Method and device for measuring center of photomask and method for detecting machine table of photoetching machine

Abstract

The invention provides a photomask center measurement method, a photomask center measurement device and a photoetching machine table detection method. The photomask centrality measurement method comprises the steps of obtaining measurement marks in a photomask centrality preset area, determining coordinates of all the measurement marks, calculating the distance between the coordinates of all the measurement marks and the boundary of a photomask, and obtaining the centrality of the photomask; the centrality of the photomask is applied to a conventional process control system for visual monitoring. According to the method for measuring the center of the photomask, about 20 minutes of measurement processing in a traditional mode are shortened to about 2 minutes, the measurement efficiency is greatly improved, meanwhile, the center data are uploaded to an SPC system to generate a visual graph, the center of a photoetching machine is monitored in real time through an SPC chart, center monitoring automation is achieved, the method is particularly suitable for all photomasks, and monitoring of each photomask is achieved.

Description

Technical Field

[0001] This application relates to the technical field of photomask manufacturing, and particularly to a method and device for measuring the center degree of a photomask, and a method for detecting a lithography machine platform Background Art

[0002] The center degree of a photomask is a deviation between the center position of the photomask and the designed center position, and is an important index for the photomask lithography process; if the center degree of the photomask exceeds the control range, it will cause many problems such as the exposure pattern exceeding the substrate range, the subsequent film laminating process being unable to be completed, and the client being unable to mount the machine. Therefore, it is necessary to regularly measure the center degree of the photomask

[0003] At present, the method for measuring the center degree of a photomask is to manually measure the center degree fixed Mark, and calculate the data manually to obtain the center degree result. The measurement time is long, and it is more wasteful of manpower and equipment time, and the measurement effect of the photomask center degree is not good

[0004] Therefore, a new measurement scheme for the center degree of a photomask is needed Summary of the Invention

[0005] In view of this, embodiments of this specification provide a method and device for measuring the center degree of a photomask, and a method for detecting a lithography machine platform

[0006] Embodiments of this specification provide the following technical solutions

[0007] Embodiments of this specification provide a method for measuring the center degree of a photomask, including

[0008] Obtaining measurement marks within a preset area of the photomask center degree, and determining the coordinates of each measurement mark

[0009] Calculating the distance between the coordinate of each measurement mark and the boundary of the photomask to obtain the center degree of the photomask

[0010] Uploading the center degree of the photomask to the statistical process control system for visual monitoring of the photomask

[0011] Embodiments of this specification also provide a method for detecting a lithography machine platform, applying the method for measuring the center degree of a photomask as described in the above technical solution to obtain the center degree of the photomask, and making photomasks for the same lithography machine platform, respectively obtaining different color displays to reflect the working performance of each lithography machine

[0012] Embodiments of this specification also provide a device for measuring the center degree of a photomask, including

[0013] An obtaining module, configured to obtain measurement marks within a preset area of the photomask center degree, and determine the coordinates of each measurement mark

[0014] A calculation module, configured to calculate the distance between each measured mark coordinate and the boundary of the photomask to obtain the centrality of the photomask.

[0015] A monitoring module, configured to upload the centrality of the photomask to a statistical process control system for visual monitoring of the photomask.

[0016] Compared with the prior art, the at least one technical solution adopted in the embodiments of this specification can achieve at least the following beneficial effects:

[0017] This application provides an automated method for measuring the centrality of a photomask. By measuring the actual coordinates of the centrality Mark of a fixed measurement task (job), calculating the distance between the actual coordinates of Mark and the boundary to obtain the centrality of the photomask, and processing the measurement results through an automated script, uploading the data to an SPC system to generate a visual view, forming an SPC chart to monitor the centrality of the lithography machine in real time. The processing time is about 2 minutes, which improves the efficiency of centrality monitoring, realizes the automation of centrality monitoring, especially applicable to all photomasks, and realizes the monitoring of each photomask. Furthermore, it will efficiently calculate the centrality result of the photomask, form a system visual chart, and further achieve the purpose of reflecting the performance of the lithography machine. Ensure the stability of the lithography machine, improve the manufacturing efficiency and yield of the photomask, and optimize the production process with low manpower and production costs. Description of the Drawings

