A method for calibrating a wafer alignment focus surface of a wafer stage of an ion implanter

Abstract

This invention discloses a method for calibrating the focal plane of a silicon wafer stage in an ion implanter, relating to the field of photolithography focusing technology. This method involves acquiring and processing image data of the silicon wafer on the stage using an optical system. After data processing, the stage position is initially calibrated based on alignment marks. Then, the focal length of the optical system is adjusted to determine the focal point at the alignment marks. A punctuation algorithm combined with optical system measurements is used to calculate the focal plane deviation. The deviation value is then compensated for and used to correct the alignment of the silicon wafer stage, thus combining focal length adjustment and product tilt adjustment. This ensures that after alignment, the silicon wafer's center is aligned, and the product's position is always on the plane of the alignment focal plane, improving calibration efficiency while maintaining calibration accuracy.

Description

Technical Field

[0001] This invention relates to the field of photolithography focusing technology, specifically to a method for calibrating the silicon wafer alignment focal plane of a silicon wafer stage in an ion implanter. Background Technology

[0002] An ion implanter is a key piece of equipment used to precisely implant dopant ions into silicon wafers. The wafer stage, as an important component of the ion implanter, is responsible for supporting the silicon wafer and ensuring its accurate positioning during the ion implantation process.

[0003] The reference patent title is: A method and system for defocus tilt calibration and compensation in a multi-sensor alignment system (Patent Publication No.: CN104460234A, Patent Publication Date: 2015-03-25). The method includes obtaining the optimal focal plane position of the main alignment sensor and each auxiliary alignment sensor; obtaining the optimal focal plane deviation between each auxiliary alignment sensor and the main alignment sensor based on the optimal focal plane position; obtaining the relative tilt amount between each auxiliary alignment sensor and the main alignment sensor; obtaining the vertical position deviation between the silicon wafer mark corresponding to each auxiliary alignment sensor and the silicon wafer mark corresponding to the main alignment sensor; obtaining the defocus difference between each auxiliary alignment sensor and the main alignment sensor; obtaining the alignment position deviation between each auxiliary alignment sensor and the main alignment sensor; and compensating the original alignment position of each auxiliary alignment sensor based on the alignment position deviation. This method can accurately obtain the alignment deviation between each alignment sensor to compensate for the original alignment position of each auxiliary alignment sensor.

[0004] Based on the description in the above document, the optical system of the existing ion implanter is affected by external factors, such as changes in temperature and time, and the focused position or the data collected may differ from the initial set calibration position or data, resulting in deviations during subsequent operations. Adjusting the system parameters also introduces errors. Therefore, the above problems are solved by calibrating and adjusting the product during the calibration process. To this end, the present invention provides a silicon wafer alignment focal plane calibration method for the silicon wafer stage of an ion implanter. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a silicon wafer alignment focal plane calibration method for a silicon wafer stage in an ion implanter. This method solves the problem that in existing ion implanters, the optical system is affected by external factors, such as temperature and time variations, resulting in differences between the focused position or the collected data and the initially set calibration position or data. This leads to deviations during subsequent operations, and errors also exist when adjusting parameters through the system.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for calibrating the focal plane of a silicon wafer for use in an ion implanter stage, specifically comprising the following steps:

[0007] A1. Place the silicon wafer to be calibrated on the silicon wafer stage, and ensure that the silicon wafer has alignment marks for alignment, and that the alignment marks are located at the center of the silicon wafer.

[0008] A2. The image data of the silicon wafer on the silicon wafer stage is acquired and processed using an optical system. After data processing, the position of the silicon wafer stage is initially calibrated based on the alignment mark. Then, the focal length of the optical system is adjusted to determine the focal point at the alignment mark. The deviation of the focal plane is calculated by combining the punctuation algorithm with the test of the optical system. The deviation value is then compensated to the silicon wafer stage for correction to determine the alignment focal plane.

[0009] A3. Use new standard silicon wafers or silicon wafers with specific patterns for verification testing. Verify the accuracy of the alignment plane by measuring the pattern or doping distribution on the silicon wafer after ion implantation.

[0010] Preferably, the optical system in A2 performs the image data acquisition and processing operation on the silicon wafer on the silicon wafer stage as follows:

[0011] a21. Perform grayscale processing on the collected data, determine the silicon wafer features in the image based on the changes in grayscale values, and determine whether the alignment mark is located in the image. If it does not exist, complete the movement operation below the optical system by combining human visual observation and image data until the alignment mark on the silicon wafer features is displayed in the image data.

