CMP process monitoring method and semiconductor device

Abstract

The invention provides a monitoring method of a CMP (Chemical Mechanical Polishing) process and semiconductor equipment. According to the monitoring method of the CMP process, an optical detection method is applied, and efficient detection of the effect of the CMP process is achieved. In the detection process, the method comprises the following steps: firstly, simulating a measurement point by adopting an MTD, and screening out a recommended light source; and an overlay error measurement device is adopted to execute actual process verification so as to select a target light source. Based on the target light source after two-stage screening, the measurement point can present different image gray expressions under normal CMP and abnormal CMP. Therefore, by judging the ratio of the first gray-scale value of the overlay mark in the measurement point to the second gray-scale value of the background area, whether the CMP process is abnormal or not can be rapidly detected. According to the method, the semiconductor structure does not need to be damaged, the detection result is accurate, the efficiency is high, the sensitivity is high, and the CMP process effect can be monitored easily.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor manufacturing, and in particular, to a CMP process monitoring method and a semiconductor device. BACKGROUND

[0002] Chemical mechanical polishing (CMP) is one of the key processes in semiconductor manufacturing, which realizes wafer surface planarization through the synergistic effect of chemical corrosion and mechanical polishing. However, in actual process, CMP is prone to over-polishing problems. Over-polishing refers to excessive polishing time, which leads to adverse consequences. These adverse consequences mainly include:

[0003] 1. Material loss: Over-polishing will cause excessive removal of wafer surface material, affecting the thickness and performance of the device.

[0004] 2. Surface defects: Over-polishing will cause scratches, dishing, and other defects on the wafer surface, and increase the roughness of the wafer surface.

[0005] 3. Poor size control: Over-polishing will cause critical dimension (CD) changes, affecting device performance.

[0006] 4. Electrical performance degradation: Over-polishing will expose the underlying material or change the interface characteristics, leading to increased leakage current or capacitance changes.

[0007] Based on the above-mentioned adverse consequences caused by CMP over-polishing problems, the scrap rate is also increased, leading to a decrease in device yield. To this end, the existing technology identifies and determines the over-polishing position point through slice detection. Slice detection requires physical cutting, grinding of the chip, preparation of cross-section samples, and then microscopic observation and data analysis to obtain the detection results. This process not only destroys the chip structure, but also takes a long time and is low in efficiency. It can only be used for offline analysis or failure troubleshooting, and cannot meet the rapid feedback requirements in mass production scenarios.

[0008] Therefore, there is an urgent need for a new CMP over-polishing detection method to solve the above technical problems. SUMMARY

[0009] The present application aims to provide a CMP process monitoring method and a semiconductor device to solve at least one of the problems of how to efficiently detect the process effect of the CMP process and how to monitor the process effect of the CMP process.

[0010] To solve the above technical problems, the present application provides a CMP process monitoring method, comprising:

[0011] Step 1: Use MTD simulation to select recommended light sources;

[0012] Step 2: Verify each of the recommended light sources using an overlay error measurement device, and select the target light source;

[0013] Step 3: Provide a measurement point on a semiconductor film layer; wherein the semiconductor film layer has undergone CMP process, and the measurement point includes an overlay mark and a background area around the overlay mark;

[0014] Step 4: Using the overlay error measurement device and the target light source, measure and obtain the first grayscale value of the overlay mark and the second grayscale value of the background area;

[0015] Step 5: Determine whether the ratio of the first grayscale value to the second grayscale value is within the threshold range; if yes, the CMP process performed at the measurement point is normal; if no, the CMP process performed at the measurement point is abnormal, record the location of the measurement point and issue an alarm.

[0016] Optionally, in the CMP process monitoring method, step one includes:

[0017] Sub-step 1: Establish a first measurement point model and a second measurement point model using MTD; wherein, the first measurement point model is used to simulate the measurement point whose thickness is removed by CMP process and conforms to the grinding specifications, and the second measurement point model is used to simulate the measurement point whose thickness is removed by CMP process and exceeds the grinding specifications.