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0019] Figure 1 It is a schematic diagram of manually measuring the centrality of a photomask in the prior art;

[0020] Figure 2 It is a schematic diagram of a data processing template for a new measurement method provided in the embodiments of this specification;

[0021] Figure 3 It is a schematic diagram of a data visualization chart provided in the embodiments of this specification;

[0022] Figure 4 It is a schematic diagram of comparing the measurement of the centrality of a photomask between the prior art and the embodiments of this specification;

[0023] Figure 5 It is a flowchart of a new method for measuring the centrality of a photomask provided in the embodiments of this specification. Detailed Embodiments

[0024] The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0025] The following specific examples illustrate the implementation manners of the present application. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts belong to the scope of protection of the present application.

[0026] It should be noted that the following describes various aspects of the embodiments within the scope of the appended claims. It should be apparent that the aspects described herein can be embodied in a wide variety of forms, and any specific structure and / or function described herein is illustrative only. Based on the present application, those skilled in the art should understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects described herein can be used to implement the device and / or practice the method. Additionally, this device can be implemented and this method can be practiced using other structures and / or functionality in addition to one or more of the aspects described herein.

[0027] It should also be noted that the drawings provided in the following embodiments only schematically illustrate the basic concept of the present application. The drawings only show the components related to the present application, rather than being drawn according to the number, shape, and size of the components in actual implementation. The type, quantity, and ratio of each component in actual implementation can be arbitrarily changed, and the component layout type may also be more complex.

[0028] In addition, in the following description, specific details are provided to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the examples can be practiced without these specific details.

[0029] Optical mask manufacturing is to change the chemical properties of the photoresist on a photosensitive quartz substrate using laser or electron beam lithography, and then form an optical mask pattern through development and etching.

[0030] The centrality of a photomask measures the deviation between the central position of the photomask and the designed central position, and it is an important indicator in the photolithography process of the photomask. If the centrality of the photomask exceeds the controlled range, it will lead to problems such as the exposure pattern exceeding the substrate range, the inability to complete the subsequent film laminating process, and the inability to be loaded onto the client's machine. Therefore, it is necessary to regularly measure the centrality of the photomask.

[0031] Currently, the measurement method of the centrality of the photomask can only manually measure the centrality. As Figure 1 shown, it is necessary to manually calculate the data to obtain the centrality result, and the measurement time is about 20 minutes, which is relatively wasteful of manpower and equipment time. Manual monitoring has low efficiency, and it is impossible to monitor every photomask. At the same time, it is impossible to timely feedback the change of the centrality of the lithography machine, resulting in the inability to timely detect problems if the lithography machine has problems.

[0032] In view of this, aiming at the traditional method that requires manual measurement, the inventor hopes to adopt an automated measurement method, which can not only quickly measure and timely monitor each photomask, but also form a systematic visualization chart for monitoring the photomasks manufactured by each lithography machine, so as to realize the timely feedback of the change of the centrality of the lithography machine and meet the requirement of real-time monitoring of the centrality of the lithography machine, thereby improving the stability and output efficiency of the machine tool.

[0033] The following combines the drawings to illustrate the technical solutions provided by the embodiments of the present application.

[0034] Among them, the explanations of the professional terms in the embodiments of this specification are as follows:

[0035] SPC: (Statistical Process Control) A method of using statistical principles to monitor and control the production process. It collects and analyzes the data in the production process, timely discovers the abnormal fluctuations and trends in the process, and then takes measures to eliminate the abnormalities, so as to achieve the efficient monitoring and management of the centrality of the photomask.

[0036] The centrality of the photomask: It is an important concept in the field of photomask manufacturing. It describes the exposure offset of the overall pattern, that is, the deviation relative to the central position of the entire mask. It has nothing to do with the critical dimension CD measurement.

[0037] MMES (Mask Measurement and Evaluation System) is a system for mask measurement and evaluation.

[0038] The overlay measurement machine is mainly used to measure the alignment accuracy between multiple layers of patterns, that is, the overlay accuracy. It measures the alignment marks between different layers through image acquisition and processing technology to evaluate the alignment deviation between patterns.

