A method and related equipment for measuring wafer surface properties based on ellipsometry

Abstract

The application provides a kind of ellipsometer-based wafer surface property measurement method and related equipment, it is related to ellipsometer measurement technical field.The method includes the following steps: selecting any one measurement point as a reference point from the wafer surface to be measured;For other measurement points except the reference point, determine the focusing height adjustment amount of each measurement point according to the reference point, and calculate the best focusing height corresponding to each measurement point based on the focusing height adjustment amount;According to the best focusing height corresponding to each measurement point, the ellipsometric light dispersion curve of each measurement point is measured, and the film properties of each measurement point are analyzed based on the ellipsometric light dispersion curve.The method of the application aims to solve the problem that the existing measurement method cannot simultaneously consider measurement efficiency and accuracy, can reduce the total time of focusing process, improve the focusing efficiency, and consider the focusing accuracy.

Description

Technical Field

[0001] This invention relates to the field of ellipsometer measurement technology, and more specifically, to a method and related equipment for measuring the surface properties of wafers based on an ellipsometer. Background Technology

[0002] Ellipsometry is a commonly used characterization instrument for thin films. It can characterize physical quantities such as thickness, optical constants, and microstructure of transparent or semi-transparent thin films. It offers advantages such as speed, accuracy, and non-destructive operation, and can characterize a wide range of thin film materials, including semiconductors, dielectrics, polymers, organic materials, and metals. The basic principle of ellipsometric characterization of thin film properties is that after ellipsometric light is reflected from the sample surface, the amplitude and phase of the ellipsometric light change. By establishing an optical model and analyzing the changes in the properties of the ellipsometric light, information such as the thickness and optical constants of the thin film can be obtained. Before formally measuring the thin film, the ellipsometer needs to be focused to maximize the intensity of the reflected light entering the detector (ensuring the reflected light is directly in the center of the detector). This improves signal quality and measurement accuracy. Defocusing leads to a decrease in the intensity of the reflected light entering the detector, resulting in poor signal quality, low measurement accuracy, and unreliable results. Therefore, focusing is a crucial step affecting the measurement accuracy of the ellipsometer.

[0003] For large-size semiconductor wafers, it is often necessary to characterize the thin film properties at multiple measurement points to obtain information such as the spatial uniformity of the thin film properties. The wafer surface is not an ideally flat surface but has certain height variations, which causes the optimal focusing height to differ at different measurement points. Existing measurement methods include focusing on all measurement points; while this method offers the highest measurement accuracy, the total focusing time is excessively long. Another method involves focusing on only one point and using its optimal focusing height as the optimal focusing height for other measurement points. Although this method significantly reduces the total focusing time, it sacrifices measurement accuracy, especially when the wafer surface has poor flatness. This can lead to severe data distortion at some measurement points, or even make it impossible to analyze the thin film properties.

[0004] Therefore, the focusing method of ellipsometers still needs further improvement in order to effectively increase measurement efficiency, reduce time costs, and at the same time take into account measurement accuracy. Summary of the Invention

[0005] The purpose of this invention is to provide a wafer surface property measurement method and related equipment based on an ellipsomerometer, which aims to solve the problem that existing measurement methods cannot simultaneously achieve both measurement efficiency and accuracy, thereby reducing the total focusing time, improving focusing efficiency, and balancing focusing accuracy.

[0006] In a first aspect, the present invention provides a method for measuring the surface properties of a wafer based on an ellipsometry, comprising the following steps:

[0007] Select any measurement point on the surface of the wafer to be measured as a reference point;

[0008] For measurement points other than the reference point, the focus height adjustment amount for each measurement point is determined based on the reference point, and the optimal focus height for each measurement point is calculated based on the focus height adjustment amount.

[0009] Based on the optimal focusing height corresponding to each measurement point, the ellipsometric dispersion curve of each measurement point is obtained, and the thin film properties of each measurement point are analyzed based on the ellipsometric dispersion curve.

[0010] The wafer surface property measurement method based on ellipsometry provided by this invention can effectively solve the problem of difficulty in balancing measurement efficiency and measurement accuracy in the prior art, and significantly improve measurement efficiency while ensuring measurement accuracy.

[0011] Furthermore, for measurement points other than the reference point, the steps of determining the focus height adjustment amount for each measurement point based on the reference point, and calculating the optimal focus height for each measurement point based on the focus height adjustment amount, include:

[0012] A1. Based on the reference point, a standard focusing method is used to obtain the relationship between the reflected light intensity and the focusing height, and the optimal focusing height of the reference point is measured and used as the reference height;

[0013] A2. For measurement points other than the reference point, the reflected light intensity corresponding to each measurement point is measured based on the reference height;

[0014] A3. Based on the aforementioned relationship, calculate the focus height adjustment amount for each measurement point according to the reflected light intensity at each measurement point;

[0015] A4. Determine the focusing height adjustment direction for each measurement point, and based on the focusing height adjustment direction, obtain the optimal focusing height for each measurement point according to the focusing height adjustment amount corresponding to each measurement point.

[0016] This not only significantly reduces the time required for focusing and lowers the overall measurement cost, but also avoids measurement errors caused by inaccurate focusing due to the optimization of the focusing process, thereby ensuring the measurement quality of the ellipsometric dispersion curve and the reliability of subsequent thin film property analysis.

[0017] Furthermore, for measurement points other than the reference point, the steps of determining the focus height adjustment amount for each measurement point based on the reference point, and calculating the optimal focus height for each measurement point based on the focus height adjustment amount, include:

[0018] B1. Based on the reference point, a standard focusing method is used to obtain the optimal focusing height of the reference point and use it as the reference height;

[0019] B2. Based on the reference height, the ellipsoidal dispersion curve of the reference point is measured;

[0020] B3. For other measurement points besides the reference point, the ellipsoidal dispersion curves corresponding to each measurement point are obtained based on the reference height.

[0021] B4. Based on the ellipsoidal dispersion curve of the reference point, evaluate the noise level of the corresponding ellipsoidal dispersion curve of each measurement point, and obtain the noise evaluation statistics for each measurement point.

[0022] B5. Based on the noise assessment statistics corresponding to each measurement point, and using a preset threshold, determine the measurement points that require adjustment of the focus height and use them as target points;

[0023] B6. Calculate the focus height adjustment amount corresponding to each target point, and calculate the optimal focus height for each target point based on the focus height adjustment amount.