[0018] Sub-step two: Provide multiple alternative light sources; and at least one optical parameter differs between each of the alternative light sources;

[0019] Sub-step 3: Using one of the alternative light sources described above, the MTD application measures the first measurement point model and the second measurement point model, and obtains the first measurement data and the second measurement data respectively;

[0020] Sub-step four: Determine whether the first measurement data and the second measurement data meet the first screening condition. If yes, the candidate light source belongs to the recommended light source; if no, the candidate light source does not belong to the recommended light source.

[0021] Sub-step five: Replace with another candidate light source and repeat sub-steps three through five until all candidate light sources have passed the first screening condition and the screening ends;

[0022] Sub-step six: Determine whether the number of recommended light sources is zero; if yes, execute sub-step two and provide multiple alternative light sources again; if no, execute step two.

[0023] Optionally, in the monitoring method of the CMP process, in sub-step one, the first measurement point model includes a first simulated marker and a first simulated background area around the first simulated marker; the second measurement point model includes a second simulated marker and a second simulated background area around the second simulated marker.

[0024] In sub-step three, the first measurement data includes the grayscale value of the first simulated marker and the grayscale value of the first simulated background region; the second measurement data includes the grayscale value of the second simulated marker and the grayscale value of the second simulated background region; and,

[0025] In sub-step four, the first screening condition includes:

[0026] The grayscale value of the first simulated marker is higher than that of the first simulated background area; and the grayscale value of the second simulated marker is lower than that of the second simulated background area.

[0027] Optionally, in the monitoring method of the CMP process, in sub-step two, the optical parameters include optical wavelength and optical bandwidth; and focal length, numerical aperture and polarization mode configured in the overlay error measuring device.

[0028] Optionally, in the monitoring method for the CMP process, among the candidate light sources, the wavelength range includes 400nm~800nm, with a step size of 10nm; the bandwidth range includes 30nm, 60nm, and 90nm; the focal length range includes 0µm~2µm, with a step size of 100nm; the polarization mode includes S-polarization, P-polarization, and Un-polarization; and,

[0029] The target light source has a wavelength range of 550nm to 610nm and is S-polarized.

[0030] Optionally, in the CMP process monitoring method, step two includes:

[0031] A first test measurement point and a second test measurement point are provided on a test wafer, wherein the thickness of the first test measurement point removed by CMP grinding meets the grinding specifications, and the thickness of the second test measurement point removed by CMP grinding exceeds the grinding specifications.

[0032] The overlay error measurement device is used to apply each of the recommended light sources one by one, and the first test measurement point and the second test measurement point are measured to select the recommended light source that meets the second screening criteria as the target light source; and,

[0033] If none of the recommended light sources meet the second screening criteria, step one is performed to re-screen the recommended light sources using MTD simulation.

[0034] Optionally, in the CMP process monitoring method, the first test measurement point includes a first test mark and a first test background area surrounding the first test mark; the first test measurement point includes a second test mark and a second test background area surrounding the second test mark.

[0035] And, the second screening criteria include:

[0036] The grayscale value of the first test marker is higher than that of the first test background area; and the grayscale value of the second test marker is lower than that of the second test background area.

[0037] Optionally, in the monitoring method for the CMP process, the threshold range in step five includes: greater than or equal to 1.

[0038] Optionally, in the CMP process monitoring method, after performing step five, the CMP process monitoring method further includes:

[0039] Determine whether all the measurement points on the semiconductor film have undergone CMP process detection;

[0040] If not, proceed to step three to switch to the next measurement point for CMP process testing;

[0041] If so, determine whether to replace the semiconductor film layer; if not, end the monitoring of the CMP process; if so, proceed to step one.

[0042] Based on the same inventive concept, the present invention also provides a semiconductor device, including: a processor, a memory, and a program or instructions stored in the memory and executable on the processor, wherein the program or instructions, when executed by the processor, implement the monitoring method of the CMP process.

