Peak value extraction method, thickness measurement method and equipment

Abstract

The invention provides a peak value extraction method, a thickness measurement method and equipment. The method is applied to the high-precision measurement field. The method comprises the following steps: acquiring a frame of spectral signal of a wafer; performing peak extraction on the current frame spectral signal according to a preset intensity threshold value; when a peak is extracted, determining the peak value of the peak as a main peak value; obtaining a thickness guess value; performing reverse solving according to the thickness guess value and the main peak-to-peak value by using a thickness equation to obtain a secondary peak-to-peak value; and taking the main peak value and the secondary peak value as initial guess values of a double-peak pseudo Voigt fitting equation, and fitting the current frame of spectral signal to obtain a main peak value and a secondary peak value of the current frame of spectral signal. The method successfully solves the problem that the position of the secondary peak is difficult to accurately identify due to the fact that initial guess is missing and two peaks approach, and can accurately fit the peak value of the main peak and the peak value of the secondary peak of one frame of spectral signal.

Description

Technical Field

[0001] The present invention relates to the field of high-precision measurement, and particularly to a peak extraction method, a thickness measurement method and a device. Background Art

[0002] In modern scientific research and industrial applications, the spectral analysis technology is widely used in fields such as material property analysis, chemical composition identification and thickness measurement of materials including wafers due to its powerful functions. In terms of thickness measurement, accurately mastering the thickness of each layer of the wafer is crucial for controlling the performance of semiconductor devices. Spectral analysis can achieve high-precision measurement of the wafer thickness through the analysis of the reflection spectrum.

[0003] Currently, the spectral analysis technology has become a key means to achieve accurate measurement of the wafer thickness due to its high precision and high reliability. Traditional spectral analysis usually extracts the peaks of the wafer surface spectrum to obtain the required information. Spectral analysis can accurately separate and identify the peak information in the spectrum, and then accurately determine the thickness of each layer of the wafer. This not only helps to ensure the quality of the wafer, but also provides a strong basis for the optimization of the manufacturing process, promoting the development of wafer manufacturing to a higher level.

[0004] However, the peak extraction method of the existing technology has obvious defects. When the distance between two peaks in the spectral signal is relatively close, the peak extraction method in the existing technology is extremely vulnerable to the interference of adjacent peaks, and it is very difficult to accurately distinguish the position of the second peak (the second peak is a smaller peak relative to the first peak), resulting in a large deviation in the analysis result. Summary of the Invention

[0005] In view of this, on the one hand, the present invention provides a peak extraction method, including: Obtaining a frame of spectral signal of the wafer; Performing peak extraction on the current frame of spectral signal according to a preset intensity threshold; When a peak is extracted, determining the peak value of the peak as the main peak value; Obtaining a thickness guess value; Using the thickness equation to inversely solve for the secondary peak value according to the thickness guess value and the main peak value; Taking the main peak value and the secondary peak value as the initial guess values of the double-peak pseudo Voigt fitting equation, and fitting the current frame of spectral signal to obtain the main peak value and the secondary peak value of the current frame of spectral signal.

[0006] Optionally, when two peaks are extracted, determining the peak values of the two peaks as the main peak value and the secondary peak value respectively; Taking the main peak value and the secondary peak value as the initial guess values of the double-peak pseudo Voigt fitting equation, fitting the spectral signal of the current frame, and obtaining the main peak value and the secondary peak value of the spectral signal of the current frame.

[0007] Optionally, the thickness equation is: ; Wherein, represents the thickness, is the main peak value, is the secondary peak value, , , , , , , , are the parameter results fitted according to the measurement data of the displacement stage and the spectrometer.

[0008] Optionally, taking the main peak value and the secondary peak value as the initial guess values of the double-peak pseudo Voigt fitting equation to fit the spectral signal of the current frame includes: Taking the main peak value, the secondary peak value and the preset parameters as the initial guess values of the double-peak pseudo Voigt fitting equation to fit the spectral signal of the current frame, where the preset parameters include the intensity maximum value of the spectral signal, the proportion of the Gaussian signal in the spectral signal, and the width of the peak in the spectral signal; Wherein, the double-peak pseudo Voigt fitting equation is: ; Wherein, represents the intensity at any wavelength in the spectral signal of the current frame, and represent the intensity maximum value of the spectral signal, and represent the proportion of the Gaussian signal in the spectral signal, and represent the main peak value and the secondary peak value in the spectral signal, and represent the width of the peak in the spectral signal, is the wavelength independent variable in the spectral signal of the current frame.