[0012] a22. Then, a coordinate system is established with the center position of the image acquired by the optical system as the origin, and the distance that needs to be moved to the alignment mark is obtained.

[0013] a23. Generate a movement command and transmit it to the silicon wafer stage to adjust the silicon wafer stage so that the center position of the acquired image coincides with the alignment mark.

[0014] Preferably, the operation in a22 to determine the required movement distance at the alignment mark is as follows:

[0015] a221. Establish a coordinate system with the center of the acquired image as the origin, and establish the X-axis and Y-axis in directions parallel to the edge of the image data, respectively.

[0016] a222. Set the coordinates of the current alignment mark in the coordinate system to (x, y), then calculate the actual distances that the alignment mark needs to move based on the coordinates (x, y), denoted as L1 and L2.

[0017] a223, and the ratio of the distance in the image data to the distance between the actual objects is n, therefore:

[0018] The required distance to move along the X-axis is: L2 = n × y;

[0019] The distance required to move along the Y-axis is: L1 = n × x.

[0020] Preferably, the operation in A2 that performs preliminary calibration of the silicon wafer stage position and adjusts the focal length of the optical system is as follows:

[0021] B1. Based on the actual distances L1 and L2 required to move the alignment mark, the position of the silicon wafer stage is moved parallel to the X-axis and Y-axis directions to achieve the center position of the acquired image coinciding with the alignment mark.

[0022] B2. Then, by adjusting the focal length of the optical system, the image at the alignment mark is made to meet the pixel requirements, and the distance between the optical system and the silicon wafer stage is determined.

[0023] Preferably, the specific operation of the punctuation algorithm in A2 is as follows:

[0024] C1. Set reference points at equal intervals in a cross direction around the alignment mark as P1, P2, P3 and P4 respectively, and the included angles from the measurement point of the optical system to the four reference points are consistent and all are 30°.

[0025] C2. Then, record the distance data from the measurement point to the four reference points and label them as H1, H2, H3 and H4, and record the distance data from the measurement point to the alignment mark and label it as Q;

[0026] C3. Calculate the required deviation values ​​for reference points P1 and P3, as well as P2 and P4, based on the data.

[0027] Preferably, the calculation steps for the required deviation value of the reference point in C3 are as follows:

[0028] c31. Set the point at which the silicon wafer stage is rotated and adjusted to be located at the center of the bottom of the silicon wafer stage and directly below the alignment mark;

[0029] c32. Construct a planar model that includes the measurement point, reference point, and alignment mark. Starting from the alignment mark, draw a ray that intersects the line segment from the measurement point to the reference point. Divide the line segment from the measurement point to the reference point into two segments, labeled r1 and r2. The ray is perpendicular to the line segment from the measurement point to the alignment mark.

[0030] c33. Based on the data, the lengths of line segments r1 and r2 are obtained respectively, and the final deviation value required to be adjusted at the alignment mark is obtained based on line segment r2.

[0031] Preferably, the deviation values ​​that need to be adjusted for reference points P1 and P3 calculated in c33 are:

[0032] Furthermore, the required deviation values ​​for reference points P1 and P3 are the same, and the deviation value is calculated using reference point P3.

[0033] The formula for calculating line segment r1 is:

[0034] The distance between the alignment mark and the intersection of the line segments from the measurement point to the reference point is:

[0035]

[0036] And the formula for calculating line segment r2 is: r2 = H3 - r1;

[0037] Therefore, the perpendicular distance from the reference point P3 to the ray is:

[0038]

[0039] The perpendicular distance from the reference point P3 to the line segment from the measurement point to the alignment mark is: w1=s1+s2=s1+r2×sin30°=(2s1+r2) / 2;

[0040] Based on the above formula, the deviation value of the vertical rotation to the left and right sides with the alignment mark as the center is: tanα=t1 / w1, where α is the angle of vertical rotation to the left and right sides.

[0041] Preferably, the deviation values ​​that need to be adjusted for reference points P2 and P4 calculated in c33 are:

[0042] Furthermore, the required deviation values ​​for reference points P2 and P4 are the same, and the deviation value is calculated using reference point P4.