[0024] This significantly improves the accuracy and reliability of focusing, thereby ensuring the precision of subsequent thin film property analysis. Furthermore, since fine focusing is performed only on the measurement points that require adjustment, the time-consuming operation of repeatedly focusing on all points is avoided, thus improving the overall efficiency of the measurement process.

[0025] Furthermore, the specific steps in step B4 include:

[0026] B41. Denoise the ellipsoidal dispersion curve of the reference point to obtain the processed ellipsoidal dispersion curve of the reference point;

[0027] B42. Using the least squares method, evaluate the deviation of the corresponding ellipsoidal dispersion curve of each measurement point from the processed ellipsoidal dispersion curve of the reference point, and use this deviation as the noise level.

[0028] B43. Normalize the noise level to obtain the normalized root mean square error, which is then used as the noise evaluation statistic.

[0029] Further denoising processes include using Fourier transform, wavelet transform, moving average, local weighted regression, or Savitzky-Golay smoothing.

[0030] Furthermore, for measurement points other than the reference point, the steps of determining the focus height adjustment amount for each measurement point based on the reference point, and calculating the optimal focus height for each measurement point based on the focus height adjustment amount, include:

[0031] C1. Obtain the surface profile data of the wafer to be measured;

[0032] C2. Based on the reference point, a standard focusing method is used to obtain the optimal focusing height of the reference point and use it as the reference height;

[0033] C3. For measurement points other than the reference point, calculate the focus height adjustment amount corresponding to each measurement point based on the reference height and the surface data;

[0034] C4. Based on the adjustment amount of the focusing height corresponding to each measurement point, obtain the optimal focusing height for each measurement point.

[0035] This predictive adjustment based on surface data enables the ellipsometer to quickly adjust the focus position to near the optimal focus height for each measurement point, thereby significantly reducing the time and steps required for focusing.

[0036] Furthermore, the specific steps in step C1 include:

[0037] C11. Select multiple test points on the surface of the wafer to be measured and calculate the focus height adjustment amount corresponding to each test point;

[0038] C12. Based on a preset polynomial, the fitting coefficients corresponding to each test point are calculated according to the focus height adjustment amount and position coordinates of each test point in the preset polynomial.

[0039] C13. Determine the functional relationship between the position coordinates of each location on the surface of the wafer to be measured and the focusing height adjustment amount based on the fitting coefficients;

[0040] C14. Obtain the surface profile data of the wafer to be measured based on the aforementioned functional relationship.

[0041] Secondly, the present invention provides a wafer surface property measurement device based on an ellipsomerometer, comprising:

[0042] The reference module is used to select any measurement point from the surface of the wafer to be measured as a reference point;

[0043] The determination module is used to determine the focus height adjustment amount for each measurement point other than the reference point, based on the reference point, and to calculate the optimal focus height corresponding to each measurement point based on the focus height adjustment amount.

[0044] The analysis module is used to measure the ellipsoidal dispersion curve of each measurement point according to the optimal focusing height corresponding to each measurement point, and to analyze the thin film properties of each measurement point based on the ellipsoidal dispersion curve.

[0045] The wafer surface property measurement device based on an ellipsomer provided by this invention avoids the time-consuming standard focusing of all measurement points, significantly shortening the total measurement time. Simultaneously, since each measurement point can ultimately be adjusted to its optimal focusing height, measurement accuracy is guaranteed.

[0046] Thirdly, the present invention provides an electronic device including a processor and a memory, the memory storing computer-readable instructions, which, when executed by the processor, perform the steps of the wafer surface property measurement method based on ellipsometry provided in the first aspect above.

[0047] Fourthly, the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, performs the steps of the wafer surface property measurement method based on an ellipsomer provided in the first aspect above.

[0048] As described above, the wafer surface property measurement method based on an ellipsometer provided by this invention selects a measurement point on the surface of the wafer to be measured as a reference point. For other measurement points besides this reference point, the focusing height adjustment amount for each measurement point is determined based on the reference point, and then the optimal focusing height corresponding to each measurement point is calculated. Subsequently, the ellipsometric dispersion curve of each measurement point is measured based on these optimal focusing heights, and the thin film properties are analyzed. This method effectively solves the problems in the prior art, such as excessive time consumption due to focusing on all measurement points, or sacrificing measurement accuracy by focusing on only one point. By introducing a reference point and calculating the focusing height adjustment amount, this application can significantly reduce the focusing steps while ensuring measurement accuracy, thereby greatly improving measurement efficiency and overcoming the limitation of prior art where measurement efficiency and measurement accuracy are difficult to balance. It provides an efficient and reliable solution for the characterization of thin film properties on large-size wafers.

[0049] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing embodiments of the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0050] Figure 1 This is a flowchart of a wafer surface property measurement method based on an ellipsomer provided in an embodiment of the present invention.

[0051] Figure 2 This is a schematic diagram of a wafer surface property measurement device based on an ellipsomer provided in an embodiment of the present invention.

[0052] Figure 3 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention.

[0053] Label Explanation:

[0054] 100. Reference module; 200. Determining module; 300. Analyzing module; 13. Electronic device; 1301. Processor; 1302. Memory; 1303. Communication bus. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0056] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0057] Reference Appendix Figure 1 This invention provides a method for measuring the surface properties of a wafer based on an ellipsometry, comprising the following steps:

[0058] Select any measurement point on the surface of the wafer to be measured as a reference point;

[0059] For measurement points other than the reference point, the focus height adjustment amount for each measurement point is determined based on the reference point, and the optimal focus height for each measurement point is calculated based on the focus height adjustment amount.

[0060] Based on the optimal focusing height corresponding to each measurement point, the ellipsometric dispersion curve of each measurement point is obtained, and the thin film properties of each measurement point are analyzed based on the ellipsometric dispersion curve.

[0061] The core of the wafer surface property measurement method based on ellipsometry proposed in this invention lies in significantly improving measurement efficiency while ensuring measurement accuracy by optimizing the focusing process.

[0062] Specifically, the method first selects an arbitrary measurement point on the surface of the wafer to be measured as a reference point. This reference point can be selected randomly or according to preset rules (e.g., selecting the wafer's center point or edge point). For example, the operator can manually select a measurement point as a reference point by clicking on the ellipsometer's software interface, or a preset automated program can automatically set the wafer's geometric center point as the reference point after the wafer is loaded.

