Methods, devices, systems, and storage media for monitoring wafer stage flatness

Abstract

This invention relates to a method, apparatus, system, and storage medium for monitoring the flatness of a wafer stage, comprising: real-time acquisition of wafer yield and raw focal length data; obtaining an edge flatness curve of the wafer stage based on the raw focal length data; obtaining a wafer yield curve based on the wafer yield; obtaining a trend graph of edge flatness and yield over time based on the edge flatness curve and the yield curve; and determining the edge flatness value of the wafer stage at the time of stage replacement based on the trend graph. The above-mentioned method for monitoring wafer stage flatness improves the applicability of the monitoring method and reduces costs; and achieves online monitoring of wafer stage flatness without affecting wafer processing efficiency. Furthermore, it helps operators know when to replace the wafer stage, preventing excessively low wafer yield due to wafer stage wear exceeding a certain level.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a method, apparatus, system and storage medium for monitoring the flatness of a wafer stage. Background Technology

[0002] In the wafer fabrication process, the flatness of the wafer table directly affects the exposure results, causing chuck spots on the wafer carrier and reducing wafer yield. Currently, wafers need to be mounted on a wafer table during processing. During loading and unloading, due to factors such as gravity, the wafer has more contact with the edge of the wafer table, resulting in faster wear of the wafer table edge. This, in turn, affects the production wafer edge process window, reducing the yield of the wafer portion located at the edge of the wafer table.

[0003] There are two common methods for monitoring wafer stage flatness in traditional technologies. The first is to use manufacturer-standard wafers to achieve in-line measurement of wafer stage flatness. However, standard wafers have a short lifespan and are expensive. The second is to use control wafers for measurement while the machine is stopped. However, this method cannot be measured in-line and requires the workpiece to be stopped, which increases the tool-up time and thus affects wafer processing efficiency. Summary of the Invention

[0004] Therefore, it is necessary to provide a method, device, system, and storage medium for monitoring the flatness of a wafer stage, addressing the problems of short lifespan and high cost of standard wafers when using them for monitoring wafer stage flatness in existing technologies, and the increased workpiece startup time required for using control wafers during downtime.

[0005] To achieve the above objectives, in one aspect, the present invention provides a method for monitoring the flatness of a wafer stage, comprising:

[0006] Real-time acquisition of wafer yield and raw focal length data of the wafer detected by the focal length monitor;

[0007] Based on the original focal length data, an edge flatness curve of the wafer stage is obtained, which reflects the change of the edge flatness of the wafer stage with respect to time.

[0008] Based on the yield of the wafer, a yield curve of the wafer is obtained, which reflects the change of the yield of the wafer with respect to time.

[0009] Based on the edge smoothness curve and the yield curve, a trend graph of the edge smoothness and the yield with respect to time is obtained;

[0010] Based on the trend graph, determine the edge flatness value of the wafer stage when the wafer stage is replaced.

[0011] In one embodiment, the raw focal length data includes focal length data corresponding to different radii of the wafer;

[0012] The step of obtaining the edge flatness curve of the wafer stage based on the original focal length data includes:

[0013] Extract focal length data with a preset radius from the original focal length data;

[0014] Based on the focal length data with a preset radius, a curve showing the change of the standard deviation of the focal length over time is obtained; the curve showing the change of the standard deviation of the focal length over time is the edge smoothness curve.

[0015] In one embodiment, the preset radius range is 0 to 10 mm from the edge of the wafer along the wafer radius.

[0016] In one embodiment, determining the edge flatness value of the wafer stage corresponding to the replacement of the wafer stage based on the trend graph includes:

[0017] The time point for replacing the wafer workbench is determined based on the time point when the slope of yield versus time in the trend graph reaches the preset slope.

[0018] The edge smoothness value on the edge smoothness curve is determined based on the time point at which the wafer stage is replaced.

[0019] In one embodiment, it further includes:

[0020] The replacement time for the next batch of wafer stages is determined based on the edge flatness value of the wafer stage at the time of replacement.

[0021] In one embodiment, the preset slope ranges from 0.1 to 0.5.

[0022] A device for monitoring the flatness of a wafer stage, comprising:

[0023] The acquisition module is used to acquire the wafer yield and the raw focal length data of the wafer detected by the focal length monitor in real time.

[0024] The processing module is used to obtain the edge flatness curve of the wafer stage based on the original focal length data. The edge flatness curve reflects the change of the edge flatness of the wafer stage with respect to time.