[0043] Formula for calculating line segment r3:

[0044] The distance between the alignment mark and the intersection of the line segments from the measurement point to the reference point is:

[0045]

[0046] And the formula for calculating line segment r4 is: r4 = H4 - r3;

[0047] Therefore, the perpendicular distance from the reference point P4 to the ray is:

[0048]

[0049] The perpendicular distance from the reference point P4 to the line segment from the measurement point to the alignment mark is: w2=s3+s4=s3+r4×sin30°=(2s3+r4) / 2;

[0050] Based on the above formula, the deviation value of the vertical angle rotation in the front and back directions with the alignment mark as the center is: tanβ=t2 / w2, where β is the angle of vertical rotation in the front and back directions.

[0051] Preferably, the operation in A2 of compensating for the deviation value to the silicon wafer stage for correction and determining the alignment focal plane is as follows:

[0052] D1. Based on the calculated vertical rotation angles α in the left and right directions and β in the front and back directions, the silicon wafer stage is adjusted sequentially.

[0053] D2. Based on the optical system, acquire image data of the silicon wafer on the adjusted silicon wafer stage, determine that the image data meets the required requirements, and thus determine the height position of the alignment focal plane.

[0054] Preferably, the verification test operation in A3 is as follows:

[0055] a31. Select new, defect-free standard silicon wafers or silicon wafers with specific patterns as test objects, and clean and dry the silicon wafers.

[0056] a32. Place the silicon wafer on the calibrated silicon wafer stage and move it horizontally to align the implantation port with the ion beam. Select the appropriate ion type, energy, and dose for ion implantation according to the testing requirements.

[0057] a33. Collect data after implantation, compare the shape, size and position of the pattern before and after ion implantation, verify whether the current alignment of the focal plane is accurate, and if there is a deviation, continue to compensate the value and adjust until the alignment of the focal plane is accurate after multiple tests.

[0058] This invention provides a method for calibrating the focal plane of a silicon wafer for use in an ion implanter stage.

[0059] Compared with existing technologies, it has the following advantages:

[0060] 1. The silicon wafer stage of this ion implanter uses a silicon wafer alignment focal plane calibration method. An optical system acquires and processes image data of the silicon wafer on the stage. After data processing, the stage position is initially calibrated based on alignment marks. Then, the focal length of the optical system is adjusted to determine the focal point at the alignment marks. A punctuation algorithm combined with optical system measurements is used to calculate the focal plane deviation. The deviation value is then compensated to the silicon wafer stage for correction to determine the alignment focal plane. This combines focal length adjustment and product tilt adjustment, ensuring that the silicon wafer's center is aligned after alignment focal plane calibration, and that the product's position is always on the plane of the alignment focal plane, improving calibration efficiency while ensuring calibration accuracy.

[0061] 2. The silicon wafer stage of the ion implanter uses a silicon wafer alignment focal plane calibration method. By establishing a coordinate system with the center position of the image acquired by the optical system as the origin, and obtaining the distance that the alignment mark needs to be moved, the silicon wafer stage can be adjusted so that the center position of the acquired image coincides with the alignment mark. This determines the calibration center in the current calibration operation, thereby determining the subsequent adjustment center and improving the calculation efficiency of subsequent deviation values.

[0062] 3. The silicon wafer stage of this ion implanter uses a silicon wafer alignment focal plane calibration method. This method involves setting reference points at equal intervals in a cross-shaped direction around the alignment mark, measuring the distances from the measurement point to the four reference points and recording them. Based on the data, the required adjustment deviation of the reference points is calculated, thereby compensating for the optical system by adjusting the silicon wafer stage. This makes the silicon wafer alignment focal plane calibration operation more precise, and the alignment focal plane is verified through validation, thus ensuring the accuracy of the final alignment focal plane calibration. Attached Figure Description

[0063] Figure 1 This is a flowchart illustrating the operation of the alignment and focal plane calibration method of the present invention.

[0064] Figure 2 This is a schematic diagram of the planar model of the present invention. Detailed Implementation

[0065] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0066] Please see Figures 1-2 This invention provides two technical solutions:

[0067] Example 1: A method for calibrating the focal plane of a silicon wafer on a silicon wafer stage of an ion implanter, specifically including the following steps:

[0068] A1. Place the silicon wafer to be calibrated on the silicon wafer stage, and ensure that the silicon wafer has alignment marks for alignment, and that the alignment marks are located at the center of the silicon wafer.