[0063] Next, for the measurement points other than the aforementioned reference point, the focus height adjustment amount for each measurement point is determined based on the reference point, and the optimal focus height for each measurement point is calculated based on this adjustment amount. For example, the reference point can be precisely focused first to obtain its optimal focus height. Then, for the other measurement points, a simplified focusing method can be used, such as estimating the focus height adjustment amount relative to the reference point by measuring the difference between the reflected light intensity of the measurement point and the reflected light intensity of the reference point, or by initially scanning its focus height range. Based on this adjustment amount, the optimal focus height for each measurement point can be calculated.

[0064] Finally, based on the optimal focusing height for each measurement point, the ellipsometric dispersion curves for each point are measured, and the thin film properties at each point are analyzed based on these curves. For example, after determining the optimal focusing height for a certain measurement point, the ellipsometer's sample stage automatically adjusts to that height, and then ellipsometric spectroscopy is performed to obtain the ellipsometric dispersion curve for that point. Subsequently, using specialized ellipsometric data analysis software, this curve is fitted to a preset optical model, thereby retrieving the film's thickness, refractive index, and other properties at that measurement point.

[0065] The overall working principle of this invention lies in introducing a reference point and using it as a benchmark to quickly and accurately estimate and adjust the focusing height of other measurement points, thereby avoiding the time-consuming standard focusing process for all measurement points. Specifically, when there are height variations on the wafer surface, the optimal focusing height for different measurement points is different. If each measurement point is subjected to independent standard focusing, although accuracy can be guaranteed, the total measurement time will be greatly increased. If only one point is focused and its optimal focusing height is applied to all points, the unevenness of the wafer surface will cause the measurement of other points to be out of focus, thereby reducing the measurement accuracy. This invention selects a reference point and calculates the focusing height adjustment amount for other measurement points based on it, so that other measurement points can be quickly adjusted to a preset height value close to their optimal focusing height. The more accurate this preset height value is, the smaller the preset range required for subsequent fine focusing, and the fewer focusing steps are needed, thereby significantly shortening the focusing time. At the same time, since each measurement point can eventually be adjusted to near its optimal focusing height, the measurement accuracy of the ellipsometer is guaranteed. In this way, the present invention effectively solves the problem of excessive focusing time in traditional methods while ensuring measurement accuracy, and achieves a dual improvement in measurement efficiency and measurement accuracy.

[0066] Compared to existing technologies, the core innovation of this invention lies in proposing a focusing strategy that balances measurement efficiency and accuracy. Traditional methods either sacrifice efficiency to ensure accuracy (focusing on all points) or sacrifice accuracy to improve efficiency (focusing on only one point). This invention introduces a reference point and determines the focus height adjustment amount for other measurement points based on this reference point, thereby calculating the optimal focus height for each measurement point. This method avoids time-consuming standard focusing on all measurement points, significantly shortening the total measurement time. Simultaneously, since each measurement point can ultimately be adjusted to its optimal focus height, measurement accuracy is guaranteed. For example, when measuring a wafer with 100 measurement points, if standard focusing on each point takes 30 seconds, the total focusing time is 3000 seconds. However, the method of this invention may only require 30 seconds of standard focusing on the reference point, and then, through rapid calculation and adjustment, the focus height determination for the other 99 points can be completed within seconds, thereby drastically reducing the total focusing time to hundreds of seconds, greatly improving measurement efficiency while ensuring the quality of measurement data at each measurement point.

[0067] In some embodiments, the steps of determining the focus height adjustment amount for each measurement point other than the reference point, based on the reference point, and calculating the optimal focus height for each measurement point based on the focus height adjustment amount include:

[0068] A1. Based on the reference point, a standard focusing method is used to obtain the relationship between the reflected light intensity and the focusing height, and the optimal focusing height of the reference point is measured and used as the reference height;

[0069] A2. For measurement points other than the reference point, the reflected light intensity of each measurement point is obtained based on the reference height.

[0070] A3. Based on the changing relationship, calculate the focus height adjustment amount corresponding to each measurement point according to the reflected light intensity corresponding to each measurement point;

[0071] A4. Determine the focusing height adjustment direction for each measurement point, and based on the focusing height adjustment direction, obtain the optimal focusing height for each measurement point according to the corresponding focusing height adjustment amount.

[0072] Specifically, in step A1, a standard focusing operation is first performed on the selected reference point. The standard focusing method typically involves progressively adjusting the ellipsometer's focus position within a certain focusing height range, while simultaneously recording the intensity of reflected light from the wafer surface at each focusing height. By analyzing this data, a curve showing the relationship between reflected light intensity and focusing height can be established. This curve typically exhibits the characteristic that the reflected light intensity reaches its maximum at the optimal focusing height. During this process, the optimal focusing height of the reference point can be accurately measured and determined; this height will be recorded and used as a benchmark, i.e., a reference height, for subsequent focusing adjustments at other measurement points.

[0073] In step A2, once the reference height is obtained, the ellipsometer's focusing position is initially set at the reference height for all measurement points on the wafer surface other than the reference point. At this preset height, the reflected light intensity is measured at each measurement point. Because the wafer surface may have local unevenness, the reflected light intensity at the reference height may differ from the reflected light intensity at their respective optimal focusing heights.

[0074] In step A3, using the curve showing the relationship between reflected light intensity and focus height established in step A1, and combining it with the reflected light intensity at the reference height measured at each measurement point in step A2, the required focus height adjustment for each measurement point relative to the reference height can be calculated. For example, if the reflected light intensity at a certain measurement point at the reference height is lower than the reflected light intensity at its optimal focus, the required focus height adjustment can be inferred from the curve showing the relationship.

[0075] In step A4, after calculating the focus height adjustment amount, it is also necessary to determine the specific adjustment direction (for example, by using trial and error). This can usually be determined by comparing the trend of the current reflected light intensity with the curve of change. For example, if the reflected light intensity is too low, it may be necessary to adjust the focus height upwards or downwards to achieve the maximum reflected light intensity. Once the adjustment direction is determined, the optimal focus height for each measurement point can be accurately obtained by combining it with the calculated focus height adjustment amount.