[0009] Optionally, using the thickness equation to inversely solve the secondary peak value according to the thickness guess value and the main peak value includes: Obtaining the wavelength interval; Calculating the predicted secondary peak value according to the wavelength interval and the main peak value; Calculate the thickness according to the peak value of the main peak and the predicted peak value of the secondary peak using the thickness equation. Continuously update the wavelength interval based on the difference between the guessed thickness value and the thickness, and then update the predicted peak value of the secondary peak until the difference between the guessed thickness value and the thickness is less than the preset convergence threshold, so as to obtain the peak value of the secondary peak that meets the accuracy requirements.

[0010] Optionally, before performing peak extraction on the current frame spectral signal according to the preset intensity threshold, it further includes: Obtain the background spectral signal originating from the measurement conditions; Subtract the background spectral signal from the current frame spectral signal of the wafer to obtain the true spectral signal of the wafer in the current frame; Perform main peak judgment on the true spectral signal; If there is a main peak, perform smoothing processing on the true spectral signal according to the preset smoothing intensity; If there is no main peak, stop peak extraction of the current frame spectral signal.

[0011] The second aspect of the present invention provides a thickness measurement method, including: Obtain the peak value of the main peak and the peak value of the secondary peak by using the method described in any one of the above; Calculate the thickness of the wafer at the current frame according to the peak value of the main peak and the peak value of the secondary peak.

[0012] The third aspect of the present invention provides a peak extraction device, which includes: a processor and a memory connected to the processor; wherein, the memory stores instructions executable by the processor, and the instructions are executed by the processor to enable the processor to execute the peak extraction method described in any one of the above.

[0013] The fourth aspect of the present invention provides a thickness measurement device, which includes: a processor and a memory connected to the processor; wherein, the memory stores instructions executable by the processor, and the instructions are executed by the processor to enable the processor to execute the thickness measurement method described above.

[0014] The fifth aspect of the present invention provides a thinning machine, which is characterized in that it is used for thinning the wafer and performing the method described in any one of the above during the thinning process.

[0015] When only one frame of spectral signal is obtained in the present invention, peak extraction is performed using a preset intensity threshold. When only one peak is extracted, it indicates that the distance between the main peak and the secondary peak is small and the secondary peak is covered by the main peak. Therefore, it is necessary to find the position of the secondary peak. Specifically, the peak value of the peak can be set as the peak value of the main peak and a preset thickness guess value is obtained. The peak value of the secondary peak is obtained by solving the thickness equation in reverse, and this is used as the initial guess. The pseudo Voigt fitting equation for two peaks is used to accurately fit this frame of spectral signal, successfully solving the problems of the lack of initial guess for only one frame of spectral signal and the difficulty in accurately identifying the position of the secondary peak due to the proximity of the two peaks, and being able to accurately fit the peak values of the main peak and the secondary peak of one frame of spectral signal.

[0016] When two peaks are extracted from one frame of spectral signal of a wafer in the present invention, the two peak values can be directly used as the initial guess of the pseudo Voigt fitting equation for two peaks to fit this frame of spectral signal, effectively solving the problem of the lack of initial guess for only one frame of spectral signal, and being able to more accurately fit the peak values of the main peak and the secondary peak in one frame of spectral signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0018] Figure 1 It is a flowchart of a peak extraction method in an embodiment of the present invention; Figure 2 It is a flowchart of another peak extraction method in an embodiment of the present invention; Figure 3 It is a spectral signal diagram when one peak is extracted in an embodiment of the present invention; Figure 4 It is a spectral signal diagram when two peaks are extracted in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] The following will clearly and completely describe the technical solutions of the present invention with reference to the drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0020] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0021] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can also be the communication inside two elements. It can be a wireless connection or a wired connection. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0022] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0023] As Figure 1 shown, an embodiment of the present invention provides a peak extraction method, which is executed by an electronic device such as a computer or a server, and specifically includes: S1. Obtain a frame of spectral signal of the wafer.