[0069] A2. The image data of the silicon wafer on the silicon wafer stage is acquired and processed using an optical system. After data processing, the position of the silicon wafer stage is initially calibrated based on the alignment mark. Then, the focal length of the optical system is adjusted to determine the focal point at the alignment mark. The deviation of the focal plane is calculated by combining the punctuation algorithm with the test of the optical system. The deviation value is then compensated to the silicon wafer stage for correction to determine the alignment focal plane.

[0070] A3. Use new standard silicon wafers or silicon wafers with specific patterns for verification testing. Verify the accuracy of the alignment plane by measuring the pattern or doping distribution on the silicon wafer after ion implantation.

[0071] The process involves acquiring and processing image data of the silicon wafer on the wafer stage using an optical system. After data processing, the position of the wafer stage is initially calibrated based on alignment marks. Then, the focal length of the optical system is adjusted to determine the focal point at the alignment marks. The deviation of the focal plane is calculated by combining a punctuation algorithm with the measurement of the optical system. The deviation value is then compensated to the wafer stage for correction to determine the alignment focal plane. This combines focal length adjustment and product tilt adjustment, ensuring that the center of the silicon wafer corresponds to the alignment focal plane after calibration, and that the product position is always on the plane of the alignment focal plane, thus improving calibration efficiency while ensuring calibration accuracy.

[0072] In this embodiment of the invention, the optical system in A2 performs the following operations to acquire and process image data of the silicon wafer on the silicon wafer stage:

[0073] a21. Perform grayscale processing on the collected data, determine the silicon wafer features in the image based on the changes in grayscale values, and determine whether the alignment mark is located in the image. If it does not exist, complete the movement operation below the optical system by combining human visual observation and image data until the alignment mark on the silicon wafer features is displayed in the image data.

[0074] a22. Then, a coordinate system is established with the center position of the image acquired by the optical system as the origin, and the distance that needs to be moved to the alignment mark is obtained.

[0075] a23. Generate a movement command and transmit it to the silicon wafer stage to adjust the silicon wafer stage so that the center position of the acquired image coincides with the alignment mark.

[0076] In this embodiment of the invention, the operation in a22 to determine the required moving distance at the alignment mark is as follows:

[0077] a221. Establish a coordinate system with the center of the acquired image as the origin, and establish the X-axis and Y-axis in directions parallel to the edge of the image data, respectively.

[0078] a222. Set the coordinates of the current alignment mark in the coordinate system to (x, y), then calculate the actual distances that the alignment mark needs to move based on the coordinates (x, y), denoted as L1 and L2.

[0079] a223, and the ratio of the distance in the image data to the distance between the actual objects is n, therefore:

[0080] The required distance to move along the X-axis is: L2 = n × y;

[0081] The distance required to move along the Y-axis is: L1 = n × x.

[0082] In this embodiment of the invention, the operations in A2 for preliminary calibration of the silicon wafer stage position and adjustment of the focal length of the optical system are as follows:

[0083] B1. Based on the actual distances L1 and L2 required to move the alignment mark, the position of the silicon wafer stage is moved parallel to the X-axis and Y-axis directions to achieve the center position of the acquired image coinciding with the alignment mark.

[0084] B2. Then, by adjusting the focal length of the optical system, the image at the alignment mark is made to meet the pixel requirements, and the distance between the optical system and the silicon wafer stage is determined.

[0085] Specifically, by establishing a coordinate system with the center position of the image acquired by the optical system as the origin and obtaining the distance that needs to be moved at the alignment mark, the silicon wafer stage is adjusted so that the center position of the acquired image coincides with the alignment mark. This determines the calibration center in the current calibration operation, thereby determining the subsequent adjustment center and improving the calculation efficiency of subsequent deviation values.

[0086] In this embodiment of the invention, the specific operation of the punctuation algorithm in A2 is as follows:

[0087] C1. Set reference points at equal intervals in a cross direction around the alignment mark as P1, P2, P3 and P4 respectively, and the included angles from the measurement point of the optical system to the four reference points are consistent and all are 30°.

[0088] C2. Then, record the distance data from the measurement point to the four reference points and label them as H1, H2, H3 and H4, and record the distance data from the measurement point to the alignment mark and label it as Q;

[0089] C3. Calculate the required deviation values ​​for reference points P1 and P3, as well as P2 and P4, based on the data.

