Exposure machine focus compensation method and exposure machine focus compensation system

Abstract

The application provides an exposure machine focus compensation method and an exposure machine focus compensation system. The exposure machine focus compensation method obtains multiple sets of GRP deformation correction mapping graphs after rotation and Z-direction fluctuation amounts after rotation through rotation, calculates the Z-direction fluctuation difference values by taking the first Z-direction fluctuation amount, identifies whether the wafer surface is abnormal by taking the Z-direction fluctuation difference values, and stops compensation when the wafer surface is abnormal, so as to avoid misoperation, actively exclude abnormal wafers, reduce the production wafer scrapping, and quickly screen the standard wafer state during the test process. Unexpected technical effects are achieved: abnormal standard wafers (such as particle pollution) can be screened in advance, the MGSC miscompensation link is blocked, and the key size defocus is avoided from the source.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and in particular to a focus compensation method and system for an exposure machine. Background Technology

[0002] In the semiconductor manufacturing industry, the focus accuracy of a photolithography exposure machine directly affects the control of the chip's critical dimension (CD). The exposure machine measures the stage displacement using a grating ruler (GRP). However, due to long-term mechanical stress, the GRP is prone to deformation, resulting in a displacement error of the stage in the Z-axis (i.e., the height direction) (i.e., focus offset).

[0003] To compensate for the above errors, a clean standard wafer (Golden Wafer / IRW) is typically used to simulate the exposure trajectory scan, measuring the Z-axis fluctuation data of the stage and generating an MGSC map (GRP deformation correction map) to store the focus compensation values ​​of the exposure machine's stage at different coordinates. During wafer exposure in production, the exposure machine's stage dynamically adjusts its Z-axis height using the MGSC map, thus achieving focus correction. However, this method is susceptible to errors when particles are present on the standard wafer surface, especially when particles are located in alignment mark areas. This can lead to abnormal MGSC map measurements (e.g., particles lift local height, causing Z-axis data distortion). When this abnormal MGSC map is directly imported into the compensation system for production exposure, it triggers incorrect focus compensation, causing CD defocus (critical dimension defocus), resulting in wafer scrap and reduced yield (such as the low yield problem caused by CD offset in 40nm processes).

[0004] In addition, since the focus drift caused by particles in standard wafers cannot be identified, manual sampling is required to intercept the risk. However, traditional single measurement cannot distinguish the source of error (GRP deformation or wafer surface abnormality). Particle contamination relies on manual sampling, which is inefficient and cannot intercept risks in real time. Summary of the Invention

[0005] The purpose of this invention is to provide a focus compensation method and system for an exposure machine, which can solve the chain reaction of being unable to identify abnormalities in standard wafers and lack of compensation.

[0006] To solve the above technical problems, the present invention provides a focus compensation method for an exposure machine, comprising the following steps:

[0007] A standard wafer is placed on the worktable of the exposure machine, and a first measurement is performed in the initial orientation to generate a first GRP deformation correction map. The first Z-axis fluctuation is then extracted based on the GRP deformation correction map.

[0008] The standard wafer is rotated at least two preset angles, and measurements are taken at each preset angle to generate a rotational GRP deformation correction mapping map corresponding to each preset angle. The rotational Z-axis fluctuation is extracted based on each rotational GRP deformation correction mapping map.

[0009] Based on the first Z-axis fluctuation and all the Z-axis fluctuations after rotation, the Z-axis fluctuation difference value of the standard wafer is calculated. When the Z-axis fluctuation difference value is greater than a threshold, the standard wafer is determined to be abnormal, focus compensation is stopped, and the standard wafer is replaced.

[0010] Optionally, specific methods for performing the first measurement at the initial bearing include:

[0011] Place the standard wafer at 0° on the worktable of the exposure machine, and move the worktable along the set trajectory;

[0012] A laser interferometer is used to project a beam perpendicularly onto the surface of the standard wafer and record the Z-axis displacement data.