[0039] An embodiment of this specification provides a method for measuring the center degree of a photomask, including S501 - S503. S501: Obtain the marks in the preset area of the center degree of the photomask and determine the coordinates of each mark; S502: Calculate the distance between the coordinates of each mark and the boundary of the photomask to obtain the center degree of the photomask; S503: Upload the center degree of the photomask to the SPC system for monitoring.

[0040] As described above about the importance of the center degree of the photomask, if the center degree of the photomask exceeds the control range, it will cause problems such as the exposure pattern exceeding the substrate range, the subsequent film - sticking process being unable to be completed, or the client being unable to use the machine.

[0041] Currently, the measurement method of the center degree of the photomask is manual measurement of the center degree. The CD measurement machine is used to manually measure the distance from the center degree Mark to the boundary, and the center degree result is obtained by manually calculating the data. The measurement time is about 20 minutes, which is a waste of manpower and equipment time.

[0042] The inventor found through research on each device in the photomask manufacturing process that: in the traditional method, the overlay machine is mainly used to measure the alignment accuracy between different process layers, that is, the overlay error. It calculates the offset between two layers of patterns by detecting the alignment marks of the upper and lower layer patterns (such as Box - in - Box, Frame - in - Frame, etc.).

[0043] The CD measurement machine is mainly used to measure critical dimensions (Critical Dimension, CD), such as line width, pitch, etc., to ensure that these dimensions meet the design specifications. The CD measurement machine usually requires operators to manually select the measurement position and perform high - resolution imaging and dimension calculation through equipment such as a scanning electron microscope (CD - SEM). It is mainly used to detect whether the critical dimensions meet the design requirements, and is often used for post - lithography development inspection, dimension confirmation after etching, etc. And it is usually applicable to wafers of specific sizes, and the automation degree of the equipment is relatively low.

[0044] Therefore, the inventor tries to explore and utilize existing equipment to see if the existing equipment can be reused multiple times in the process of process production, or adjust the usage order in the process production steps to achieve the measurement of the center degree of the photomask.

[0045] That is, the inventors of the present application utilized an existing Overlay measurement machine tool to measure the actual coordinates of the fixed centering Mark, calculate the centering of the photomask, and process the measurement results through an automated script, uploading the data to the SPC system to generate a visual graph, thereby improving the efficiency of centering monitoring.

[0046] Specifically, in the method for measuring the centering of a photomask in the embodiments of this specification, in step S501, measurement marks within a preset area for the centering of the photomask are obtained through an Overlay measurement machine tool, and the coordinates of each measurement mark are determined. Among them, the preset area represents the area that can reflect the centering of the photomask, and can be specifically defined according to actual circumstances. During the photomask design stage, specific alignment marks (such as cross marks, marks within a frame, etc.) will be designed on the mask plate for subsequent centering measurement.

[0047] In the embodiments of this specification, the coordinates corresponding to each mark for measuring centering within the preset area are determined through an Overlay measurement machine tool.

[0048] In step S502, the centering of the photomask is obtained based on the distance between the coordinates of each calculated mark and the boundary of the photomask.

[0049] Such as Figure 4 in which the left sides of 4 symmetric marks are automatically measured by the Overlay machine tool, and then the distances from each mark coordinate to the edge of the photomask are calculated to obtain X1, X2, X3, X4, Y1, Y2, Y3, Y4, and the results of calculating (X1 - X2) / 2, (X3 - X4) / 2, (Y1 - Y3) / 2, (Y2 - Y4) / 2 are used to obtain the centrality (i.e., the centering of the photomask).

[0050] That is, the Overlay measurement machine tool can measure the boundary of the photomask. By measuring the coordinates of the centering mark, the distance from the mark to the boundary can be confirmed, and the centrality can be calculated after obtaining the distance data.

[0051] In step S503, the centering of the photomask is uploaded to the SPC system, thereby performing visual monitoring on the photomask.

[0052] After calculating according to the above embodiments, the centrality result is obtained and uploaded to the SPC system to form an SPC chart for real-time monitoring of the centrality of the lithography machine. The processing time is about 2 minutes; while improving the efficiency of centrality measurement, the automation of centrality monitoring is realized.