[0076] The present invention establishes a relationship between reflected light intensity and focusing height at a reference point and determines the reference height, thus providing a reliable benchmark for focusing adjustments at other measurement points. Subsequently, by measuring the reflected light intensity at other measurement points at the reference height and combining this with the pre-established relationship, the required focusing height adjustment for each measurement point can be calculated quickly and effectively. This method avoids the time-consuming standard focusing process for each measurement point, instead utilizing the similarity of local areas on the wafer surface and the physical relationship between light intensity and focusing height to indirectly and accurately determine the optimal focusing height. Therefore, the ellipsometer's focusing system can be guided to the optimal focusing position at each measurement point, ensuring the accuracy of subsequent ellipsometric measurement data.

[0077] The above technical solution significantly improves the efficiency and accuracy of wafer surface property measurement methods based on ellipsometers. Compared to performing independent standard focusing operations for each measurement point, this solution uses data from a reference point as a benchmark and quickly calculates the optimal focusing height for other measurement points by analyzing the relationship between reflected light intensity and focusing height. This not only drastically reduces the focusing time and lowers the overall measurement cost, but also avoids measurement errors caused by inaccurate focusing due to the optimized focusing process, thus ensuring the measurement quality of the ellipsometric dispersion curve and the reliability of subsequent thin film property analysis.

[0078] In some embodiments, the steps of determining the focus height adjustment amount for each measurement point other than the reference point, based on the reference point, and calculating the optimal focus height for each measurement point based on the focus height adjustment amount include:

[0079] B1. Based on the reference point, a standard focusing method is used to obtain the optimal focusing height of the reference point and use it as the reference height;

[0080] B2. Based on the reference height, the ellipsoidal dispersion curve of the reference point is measured;

[0081] B3. For measurement points other than the reference point, the ellipsoidal dispersion curves corresponding to each measurement point are obtained based on the reference height.

[0082] B4. Based on the ellipsoidal dispersion curve of the reference point, evaluate the noise level of the corresponding ellipsoidal dispersion curve of each measurement point, and obtain the noise evaluation statistics for each measurement point.

[0083] B5. Based on the noise assessment statistics corresponding to each measurement point, and using a preset threshold, determine the measurement points that require adjustment of the focus height and use them as target points;

[0084] B6. Calculate the focus height adjustment amount corresponding to each target point, and calculate the optimal focus height for each target point based on the focus height adjustment amount.

[0085] Specifically, in step B1, the "standard focusing method" can be understood as a technique for determining the optimal focusing position by systematically changing the focusing height and monitoring changes in a certain optical signal (such as reflected light intensity or image sharpness). Its purpose is to establish an accurate focusing benchmark for the reference point. In steps B2 and B3, the "ellipsoidal dispersion curve" refers to the curve showing the variation of ellipsoidal parameters (such as Psi and Delta) with wavelength, measured by an ellipsometer at different wavelengths. These curves contain information about the optical properties of the thin film, such as thickness and refractive index. Measuring the ellipsoidal dispersion curve based on the reference height aims to provide a unified comparison benchmark for subsequent noise assessment. In step B4, "evaluating the noise level of the ellipsoidal dispersion curve corresponding to each measurement point" refers to quantifying the difference in data quality at each measurement point by comparing the ellipsoidal dispersion curve of each measurement point with that of the reference point. This difference is usually manifested as fluctuations, deviations, or irregularities in the curve, which can be considered noise. In step B5, the "preset threshold" is a standard used to determine whether the noise of the ellipsoidal dispersion curve is too high. When the noise assessment statistic at a measurement point exceeds this threshold, it indicates a potential focusing problem at that point, requiring adjustment. In step B6, "calculating the focus height adjustment amount corresponding to each target point" refers to determining the extent to which the focus height of the target point needs to be changed based on the noise assessment results. Here, the "optimal focus height" refers to the focusing position that allows the ellipsometer to obtain the highest quality ellipsometric dispersion curve at that measurement point. Various techniques can be used to calculate the optimal focus height; for example, the standard focusing method or the methods described in steps A1-A4 above can be applied again.

[0086] This invention effectively addresses the blind spots and efficiency issues that may exist in traditional methods when identifying and adjusting poorly focused measurement points by introducing an assessment of the noise in the ellipsometric dispersion curve. First, a high-quality benchmark is established by standard focusing on a reference point and measuring its ellipsometric dispersion curve. Then, for other measurement points, their ellipsometric dispersion curves are measured at the same reference height and compared with the curve of the reference point. This comparison directly reflects the quality of the ellipsometric dispersion curve at each measurement point, as inaccurate focusing typically leads to signal distortion and increased noise. By quantifying this noise level and comparing it with a preset threshold, the system can intelligently identify those "target points" that truly require focus adjustment, avoiding time-consuming and potentially unnecessary fine focusing on all measurement points. Thus, only those target points identified as poorly focused are calculated for focus height adjustment and the optimal focus height is determined, ensuring the accuracy of subsequent thin film property analysis while improving the overall efficiency of the measurement process.

[0087] Through the above technical solution, this invention can more accurately identify measurement points on the wafer surface where the ellipsometer's focusing is inaccurate due to local unevenness or other factors. Compared to methods that rely solely on reflected light intensity or preset surface data to adjust the focus, this solution directly uses the quality of the ellipsometric dispersion curve as an evaluation criterion, making focus adjustment more targeted and effective. This data quality-based feedback mechanism significantly improves the accuracy and reliability of focusing, thereby ensuring the precision of subsequent thin film property analysis. Furthermore, since fine focusing is performed only on the measurement points that require adjustment, the time-consuming operation of repeatedly focusing on all points is avoided, thus improving the overall efficiency of the measurement process.

[0088] In some embodiments, the specific steps in step B4 include:

[0089] B41. Denoise the ellipsoidal dispersion curve of the reference point to obtain the processed ellipsoidal dispersion curve of the reference point.

[0090] B42. Using the least squares method, evaluate the deviation of the corresponding ellipsoidal dispersion curve of each measurement point from the processed ellipsoidal dispersion curve of the reference point and use it as the noise level.

[0091] B43. Normalize the noise level to obtain the normalized root mean square error, which is then used as a noise assessment statistic.

[0092] In step B41, the ellipsometric dispersion curve of the reference point is denoised to eliminate random noise or interference that may be introduced during the measurement process, resulting in a smoother ellipsometric dispersion curve that better represents the true properties of the thin film. This denoised curve can serve as a benchmark for evaluating noise at other measurement points. Various mature signal processing techniques can be employed for denoising, including Fourier transform, wavelet transform, moving average, local weighted regression, or Savitzky-Golay smoothing, to effectively filter out high-frequency noise and preserve the essential characteristics of the curve.