[0024] The spectral signal of the wafer is collected in real time by a spectrometer, or the spectral signal for a period of time is collected, and a frame of the spectral signal is selected. In this embodiment, only in the case of only one frame of spectral signal, peak extraction is performed. The spectral signal has the wavelength or pixel as the abscissa and the intensity of the spectral signal as the ordinate.

[0025] S2. Perform peak extraction on the current frame of spectral signal according to a preset intensity threshold, and determine whether it is a single peak; when a single peak is extracted, step S3 is executed.

[0026] The preset intensity threshold is an empirical value, and the corresponding empirical value can be selected according to the type of experiment. For example, if it is all spectral confocal, the same set of threshold empirical values can be used.

[0027] S3. Determine the peak value of the peak as the main peak value.

[0028] Take the wavelength at the peak center position of the peak as the main peak value.

[0029] S4. Obtain a thickness guess value.

[0030] The thickness guess value can be obtained in various ways, such as: empirical values measured through multiple measurements or experiments, approximate thickness parameters measured by other contact measurement methods, and an approximate initial thickness value added to the wafer at the initial frame.

[0031] S5. Use the thickness equation to inversely solve for the secondary peak value based on the thickness guess value and the main peak value.

[0032] When only one peak is extracted, it indicates that the distance between the main peak and the secondary peak is small at this time, and the secondary peak is covered by the main peak. A relatively accurate secondary peak value can be inversely solved through the thickness guess value.

[0033] S6. Use the main peak value and the secondary peak value as the initial guess values of the double-peak pseudo Voigt fitting equation to fit the spectral signal of the current frame, and obtain the main peak value and the secondary peak value of the spectral signal of the current frame.

[0034] The double-peak pseudo Voigt fitting equation can be used to fit two peaks in the spectral signal simultaneously. This method can not only avoid the interference of adjacent peaks, but also normally fit the area where the spectral derivative is always less than 0. The introduction of the double-peak pseudo Voigt fitting equation makes the fitting result more accurate and stable. At the same time, since the fitting probability of the double-peak pseudo Voigt fitting equation depends on the symmetry center (peak) of the signal, the main peak and secondary peak positions of the real spectral signal can be used to accurately fit the spectral signal of this frame. The finally fitted equation can obtain the real main peak and secondary peak positions of the spectral signal of the current frame.

[0035] In this embodiment, in the analysis of the spectral signal, when there is only one frame of spectral signal, if directly processed, it may face the problems of lack of initial guess and difficulty in accurately identifying the position of the secondary peak when the two peaks are close. Specifically, for this frame of spectral signal, peak extraction is performed using a preset intensity threshold. When only one peak is extracted, it indicates that the distance between the main peak and the secondary peak is small and the secondary peak is covered by the main peak. Therefore, it is necessary to find the position of the secondary peak. Specifically, the peak value of the peak can be set as the main peak value and the preset thickness guess value can be obtained, and the secondary peak value is inversely solved through the thickness equation and used as the initial guess. The double-peak pseudo Voigt fitting equation is used to accurately fit this frame of spectral signal, successfully solving the problems of lack of initial guess for only one frame of spectral signal and difficulty in accurately identifying the position of the secondary peak due to the proximity of the two peaks, and being able to accurately fit the main peak value and the secondary peak value of a frame of spectral signal.

[0036] As Figure 2 shown, when determining the number of peaks in step S2, when two peaks are extracted, step S7 is executed: S7. Determine that the peak values of the two peaks are the main peak value and the secondary peak value respectively.

[0037] When two peaks are extracted, the first peak is regarded as the main peak and the second peak is regarded as the secondary peak.

[0038] S8, taking the main peak peak value and the secondary peak peak value as the initial guess values of the double-peak pseudo Voigt fitting equation, fitting the spectral signal of the current frame, and obtaining the main peak peak value and the secondary peak peak value of the spectral signal of the current frame.

[0039] In this embodiment, when two peaks are extracted from the spectral signal of only one frame, the center positions of the main peak and the secondary peak can be accurately determined. The two peak values can be directly used as the initial guess of the double-peak pseudo Voigt fitting equation to fit the spectral signal of this frame, effectively solving the problem of the lack of initial guess of the spectral signal of only one frame, and being able to more accurately fit the main peak peak value and the secondary peak peak value in the spectral signal of one frame.

[0040] Among them, the thickness equation in step S5 is: ; Among them, represents the thickness, is the main peak peak value, is the secondary peak peak value, , , , , , , , are the parameter results fitted according to the displacement stage and spectrometer measurement data.