[0090] In this embodiment of the invention, the steps for calculating the required deviation value of the reference point in C3 are as follows:

[0091] c31. Set the point at which the silicon wafer stage is rotated and adjusted to be located at the center of the bottom of the silicon wafer stage and directly below the alignment mark;

[0092] c32. Construct a planar model that includes the measurement point, reference point, and alignment mark. Starting from the alignment mark, draw a ray that intersects the line segment from the measurement point to the reference point. Divide the line segment from the measurement point to the reference point into two segments, labeled r1 and r2. The ray is perpendicular to the line segment from the measurement point to the alignment mark.

[0093] c33. Based on the data, the lengths of line segments r1 and r2 are obtained respectively, and the final deviation value required to be adjusted at the alignment mark is obtained based on line segment r2.

[0094] In this embodiment of the invention, the deviation values ​​that need to be adjusted for reference points P1 and P3 are calculated in c33 as follows:

[0095] Furthermore, the required deviation values ​​for reference points P1 and P3 are the same, and the deviation value is calculated using reference point P3.

[0096] The formula for calculating line segment r1 is:

[0097] The distance between the alignment mark and the intersection of the line segments from the measurement point to the reference point is:

[0098]

[0099] And the formula for calculating line segment r2 is: r2 = H3 - r1;

[0100] Therefore, the perpendicular distance from the reference point P3 to the ray is:

[0101]

[0102] The perpendicular distance from the reference point P3 to the line segment from the measurement point to the alignment mark is: w1=s1+s2=s1+r2×sin30°=(2s1+r2) / 2;

[0103] Based on the above formula, the deviation value of the vertical rotation to the left and right sides with the alignment mark as the center is: tanα=t1 / w1, where α is the angle of vertical rotation to the left and right sides.

[0104] In this embodiment of the invention, the deviation values ​​that need to be adjusted for reference points P2 and P4 are calculated in c33 as follows:

[0105] Furthermore, the required deviation values ​​for reference points P2 and P4 are the same, and the deviation value is calculated using reference point P4.

[0106] Formula for calculating line segment r3:

[0107] The distance between the alignment mark and the intersection of the line segments from the measurement point to the reference point is:

[0108]

[0109] And the formula for calculating line segment r4 is: r4 = H4 - r3;

[0110] Therefore, the perpendicular distance from the reference point P4 to the ray is:

[0111]

[0112] The perpendicular distance from the reference point P4 to the line segment from the measurement point to the alignment mark is: w2=s3+s4=s3+r4×sin30°=(2s3+r4) / 2;

[0113] Based on the above formula, the deviation value of the vertical angle rotation in the front and back directions with the alignment mark as the center is: tanβ=t2 / w2, where β is the angle of vertical rotation in the front and back directions.

[0114] In this embodiment of the invention, the operation in A2 of compensating for the deviation value to the silicon wafer stage for correction and determining the alignment focal plane is as follows:

[0115] D1. Based on the calculated vertical rotation angles α in the left and right directions and β in the front and back directions, the silicon wafer stage is adjusted sequentially.

[0116] D2. Based on the optical system, acquire image data of the silicon wafer on the adjusted silicon wafer stage, determine that the image data meets the required requirements, and thus determine the height position of the alignment focal plane.

[0117] Specifically, reference points are set at equal intervals in a cross shape around the alignment mark. The distance data from the measurement point to the four reference points is then recorded. Based on the data, the required adjustment deviation value of the reference points is calculated. This allows the adjustment of the silicon wafer stage to compensate for the optical system, making the silicon wafer alignment focal plane calibration operation more horizontal. The alignment focal plane is verified through verification, thereby ensuring the accuracy of the final alignment focal plane calibration.

[0118] In this embodiment of the invention, the verification test operation in A3 is as follows:

[0119] a31. Select new, defect-free standard silicon wafers or silicon wafers with specific patterns as test objects, and clean and dry the silicon wafers.

[0120] a32. Place the silicon wafer on the calibrated silicon wafer stage and move it horizontally to align the implantation port with the ion beam. Select the appropriate ion type, energy, and dose for ion implantation according to the testing requirements.