[0093] Further, in step B42, the deviation of the ellipsoidal dispersion curve corresponding to each measurement point from the processed ellipsoidal dispersion curve of the reference point is evaluated using the least squares method. The least squares method is a commonly used curve fitting and data analysis method, aiming to find a match that minimizes the sum of squared errors between a curve (in this case, the processed ellipsoidal dispersion curve of the reference point) and the given data points (the ellipsoidal dispersion curves corresponding to each measurement point). By calculating the sum of squared residuals between the curves at each measurement point and the processed curve at the reference point, the degree of deviation can be quantified; this deviation is considered the noise level. A larger deviation usually indicates that the ellipsoidal dispersion curve at that measurement point has been significantly affected by noise, which may be related to inaccurate focusing.

[0094] Subsequently, in step B43, the noise level is normalized to obtain the normalized root mean square error (NRMSE), which is used as a noise assessment statistic. The purpose of normalization is to eliminate potential dimensional differences between different measurement points, ensuring the noise levels are comparable under different conditions. The normalized root mean square error (NRMSE) is a commonly used statistic to measure the difference between predicted and actual values. Here, it is used to quantify the relative deviation of the ellipsometric dispersion curve at each measurement point from the processed curve at the reference point, thus providing a unified noise assessment metric that can be used for comparison and threshold setting.

[0095] The present invention, through the aforementioned steps, first denoises the ellipsometric dispersion curve of the reference point, ensuring the accuracy of subsequent evaluations. Then, the least squares method is used to quantify the deviation of each measurement point's curve from the denoised reference curve; this deviation is considered noise. Finally, through normalization, the noise magnitude is converted into a uniform normalized root mean square error, allowing for objective comparison of noise levels between different measurement points. This systematic evaluation method can accurately identify measurement points where inaccurate focusing leads to a deterioration in the quality of the ellipsometric dispersion curve, providing a reliable basis for subsequent focus height adjustments.

[0096] Through the above technical solution, this invention provides a refined and quantitative noise assessment method. This method establishes a reliable assessment benchmark by denoising the reference point curve; it accurately calculates the deviation using the least squares method, making noise quantification more accurate; and through normalization, the noise assessment statistics can effectively overcome the dependence on numerical magnitude, making them highly comparable for comparison between different data. Therefore, it can more accurately and objectively identify measurement points requiring focus height adjustment, avoiding errors that may be caused by subjective judgment or rough assessment, thereby improving the accuracy and efficiency of wafer surface property measurement.

[0097] In some embodiments, the steps of determining the focus height adjustment amount for each measurement point other than the reference point, based on the reference point, and calculating the optimal focus height for each measurement point based on the focus height adjustment amount include:

[0098] C1. Obtain the surface profile data of the wafer to be measured;

[0099] C2. Based on the reference point, a standard focusing method is used to obtain the optimal focusing height of the reference point and use it as the reference height;

[0100] C3. For measurement points other than the reference point, calculate the focus height adjustment amount corresponding to each measurement point based on the reference height and surface data;

[0101] C4. Based on the adjustment amount of the focusing height corresponding to each measurement point, obtain the optimal focusing height for each measurement point.

[0102] Specifically, surface profile data refers to the height information or topographic features of various locations on the surface of the wafer to be measured. This data can be acquired in advance using other measurement equipment (e.g., white light interferometer, atomic force microscope, or specialized wafer surface profile measuring instrument), or it can be obtained by focusing and measuring a small number of test points on the wafer surface and then fitting the data. Its purpose is to provide overall topographic information of the wafer surface for subsequent calculation of the focus height adjustment amount for each measurement point. The standard focusing method typically involves moving the focusing mechanism of an ellipsometer to collect reflected light intensity or ellipsometric parameters at different height positions, and determining the position with the maximum light intensity or the most stable ellipsometric parameter change as the optimal focusing height. This optimal focusing height is set as the reference height, serving as the benchmark for subsequent calculations of the focusing height of other measurement points. In practical applications, the focus height adjustment amount refers to the vertical displacement required for each measurement point relative to the reference height. This adjustment amount is calculated based on the known wafer surface profile data and the height information of the reference point. For example, if the surface profile data shows a height difference between a measurement point and the reference point in the vertical direction, this height difference can be used as the focus height adjustment amount for that measurement point. This method avoids the need for an independent focusing process for each measurement point, thus improving efficiency. The optimal focusing height for each measurement point can be directly determined by performing algebraic operations (e.g., adding or subtracting the adjustment amount from the reference height) between the reference height and the calculated focusing height adjustment amount. This allows for quick and accurate adjustment of the ellipsometer's focusing position to near the optimal focusing height for each measurement point before performing ellipsometric measurements.

[0103] The present invention effectively solves the efficiency problem that may exist when adjusting the focus height of measurement points other than the reference point by introducing the surface profile data of the wafer to be measured. Specifically, after obtaining the optimal focus height of the reference point as the reference height, it is no longer necessary to perform a time-consuming standard focusing process for each measurement point independently. Instead, by utilizing the overall surface profile data of the wafer, the required focus height adjustment amount for each measurement point can be directly calculated based on the relative height difference between each measurement point and the reference point. This predictive adjustment based on surface profile data enables the ellipsometer to quickly adjust the focus position to be close to the optimal focus height of each measurement point, thereby significantly reducing the time and steps required for focusing.

[0104] Through the above technical solution, this invention can significantly improve the efficiency of wafer surface property measurement based on ellipsometer. Since the optimal focusing height at each measurement point is predicted based on wafer profile data rather than iteratively measured point by point, focusing time is greatly shortened, making it particularly suitable for scenarios requiring rapid measurement of a large number of points. Furthermore, using the overall wafer profile information for focusing adjustment also helps improve the accuracy and stability of focusing, thereby ensuring the reliability of subsequent ellipsometric dispersion curve measurements and ultimately improving the accuracy of thin film property analysis.

[0105] In some embodiments, the specific steps in step C1 include:

[0106] C11. Select multiple test points on the surface of the wafer to be measured and calculate the focus height adjustment amount corresponding to each test point (test points are different from measurement points; test points are only used to obtain the surface data of the wafer to be measured, while measurement points are used to analyze the thin film properties).