[0025] It is also used to obtain a yield curve of the wafer based on the wafer's yield, the yield curve reflecting the change of the wafer's yield with respect to time; and to obtain a trend graph of the edge smoothness and the yield with respect to time based on the edge smoothness curve and the yield curve; and

[0026] The flatness determination module is used to determine the edge flatness value of the wafer stage when the wafer stage is replaced, based on the trend graph.

[0027] In one embodiment, the raw focal length data includes focal length data corresponding to different radii of the wafer;

[0028] The processing module includes:

[0029] The cropping unit is used to crop the focal length data with a preset radius from the original focal length data;

[0030] The standard deviation processing unit is used to obtain the standard deviation of the focal length as a function of time based on the focal length data with a preset radius, and the standard deviation of the focal length as a function of time is the edge smoothness curve.

[0031] In one embodiment, the preset radius range is 0 to 10 mm from the edge of the wafer along the wafer radius.

[0032] In one embodiment, the flatness determination module includes: a replacement time determination unit, used to determine the time point for replacing the wafer worktable based on the time point when the slope of the yield versus time in the trend graph reaches a preset slope;

[0033] A flatness determination unit is used to determine the edge flatness value on the edge flatness curve based on the time point at which the wafer stage is replaced.

[0034] In one embodiment, the flatness determination module is further configured to determine the replacement time point of the subsequent batch of wafer stages based on the edge flatness value of the wafer stage corresponding to the replacement of the wafer stage.

[0035] In one embodiment, the preset slope ranges from 0.1 to 0.5.

[0036] A wafer stage flatness monitoring system includes a yield testing device, a focal length monitor, and a controller.

[0037] The yield testing device is used to detect the yield of wafers in real time;

[0038] The focal length monitor is used to detect the raw focal length data of the wafer in real time;

[0039] The controller includes a memory and a processor;

[0040] The memory stores a computer program, and when the processor executes the computer program, it implements the steps of the method described in any of the preceding methods.

[0041] In one embodiment, the focal length monitor includes a phase shift focal length monitor.

[0042] A storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method described in any of the preceding claims.

[0043] The aforementioned method, apparatus, system, and storage medium for monitoring wafer stage flatness acquires the raw focal length data of the wafer in real time to obtain the change in wafer stage edge flatness over time. The wafers used are not limited to standard wafers but can also be ordinary wafers, thereby improving the applicability of the monitoring method and reducing costs. Furthermore, the real-time acquisition of raw focal length data by the focal length monitor does not require system downtime, thus achieving online monitoring of wafer stage flatness without affecting wafer processing efficiency. In addition, the aforementioned method for monitoring wafer stage flatness also acquires wafer yield in real time to obtain a wafer yield curve. Based on the edge flatness curve and yield curve, a trend graph of wafer stage edge flatness and wafer yield over time is generated to determine the appropriate edge flatness of the wafer stage when replacing it. This helps operators know when to replace the wafer stage, preventing excessive wear and tear that could lead to low wafer yield. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 This is a flowchart of a method for monitoring the flatness of a wafer stage provided in one embodiment of this application;

[0046] Figure 2 A flowchart of a method for monitoring the flatness of a wafer stage provided in another embodiment of this application;

[0047] Figure 3 This is a schematic diagram of the relationship between focal length and radius at various locations on a wafer provided in one embodiment of this application;

[0048] Figure 4 This is a schematic diagram of the edge flatness curve of a wafer stage provided in one embodiment of this application;

[0049] Figure 5 This is a trend graph of the edge flatness of the wafer stage and the wafer yield over time, provided in one embodiment of this application.

[0050] Figure 6 This is a structural block diagram of a wafer stage flatness monitoring device provided in one embodiment of this application.

[0051] Explanation of reference numerals in the attached figures:

[0052] 60. Wafer stage flatness monitoring device; 61. Acquisition module; 62. Processing module; 63. Flatness determination module. Detailed Implementation

[0053] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate preferred embodiments of the application. However, this application may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0054] Figure 1 This is a flowchart illustrating a method for monitoring the flatness of a wafer stage in one embodiment. Please refer to [link / reference]. Figure 1 Methods for monitoring the flatness of the wafer stage include:

[0055] Step S11: Real-time acquisition of wafer yield and raw focal length data of the wafer detected by the focal length monitor.