[0121] a33. Collect data after implantation, compare the shape, size and position of the pattern before and after ion implantation, verify whether the current alignment of the focal plane is accurate, and if there is a deviation, continue to compensate the value and adjust until the alignment of the focal plane is accurate after multiple tests.

[0122] Example 2 differs from Example 1 in that it uses both existing silicon wafer alignment focal plane calibration methods and the silicon wafer alignment focal plane calibration method of this invention to perform calibration tests on different silicon wafers with known specific data. Then, it uses multiple identical new silicon wafers to perform the test, and records the average time and accuracy of the calibration test. The specific results are shown in Table 1.

[0123] Table 1 Test Results

[0124] Average time to complete calibration Accuracy after calibration Existing alignment focal plane calibration methods 156s 82.6％ This invention provides a method for calibrating the focal plane. 54s 99.4％

[0125] In summary, the silicon wafer alignment focal plane calibration method of this invention enables the calibration and adjustment of silicon wafers in a shorter time and with higher accuracy in post-calibration testing, thus enabling better application in practical operations.

[0126] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0127] It should be noted that, in this document, relational terms such as "first" and "second" are used only 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 those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0128] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for calibrating the focal plane of a silicon wafer for use in an ion implanter stage, characterized in that: Specifically, the following steps are included: A1. Place the silicon wafer to be calibrated on the silicon wafer stage, and ensure that the silicon wafer has alignment marks for alignment, and that the alignment marks are located at the center of the silicon wafer. A2. The image data of the silicon wafer on the silicon wafer stage is acquired and processed using an optical system. After data processing, the position of the silicon wafer stage is initially calibrated based on the alignment mark. Then, the focal length of the optical system is adjusted to determine the focal point at the alignment mark. The deviation of the focal plane is calculated by combining the punctuation algorithm with the test of the optical system. The deviation value is then compensated to the silicon wafer stage for correction to determine the alignment focal plane. A3. Use new standard silicon wafers or silicon wafers with specific patterns for verification testing. Verify the accuracy of the alignment focal plane by measuring the pattern or doping distribution on the silicon wafer after ion implantation. The specific operation of the A2 punctuation algorithm is as follows: C1. Set reference points at equal intervals in a cross direction around the alignment mark as P1, P2, P3 and P4 respectively, and the included angles from the measurement point of the optical system to the four reference points are consistent and all are 30°. C2. Then, record the distance data from the measurement point to the four reference points and label them as H1, H2, H3 and H4, and record the distance data from the measurement point to the alignment mark and label it as Q; C3. Calculate the required adjustment values ​​for reference points P1 and P3, as well as P2 and P4, based on the data; The steps for calculating the required deviation value of the reference point in C3 are as follows: c31. Set the point at which the silicon wafer stage is rotated and adjusted to be located at the center of the bottom of the silicon wafer stage and directly below the alignment mark; c32. Construct a planar model that includes the measurement point, reference point, and alignment mark. Starting from the alignment mark, draw a ray that intersects the line segment from the measurement point to the reference point. Divide the line segment from the measurement point to the reference point into two segments, labeled r1 and r2. The ray is perpendicular to the line segment from the measurement point to the alignment mark. c33. Based on the data, the lengths of line segments r1 and r2 are obtained respectively, and the final deviation value required to be adjusted at the alignment mark is obtained based on line segment r2.

2. The silicon wafer alignment focal plane calibration method for a silicon wafer stage in an ion implanter according to claim 1, characterized in that: The optical system in A2 performs the following operations to acquire and process image data of the silicon wafer on the silicon wafer stage: a21. Perform grayscale processing on the collected data, determine the silicon wafer features in the image based on the changes in grayscale values, and determine whether the alignment mark is located in the image. If it does not exist, complete the movement operation below the optical system by combining human visual observation and image data until the alignment mark on the silicon wafer features is displayed in the image data. a22. Then, a coordinate system is established with the center position of the image acquired by the optical system as the origin, and the distance that needs to be moved to the alignment mark is obtained. a23. Generate a movement command and transmit it to the silicon wafer stage to adjust the silicon wafer stage so that the center position of the acquired image coincides with the alignment mark.