[0053] The method for measuring the centering of a photomask in the embodiments of this specification realizes the monitoring of the centering of the photomask based on the overlay measurement equipment and is applicable to all photomasks.

[0054] In some embodiments, the preset area of the photomask includes the peripheral area of the photomask, where fixed measurement marks are set in the peripheral area; after obtaining the coordinates of the symmetric measurement marks, the abscissa and ordinate of the centrality of the photomask are obtained by calculating the horizontal center point and vertical center point of each measurement mark.

[0055] Specifically, when calculating the centrality of the photomask, according to the photomask pattern design, the internal patterns of the photomask are all used to design the exposure patterns required by the customer, and there is no fixed Mark designed for measuring the centrality. Therefore, in our solution during the photomask pattern design, we use the peripheral pattern to design a fixed frame, and can design fixed measurement Marks to reduce the difficulty of result processing caused by the change in centrality measurement.

[0056] In this application, the preset area of the photomask includes the peripheral area of the photomask. By using the fixed measurement marks set in the peripheral area, such as Figure 4 In the example, the Overlay machine automatically measures and obtains the coordinates corresponding to the fixed marks in the peripheral area. For example, the coordinates of the symmetric measurement marks in the upper left, upper right, lower left, and lower right are obtained as X1, X2, X3, X4, Y1, Y2, Y3, Y4 respectively. Then, the horizontal center point and vertical center point are calculated according to each measurement mark. For example, the above symmetric measurement marks correspond to a rectangular pattern on the photomask, and the geometric center of this rectangular pattern is the physical center, which usually represents the centrality of the photomask. According to the calculations of (X1 - X2) / 2, (X3 - X4) / 2, (Y1 - Y3) / 2, (Y2 - Y4) / 2, the abscissa and ordinate of the centrality of the photomask are obtained.

[0057] It should be noted that according to different symmetric design methods of the symmetric measurement marks and the different compositions of the measurement marks in the photomask design pattern, the method of calculating the centrality of the photomask changes adaptively. However, any method of finally obtaining the horizontal coordinate and vertical coordinate of the centrality of the photomask by calculating the horizontal center point and vertical center point through each measurement mark belongs to the protection scope of this application.

[0058] In some embodiments, an Overlay measurement machine is used to obtain the measurement marks in the peripheral area of the centrality of the photomask.

[0059] Combined with the above embodiments, the inventors of this embodiment found that the Overlay machine, which is used to measure the alignment accuracy between different process layers in the traditional method, can be used for measuring the centrality of the photomask, aiming to ensure the precise alignment of the graphic center and the physical center of the mask plate, thereby improving the accuracy and yield of the lithography process.

[0060] Specifically, in the embodiments of the present specification, it is ensured that the Overlay metrology tool is calibrated and in a normal working state. A fixed measurement Job is set on the Overlay metrology tool, including the centrality corresponding Mark on the photomask. The optical imaging system of the Overlay metrology tool locates the centrality Mark on the photomask. These Marks are usually symmetrically distributed. The actual coordinates (X, Y coordinates) of these Marks are measured. Furthermore, the calculation result of the photomask centrality is finally determined based on these measurement marks, such as Figure 2 shown, demonstrating that the Overlay metrology tool adopts an Overlay processing template for processing the photomask centrality. And the centrality of the photomask is uploaded to the SPC system for visual monitoring.

[0061] In some embodiments, it further includes: uploading the centrality data measured for each photomask to the SPC system and forming a display chart.

[0062] Specifically, the traditional method for measuring the photomask centrality is to manually measure the distance from the centrality Mark to the boundary using a CD metrology tool, and the photomask centrality is obtained manually. This results in low efficiency in monitoring the photomask centrality. For example, the processing time for obtaining the photomask centrality in the traditional method is about 20 minutes. Due to high labor costs and long time consumption, it is impossible to monitor every photomask. Even when using the traditional photomask centrality monitoring method, only one product photomask is selected for centrality measurement per week for each lithography machine, resulting in a long monitoring cycle.