[0013] A first GRP deformation correction mapping map is generated, and the Z-axis fluctuation amount of the entire map in the first GRP deformation correction mapping map is extracted to obtain the first Z-axis fluctuation amount.

[0014] Optionally, the standard wafer can be rotated to two preset angles, which include any two of the following: 90°, 180°, and 270°.

[0015] Optionally, the standard wafer can be rotated to three preset angles, namely 90°, 180° and 270°.

[0016] Furthermore, the specific method for extracting the Z-axis fluctuation after rotation at a preset angle includes:

[0017] The standard wafer is rotated to a 90° orientation and a measurement is performed at that orientation to generate a first rotational GRP deformation correction map. The first rotational Z-axis fluctuation is then extracted based on the first rotational GRP deformation correction map.

[0018] The standard wafer is rotated to a 180° orientation and measurements are taken at that orientation to generate a second rotated GRP deformation correction map. The second rotated Z-axis fluctuation is then extracted based on the second rotated GRP deformation correction map.

[0019] The standard wafer is rotated to a 270° orientation and measurements are taken at this orientation to generate a third-rotation GRP deformation correction map. The Z-axis fluctuation after the third rotation is then extracted based on the third-rotation GRP deformation correction map.

[0020] Furthermore, "based on the first Z-axis fluctuation and all the rotated Z-axis fluctuations, the Z-axis fluctuation difference value of the standard wafer is calculated. When the Z-axis fluctuation difference value is greater than a threshold, the standard wafer is determined to be abnormal, focus compensation is stopped, and the standard wafer is replaced" specifically includes:

[0021] Establish a formula that satisfies the Z-axis fluctuation difference value;

[0022] Determine the relationship between the Z-axis fluctuation difference value N and the threshold: if the value of N is less than or equal to the threshold, the first GRP deformation correction mapping is determined to be valid and imported into the focus compensation system; if the value of N is greater than the threshold, the standard wafer is determined to be abnormal and the standard wafer is replaced.

[0023] Furthermore, the Z-axis fluctuation difference value N satisfies the formula:

[0024] ;

[0025] Wherein, WSZ1 is the first Z-axis fluctuation; WSZ i+1 Let be the Z-axis fluctuation after the i-th rotation, where i ranges from 1 to m; m is the number of rotation measurements, where m ≥ 2 and is a positive integer.

[0026] Optionally, the threshold value is 0.8 μm.

[0027] Optionally, the standard wafer is a bare silicon wafer or a wafer with a silicon oxide coating.

[0028] On the other hand, the present invention provides an exposure machine focus compensation system, employing the aforementioned exposure machine focus compensation method, comprising:

[0029] The rotation control module is used to drive the standard wafer to rotate and position at a preset angle;

[0030] The measurement execution module is used to perform a first measurement at an initial orientation to generate a first GRP deformation correction map and extract a first Z-axis fluctuation based on the GRP deformation correction map; and to perform measurements at each preset angle to generate a rotated GRP deformation correction map corresponding to each preset angle and extract a rotated Z-axis fluctuation based on each rotated GRP deformation correction map.

[0031] The data processing module is used to calculate the Z-axis fluctuation difference value of the standard wafer based on the first Z-axis fluctuation amount and all the rotated Z-axis fluctuation amounts.

[0032] The decision output module is used to compare the Z-axis fluctuation difference value with a threshold, output the validity determination result of the first GRP deformation correction mapping map, and determine the standard wafer as abnormal when the Z-axis fluctuation difference value is greater than the threshold, stop compensation and notify the replacement of the standard wafer.

