquired; The calibration parameters for the wafer position are obtained based on the edge contour data; The movement trajectory of the sample stage is adjusted according to the calibration parameters so that the area to be observed on the wafer is moved into the observable range of the observation instrument.
2. The automatic wafer positioning calibration method as described in claim 1, characterized in that, The step of obtaining the calibration parameters for the wafer position based on the edge contour data includes: The relative position information between the wafer and the annular electrode is obtained based on the edge contour data; The coordinates of the wafer in the sample stage coordinate system are obtained based on the relative position information.
3. The automatic wafer positioning calibration method as described in claim 2, characterized in that, A scanning device is positioned above the movement trajectory, and the acquisition of edge contour data of the wafer and the annular electrode includes: The sample stage is controlled to carry the wafer and the ring electrode as it passes beneath the scanning instrument. The scanning instrument is controlled to scan a portion of the edge contour of the wafer and the annular electrode to obtain the edge contour data.
4. The automatic wafer positioning calibration method as described in claim 3, characterized in that, When the scanning device scans the wafer, the scanning area at least covers the positioning marks on the edge of the wafer.
5. The automatic wafer positioning calibration method as described in claim 3, characterized in that, The scanning instrument includes a line scan camera or a line scan sensor.
6. The automatic wafer positioning calibration method as described in claim 2, characterized in that, An imaging device is positioned above the wafer loading location or the movement trajectory; acquiring the edge contour data of the wafer and the annular electrode includes: The sample stage is controlled to move the wafer and the ring electrode to the underside of the imaging instrument and remain there for a first preset time; The camera is controlled to capture partial edge contours of the wafer and the annular electrode to obtain edge contour data.
7. The automatic wafer positioning calibration method as described in claim 6, characterized in that, The number of photographing instruments is at least two, so as to capture at least two edge contours of the wafer and two edge contours of the annular electrode.
8. The automatic wafer positioning calibration method as described in claim 6, characterized in that, When the photographing instrument captures the edge contour of the wafer, the shooting area includes at least the positioning marks on the edge of the wafer.
9. The automatic wafer positioning calibration method as described in claim 6, characterized in that, The photographing instrument includes an optical microscope or a camera.
10. The automatic wafer positioning calibration method as described in claim 2, characterized in that, The step of obtaining the relative position information between the wafer and the annular electrode based on the edge contour data includes: The center coordinates of the wafer are calculated based on the edge contour data of the wafer. The center coordinates of the annular electrode are calculated based on the edge contour data of the annular electrode. Based on the center coordinates of the wafer and the center coordinates of the annular electrode, the difference ΔX0 between the center of the wafer and the center of the annular electrode in the X direction and the difference ΔY0 in the Y direction are calculated.
11. The automatic wafer positioning calibration method as described in claim 4 or 8, characterized in that, The step of obtaining the relative position information between the wafer and the annular electrode based on the edge contour data further includes: The center coordinates of the wafer are calculated based on the edge contour data of the wafer. The coordinates of the positioning mark are obtained based on the edge contour data of the wafer; The rotation angle of the wafer is calculated based on the coordinates of the positioning mark and the center coordinates of the wafer.
12. The automatic wafer positioning calibration method as described in claim 2, characterized in that, The step of obtaining the relative position information between the wafer and the annular electrode based on the edge contour data further includes: The expansion coefficient of the wafer is calculated based on the edge contour data of the wafer.
13. The automatic wafer positioning calibration method as described in claim 1, characterized in that, Before acquiring the edge contour data of the wafer and the annular electrode, the process also includes: Pre-calibration step: Obtain the coordinates of the annular electrode in the sample stage coordinate system.