[0063] However, the present application utilizes the existing Overlay metrology equipment. By measuring the coordinates of the fixed centrality Mark and importing the data into MMES using a fixed data processing template, the processing time is about 2 minutes. The photomask centrality result is efficiently calculated, and the centrality data measured for each photomask is uploaded to the SPC system, such as Figure 3 shown. The abscissa in the figure represents the time change, and the ordinate represents the centrality offset of the lithography machine. This offset is marked in the visualization chart and a systematic visualization chart is formed. Not only is the time for calculating the centrality of each photomask shortened from the original processing time of about 20 minutes to about 2 minutes, improving the photomask calculation efficiency, but also by uploading the centrality data of each photomask to the SPC system to form an SPC chart for real-time monitoring of the centrality of the lithography machine, with a processing time of about 2 minutes, the centrality data of each photomask is monitored, achieving the purpose of efficiently monitoring the centrality data of the lithography machine. Whether it is specifically necessary to efficiently monitor the centrality data of each photomask depends on the actual production plan. However, the present application mainly highlights the implementation method of our solution, which improves the centrality measurement efficiency and realizes the automation of centrality monitoring compared with the prior art with a long monitoring cycle.

[0064] In some embodiments, it further includes: forming different display charts with different colors respectively through statistics of the photomask centrality corresponding to different lithography machines, so as to display the working performance of each lithography machine.

[0065] Combined with the above embodiments, as Figure 3 shown, for the photomask centrality corresponding to different lithography machines, upload it to the SPC system, and form different display icons with different colors respectively through statistics, so as to display and reflect the working performance of each lithography machine.

[0066] As Figure 3 shown, for the photomask centrality corresponding to each lithography machine, use one color for statistical representation, that is, each color on the visualization chart reflects the monitoring of each lithography machine.

[0067] If the monitoring of each lithography machine is reflected by the same color, and it is found that the statistical photomask centrality corresponding to the color has a large error deviation from the physical center range of the photomask pattern design, that is, the curve shows a large fluctuation on the curve, it indicates that the accuracy of this lithography machine has decreased, thus reflecting the performance of the lithography machine to a certain extent through the visualization chart. Thereby ensuring the stability of the lithography machine, improving the manufacturing efficiency and yield of the photomask, and optimizing the production process with low labor and production costs. Among them, the range of the photomask centrality error deviation, the specific range of the curve fluctuation or the curve fluctuation trend, etc. are all set according to the actual situation, and the embodiments of this specification do not make specific limitations.

[0068] Combined with the above embodiments, the embodiments of this specification also provide a method for detecting a lithography machine, which is characterized in that the photomask centrality measurement method as described in the above technical solution is applied to obtain the centrality of the photomask, and for different lithography machines, the photomask centrality corresponding to different lithography machines is displayed in different colors respectively to reflect the working performance of each lithography machine.

[0069] Specifically as Figure 3 shown, for the photomask centrality corresponding to each lithography machine, use one color for statistical representation, that is, each color on the visualization chart reflects the monitoring of each lithography machine.

[0070] If the monitoring of each lithography machine is carried out for the same color, and it is found that the statistical centering degree of the corresponding color has a large error deviation from the physical center of the photomask pattern design within a large range, that is, the curve shows a large fluctuation on the curve, it indicates that the accuracy of this lithography machine has decreased. Thus, the performance of the lithography machine can be reflected to a certain extent through the visualization chart. Thereby, the stability of the lithography machine is ensured, the manufacturing efficiency and yield of the photomask are improved, and the production process is optimized with low manpower and production costs. Among them, the range of the centering degree error deviation of the photomask, the specific range of the curve fluctuation or the curve fluctuation trend, etc. are all set according to the actual situation, and the embodiments of this specification do not make specific limitations.

[0071] The embodiments of this specification also provide a photomask centering measurement device, which includes:

[0072] An acquisition module, configured to acquire measurement marks within a preset area of the photomask centering degree and determine the coordinates of each measurement mark;

[0073] A calculation module, configured to calculate the distance between the coordinate of each measurement mark and the boundary of the photomask to obtain the centering degree of the photomask;

[0074] A monitoring module, configured to upload the centering degree of the photomask to the statistical process control system for visual monitoring of the photomask.

[0075] This device can correspondingly be used to execute Figure 5 the steps in the method embodiments shown, and its implementation principle and technical effects are similar, which will not be elaborated here.