[0033] Compared with the prior art, the present invention has the following unexpected technical effects:

[0034] This invention provides a focus compensation method and system for an exposure machine. The focus compensation method includes the following steps: placing a standard wafer on the worktable of the exposure machine, performing a first measurement at an initial orientation to generate a first GRP deformation correction map, and extracting a first Z-axis fluctuation amount based on the GRP deformation correction map; rotating the standard wafer by at least two preset angles, and performing measurements at each preset angle to generate a rotated GRP deformation correction map corresponding to each preset angle, and extracting the rotated Z-axis fluctuation amount based on each rotated GRP deformation correction map; calculating the Z-axis fluctuation difference value of the standard wafer based on the first Z-axis fluctuation amount and all the rotated Z-axis fluctuation amounts, and determining that the standard wafer is abnormal when the Z-axis fluctuation difference value is greater than a threshold, stopping focus compensation and replacing the standard wafer. This invention obtains multiple sets of rotated GRP deformation correction mapping maps and rotated Z-axis fluctuation values ​​through rotation. These are then compared with the first Z-axis fluctuation value to calculate the Z-axis fluctuation difference value. This difference value is used to identify whether the wafer surface is abnormal, and compensation is stopped when an abnormality is detected. This avoids erroneous operations, proactively eliminates abnormal wafers, reduces wafer scrap, and allows for rapid screening of standard wafer states during testing. Unexpected technical benefits include: early screening of abnormal standard wafers (such as those contaminated with particulate matter), blocking the MGSC miscompensation chain, and preventing critical dimension defocusing from the source. Attached Figure Description

[0035] Figure 1 This is a schematic flowchart of an exposure machine focus compensation method provided in an embodiment of the present invention. Detailed Implementation

[0036] The following will provide a more detailed description of an exposure machine focus compensation method and system according to the present invention. The invention will now be described in more detail with reference to the accompanying drawings, which illustrate preferred embodiments of the invention. It should be understood that those skilled in the art can modify the invention described herein while still achieving its advantageous effects. Therefore, the following description should be understood as being of general knowledge to those skilled in the art and is not intended to limit the invention.

[0037] For clarity, not all features of the actual embodiments are described. In the following description, well-known functions and structures are not detailed in detail, as they would obscure the invention with unnecessary detail. It should be understood that in the development of any actual embodiment, numerous implementation details must be made to achieve the developer's specific objectives, such as changes from one embodiment to another according to limitations related to the system or business. Furthermore, it should be understood that such development work may be complex and time-consuming, but is merely routine work for those skilled in the art.

[0038] To make the objectives and features of the present invention more apparent and understandable, the specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that the drawings are all in a very simplified form and use non-precise ratios, and are only used to conveniently and clearly assist in illustrating the objectives of the embodiments of the present invention.

[0039] It should be noted that in the exposure machine, the X-axis is parallel to the standard wafer transport direction; the Y-axis is perpendicular to the transport direction and orthogonal to the X-axis; the Z-axis is perpendicular to the surface of the standard wafer, i.e., the normal direction; the rotation center is the center of the standard wafer, which coincides with the stage rotation axis; the 0° orientation of the wafer is the orientation of the wafer's notch pointing towards the -Y-axis; the 90° orientation of the wafer is the orientation of the wafer's notch pointing towards the +X-axis; the 180° orientation of the wafer is the orientation of the wafer's notch pointing towards the +Y-axis; and the 270° orientation of the wafer is the orientation of the wafer's notch pointing towards the -X-axis.

[0040] Figure 1 This is a flowchart illustrating a focus compensation method for an exposure machine provided in this embodiment. Figure 1 As shown, this embodiment provides a focus compensation method for an exposure machine, including the following steps:

[0041] Step S1: Place the standard wafer on the worktable of the exposure machine, perform the first measurement in the initial orientation to generate the first GRP deformation correction map, and extract the first Z-axis fluctuation amount according to the GRP deformation correction map;

[0042] Step S2: Rotate the standard wafer by at least two preset angles and measure at each preset angle to generate a rotational GRP deformation correction mapping map corresponding to each preset angle, and extract the rotational Z-axis fluctuation amount according to each rotational GRP deformation correction mapping map;

[0043] Step S3: Calculate the Z-axis fluctuation difference value of the standard wafer based on the first Z-axis fluctuation amount and all the Z-axis fluctuation amounts after rotation. If the Z-axis fluctuation difference value is greater than the threshold, the standard wafer is determined to be abnormal, focus compensation is stopped and the standard wafer is replaced.