[0056] Specifically, a focus monitor is used to monitor the focus at various locations on the wafer in real time. This focus monitor could be, for example, a phase shift focus monitor (PSFM). At any given moment, a focus value corresponds to a different location on the wafer. The focus monitor can monitor the focus at all locations on the wafer at any given time. Since wafers are generally circular, the raw focus data can be categorized based on the distance from the wafer's center point along the radial direction. The focus at each location on the wafer can also be referred to as the focus at different radii (here, the radius refers to the distance from the wafer's focal point). For example, the focus at a distance of 100mm from the wafer's center point is called the focus corresponding to a radius of 100mm. The wafer used in this embodiment is not limited to a standard wafer; it can also be a common wafer. The raw focus data of the wafer detected by the focus monitor can be recorded in the lithography machine process flow report, through which the raw focus data of the wafer can be obtained in real time.

[0057] As the wafer stage is used for longer periods, edge wear gradually increases, leading to a decrease in wafer yield. A yield testing device can be configured to monitor wafer yield in real time. The yield of the wafers at different times can be recorded in the lithography machine process flow report, allowing for real-time acquisition of wafer yield data.

[0058] Step S12: Based on the original focal length data, the edge flatness curve of the wafer stage is obtained. The edge flatness curve reflects the change of the edge flatness of the wafer stage with time.

[0059] Specifically, the inventors made the ingenious discovery that as the wafer stage is used for longer periods, edge wear gradually worsens, meaning the flatness of the wafer stage edges changes. This affects the wafers fixed on it, causing different wafers at the same location to have different focal lengths at different times. Therefore, based on real-time acquired raw focal length data, an edge flatness curve reflecting the change in wafer stage edge flatness over time can be obtained.

[0060] Step S13: Based on the wafer yield, obtain the wafer yield curve, which reflects the change of wafer yield with time.

[0061] Specifically, the yield of wafers at different times can be obtained through the lithography machine process flow report, thereby obtaining a wafer yield curve that reflects the change of wafer yield with time.

[0062] Step S14: Based on the edge smoothness curve and yield curve, obtain the trend graphs of edge smoothness and yield with respect to time.

[0063] Specifically, the edge smoothness curve and yield curve can be integrated into a single trend chart. The horizontal axis of both the edge smoothness and yield curves represents time, while the vertical axis of the edge smoothness curve represents edge smoothness, and the vertical axis of the yield curve represents yield. This allows the trends of edge smoothness and yield over time to be displayed on the same coordinate system. Alternatively, in other examples, the vertical axis of the coordinate system can be time, the horizontal axis of the edge smoothness curve can represent edge smoothness, and the horizontal axis of the yield curve can represent yield.

[0064] Step S15: Based on the trend chart, determine the edge flatness value of the wafer stage when changing the wafer stage.

[0065] Specifically, the trend graph includes the edge flatness curve of the wafer stage and the wafer yield curve. Based on the fact that the edge flatness curve and the wafer yield curve satisfy a certain preset relationship, a certain edge flatness value on the edge flatness curve can be determined as the edge flatness value of the wafer stage when the wafer stage is replaced.

[0066] The aforementioned method for monitoring wafer stage flatness acquires the raw focal length data of the wafer in real time to obtain the change in wafer stage edge flatness over time. The wafers used are not limited to standard wafers but can also be ordinary wafers, thereby improving the applicability of the monitoring method and reducing costs. Furthermore, the real-time acquisition of raw focal length data by the focal length monitor does not require system downtime, thus achieving online monitoring of wafer stage flatness without affecting wafer processing efficiency. In addition, the method also acquires wafer yield in real time to obtain a wafer yield curve. Based on the edge flatness curve and the yield curve, a trend graph of wafer stage edge flatness and wafer yield over time is generated to determine the appropriate edge flatness for wafer stage replacement. This helps operators know when to replace the wafer stage, preventing excessive wafer yield caused by wafer stage wear exceeding a certain level.

[0067] In some examples, the raw focal length data includes focal length data corresponding to different radii on the wafer. See also... Figure 2 Step S12, based on the original focal length data, obtains the edge flatness curve of the wafer stage, including steps S121 to S122.

[0068] Step S121: Extract the focal length data with a preset radius from the original focal length data.

[0069] In some examples, please refer to Figure 3Based on the original focal length data, a curve showing the relationship between focal length and radius at various locations on the wafer can be obtained. The horizontal axis of the curve represents the radius, and the vertical axis represents the focal length. A portion of this curve can be extracted; specifically, a curve with a preset radius can be extracted based on the value of the horizontal axis. Figure 3 The curve within the Chinese box represents the cropped portion.