[0043] In summary, this invention provides a monitoring method and semiconductor device for CMP processes. Compared to existing technologies, the CMP process monitoring method utilizes optical detection to achieve efficient detection of CMP process effects. Specifically, during the detection process, the method first uses an MTD (Measuring Device to Analyze) to simulate measurement points and select recommended light sources; then, an overlay error measurement device is used to perform actual process verification to select a target light source. Based on the target light source selected through these two stages, the measurement points exhibit different image grayscale representations under normal and abnormal CMP conditions. Therefore, by determining the ratio of the first grayscale value of the overlay mark in the measurement point to the second grayscale value of the background area, rapid detection of CMP process abnormalities can be achieved. This method does not damage the semiconductor structure, and the detection results are accurate, efficient, and sensitive, facilitating the monitoring of CMP process effects. Attached Figure Description

[0044] Those skilled in the art will understand that the accompanying drawings are provided to better understand the invention and do not constitute any limitation on the scope of the invention.

[0045] Figure 1 This is a flowchart of the monitoring method for the CMP process in an embodiment of the present invention.

[0046] Figure 2 This is a cross-sectional schematic diagram of the first measurement point model and the second measurement point model in an embodiment of the present invention.

[0047] Figure 3 This is a planar schematic diagram of the first measurement point model and the second measurement point model in an embodiment of the present invention.

[0048] Figure 4 This is an optical measurement diagram of the first measurement point model in this embodiment of the invention.

[0049] Figure 5 This is a curve distribution diagram of grayscale value-distance between the first simulated marker and the first simulated background area in an embodiment of the present invention.

[0050] Figure 6 This is an optical measurement diagram of the second measurement point model in this embodiment of the invention.

[0051] Figure 7 This is a curve distribution diagram of grayscale values ​​and distances of the second simulated marker and the second simulated background region in an embodiment of the present invention.

[0052] Figure 8 This is a planar schematic diagram of the first test measurement point and the second test measurement point in an embodiment of the present invention.

[0053] Figure 9 This is a planar schematic diagram of the measurement points of the semiconductor film layer in an embodiment of the present invention.

[0054] And, in the attached image:

[0055] 11-First measurement point model; 110-First simulated stacked film layer; 111-First simulated marker; 112-First simulated background region;

[0056] 12-Second measurement point model; 120-Second simulated stacked film layer; 121-Second simulated marker; 122-Second simulated background region;

[0057] 21-First test measurement point; 211-First test mark; 212-First test background area;

[0058] 22-Second test measurement point; 221-Second test mark; 222-Second test background area;

[0059] 31 - Measurement point on semiconductor film; 311 - Overlay mark; 312 - Background area around overlay mark. Detailed Implementation

[0060] To make the objectives, advantages, and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are not drawn to scale, and are only used to facilitate and clearly illustrate the objectives of the embodiments of the present invention. Furthermore, the structures shown in the drawings are often part of the actual structure. In particular, different figures may have different focuses and sometimes use different scales. It should also be understood that, unless specifically stated or indicated, the terms "first," "second," "third," etc., in the specification are only used to distinguish various components, elements, steps, etc., in the specification, and are not used to indicate logical or sequential relationships between various components, elements, steps, etc. Also, the X-axis, Y-axis, and Z-axis directions referred to in this application specification are three mutually perpendicular directions in three-dimensional space.

[0061] Please see Figure 1 This embodiment provides a method for monitoring CMP process, including:

[0062] Step 1 S10: Use MTD simulation to select recommended light sources;

[0063] Step 2 S20: Verify each of the recommended light sources using an overlay error measurement device, and select the target light source;

[0064] Step 3 S30: Provide a measurement point on a semiconductor film layer; wherein the semiconductor film layer has undergone CMP process, and the measurement point includes an overlay mark and a background area around the overlay mark;

[0065] Step 4S40: Using the overlay error measuring device and the target light source, measure and obtain the first grayscale value of the overlay mark and the second grayscale value of the background area;

[0066] Step 5 S50: Determine whether the ratio of the first grayscale value to the second grayscale value is within the threshold range; if yes, the CMP process performed at the measurement point is normal; if no, the CMP process performed at the measurement point is abnormal, record the location of the measurement point and issue an alarm.

[0067] Based on this, the CMP process monitoring method provided in this embodiment first uses MTD to simulate measurement points and screen out recommended light sources; then, it uses an overlay error measurement device to perform actual process verification to select a target light source. The target light source, after two levels of screening, enables the measurement points to exhibit different image grayscale representations under normal and abnormal CMP conditions. Therefore, by determining the ratio of the first grayscale value of the overlay mark in the measurement point to the second grayscale value of the background area, rapid detection of CMP process abnormalities can be achieved with accurate results, facilitating the monitoring of CMP process effectiveness.