[0044] This embodiment obtains multiple sets of rotated GRP deformation correction mapping maps and rotated Z-axis fluctuation values ​​through rotation. These are then compared with the first Z-axis fluctuation value to calculate the Z-axis fluctuation difference value. This difference value is used to identify whether the wafer surface is abnormal, and compensation is stopped when an abnormality is detected. This avoids erroneous operations, proactively eliminates abnormal wafers, reduces wafer scrap, and allows for rapid screening of standard wafer states during testing. Unexpected technical effects achieved include: early screening of abnormal standard wafers (such as particulate contamination), blocking the MGSC miscompensation link, and preventing critical dimension defocusing from the source.

[0045] The following provides a detailed description of an exposure machine focus compensation method provided in this embodiment.

[0046] First, step S1 is executed, where a standard wafer is placed on the worktable of the exposure machine, and a first measurement is performed in the initial orientation to generate a first GRP deformation correction mapping map. The first Z-axis fluctuation amount is then extracted based on the GRP deformation correction mapping map.

[0047] This step specifically includes:

[0048] First, wafer preparation: Select a standard wafer with a clean surface; then remove surface dust by purging with nitrogen and confirm the absence of particles (no particles with a diameter greater than 0.3μm) by dark-field microscopy.

[0049] In one embodiment, the standard wafer has, for example, a diameter of 300 mm and a thickness of 775 μm, and the standard wafer can be a bare silicon wafer or a wafer with a silicon oxide coating.

[0050] Next, the initial orientation test is performed: First, the standard wafer is placed at 0° on the worktable of the exposure machine, and the worktable is moved according to the set trajectory (simulating the chip exposure path); then, a laser beam is vertically projected onto the surface of the standard wafer through a laser interferometer, and Z-direction displacement data is recorded along the Y direction at a sampling rate of 10kHz; a first GRP (grating ruler) deformation correction mapping map (e.g., a grid pattern with a resolution of 1mm×1mm) is generated, and the Z-direction fluctuation amount of the entire first GRP deformation correction mapping map is extracted to obtain the first Z-direction fluctuation amount WSZ1, where the Z-direction fluctuation amount WSZ1 is the difference between the maximum displacement data and the minimum displacement data in the entire Z-direction displacement data.

[0051] Next, step S2 is executed, the standard wafer is rotated at least two preset angles, and measurements are taken at each preset angle to generate a rotational GRP deformation correction mapping map corresponding to each preset angle, and the rotational Z-axis fluctuation amount is extracted according to each rotational GRP deformation correction mapping map.

[0052] The standard wafer is rotated at least two preset angles, all of which include at least two orientations between 0° and 360°, and can be specifically determined according to actual needs. In some embodiments, the standard wafer is rotated to two preset angles, such as any two orientations of 90°, 180°, and 270°. In some embodiments, the standard wafer is rotated to three preset angles, such as 90°, 180°, and 270°. This step is described below using the example of rotating the standard wafer to three preset angles, such as 90°, 180°, and 270°.

[0053] This step specifically includes:

[0054] First, the standard wafer is rotated to a 90° orientation, and a laser interferometer is used to vertically project a beam onto the surface of the standard wafer at this orientation to record the Z-direction displacement data after the first rotation, generate the first rotation GRP deformation correction mapping map, and extract the full Z-direction fluctuation amount in the first rotation GRP deformation correction mapping map to obtain the first rotation Z-direction fluctuation amount WSZ2.