[0070] In other examples, instead of forming a curve showing the relationship between focal length and radius at various locations on the wafer, a preset radius and its corresponding focal length data can be directly extracted from the original focal length data.

[0071] In some examples, the preset radius range is 0–10 mm from the wafer edge along the wafer radius, which corresponds to the focal length data at various positions within a preset range along the wafer edge. For example, when the wafer diameter is 300 mm, the preset radius range is the position at a wafer radius of 140–150 mm. Optionally, the preset radius range can be 0–5 mm from the wafer edge along the wafer radius; for example, when the wafer diameter is 300 mm, the preset radius range is the position at a wafer radius of 145–150 mm. Optionally, the preset radius range can be 3–5 mm from the wafer edge along the wafer radius; for example, when the wafer diameter is 300 mm, the preset radius range is the position at a wafer radius of 145–147 mm.

[0072] Step S122: Based on the focal length data with the preset radius, obtain the curve of the standard deviation of the focal length changing with time. The curve of the standard deviation of the focal length changing with time is the edge smoothness curve.

[0073] For details, please refer to Figure 4 The standard deviation (Focus STD) of the focal length at each preset radius on the wafer is calculated at each time point. A coordinate system is established, with the horizontal axis representing time and the vertical axis representing the standard deviation of the focal length at each preset radius. Curves depicting the change of the standard deviation of the focal length with respect to time are plotted for different time points, forming the edge smoothness curve. On the edge smoothness curve, the magnitude of the standard deviation of the focal length at each time point reflects the overall smoothness of the wafer stage at that moment.

[0074] In some examples, the average focal length at locations with the same radius on the wafer can be taken as the focal length corresponding to that radius. Each radius corresponds to one focal length. Step S122 calculates the standard deviation of the focal length corresponding to each preset radius on the wafer at each time step.

[0075] In other examples, the average focal length of each point on the wafer at the location in contact with the wafer stage (i.e., where the wafer may be worn) with the same radius can be taken as the focal length corresponding to that radius. Each radius corresponds to one focal length. Step S122 calculates the standard deviation of the focal length corresponding to each preset radius on the wafer at each time step.

[0076] In some other examples, step S122 can calculate the standard deviation of the focal length at all positions on the wafer at each preset radius at each time step. Each radius corresponds to multiple focal lengths.

[0077] In some other examples, step S122 may calculate the standard deviation of the focal length at all locations on the wafer at each preset radius where the wafer may be worn at each moment. Each radius corresponds to multiple focal lengths.

[0078] In some examples, please refer to Figure 2 Step S15, based on the trend chart, determines the edge flatness value of the wafer stage when changing the wafer stage, including steps S151 to S152.

[0079] Step S151: Determine the time point for changing the wafer stage based on the time point when the slope of yield versus time in the trend chart reaches the preset slope.

[0080] For details, please refer to Figure 5 In the trend graph, the time point when the slope of yield versus time on the yield curve reaches a preset slope is defined as the time point t for changing the wafer stage. The value of the preset slope can be determined by comprehensive considerations such as cost and benefit, and can also be adjusted according to the process technology or characteristics of the wafer processing. The preset slope indicates that the rate of yield decline has reached the preset slope. At the time point t corresponding to the preset slope, the wafer yield is relatively low. Determining this time point as the time point t for changing the wafer stage can prevent the subsequent use of severely worn wafer stages, which would lead to excessively low wafer yields. In other examples, the time point in the trend graph where the yield reaches a preset yield can also be used to determine the time point for changing the wafer stage.

[0081] In some examples, the preset slope ranges from 0.1 to 0.5. Optionally, the preset slope is 0.1, 0.2, 0.3, 0.4, or 0.5.

[0082] Step S152: Determine the edge smoothness value on the edge smoothness curve based on the time point of changing the wafer stage.

[0083] Specifically, find the ordinate on the edge flatness curve corresponding to the time point t when the wafer stage is replaced. This ordinate is the edge flatness value Y of the wafer stage at the time of replacement. When the edge flatness of the wafer stage reaches this value Y, the wafer stage can be replaced.

[0084] In other examples, when obtaining the trend graphs of edge smoothness and yield over time based on the yield curve and the edge smoothness curve, the vertical axis of the standard deviation of yield and focal length can be reasonably set so that the starting position of the yield curve and the edge smoothness curve is determined, and the edge smoothness value corresponding to the intersection of the yield curve and the edge smoothness curve is determined as the edge smoothness value of the wafer stage when changing the wafer stage.