[0041] Substituting the center position of the main peak into the main peak peak value in the formula , and substituting the thickness guess value into the thickness in the formula , the secondary peak peak value can be solved inversely.

[0042] Furthermore, taking the main peak peak value and the secondary peak peak value as the initial guess values of the double-peak pseudo Voigt fitting equation to fit the spectral signal of the current frame in step S6 includes: Taking the main peak peak value, the secondary peak peak value and the preset parameters as the initial guess values of the double-peak pseudo Voigt fitting equation to fit the spectral signal of the current frame, and the preset parameters include the intensity maximum value of the spectral signal, the Gaussian signal proportion in the spectral signal and the width of the peak in the spectral signal; Among them, the double-peak pseudo Voigt fitting equation is: ; Among them, represents the intensity at any wavelength in the spectral signal of the current frame, and represents the maximum intensity of the spectral signal, and represents the proportion of Gaussian signal in the spectral signal, and represents the peak value of the main peak and the peak value of the secondary peak in the spectral signal, and represents the width of the peak in the spectral signal, is the wavelength independent variable in the spectral signal of the current frame.

[0043] When fitting the spectral signal of this frame, it is necessary to continuously fit the double-peak pseudo Voigt fitting equation according to the wavelength in this frame signal as the independent variable and the corresponding intensity until the spectral signal is successfully fitted. The fitting equation contains eight parameters. Among them, and The accuracy of can determine the fitting probability of the double-peak pseudo Voigt fitting equation. By extracting the peak value of the main peak and the peak value of the secondary peak of a frame of spectral signal, the spectral signal of the first frame can be accurately and successfully fitted. Even if the initial guess of the remaining parameters deviates greatly from the actual value, it can be successfully fitted with a high probability and can directly use empirical values without specifically analyzing the data to estimate.

[0044] The double-peak pseudo Voigt fitting equation in this embodiment includes the maximum intensity of the spectral signal, the proportion of Gaussian signal, peak values and peak widths, and continuously fits with the wavelength in a frame of signal as the independent variable and its corresponding intensity. Since among the eight parameters in the fitting equation, the accuracy of the two peak values plays a decisive role in the fitting probability, by accurately extracting the central positions of the main and secondary peaks of a frame of spectral signal, the spectral signal of this frame can be accurately and successfully fitted. Moreover, even if the initial guess of the remaining parameters deviates greatly from the actual value, it has a high probability of being successfully fitted and can directly use empirical values without specifically analyzing the data for estimation, improving the efficiency and accuracy of fitting a frame of spectral signal.

[0045] In one embodiment, before step S2 extracts peaks from the spectral signal of the current frame according to the preset intensity threshold, it further includes: Obtain the background spectral signal from the measurement conditions.

[0046] Specifically, the spectrometer can be used to collect signals from the thinning machine without placing the wafer; or multiple groups of spectral signals of multiple measured samples can be collected, and each group of spectral signals is collected based on the same measurement conditions.

[0047] The sample to be measured can be any substance. A spectrometer is used to collect signals from the sample to be measured placed on the measurement table. Specifically, different samples are placed under the same measurement conditions, and multiple sets of spectral signals are collected. Then, the error that appears in each set and does not change with the measurement conditions and the sample is extracted from the multiple sets of spectral signals, which is the background spectral signal. The measurement conditions cover all customizable input parameters such as specific light source intensity, wavelength range, measurement angle, and environmental temperature, humidity, resolution, etc., to ensure the diversity and representativeness of the data.

[0048] Subtract the background spectral signal from the current frame spectral signal of the wafer to obtain the true spectral signal of the wafer in the current frame.

[0049] Subtract the background noise signal in the current frame spectral signal to reduce the interference of background error on the data and improve the accuracy of the signal.

[0050] Judge the main peak of the true spectral signal; If there is a main peak, smooth the true spectral signal according to the preset smoothing intensity.

[0051] If there is no main peak, stop extracting the peak of the current frame spectral signal.

[0052] Among them, the smoothing processing methods can adopt methods such as low-pass filtering, wavelet transform, moving average, Savitzky-Golay filtering, etc. The corresponding preset smoothing intensity is an empirical value. There is a set of corresponding intensity empirical values for different experimental types, and the empirical value can be selected according to the actual situation specifically.