3. The silicon wafer alignment focal plane calibration method for a silicon wafer stage in an ion implanter according to claim 2, characterized in that: The operation in a22 to determine the required movement distance at the alignment mark is as follows: a221. Establish a coordinate system with the center of the acquired image as the origin, and establish the X-axis and Y-axis in directions parallel to the edge of the image data, respectively. a222. Set the coordinates of the current alignment mark in the coordinate system to (x, y), then calculate the actual distances that the alignment mark needs to move based on the coordinates (x, y), denoted as L1 and L2. a223, and the ratio of the distance in the image data to the distance between the actual objects is n, therefore: The required distance to move along the X-axis is: L2 = n × y; The distance required to move along the Y-axis is: L1 = n × x.

4. The silicon wafer alignment focal plane calibration method for a silicon wafer stage in an ion implanter according to claim 3, characterized in that: The operations in A2 that perform preliminary calibration of the silicon wafer stage position and adjustment of the focal length of the optical system are as follows: B1. Based on the actual distances L1 and L2 required to move the alignment mark, the position of the silicon wafer stage is moved parallel to the X-axis and Y-axis directions to achieve the center position of the acquired image coinciding with the alignment mark. B2. Then, by adjusting the focal length of the optical system, the image at the alignment mark is made to meet the pixel requirements, and the distance between the optical system and the silicon wafer stage is determined.

5. The silicon wafer alignment focal plane calibration method for a silicon wafer stage in an ion implanter according to claim 1, characterized in that: The deviation values ​​that need to be adjusted for reference points P1 and P3 are calculated in c33 as follows: Furthermore, the required deviation values ​​for reference points P1 and P3 are the same, and the deviation value is calculated using reference point P3. The formula for calculating line segment r1 is: ; The distance between the alignment mark and the intersection of the line segments from the measurement point to the reference point is: ； And the formula for calculating line segment r2 is: r2 = H3 - r1; Therefore, the perpendicular distance from the reference point P3 to the ray is: ； The perpendicular distance from the reference point P3 to the line segment from the measurement point to the alignment mark is: w1=s1+s2=s1+r2×sin30°=(2s1+r2) / 2; Based on the above formula, the deviation value of the vertical rotation to the left and right sides with the alignment mark as the center is: tanα=t1 / w1, where α is the angle of vertical rotation to the left and right sides.

6. The silicon wafer alignment focal plane calibration method for a silicon wafer stage in an ion implanter according to claim 5, characterized in that: The required adjustment values ​​for reference points P2 and P4 calculated in c33 are as follows: Furthermore, the required deviation values ​​for reference points P2 and P4 are the same, and the deviation value is calculated using reference point P4. Formula for calculating line segment r3: ; The distance between the alignment mark and the intersection of the line segments from the measurement point to the reference point is: ； And the formula for calculating line segment r4 is: r4 = H4 - r3; Therefore, the perpendicular distance from the reference point P4 to the ray is: ； The perpendicular distance from the reference point P4 to the line segment from the measurement point to the alignment mark is: w2 = s3 + s4 = s3 + r4 × sin30° = (2s3 + r4) / 2; Based on the above formula, the deviation value of the vertical angle rotation in the front and back directions with the alignment mark as the center is: tanβ=t2 / w2, where β is the angle of vertical rotation in the front and back directions.

7. The silicon wafer alignment focal plane calibration method for a silicon wafer stage in an ion implanter according to claim 6, characterized in that: The operation in A2 that compensates for the deviation value to the silicon wafer stage for correction and to determine the alignment of the focal plane is as follows: D1. Based on the calculated vertical rotation angles α in the left and right directions and β in the front and back directions, the silicon wafer stage is adjusted sequentially. D2. Based on the optical system, acquire image data of the silicon wafer on the adjusted silicon wafer stage, determine that the image data meets the required requirements, and thus determine the height position of the alignment focal plane.

8. The silicon wafer alignment focal plane calibration method for a silicon wafer stage in an ion implanter according to claim 1, characterized in that: The verification test operation in A3 is as follows: a31. Select new, defect-free standard silicon wafers or silicon wafers with specific patterns as test objects, and clean and dry the silicon wafers. a32. Place the silicon wafer on the calibrated silicon wafer stage and move it horizontally to align the implantation port with the ion beam. Select the appropriate ion type, energy, and dose for ion implantation according to the testing requirements. a33. Collect data after implantation, compare the shape, size and position of the pattern before and after ion implantation, verify whether the current alignment of the focal plane is accurate, and if there is a deviation, continue to compensate the value and adjust until the alignment of the focal plane is accurate after multiple tests.

Images