[0107] C12. Based on the preset polynomial, according to the focus height adjustment amount and position coordinates corresponding to each test point, solve for the fitting coefficients in the preset polynomial corresponding to each test point;

[0108] C13. Determine the functional relationship between the position coordinates of each location on the surface of the wafer to be measured and the focusing height adjustment amount based on the fitting coefficients;

[0109] C14. Obtain the surface profile data of the wafer to be measured based on the functional relationship.

[0110] Specifically, in step C11, multiple test points are selected on the surface of the wafer to be measured. These test points can be evenly distributed on the wafer surface or densely selected according to specific areas of the wafer. The purpose of selecting these test points is to characterize the surface morphology of the entire wafer using a limited number of sampling points. For each selected test point, the optimal focusing height can be calculated first, and then the corresponding focusing height adjustment amount can be calculated based on the optimal focusing height. The method for calculating the optimal focusing height can be flexibly chosen. For example, the method described in steps A1-A4 above can be used, which is determined based on the relationship between the reflected light intensity and the reference point; or the method described in steps B1-B6 above can be used, which is determined based on the noise assessment of the ellipsometric dispersion curve; or a standard focusing method can be used, such as by scanning the focusing range and finding the maximum reflected light intensity or the optimal ellipsometric signal. The choice of method depends on the required accuracy, speed, and available equipment capabilities.

[0111] In step C12, after obtaining the position coordinates of multiple test points and their corresponding focus height adjustments, these data can be fitted based on a preset polynomial. The preset polynomial can be a two-dimensional polynomial, such as the Zernike polynomial, Legendre polynomial, or other polynomials suitable for describing wafer surface morphology. The fitting coefficients corresponding to each test point in the preset polynomial can be solved using the least squares method or other fitting algorithms. These fitting coefficients are key parameters characterizing the wafer surface morphology.

[0112] For example, by using a bivariate quadratic polynomial for fitting, the relationship function between the height adjustment Z and the position (x,y) is Z=C1x 2 +C2y 2+C3xy+C4x+C5y+C6, where C1-C6 are 6 undetermined coefficients. Therefore, it is necessary to reasonably select 6 different measurement points, focus on them to obtain Z, and then solve for the 6 undetermined coefficients. Finally, the functional relationship between the focusing height adjustment Z and the position (x,y) can be obtained, based on which the wafer surface data can be obtained.

[0113] In practical applications, in step C13, once the fitting coefficients are obtained, a functional relationship can be established between the position coordinates of any location on the surface of the wafer to be measured and the corresponding focus height adjustment amount, based on the preset polynomial and these fitting coefficients. This functional relationship is essentially a mathematical model of the wafer surface morphology.

[0114] Therefore, in step C14, the surface profile data of the wafer to be measured can be obtained based on the established functional relationship. The surface profile data can be wafer surface topography information represented by height maps, contour maps, or other forms, which reflects the relative height or focus height of each point on the wafer surface, providing basic data for subsequent precise adjustment of the focus height of each measurement point.

[0115] The present invention avoids performing individual focusing measurements on every point on the wafer surface by selecting a limited number of test points on the wafer surface and accurately measuring the focusing height adjustment of these test points. The fact that wafer surface morphology typically exhibits a certain continuity and regularity makes polynomial fitting using a limited number of sampling points possible. By fitting these discrete measurement data points to a preset polynomial, the overall morphological characteristics of the wafer surface can be effectively captured and expressed as a mathematical function. This functional relationship can accurately describe the height information at any location on the wafer surface, thus transforming discrete measurement results into continuous surface data. This method not only reduces measurement time and improves efficiency but also effectively suppresses local measurement noise and improves the accuracy and reliability of the surface data through the smoothing properties of polynomial fitting.

[0116] Through the above technical solution, this invention provides a method for efficiently and accurately acquiring wafer surface profile data during ellipsometer measurement. Compared to measurements relying on external equipment or time-consuming full-scan measurements, this solution significantly improves the efficiency of surface profile data acquisition by selecting a limited number of test points and performing polynomial fitting. Simultaneously, the mathematical fitting method effectively smooths measurement noise, making the obtained wafer surface profile data more accurate and reliable. This provides a solid foundation for the precise adjustment of the focusing height of each measurement point, ultimately improving the overall accuracy and efficiency of wafer surface property measurement.

[0117] It should be noted that this invention proposes three methods for calculating the optimal focusing height of the measurement point (i.e., Method 1: A1-A4, Method 2: B1-B6, and Method 3: C1-C4). In practical applications, these methods can also be used in combination to further reduce focusing time. For example, for a 12-inch wafer sample, the center point is first focused to obtain its optimal focusing height. Considering that the closer the measurement point is to the center point, the smaller the difference in optimal focusing height, the optimal focusing height of the center point can be used for all measurement points within a preset radius. The preset radius can be determined based on the noise level measured by Method 2 and combined with historical data. Outside the preset radius, the focusing height is adjusted to the optimal value according to Method 1 or Method 3.

[0118] Specifically, methods 1 and 3 of the present invention are a priori methods (i.e., "pre-improvement"), which effectively reduce the number of focusing steps and reduce the total time of focusing by obtaining a preset height value that is as close as possible to the optimal focusing height; method 2 is a retrospective method (i.e., "post-correction"), which reduces the number of measurement points that need to be focused by evaluating the noise of the measurement signal, thereby shortening the total time of focusing.

[0119] Method 1 of the present invention measures the relationship between reflected light intensity and focusing height, and calculates the optimal focusing height based on the reflected light intensity. This reduces the number of focusing steps for measurement points other than the reference point to a single step, avoiding the multiple focusing steps of the standard focusing process, significantly shortening the total time of the focusing process, effectively improving measurement efficiency, and simultaneously ensuring measurement accuracy.

[0120] Method 2 of the present invention evaluates the quality of the measurement signal by calculating the noise level of the ellipsometric dispersion curve, and then determines whether the focus height needs to be adjusted. This avoids the need to focus on all measurement points in the standard focusing process, effectively reduces the number of measurement points that need to be focused, effectively improves measurement efficiency, and at the same time takes into account measurement accuracy.