[0068] The monitoring method for the CMP process provided in this embodiment is described in detail below with reference to the accompanying drawings.

[0069] Specifically, the monitoring method for the CMP process includes:

[0070] Step 1 S10: Use MTD simulation to select recommended light sources;

[0071] It should be noted that Measurement Target Design (MTD) is a core simulation and optimization tool in the field of semiconductor lithography and metrology. MTD is mainly designed for specific wafer film stacks, using algorithms such as FDTD and RCWA to simulate different target parameters and optimize the design of measurement patterns such as overlay marks (OVL marks).

[0072] Based on this, please refer to Figures 2 to 7 The specific process of selecting recommended light sources using MTD simulation includes:

[0073] Sub-step one: such as Figure 2 and Figure 3 As shown, a first measurement point model 11 and a second measurement point model 12 are established using MTD; wherein, the first measurement point model 11 is used to simulate the measurement point whose thickness meets the grinding specifications after being removed by CMP grinding process, and the second measurement point model 12 is used to simulate the measurement point whose thickness exceeds the grinding specifications after being removed by CMP grinding process.

[0074] It is understood that both the first measurement point model 11 and the second measurement point model 12 are model structures simulated by MTD based on actual process products. For example, ... Figure 2 The first measurement point model 11 shown includes a first simulated stacked film layer 110 and a first simulated mark 111 formed on the first simulated stacked film layer 110; the second measurement point model 12 includes a second simulated stacked film layer 120 and a second simulated mark 12 formed on the second simulated stacked film layer 120. The specific stacked film layers within the first simulated stacked film layer 110 and the second simulated stacked film layer 120 are the same and consistent with the actual process product. The first simulated mark 111 and the second simulated mark 121 are used to simulate the outer bar. Furthermore, the heights of the first simulated mark 111 and the second simulated mark 121 are different, used to simulate the state of the outer bar after normal CMP polishing and the state of the outer bar after abnormal CMP polishing. Specifically, the first simulated mark 111 corresponds to a thickness removed after normal CMP polishing that meets the polishing specifications; the second simulated mark 121 corresponds to a thickness removed after abnormal CMP polishing that exceeds the polishing specifications; that is, an over-polishing problem occurs.

[0075] exist Figure 3 In the schematic diagram shown, the top surface of the first simulated stacked film layer 110 surrounds the first simulated mark 111 to serve as the first simulated background region 112; the top surface of the second simulated stacked film layer 120 surrounds the second simulated mark 121 to serve as the second simulated background region 122. No other marking structures are provided in the first simulated background region 112 and the second simulated background region 122.

[0076] Sub-step two: Provide multiple alternative light sources; and at least one optical parameter is different among the alternative light sources.

[0077] The CMP process monitoring method provided in this embodiment employs optical imaging detection to quickly identify whether the CMP process is abnormal. Therefore, the light source used in this method must illuminate the overlay marks corresponding to normal and abnormal CMP processes, resulting in a clear difference in the image.

[0078] To obtain the required light source, multiple alternative light sources need to be prepared in advance, and a series of screening and verification processes are required to determine the final target light source to ensure optimal monitoring efficiency and effect. Among these alternative light sources, at least one optical parameter differs, and these optical parameters include, but are not limited to: the light wavelength and wavelength width of the light source; and the focal length, numerical aperture, and polarization mode configured in the overlay error measurement device. Optionally, the optical parameters of the alternative light sources are: wavelength range of 400nm~800nm ​​with a step size of 10nm; wavelength width range of 30nm, 60nm, and 90nm; focal length range of 0µm~2µm with a step size of 100nm; polarization modes including S-polarization, P-polarization, and Un-polarization; and, according to the division within the overlay error measurement device, the numerical aperture can be divided into three different levels: high, medium, and low. For example, three alternative light sources are provided: the first alternative light source has a wavelength of 430nm~460nm, a focal length of 1µm, and S-polarization. The second alternative light source has a wavelength of 550nm~610nm, a focal length of 1µm, and is S-polarized. The third alternative light source has a wavelength of 550nm~610nm, a focal length of 1.5µm, and is S-polarized.