[0055] Next, the standard wafer is rotated to a 180° orientation, and a laser interferometer is used to vertically project a beam onto the surface of the standard wafer at this orientation to record the Z-direction displacement data after the second rotation, generate the GRP deformation correction map after the second rotation, and extract the Z-direction fluctuation amount of the entire map in the GRP deformation correction map after the second rotation to obtain the Z-direction fluctuation amount WSZ3 after the second rotation.

[0056] Next, the standard wafer is rotated to a 270° orientation, and a laser interferometer is used to vertically project a beam onto the surface of the standard wafer at this orientation to record the Z-direction displacement data after the third rotation, generate the GRP deformation correction map after the third rotation, and extract the full-map Z-direction fluctuation amount WSZ4 from the GRP deformation correction map after the third rotation to obtain the Z-direction fluctuation amount after the third rotation.

[0057] It should be noted that the center position of the standard wafer remains unchanged after rotation, thus avoiding interference from mechanical errors.

[0058] Next, step S3 is executed. Based on the first Z-axis fluctuation amount and all the Z-axis fluctuation amounts after rotation, the Z-axis fluctuation difference value of the standard wafer is calculated. When the Z-axis fluctuation difference value is greater than the threshold, the standard wafer is determined to be abnormal, focus compensation is stopped, and the standard wafer is replaced.

[0059] This step specifically includes:

[0060] First, establish the formula that satisfies the Z-direction fluctuation difference value N:

[0061]

[0062] Wherein, WSZ1 is the first Z-axis fluctuation; WSZ i+1 Let be the Z-axis fluctuation after the i-th rotation, where i ranges from 1 to m; m is the number of rotation measurements, where m ≥ 2 and is a positive integer.

[0063] Specifically, taking the rotation of the standard wafer to three preset angles as an example: N = [|WSZ1-WSZ2|+|WSZ1-WSZ3|+|WSZ1-WSZ4|] / 3; and substituting the values ​​of the Z-axis fluctuations WSZ1, WSZ2, WSZ3, and WSZ4 into the above formula to obtain the specific values ​​of N, for example, WSZ1=1.2μm, WSZ2=0.5μm, WSZ3=1.8μm, WSZ4=0.9μm, then:

[0064] N = [|1.2-0.5|+|1.2-1.8|+|1.2-0.9|] / 3 = [0.7+0.6+0.3] / 3=0.53μm.

[0065] Next, determine the relationship between the Z-axis fluctuation difference value N and the threshold:

[0066] If the value of N is less than or equal to the threshold, the first GRP deformation correction mapping is determined to be valid and imported into the focus compensation system.

[0067] If N is greater than the threshold, the standard wafer is determined to be abnormal and replaced. Specifically, after determining the standard wafer to be abnormal, a particle scan is performed on the surface of the standard wafer to locate contaminated areas. If the particles are located in the alignment mark area, the standard wafer is discarded; if the particles are located in other positions outside the alignment mark, the standard wafer is cleaned.

[0068] In one embodiment, the threshold value is 0.8 μm. The threshold value is determined based on: a depth of focus (DOF) of 40 nm, meaning an allowable unilateral compensation of 20 nm; and a maximum compensation system coefficient K < 0.25%. This leads to the maximum allowable fluctuation X: X × K ≤ 20 nm. Further, X ≤ 20 nm / 0.0025 = 0.8 μm.

[0069] This embodiment also provides an exposure machine focus compensation system, including a rotation control module, a measurement execution module, a data processing module, and a decision output module.