[0076] An electronic device provided by the embodiments of this specification, the electronic device includes: a processor, a memory, and a computer program; where

[0077] The memory is used to store the computer program, and the memory can also be a flash memory. The computer program is, for example, an application program, a functional module, etc. that implement the above method.

[0078] The processor is configured to execute the computer program stored in the memory to implement each step executed by the device in the above method. Specifically, reference can be made to the relevant descriptions in the previous method embodiments.

[0079] Optionally, the memory can be either independent or integrated with the processor.

[0080] When the memory is a device independent of the processor, the device may further include:

[0081] A bus, configured to connect the memory and the processor.

[0082] The present application also provides a readable storage medium storing a computer program, which when executed by a processor is used to implement the methods provided by the above various embodiments.

[0083] Among them, the readable storage medium may be a computer storage medium or a communication medium. The communication medium includes any medium facilitating the transmission of a computer program from one place to another. The computer storage medium may be any available medium accessible by a general-purpose or special-purpose computer. For example, the readable storage medium is coupled to the processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium may also be a component of the processor. The processor and the readable storage medium may be located in an Application Specific Integrated Circuits (ASIC). Additionally, the ASIC may be located in a user device. Of course, the processor and the readable storage medium may also exist as discrete components in a communication device. The readable storage medium may be a read-only memory (ROM), a random access memory (RAM), a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, etc.

[0084] For the same or similar parts among the various embodiments in this specification, reference may be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the product embodiments described later, since they correspond to the methods, the descriptions are relatively simple, and reference may be made to the relevant parts of the system embodiments for the relevant content.

[0085] As described above, the above are only specific embodiments of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A method for measuring the center of a photomask, characterized in that: include: Obtaining measurement marks within a preset area of ​​the photomask center and determining the coordinates of each measurement mark; Calculate the distance between each measurement mark coordinate and the photomask boundary to obtain the center of the photomask; Upload the centering of the photomask to the statistical process control system for visual monitoring of the photomask.

2. The photomask center measurement method according to claim 1, characterized in that: The preset area of ​​the photomask includes a peripheral area of ​​the photomask, wherein a fixed measurement mark is arranged in the peripheral area; After obtaining the coordinates of the symmetrical measurement marks, the horizontal and vertical center points of each measurement mark are calculated to obtain the horizontal and vertical coordinates of the center of the photomask.

3. The photomask center measurement method according to claim 1, characterized in that: The Overlay measurement machine is used to obtain the measurement marks in the peripheral area of ​​the photomask center.

4. The photomask center measurement method according to claim 1, characterized in that: Also includes: The centering data of each photomask is uploaded to the SPC system and displayed in a chart.

5. The photomask center measurement method according to claim 1, characterized in that: Also includes: The center degrees of the photomasks corresponding to different lithography machines are statistically analyzed and displayed in different colors to form different display charts, so as to display the working performance of each lithography machine.

6. A method for detecting a photolithography machine, characterized in that: The photomask center measurement method as claimed in claim 1 is applied to obtain the center of the photomask, and photomasks are manufactured for the same photolithography machine, and different color displays are obtained to reflect the working performance of each photolithography machine.

7. A photomask center measurement device, characterized in that: include: An acquisition module, used to acquire measurement marks within a preset area of ​​the photomask center and determine the coordinates of each measurement mark; A calculation module, used for calculating the distance between each measurement mark coordinate and the border of the photomask to obtain the center of the photomask; The monitoring module is used to upload the center degree of the photomask to the statistical process control system so as to perform visual monitoring on the photomask.

8. The photomask center measurement device according to claim 7, characterized in that: The preset area of ​​the photomask includes a peripheral area of ​​the photomask, wherein a fixed measurement mark is arranged in the peripheral area; After obtaining the coordinates of the symmetrical measurement marks, the horizontal and vertical center points of each measurement mark are calculated to obtain the horizontal and vertical coordinates of the center of the photomask.

9. The photomask center measurement device according to claim 7, characterized in that: The Overlay measurement machine is used to obtain the measurement marks in the peripheral area of ​​the photomask center.

10. The photomask center measurement device according to claim 7, characterized in that: Also includes: The centering data of each photomask is uploaded to the SPC system and displayed in a chart.

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