[0079] Sub-step 3: Using one of the alternative light sources described above, the MTD application measures the first measurement point model 11 and the second measurement point model 12, and obtains the first measurement data and the second measurement data respectively.

[0080] To select suitable recommended light sources, each of the candidate light sources needs to be applied one by one using MTD to simulate the scene of measurement points illuminated by real light sources. The first measurement point model 11 and the second measurement point model 12 are measured to obtain first measurement data and second measurement data, respectively. The first measurement data includes the grayscale value of the first simulated marker 111 and the grayscale value of the first simulated background region 112; the second measurement data includes the grayscale value of the second simulated marker 121 and the grayscale value of the second simulated background region 122.

[0081] It should be noted that the grayscale value is a numerical indicator that quantifies the brightness of image pixels. In an 8-bit image, the grayscale value ranges from 0 to 255, where 0 represents pure black, 255 represents pure white, and intermediate values ​​correspond to different shades of gray. A higher grayscale value indicates a brighter pixel or region, and vice versa.

[0082] Sub-step four: Determine whether the first measurement data and the second measurement data meet the first screening criteria. If yes, the candidate light source belongs to the recommended light source; if no, the candidate light source does not belong to the recommended light source.

[0083] It should be noted that the first simulated mark 111 is used to simulate the overlay mark after normal CMP grinding. Normal CMP is used to enhance the flatness and smoothness of the film surface; therefore, under illumination, the first simulated mark 111 has high reflectivity and, under certain diffraction, can exhibit high brightness; that is, a large grayscale value. For example... Figure 4 As shown, the white line within the red box represents the first simulated marker 111, which exhibits a very noticeable brightness difference compared to the surrounding background area. Also, as... Figure 5 As shown in the grayscale value distribution curve, the grayscale value of the first simulated marker 111 is also significantly greater than the grayscale value of the first simulated background area 112.

[0084] The second simulated mark 121 is used to simulate the overlay mark after abnormal CMP polishing. Excessive polishing in the abnormal CMP process leads to a rough film surface, resulting in low surface reflectivity under illumination. Consequently, the brightness of the second simulated mark 121 is low, i.e., its grayscale value is small. Figure 6 As shown, the black line within the red box represents the second simulated marker 121, and the brightness of the second simulated marker 121 is significantly lower than the brightness of the surrounding background area. Also, as... Figure 7 As shown in the grayscale value distribution curve, the grayscale value of the second simulated marker 121 is also significantly smaller than the grayscale value of the second simulated background area 122.

[0085] Based on the above analysis, the recommended light source needs to cause the grayscale values ​​of the first simulated marker 111 and the second simulated marker 121 to show opposite trends. Therefore, in this embodiment, the first screening condition includes: the grayscale value of the first simulated marker 111 is higher than the grayscale value of the first simulated background region 112; and the grayscale value of the second simulated marker 121 is lower than the grayscale value of the second simulated background region 122. When the candidate light source meets this condition, it can be used as the recommended light source; when it does not meet this condition, it cannot be used as the recommended light source and is excluded.

[0086] Sub-step five: Replace with another candidate light source, and repeat sub-steps three through five until all candidate light sources have passed the first screening condition and the screening ends.

[0087] That is, the first screening condition needs to be applied to each of the candidate light sources. If all the candidate light sources have been screened, the screening process can end. However, after the screening ends, there may be a situation where none of the candidate light sources meet the first screening condition. Therefore, sub-step six needs to be performed after the screening ends.

[0088] Sub-step six: Determine whether the number of recommended light sources is zero; if so, execute sub-step two, and provide multiple alternative light sources again, and repeat the above screening process until the recommended light source is selected; if not, execute step two S20.

[0089] Step 2 S20: Verify each of the recommended light sources using an overlay error measurement device, and select the target light source.

[0090] Since the recommended light source in step S10 is selected using MTD simulation, in order to verify the effectiveness of the recommended light source, it is necessary to perform actual measurements in the actual process equipment to further select target light sources that meet the monitoring method requirements of the CMP process.