[0070] The rotation control module drives the standard wafer to rotate and position itself at preset angles, such as 0°, 90°, 180°, and 270°. The measurement execution module performs a first measurement at the initial orientation to generate a first GRP deformation correction map and extracts a first Z-axis fluctuation based on the GRP deformation correction map; and performs measurements at each preset angle to generate a rotated GRP deformation correction map corresponding to each preset angle, and extracts the rotated Z-axis fluctuation based on each rotated GRP deformation correction map. The data processing module calculates the Z-axis fluctuation difference value of the standard wafer based on the first Z-axis fluctuation value and all rotated Z-axis fluctuation values. The decision output module compares the Z-axis fluctuation difference value with a threshold and outputs a validity determination result for the first GRP deformation correction map; that is, if the Z-axis fluctuation difference value is greater than the threshold, the standard wafer is determined to be abnormal, compensation is stopped, and the standard wafer is notified to be replaced or cleaned; if the Z-axis fluctuation difference value is less than or equal to the threshold, the first GRP deformation correction map is determined to be valid.

[0071] In summary, this invention provides a focus compensation method and system for an exposure machine. The focus compensation method includes the following steps: placing a standard wafer on the worktable of the exposure machine, performing a first measurement at an initial orientation to generate a first GRP deformation correction mapping map, and extracting a first Z-axis fluctuation amount based on the GRP deformation correction mapping map; rotating the standard wafer by at least two preset angles, and performing measurements at each preset angle to generate a rotated GRP deformation correction mapping map corresponding to each preset angle, and extracting the rotated Z-axis fluctuation amount based on each rotated GRP deformation correction mapping map; calculating the Z-axis fluctuation difference value of the standard wafer based on the first Z-axis fluctuation amount and all the rotated Z-axis fluctuation amounts, and determining that the standard wafer is abnormal when the Z-axis fluctuation difference value is greater than a threshold, stopping focus compensation and replacing the standard wafer. This invention obtains multiple sets of rotated GRP deformation correction mapping maps and rotated Z-axis fluctuation values ​​through rotation. These are then compared with the first Z-axis fluctuation value to calculate the Z-axis fluctuation difference value. This difference value is used to identify whether the wafer surface is abnormal, and compensation is stopped when an abnormality is detected. This avoids erroneous operations, proactively eliminates abnormal wafers, reduces wafer scrap, and allows for rapid screening of standard wafer states during testing. Unexpected technical benefits include: early screening of abnormal standard wafers (such as those contaminated with particulate matter), blocking the MGSC miscompensation chain, and preventing critical dimension defocusing from the source.

[0072] Furthermore, it should be noted that, unless otherwise specified or indicated, the terms "first" and "second" in the specification are used only to distinguish the various components, elements, steps, etc. in the specification, and are not used to indicate the logical or sequential relationships between the various components, elements, steps, etc.

[0073] It is understood that although the present invention has been disclosed above with reference to preferred embodiments, these embodiments are not intended to limit the present invention. For any person skilled in the art, many possible variations and modifications can be made to the technical solutions of the present invention based on the disclosed technical content, or equivalent embodiments can be modified accordingly, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for focus compensation in an exposure machine, characterized in that, Includes the following steps: A standard wafer is placed on the worktable of the exposure machine, and a first measurement is performed in the initial orientation to generate a first grating ruler deformation correction mapping map. The first Z-axis fluctuation amount is extracted based on the grating ruler deformation correction mapping map. The standard wafer is rotated at least two preset angles, and measurements are taken at each preset angle to generate a grating ruler deformation correction mapping map corresponding to each preset angle. The Z-axis fluctuation amount after rotation is extracted based on each grating ruler deformation correction mapping map. Based on the first Z-axis fluctuation and all the Z-axis fluctuations after rotation, the Z-axis fluctuation difference value of the standard wafer is calculated. When the Z-axis fluctuation difference value is greater than a threshold, the standard wafer is determined to be abnormal, focus compensation is stopped, and the standard wafer is replaced.

2. The exposure machine focus compensation method as described in claim 1, characterized in that, The specific methods for making the first measurement at the initial azimuth include: Place the standard wafer at 0° on the worktable of the exposure machine, and move the worktable along the set trajectory; A laser interferometer is used to project a beam perpendicularly onto the surface of the standard wafer and record the Z-axis displacement data. A first grating ruler deformation correction mapping map is generated, and the Z-axis fluctuation amount of the entire first grating ruler deformation correction mapping map is extracted to obtain the first Z-axis fluctuation amount.