14. The automatic wafer positioning calibration method as described in claim 13, characterized in that, An imaging device is positioned above the movement trajectory. The step of acquiring the coordinates of the annular electrode in the sample stage coordinate system includes: The sample stage is controlled to move the ring electrode to below the imaging instrument and remain there for a second preset time; The imaging instrument is controlled to scan a portion of the edge contour of the annular electrode to obtain the edge contour data of the annular electrode. The coordinates of the annular electrode in the sample stage coordinate system are determined based on the edge contour data.
15. The automatic wafer positioning calibration method as described in claim 13, characterized in that, A scanning device is positioned above the movement trajectory. The step of acquiring the coordinates of the annular electrode in the sample stage coordinate system includes: The sample stage is controlled to carry the annular electrode as it passes beneath the scanning instrument. The scanning instrument is controlled to scan a portion of the edge contour of the annular electrode and a portion of the edge contour of the sample stage to obtain edge contour data of the annular electrode and the sample stage; The coordinates of the annular electrode in the sample stage coordinate system are determined based on the edge contour data.
16. The automatic wafer positioning calibration method as described in claim 2, characterized in that, Both the wafer loading position and the wafer observation position are located in the main chamber. Adjusting the movement trajectory of the sample stage according to the calibration parameters includes: The position information of the wafer in the main chamber is obtained based on the coordinates of the wafer in the sample stage coordinate system; Based on the position information of the wafer in the main chamber, the movement trajectory of the sample stage is adjusted so that when the sample stage reaches the wafer observation position, the area to be observed on the wafer is within the observable range of the observation instrument.
17. The automatic wafer positioning calibration method as described in claim 2, characterized in that, The step of adjusting the movement trajectory of the sample stage according to the calibration parameters includes: The position compensation amount of the wafer is obtained based on the relative position information between the wafer and the annular electrode; After the sample stage reaches the wafer observation position along the moving trajectory, the sample stage is moved according to the wafer position compensation amount so that the area to be observed on the wafer is moved into the observable range of the observation instrument.
18. The automatic wafer positioning calibration method as described in claim 1, characterized in that, The observation instruments include an electron microscope.
19. The automatic wafer positioning calibration method as described in claim 18, characterized in that, After the area to be observed on the wafer moves into the observable range of the observation instrument, the method further includes: Perform the steps for aligning the electron microscope.
20. An automatic wafer positioning calibration device, characterized in that, include: A sample stage capable of moving along a trajectory from a wafer loading position to a wafer observation position; A wafer carrier disk for holding a wafer, the wafer carrier disk being located on the sample stage; A ring electrode, wherein the ring electrode is disposed around the wafer carrier disk; The testing instrument is positioned above or to the side of the wafer loading position, or above or to the side of the movement trajectory, and the testing instrument is capable of measuring the edge contour data of the wafer and the annular electrode. The processor is connected to the detection instrument and the sample stage. The processor acquires the edge contour data from the detection instrument, acquires the calibration parameters of the wafer position based on the edge contour data, and adjusts the movement trajectory of the sample stage based on the calibration parameters so that the area to be observed on the wafer is moved into the observable range of the observation instrument.
21. The automatic wafer positioning calibration device as described in claim 20, characterized in that, The detection instrument includes at least one of a line scan camera, a line scan sensor, an optical microscope, or a camera.
22. The automatic wafer positioning calibration device as described in claim 20, characterized in that, The detection instruments include at least two optical microscopes or at least two cameras.
23. The automatic wafer positioning calibration device as described in claim 20, characterized in that, The annular electrode includes a circular base plate and an annular sidewall disposed on the circular base plate, and the wafer carrier disk is disposed on the circular base plate and surrounded by the annular sidewall. The diameter of the wafer carrier disk is smaller than the diameter of the circular base plate.
24. A charged particle beam device, characterized in that, include: The main chamber includes a wafer loading position and a wafer observation position; The particle beam irradiation device is located in the main chamber and above the wafer observation position; An automatic wafer positioning calibration apparatus as described in any one of claims 20-23; The sample stage, the wafer carrier disk, the annular electrode, and the detection instrument are located in the main chamber.