[0091] Specifically, the verification and screening process in step two S20 includes:

[0092] like Figure 3 and Figure 8 As shown, a first test measurement point 21 and a second test measurement point 22 are provided on a test wafer. The thickness of the first test measurement point 21 removed by CMP grinding conforms to the grinding specifications, while the thickness of the second test measurement point 22 removed by CMP grinding exceeds the grinding specifications. That is, the first test measurement point 21 serves as the actual semiconductor structure of the first measurement point model 11, and the second test measurement point 22 serves as the actual semiconductor structure of the second measurement point model 12. Therefore, the first test measurement point 21 includes a first test mark 211 and a first test background region 212 surrounding the first test mark 211. The first test mark 211 corresponds to the first simulated mark 111 in the first measurement point model 11, and the first test background region 212 corresponds to the first simulated background region 112 in the first measurement point model 11. The first test measurement point 22 includes a second test mark 221 and a second test background region 222 surrounding the second test mark 221. Furthermore, the second test mark 221 corresponds to the second simulation mark 121 in the second measurement point model 12, and the second test background area 222 corresponds to the second simulation background area 122 in the second measurement point model 12.

[0093] Subsequently, the overlay error measurement device is used to apply each of the recommended light sources one by one, and the first test measurement point 21 and the second test measurement point 22 are measured to select the recommended light source that meets the second screening criteria as the target light source. During the measurement of the first test measurement point 21 and the second test measurement point 22, the grayscale values ​​of the first test mark 211, the first test background area 212, the second test mark 221, and the second test background area 222 are obtained respectively. Furthermore, based on the optical imaging principle described in sub-step four, the second screening criteria include that the grayscale value of the first test mark 211 is higher than the grayscale value of the first test background area 212; and the grayscale value of the second test mark 221 is lower than the grayscale value of the second test background area 222.

[0094] When the recommended light source meets the second screening condition, it indicates that the recommended light source meets the monitoring requirements of the CMP process under both simulated and real-world conditions, and therefore can be used as the target light source. For example, the target light source has a wavelength range of 550nm to 610nm, is S-polarized, has a low numerical aperture, and is single-grab focused.

[0095] It should be noted that if all the recommended light sources fail to meet the second screening criteria after being screened, it indicates that these recommended light sources are not applicable in the actual process, and some alternative light sources need to be provided before proceeding to step one, S10. When multiple recommended light sources meet the second screening criteria, one can be randomly selected as the target light source to proceed to step three, S30.

[0096] Step 3 S30: Please refer to Figure 9 A measurement point 31 is provided on a semiconductor film layer; wherein the semiconductor film layer has undergone CMP process, and the measurement point 31 includes an overlay mark 311 and a background area 312 surrounding the overlay mark 311.

[0097] The semiconductor film layer forms the basis for the simulation model in step S10 and the design basis for the test wafer in step S20. Therefore, the stacked films within the semiconductor film layer are consistent with the stacked films in the simulation model in step S10 and the test wafer in step S20. The overlay mark 311 is a dedicated reference pattern used in photolithography to achieve precise alignment of different layer patterns. In actual CMP processes, in addition to the device layers on the semiconductor film layer, the overlay mark 311 is also simultaneously polished, thus characterizing the actual CMP process conditions. Therefore, in this embodiment, the overlay mark 311 is used as a measurement object to monitor whether the CMP process is abnormal, and the background area 312 surrounding the overlay mark 311 is another measurement object.

[0098] Step 4S40: Using the overlay error measurement device and the target light source, measure and obtain the first grayscale value of the overlay mark 311 and the second grayscale value of the background area 312.

[0099] Since the target light source is a light source selected through two levels of screening in steps S10 and S20, when the CMP is normal or abnormal, the first grayscale value of the overlay mark 311 and the second grayscale value of the background area 312 will show different differences.

[0100] Step 5 S50: Determine whether the ratio of the first grayscale value to the second grayscale value is within the threshold range; if yes, the CMP process performed by the measurement point 31 is normal; if no, the CMP process performed by the measurement point 31 is abnormal, record the position of the measurement point 31 and issue an alarm.