3. The exposure machine focus compensation method as described in claim 1, characterized in that, The standard wafer is rotated to two preset angles, which include any two of the following: 90° orientation, 180° orientation, and 270° orientation.

4. The exposure machine focus compensation method as described in claim 1, characterized in that, The standard wafer is rotated to three preset angles, namely 90°, 180° and 270°.

5. The exposure machine focus compensation method as described in claim 4, characterized in that, The specific method for extracting the Z-axis fluctuation after rotation at a preset angle includes: The standard wafer is rotated to a 90° orientation and a measurement is performed at that orientation to generate a first rotational grating ruler deformation correction mapping map, and the first rotational Z-axis fluctuation is extracted based on the first rotational grating ruler deformation correction mapping map. The standard wafer is rotated to a 180° orientation and measurements are taken at that orientation to generate a second rotated grating ruler deformation correction mapping map. The second rotated Z-axis fluctuation is then extracted based on the second rotated grating ruler deformation correction mapping map. The standard wafer is rotated to a 270° orientation and measurements are taken at this orientation to generate a third-rotation grating ruler deformation correction map. The Z-axis fluctuation after the third rotation is then extracted based on the third-rotation grating ruler deformation correction map.

6. The exposure machine focus compensation method as described in claim 5, characterized in that, "Based on the first Z-axis fluctuation and all the rotated Z-axis fluctuations, the Z-axis fluctuation difference value of the standard wafer is calculated. When the Z-axis fluctuation difference value is greater than a threshold, the standard wafer is determined to be abnormal, focus compensation is stopped, and the standard wafer is replaced." This specifically includes: Establish a formula that satisfies the Z-axis fluctuation difference value; Determine the relationship between the Z-axis fluctuation difference value N and the threshold: if the value of N is less than or equal to the threshold, the first grating ruler deformation correction mapping is determined to be valid and imported into the focus compensation system; if the value of N is greater than the threshold, the standard wafer is determined to be abnormal and the standard wafer is replaced.

7. The exposure machine focus compensation method as described in claim 6, characterized in that, The Z-axis fluctuation difference value N satisfies the formula: ； Wherein, WSZ1 is the first Z-axis fluctuation; WSZ i+1 Let be the Z-axis fluctuation after the i-th rotation, where i ranges from 1 to m; m is the number of rotation measurements, where m ≥ 2 and is a positive integer.

8. The exposure machine focus compensation method as described in claim 1, characterized in that, The threshold value is 0.8 μm.

9. The exposure machine focus compensation method as described in claim 1, characterized in that, The standard wafer is a bare silicon wafer or a wafer with a silicon oxide coating.

10. An exposure machine focus compensation system, employing the exposure machine focus compensation method as described in any one of claims 1 to 9, characterized in that, include: The rotation control module is used to drive the standard wafer to rotate and position at a preset angle; The measurement execution module is used to perform a first measurement at an initial orientation to generate a first grating ruler deformation correction mapping map, and extract a first Z-axis fluctuation amount based on the grating ruler deformation correction mapping map; And measurements are taken at each of the preset angles to generate a rotational grating ruler deformation correction mapping map corresponding to each preset angle, and a rotational Z-axis fluctuation is extracted based on each of the rotational grating ruler deformation correction mapping maps; The data processing module is used to calculate the Z-axis fluctuation difference value of the standard wafer based on the first Z-axis fluctuation amount and all the rotated Z-axis fluctuation amounts. The decision output module is used to compare the Z-axis fluctuation difference value with a threshold, output the validity determination result of the first grating ruler deformation correction mapping map, and determine the standard wafer as abnormal when the Z-axis fluctuation difference value is greater than the threshold, stop compensation and notify the replacement of the standard wafer.

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