[0121] Method 3 of the present invention obtains the surface data of the sample by measuring or fitting the sample surface, obtains the relative height of different measurement points based on the surface data, and calculates the optimal focusing height, so that the number of focusing steps for other measurement points except the reference point is reduced to zero, avoiding multiple focusing steps in the standard focusing process, greatly shortening the total time of the focusing process, and effectively improving the measurement efficiency.

[0122] Please refer to Figure 2 , Figure 2 This invention provides an ellipsometer-based wafer surface property measurement device in some embodiments. The ellipsometer-based wafer surface property measurement device is integrated into a back-end control device in the form of a computer program, and includes:

[0123] Reference module 100 is used to select any measurement point from the surface of the wafer to be measured as a reference point;

[0124] The determination module 200 is used to determine the focus height adjustment amount for each measurement point other than the reference point, based on the reference point, and to calculate the optimal focus height corresponding to each measurement point based on the focus height adjustment amount;

[0125] The analysis module 300 is used to measure the ellipsoidal dispersion curve of each measurement point according to the optimal focusing height corresponding to each measurement point, and to analyze the thin film properties of each measurement point based on the ellipsoidal dispersion curve.

[0126] In some embodiments, the determining module 200 is executed when determining the focus height adjustment amount for each measurement point other than the reference point, based on the reference point, and calculating the optimal focus height for each measurement point based on the focus height adjustment amount:

[0127] A1. Based on the reference point, a standard focusing method is used to obtain the relationship between the reflected light intensity and the focusing height, and the optimal focusing height of the reference point is measured and used as the reference height;

[0128] A2. For measurement points other than the reference point, the reflected light intensity of each measurement point is obtained based on the reference height.

[0129] A3. Based on the changing relationship, calculate the focus height adjustment amount corresponding to each measurement point according to the reflected light intensity corresponding to each measurement point;

[0130] A4. Determine the focusing height adjustment direction for each measurement point, and based on the focusing height adjustment direction, obtain the optimal focusing height for each measurement point according to the corresponding focusing height adjustment amount.

[0131] In some embodiments, the determining module 200 is executed when determining the focus height adjustment amount for each measurement point other than the reference point, based on the reference point, and calculating the optimal focus height for each measurement point based on the focus height adjustment amount:

[0132] B1. Based on the reference point, a standard focusing method is used to obtain the optimal focusing height of the reference point and use it as the reference height;

[0133] B2. Based on the reference height, the ellipsoidal dispersion curve of the reference point is measured;

[0134] B3. For measurement points other than the reference point, the ellipsoidal dispersion curves corresponding to each measurement point are obtained based on the reference height.

[0135] B4. Based on the ellipsoidal dispersion curve of the reference point, evaluate the noise level of the corresponding ellipsoidal dispersion curve of each measurement point, and obtain the noise evaluation statistics for each measurement point.

[0136] B5. Based on the noise assessment statistics corresponding to each measurement point, and using a preset threshold, determine the measurement points that require adjustment of the focus height and use them as target points;

[0137] B6. Calculate the focus height adjustment amount corresponding to each target point, and calculate the optimal focus height for each target point based on the focus height adjustment amount.

[0138] In some embodiments, the determination module 200 is executed when evaluating the noise level of the ellipsoidal dispersion curve corresponding to each measurement point based on the ellipsoidal dispersion curve of the reference point, and obtaining the noise evaluation statistics corresponding to each measurement point:

[0139] B41. Denoise the ellipsoidal dispersion curve of the reference point to obtain the processed ellipsoidal dispersion curve of the reference point.

[0140] B42. Using the least squares method, evaluate the deviation of the corresponding ellipsoidal dispersion curve of each measurement point from the processed ellipsoidal dispersion curve of the reference point and use it as the noise level.

[0141] B43. Normalize the noise level to obtain the normalized root mean square error, which is then used as a noise assessment statistic.

[0142] In some embodiments, the determining module 200 is executed when determining the focus height adjustment amount for each measurement point other than the reference point, based on the reference point, and calculating the optimal focus height for each measurement point based on the focus height adjustment amount:

[0143] C1. Obtain the surface profile data of the wafer to be measured;

[0144] C2. Based on the reference point, a standard focusing method is used to obtain the optimal focusing height of the reference point and use it as the reference height;

[0145] C3. For measurement points other than the reference point, calculate the focus height adjustment amount corresponding to each measurement point based on the reference height and surface data;

[0146] C4. Based on the adjustment amount of the focusing height corresponding to each measurement point, obtain the optimal focusing height for each measurement point.

[0147] In some embodiments, the determining module 200 performs the following when acquiring surface data of the wafer to be measured:

[0148] C11. Select multiple test points on the surface of the wafer to be measured and calculate the focus height adjustment amount corresponding to each test point;

[0149] C12. Based on the preset polynomial, according to the focus height adjustment amount and position coordinates corresponding to each test point, solve for the fitting coefficients in the preset polynomial corresponding to each test point;

[0150] C13. Determine the functional relationship between the position coordinates of each location on the surface of the wafer to be measured and the focusing height adjustment amount based on the fitting coefficients;

[0151] C14. Obtain the surface profile data of the wafer to be measured based on the functional relationship.

[0152] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention. The present invention provides an electronic device 13, including: a processor 1301 and a memory 1302. The processor 1301 and the memory 1302 are interconnected and communicate with each other through a communication bus 1303 and / or other forms of connection mechanism (not shown). The memory 1302 stores computer-readable instructions executable by the processor 1301. When the electronic device is running, the processor 1301 executes the computer-readable instructions to execute the wafer surface property measurement method based on ellipsometer in any optional implementation of the above embodiments, so as to achieve the following functions: selecting any measurement point from the surface of the wafer to be measured as a reference point; for other measurement points besides the reference point, determining the focus height adjustment amount of each measurement point according to the reference point, and calculating the optimal focus height corresponding to each measurement point based on the focus height adjustment amount; measuring the ellipsometric dispersion curve of each measurement point according to the optimal focus height corresponding to each measurement point, and analyzing the thin film properties of each measurement point based on the ellipsometric dispersion curve.

[0153] This invention provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it performs the wafer surface property measurement method based on an ellipsometer in any optional implementation of the above embodiments to achieve the following functions: selecting any measurement point from the wafer surface to be measured as a reference point; for other measurement points besides the reference point, determining the focusing height adjustment amount for each measurement point based on the reference point, and calculating the optimal focusing height corresponding to each measurement point based on the focusing height adjustment amount; measuring the ellipsometric dispersion curve of each measurement point based on the optimal focusing height corresponding to each measurement point, and analyzing the thin film properties of each measurement point based on the ellipsometric dispersion curve.