[0085] In some examples, please refer to Figure 2 Methods for monitoring the flatness of wafer stages also include:

[0086] Step S16: Determine the replacement time point of the next batch of wafer stages based on the edge flatness value of the wafer stage when the wafer stage is replaced.

[0087] Specifically, the first step requires real-time acquisition of wafer yield to obtain a yield curve. Based on the yield curve and flatness curve, a trend graph of edge flatness and yield over time is generated. The edge flatness value Y of the wafer stage is then determined based on this trend graph. Subsequent steps no longer require real-time acquisition of wafer yield; only the raw focal length data of the wafer detected by the focal length monitor needs to be acquired in real-time. Based on this raw focal length data, an edge flatness curve of the wafer stage is obtained. The time corresponding to the edge flatness value Y on the edge flatness curve is the time point for changing the wafer stage.

[0088] It should be understood that, although Figure 1-2 The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 1-2 At least some of the steps in the process may include multiple steps or multiple stages. These steps or stages are not necessarily completed at the same time, but may be executed at different times. The execution order of these steps or stages is not necessarily sequential, but may be executed in turn or alternately with other steps or at least some of the steps or stages in other steps.

[0089] Figure 6 This is a wafer stage flatness monitoring device in one embodiment. Please refer to [link / reference]. Figure 6The wafer stage flatness monitoring device 60 includes an acquisition module 61, a processing module 62, and a flatness determination module 63. The acquisition module 61 acquires in real-time the wafer yield and the raw focal length data detected by the focal length monitor. The processing module 62, based on the raw focal length data, obtains an edge flatness curve of the wafer stage, reflecting the change in the flatness of the wafer stage edge over time; it also obtains a wafer yield curve based on the wafer yield, reflecting the change in wafer yield over time; and it further obtains a trend graph of edge flatness and yield over time based on the edge flatness curve and the yield curve. The flatness determination module 63, based on the trend graph, determines the edge flatness value of the wafer stage corresponding to the stage being replaced.

[0090] In some examples, the raw focal length data includes focal length data corresponding to different radii on the wafer. Processing module 62 includes a clipping unit and a standard deviation processing unit. The clipping unit is used to clip the focal length data at a preset radius from the raw focal length data. The standard deviation processing unit is used to obtain a curve showing the change of the standard deviation of the focal length over time based on the clipped focal length data at the preset radius; this curve represents the edge smoothness curve.

[0091] In some examples, the preset radius is 0 to 10 mm from the edge of the wafer along the wafer radius.

[0092] In some examples, the flatness determination module 63 further includes a replacement time determination unit and a flatness determination unit. The replacement time determination module is used to determine the time point for replacing the wafer stage based on the time point when the slope of yield versus time in the trend graph reaches a preset slope. The flatness determination unit is used to determine the edge flatness value on the edge flatness curve based on the time point for replacing the wafer stage.

[0093] In some examples, the flatness determination module 63 is also used to determine the replacement time point of the subsequent batch of wafer stages based on the edge flatness value of the wafer stage corresponding to the replacement of the wafer stage.

[0094] In some examples, the preset slope ranges from 0.1 to 0.5. Optionally, the preset slope is 0.1, 0.2, 0.3, 0.4, or 0.5.

[0095] Specific limitations regarding the wafer stage flatness monitoring device 60 can be found in the above-described limitations of the wafer stage flatness monitoring method, and will not be repeated here. Each module in the aforementioned wafer stage flatness monitoring device 60 can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in or independent of the processor in a computer device in hardware form, or stored in the memory of a computer device in software form, so that the processor can call and execute the corresponding operations of each module.

[0096] This application also provides a wafer stage flatness monitoring system. The wafer stage flatness monitoring system includes a yield testing device, a focal length monitor, and a controller. The yield testing device is used to detect the wafer yield in real time. The focal length monitor is used to detect the raw focal length data of the wafer in real time. The controller includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements the steps of the wafer stage flatness monitoring method in any of the above embodiments.

[0097] In some examples, the focal length monitor includes a phase shift focal length monitor.

[0098] This application also provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps in the above-described method embodiments.