[0053] In this embodiment, by obtaining the background spectral signal and subtracting it from the spectral signal of this frame, the interference of background error on the data is effectively reduced, and the reliability and credibility of the entire spectral analysis result are improved. Then, by judging the main peak, the spectral signal can be processed targeted, and the analysis efficiency and accuracy are improved. When there is a main peak, smoothing is performed according to the preset smoothing intensity, which can reduce noise interference, highlight the peak characteristics, make the spectral signal more accurate, and provide reliable data for accurately extracting the peak center position. If there is no main peak, the extraction is stopped to avoid wasting computing resources and time.

[0054] The above embodiments determine the initial guess of the double-peak pseudo Voigt fitting equation according to two situations, solving the problem of no accurate initial guess when fitting only one frame of spectral signal; moreover, the initial guess obtained by the above steps has high accuracy, thereby improving the accuracy of the double-peak pseudo Voigt fitting equation fitting the spectral signal, and then obtaining the accurate positions of the two peak center values.

[0055] In addition, in step S5, using the thickness equation to inversely solve the secondary peak peak value according to the thickness guess value and the main peak peak value can also be: Obtain the wavelength interval.

[0056] Calculate the predicted peak value of the secondary peak according to the wavelength interval and the peak value of the main peak.

[0057] Use the thickness equation to calculate the thickness based on the peak value of the main peak and the predicted peak value of the secondary peak. Continuously update the wavelength interval according to the difference between the guessed thickness value and the thickness, and then update the predicted peak value of the secondary peak until the difference between the guessed thickness value and the thickness is less than the preset convergence threshold, and obtain the peak value of the secondary peak that meets the accuracy requirements.

[0058] Specifically, assume a relatively small wavelength interval deltaw. Then the predicted peak value of the secondary peak w2’ = w1 + deltaw, where w1 is the peak value of the main peak. Substitute w1 and w2’ into the thickness equation to obtain an inaccurate thickness calculation result t1’. Continuously update the value of w2’ according to the difference between the guessed thickness value t1 and t1’, and continuously search and adjust in the solution space. Each update is a more accurate approximation of the position of the secondary peak, gradually narrowing the gap with the true position of the secondary peak. Until the deviation between t1 and t1’ is less than the preset convergence threshold (such as 1e-4). At this time, the value of w2’ obtained can be considered as the position of the relatively accurate secondary peak. w1 and w2’ are the peak parameters of the double-peak pseudo Voigt fitting equation. The specific method for updating the wavelength interval can be any general method optimized by a sudden function. This method of finding the data closest to the true secondary peak through iterative update significantly improves the accuracy of determining the peak value of the secondary peak.

[0059] The following is an illustrative example of the above embodiment: Obtain the first-frame spectral signal s1 and the background spectral signal s0 of the wafer; and subtract the background spectral signal s0 to obtain the true spectral signal s2 after background removal; then perform main peak judgment on the true spectral signal s2. When there is a main peak, perform Savitzky-Golay filtering on the true spectral signal s2 again to make it smooth, obtain the smoothed spectral signal s3, and then perform peak extraction on the smoothed spectral signal s3; Such as Figure 3As shown, the abscissa represents the wavelength and the ordinate represents the intensity. If the second peak is not recognized and only one peak is extracted, the wavelength of the main peak peak value is 550.0 nm. The blue curve in the figure is the true spectral signal s2, the red curve is the smoothed spectral signal s3, and the position of the black dotted line is the center position of the peak. Then set a guessed thickness value of 100 microns, and substitute the wavelength of 550.0 nm and the guessed thickness value of 100 microns into the thickness equation for reverse solution, and the guessed wavelength of the secondary peak peak value of 552.8 nm can be obtained, that is, the position of the gray dotted line in the figure; finally, substitute the wavelengths of 550.0 and 552.8 into the double-peak pseudo Voigt fitting equation to fit the first-frame spectral signal. After successful fitting, the main peak peak value and the secondary peak peak value parameters obtained are the actual center positions of the main and secondary peaks, which are 549.9 nm and 552.7 nm respectively.