[0101] The threshold range varies depending on the semiconductor film layer or product structure. Furthermore, the threshold range can be dynamically adjusted by combining process specifications and historical data to adapt to process fluctuations. For example, the threshold range includes values ​​greater than or equal to 1. Therefore, when the ratio of the first grayscale value to the second grayscale value is greater than or equal to 1, it indicates that the first grayscale value of the overlay mark 311 is greater than the second grayscale value of the background area 312, and the brightness of the overlay mark 311 is higher than that of the background area 312. In this case, the CMP process performed at the measurement point 31 is considered normal. When the ratio of the first grayscale value to the second grayscale value is less than 1, it indicates that the first grayscale value of the overlay mark 311 is less than the second grayscale value of the background area 312, and the brightness of the overlay mark 311 is lower than that of the background area 312. In this case, the CMP process performed at the measurement point 31 is considered abnormal, indicating an over-scraping problem. For measurement points 31 with CMP process abnormalities, their coordinate positions need to be recorded, and an alarm needs to be issued to promptly notify the process engineer.

[0102] Therefore, the CMP process monitoring method provided in this embodiment does not require slicing to destroy the semiconductor structure to detect the process status. Instead, it uses a target light source selected by double-layer screening to obtain the difference in gray values ​​between the overlay mark 311 and the background area 312 in the measurement point 31, which characterizes whether the CMP process is abnormal. The detection results are not only accurate, but the detection operation is also convenient and efficient, and it can realize the monitoring of the CMP process effect.

[0103] Furthermore, since steps three (S30) to five (S50) are for detecting one measurement point 31 on the semiconductor film layer, and the target light source is selected based on the semiconductor film layer, the target light source can also be used to detect other measurement points on the semiconductor film layer. Therefore, after executing step five (S50), the CMP process monitoring method further includes: determining whether all measurement points on the semiconductor film layer have been detected using the CMP process; if not, executing step three (S30) to switch to the next measurement point for CMP process detection, until all measurement points on the semiconductor film layer are detected; if yes, determining whether to replace the semiconductor film layer; if no, ending the CMP process monitoring; if yes, executing step one (S10). It can be understood that the target light source is selected based on the semiconductor film layer. If the semiconductor film layer is replaced, the target light source needs to be re-selected to match the new semiconductor film layer.

[0104] Based on the same concept, this embodiment also provides a semiconductor device, including: a processor, a memory, and a program or instructions stored in the memory and executable on the processor, wherein the program or instructions, when executed by the processor, implement the above-described monitoring method for the CMP process.

[0105] In summary, this embodiment provides a method and semiconductor device for monitoring CMP processes. The monitoring method utilizes optical detection techniques to achieve efficient detection of CMP process effects. During the detection process, the method first uses an MTD (Measuring Device to Analyze) to simulate measurement points and select recommended light sources; then, an overlay error measurement device is used to perform actual process verification to select a target light source. Based on the target light source selected through these two stages, the measurement points exhibit different image grayscale representations under normal and abnormal CMP conditions. Therefore, by determining the ratio of the first grayscale value of the overlay mark in the measurement point to the second grayscale value of the background area, rapid detection of CMP process abnormalities can be achieved. This method does not damage the semiconductor structure, and the detection results are accurate, efficient, and sensitive, facilitating the monitoring of CMP process effects.

[0106] Furthermore, it should be 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 scope of protection of the present invention.

Claims

1. A monitoring method for CMP process, characterized in that, include: Step 1: Use MTD simulation to select recommended light sources; Step 2: Verify each of the recommended light sources using an overlay error measurement device, and select the target light source; Step 3: Provide a measurement point on a semiconductor film layer; wherein the semiconductor film layer has undergone CMP process, and the measurement point includes an overlay mark and a background area around the overlay mark; Step 4: Using the overlay error measurement device and the target light source, measure and obtain the first grayscale value of the overlay mark and the second grayscale value of the background area; Step 5: Determine whether the ratio of the first grayscale value to the second grayscale value is within the threshold range; if yes, the CMP process performed at the measurement point is normal; if no, the CMP process performed at the measurement point is abnormal, record the location of the measurement point and issue an alarm.