[0099] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium, and when executed, it can include the processes of the embodiments of the methods described above. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, or optical storage, etc. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0100] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0101] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for monitoring the flatness of a wafer stage, characterized in that, include: Real-time acquisition of wafer yield and raw focal length data of the wafer detected by the focal length monitor; Based on the original focal length data, an edge flatness curve of the wafer stage is obtained, which reflects the change of the edge flatness of the wafer stage with respect to time. Based on the yield of the wafer, a yield curve of the wafer is obtained, which reflects the change of the yield of the wafer with respect to time. Based on the edge smoothness curve and the yield curve, a trend graph of the edge smoothness and the yield with respect to time is obtained; Based on the trend graph, determine the edge flatness value of the wafer stage when the wafer stage is replaced.

2. The method for monitoring the flatness of a wafer stage according to claim 1, characterized in that, The original focal length data includes focal length data corresponding to different radii of the wafer; The step of obtaining the edge flatness curve of the wafer stage based on the original focal length data includes: Extract focal length data with a preset radius from the original focal length data; Based on the focal length data with a preset radius, a curve showing the change of the standard deviation of the focal length over time is obtained; the curve showing the change of the standard deviation of the focal length over time is the edge smoothness curve.

3. The method for monitoring the flatness of a wafer stage according to claim 2, characterized in that, The preset radius range is 0 to 10 mm from the edge of the wafer along the wafer radius.

4. The method for monitoring the flatness of a wafer stage according to claim 1, characterized in that, Determining the edge flatness value of the wafer stage when replacing it based on the trend chart includes: The time point for replacing the wafer workbench is determined based on the time point when the slope of yield versus time in the trend graph reaches the preset slope. The edge smoothness value on the edge smoothness curve is determined based on the time point at which the wafer stage is replaced.

5. The method for monitoring the flatness of a wafer stage according to claim 1, characterized in that, Also includes: The replacement time for the next batch of wafer stages is determined based on the edge flatness value of the wafer stage at the time of replacement.

6. The method for monitoring the flatness of a wafer stage according to claim 4, characterized in that, The preset slope ranges from 0.1 to 0.

5.

7. A device for monitoring the flatness of a wafer stage, characterized in that, include: The acquisition module is used to acquire the wafer yield and the raw focal length data of the wafer detected by the focal length monitor in real time. The processing module is configured to obtain an edge smoothness curve of the wafer stage based on the original focal length data, the edge smoothness curve reflecting the change of the edge smoothness of the wafer stage with respect to time; it is also configured to obtain a yield curve of the wafer based on the wafer yield, the yield curve reflecting the change of the wafer yield with respect to time; and it is also configured to obtain a trend graph of the edge smoothness and the yield with respect to time based on the edge smoothness curve and the yield curve. and The flatness determination module is used to determine the edge flatness value of the wafer stage when the wafer stage is replaced, based on the trend graph.

8. The wafer stage flatness monitoring device according to claim 7, characterized in that, The original focal length data includes focal length data corresponding to different radii of the wafer; The processing module includes: The cropping unit is used to crop the focal length data with a preset radius from the original focal length data; The standard deviation processing unit is used to obtain the standard deviation of the focal length as a function of time based on the focal length data with a preset radius, and the standard deviation of the focal length as a function of time is the edge smoothness curve.

9. The wafer stage flatness monitoring device according to claim 8, characterized in that, The preset radius range is 0 to 10 mm from the edge of the wafer along the wafer radius.

10. The wafer stage flatness monitoring device according to claim 7, characterized in that, The flatness determination module includes: The replacement time determination unit is used to determine the time point for replacing the wafer worktable based on the time point when the slope of yield versus time in the trend graph reaches a preset slope. A flatness determination unit is used to determine the edge flatness value on the edge flatness curve based on the time point at which the wafer stage is replaced.

11. The wafer stage flatness monitoring device according to claim 7, characterized in that, The flatness determination module is also used to determine the replacement time point of the next batch of wafer stages based on the edge flatness value of the wafer stage when the wafer stage is replaced.

12. The wafer stage flatness monitoring device according to claim 10, characterized in that, The preset slope ranges from 0.1 to 0.

5.

13. A wafer stage flatness monitoring system, characterized in that, Includes yield testing equipment, focal length monitor and controller; The yield testing device is used to detect the yield of wafers in real time; The focal length monitor is used to detect the raw focal length data of the wafer in real time; The controller includes a memory and a processor; The memory stores a computer program, and when the processor executes the computer program, it implements the steps of the method as described in any one of claims 1 to 6.

14. The wafer stage flatness monitoring system according to claim 13, characterized in that, The focal length monitor includes a phase shift focal length monitor.

15. A storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the method as described in any one of claims 1 to 6.

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