[0154] The computer-readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as Static Random Access Memory (SRAM), Electrically Erasable Programmable Read-Only Memory (EEPROM), Erasable Programmable Read Only Memory (EPROM), Programmable Red-Only Memory (PROM), Read-Only Memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk.

[0155] In the embodiments provided by this invention, it should be understood that the disclosed apparatus and method can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the displayed or discussed mutual couplings, direct couplings, or communication connections may be through some communication interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0156] Furthermore, the units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0157] Furthermore, the functional modules in the various embodiments of the present invention can be integrated together to form an independent part, or each module can exist independently, or two or more modules can be integrated to form an independent part.

[0158] In this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, without necessarily requiring or implying any such actual relationship or order between these entities or operations.

[0159] The above description is merely an embodiment of the present invention and is not intended to limit the scope of protection of the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An ellipsometer-based method of measuring properties of a wafer surface, the method comprising: The method comprises the following steps: selecting an arbitrary measurement point on the surface of the wafer to be measured as a reference point; for measurement points other than the reference point, determining the focus height adjustment amount of each measurement point according to the reference point, and calculating the optimal focus height corresponding to each measurement point based on the focus height adjustment amount; measuring the ellipsometric dispersion curve of each measurement point according to the optimal focus height corresponding to each measurement point, and analyzing the thin film properties of each measurement point based on the ellipsometric dispersion curve; for measurement points other than the reference point, determining the focus height adjustment amount of each measurement point according to the reference point, and calculating the optimal focus height corresponding to each measurement point based on the focus height adjustment amount, comprising: A1. based on the reference point, using a standard focusing method to obtain the relationship between the reflected light intensity and the focus height, and measuring the optimal focus height of the reference point as the reference height; A2. for measurement points other than the reference point, measuring the corresponding reflected light intensity of each measurement point based on the reference height; A3. based on the relationship, calculating the focus height adjustment amount corresponding to each measurement point according to the corresponding reflected light intensity of each measurement point; A4. determining the focus height adjustment direction of each measurement point, and obtaining the optimal focus height corresponding to each measurement point according to the focus height adjustment direction and the focus height adjustment amount corresponding to each measurement point.

2. The ellipsometer-based wafer surface property measurement method of claim 1, wherein, for measurement points other than the reference point, determining the focus height adjustment amount of each measurement point according to the reference point, and calculating the optimal focus height corresponding to each measurement point based on the focus height adjustment amount, comprising: B1. based on the reference point, using a standard focusing method to obtain the optimal focus height of the reference point as the reference height; B2. based on the reference height, measuring the ellipsometric dispersion curve of the reference point; B3. for measurement points other than the reference point, measuring the corresponding ellipsometric dispersion curve of each measurement point based on the reference height; B4. according to the ellipsometric dispersion curve of the reference point, evaluating the noise size of the ellipsometric dispersion curve corresponding to each measurement point to obtain the noise evaluation statistic corresponding to each measurement point; B5. according to the noise evaluation statistic corresponding to each measurement point, determining the measurement point that needs to adjust the focus height as the target point based on the preset threshold value; B6. calculating the focus height adjustment amount corresponding to each target point, and calculating the optimal focus height of each target point based on the focus height adjustment amount.

3. The ellipsometer-based wafer surface property measurement method of claim 2, wherein, The specific steps in step B4 include: B41. denoising the ellipsometric dispersion curve of the reference point to obtain the processed ellipsometric dispersion curve of the reference point; B42. by least square method, evaluating the deviation size of the ellipsometric dispersion curve corresponding to each measurement point relative to the processed ellipsometric dispersion curve of the reference point as the noise size; B43. normalizing the noise size to obtain the normalized root mean square error as the noise evaluation statistic.

4. The ellipsometer-based wafer surface property measurement method of claim 3, wherein, The denoising processing includes processing by using Fourier transform, wavelet transform, moving average method, local weighted regression method or Savitzky-Golay smoothing method.

5. The ellipsometer-based wafer surface property measurement method of claim 1, wherein, The step of determining the focus height adjustment amount of each measurement point according to the reference point and calculating the optimal focus height corresponding to each measurement point based on the focus height adjustment amount for the measurement points other than the reference point comprises: C1. Obtain the surface profile data of the wafer to be measured; C2. Obtain the optimal focus height of the reference point as the reference height based on the reference point using the standard focus method; C3. Calculate the focus height adjustment amount corresponding to each measurement point based on the reference height and the surface profile data for the measurement points other than the reference point; C4. Obtain the optimal focus height corresponding to each measurement point according to the focus height adjustment amount corresponding to each measurement point.

6. The ellipsometer-based wafer surface property measurement method of claim 5, wherein, The specific steps in step C1 include: C11. Select multiple test points on the surface of the wafer to be measured and calculate the focus height adjustment amount corresponding to each test point; C12. Based on a predetermined polynomial, solve the fitting coefficients in the predetermined polynomial corresponding to each test point according to the focus height adjustment amount and the position coordinates corresponding to each test point; C13. Determine the functional relationship between the position coordinates and the focus height adjustment amount of each position on the surface of the wafer to be measured according to the fitting coefficients; C14. Obtain the surface profile data of the wafer to be measured according to the functional relationship.

7. An ellipsometer-based wafer surface property measurement apparatus using the ellipsometer-based wafer surface property measurement method according to any one of claims 1 to 6, characterized by Comprise: A reference module for selecting any one measurement point on the surface of the wafer to be measured as a reference point; A determination module for determining the focus height adjustment amount of each measurement point according to the reference point and calculating the optimal focus height corresponding to each measurement point based on the focus height adjustment amount for the measurement points other than the reference point; An analysis module for measuring the ellipsometric dispersion curve of each measurement point according to the optimal focus height corresponding to each measurement point, and analyzing the thin film properties of each measurement point based on the ellipsometric dispersion curve.

8. An electronic device, comprising: Comprise a processor and a memory, the memory stores computer readable instructions, when the computer readable instructions are executed by the processor, run the steps in the wafer surface property measurement method based on ellipsometer as claimed in any one of claims 1-6.

9. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to run the steps in the wafer surface property measurement method based on ellipsometer as claimed in any one of claims 1-6.

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