2. The monitoring method for CMP process according to claim 1, characterized in that, The process of step one includes: Sub-step 1: Establish a first measurement point model and a second measurement point model using MTD; wherein, the first measurement point model is used to simulate the measurement point whose thickness is removed by CMP process and conforms to the grinding specifications, and the second measurement point model is used to simulate the measurement point whose thickness is removed by CMP process and exceeds the grinding specifications. Sub-step two: Provide multiple alternative light sources; and at least one optical parameter differs between each of the alternative light sources; Sub-step 3: Using one of the alternative light sources described above, the MTD application measures the first measurement point model and the second measurement point model, and obtains the first measurement data and the second measurement data respectively; Sub-step four: Determine whether the first measurement data and the second measurement data meet the first screening condition. If yes, the candidate light source belongs to the recommended light source; if no, the candidate light source does not belong to the recommended light source. Sub-step five: Replace with another candidate light source and repeat sub-steps three through five until all candidate light sources have passed the first screening condition and the screening ends; Sub-step six: Determine whether the number of recommended light sources is zero; if yes, execute sub-step two and provide multiple alternative light sources again; if no, execute step two.

3. The monitoring method for CMP process according to claim 2, characterized in that, In the first sub-step, the first measurement point model includes a first simulated marker and a first simulated background region surrounding the first simulated marker; the second measurement point model includes a second simulated marker and a second simulated background region surrounding the second simulated marker. In the third sub-step, the first measurement data includes the grayscale value of the first simulated marker and the grayscale value of the first simulated background area; the second measurement data includes the grayscale value of the second simulated marker and the grayscale value of the second simulated background area. as well as, In sub-step four, the first screening condition includes: The grayscale value of the first simulated marker is higher than the grayscale value of the first simulated background area; Furthermore, the grayscale value of the second simulated marker is lower than the grayscale value of the second simulated background area.

4. The monitoring method for CMP process according to claim 2, characterized in that, In the second sub-step, the optical parameters include the light wavelength and light width; and the focal length, numerical aperture, and polarization mode configured in the overlay error measuring device.

5. The monitoring method for CMP process according to claim 2 or 4, characterized in that, Among the candidate light sources, the wavelength range includes 400nm to 800nm, with a step size of 10nm; the bandwidth range includes 30nm, 60nm, and 90nm; the focal length range includes 0µm to 2µm, with a step size of 100nm; the polarization mode includes S-polarization, P-polarization, and Un-polarization; and, The target light source has a wavelength range of 550nm to 610nm and is S-polarized.

6. The monitoring method for CMP process according to claim 1, characterized in that, The process of step two includes: A first test measurement point and a second test measurement point are provided on a test wafer, wherein the thickness of the first test measurement point removed by CMP grinding meets the grinding specifications, and the thickness of the second test measurement point removed by CMP grinding exceeds the grinding specifications. The overlay error measurement device is used to apply each of the recommended light sources one by one, and the first test measurement point and the second test measurement point are measured to select the recommended light source that meets the second screening criteria as the target light source; and, If none of the recommended light sources meet the second screening criteria, step one is performed to re-screen the recommended light sources using MTD simulation.

7. The monitoring method for CMP process according to claim 6, characterized in that, The first test measurement point includes a first test marker and a first test background area surrounding the first test marker; The first test measurement point includes a second test marker and a second test background area surrounding the second test marker; And, the second screening criteria include: The grayscale value of the first test marker is higher than the grayscale value of the first test background area; Furthermore, the grayscale value of the second test marker is lower than the grayscale value of the second test background area.

8. The monitoring method for CMP process according to claim 1, characterized in that, The threshold range in step five includes: greater than or equal to 1.

9. The monitoring method for CMP process according to claim 1, characterized in that, After performing step five, the monitoring method for the CMP process further includes: Determine whether all the measurement points on the semiconductor film have undergone CMP process detection; If not, proceed to step three to switch to the next measurement point for CMP process testing; If so, determine whether to replace the semiconductor film layer; if not, end the monitoring of the CMP process; if so, proceed to step one.

10. A semiconductor device, characterized in that, include: A processor, a memory, and a program or instructions stored in the memory and executable on the processor, wherein the program or instructions, when executed by the processor, implement the monitoring method for the CMP process as described in any one of claims 1 to 9.

Images