[0060] As Figure 4 shown, the abscissa represents the wavelength and the ordinate represents the intensity. If two peaks are extracted, the wavelength of the main peak peak value is 550.0 nm, and the wavelength of the secondary peak peak value is 554.7 nm. The blue curve in the figure is the true spectral signal s2, the red curve is the smoothed spectral signal s3, and the position of the black dotted line is the center position of the peak. Then substitute the wavelengths of 550.0 and 554.7 into the double-peak pseudo Voigt fitting equation to fit the first-frame spectral signal. After successful fitting, the main peak peak value and the secondary peak peak value parameters obtained are the actual center positions of the main and secondary peaks, which are 549.9 nm and 554.9 nm respectively.

[0061] Further, in step S6, after using the main peak peak value and the secondary peak peak value as the initial guessed values of the double-peak pseudo Voigt fitting equation to fit the current frame spectral signal, it further includes: Obtain the fitting result of the double-peak pseudo Voigt fitting equation for the current frame spectral signal, and calculate the root mean square error between the fitting result and the current frame spectral signal; Judge whether the root mean square error is less than the preset root mean square error; If the root mean square error is less than the preset root mean square error, select the two peak values in the fitting result as the main peak peak value and the secondary peak peak value of the current frame spectral signal.

[0062] If the root mean square error is greater than the preset root mean square error, update the initial guess until the mean square error between the fitting result of the double-peak pseudo Voigt fitting equation for the current frame spectral signal and the current frame spectral signal is less than the preset mean square error, and select the two peak values in the fitting result as the main peak peak value and the secondary peak peak value of the current frame spectral signal; Record the update times of the initial guess. When the update times exceed the preset update times and the root mean square error requirement is still not met, skip the current frame spectral signal and process the next frame of spectral signal.

[0063] In this embodiment, the root mean square error between the fitting result and a frame of spectral signal is calculated to re-evaluate the difference degree between the fitting result and the original spectral signal. When the root mean square error is less than the preset value, it indicates that the difference between the fitting result and the original spectral signal is within an acceptable range, ensuring that the determined peak value has high accuracy. When the root mean square error is greater than the preset value, it means that the current fitting effect is not good, and the initial guess needs to be updated to optimize the fitting until the mean square error meets the requirements, so as to obtain the actual peak value closer to the real situation. At the same time, the update times of the initial guess are recorded. When the preset update times are exceeded and the root mean square error requirement is still not met, the current frame of spectral signal is skipped to process the next frame of spectral signal, avoiding excessive consumption of computing resources on difficult-to-fit spectral signals and improving the efficiency of overall spectral signal processing.

[0064] An embodiment of the present invention further provides a thickness measurement method, which is executed by an electronic device such as a computer or a server, and specifically includes: Using the above-mentioned peak extraction method to obtain the main peak value and the secondary peak value; Calculating the thickness of the wafer at the current frame according to the main peak value and the secondary peak value.

[0065] Specifically, the thickness of the wafer at the current frame can be calculated by using the thickness equation.

[0066] In this embodiment, the main peak value and the secondary peak value are accurately obtained through the above-mentioned peak extraction method, and then the thickness of the wafer at the current frame is calculated according to the obtained main peak value and secondary peak value through the thickness equation, ensuring the accuracy of the wafer thickness calculation.

[0067] An embodiment of the present invention further provides a thinning machine for thinning the wafer and performing the peak extraction method and the thickness measurement method described in any one of the above during the thinning process.

[0068] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0069] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and combinations of flows and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to the processors of general-purpose computers, special-purpose computers, embedded processors, or other programmable data processing devices to produce a machine, such that the instructions executed by the processors of the computer or other programmable data processing devices produce means for implementing the functions specified in the flow Figure 1 one flow or multiple flows and / or blocks Figure 1 means for implementing the functions specified in one block or multiple blocks.

[0070] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory produce a manufactured article including instruction means for implementing the functions specified in the flow Figure 1 one flow or multiple flows and / or blocks Figure 1 means for implementing the functions specified in one block or multiple blocks.

[0071] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, and thus the instructions executed on the computer or other programmable device provide steps for implementing the functions specified in the flow Figure 1 one flow or multiple flows and / or blocks Figure 1 means for implementing the functions specified in one block or multiple blocks.

[0072] Obviously, the above embodiments are only examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A peak extraction method, characterized in that, Including: Obtain a frame of spectral signal of the wafer; Perform peak extraction on the current frame of spectral signal according to a preset intensity threshold; When a peak is extracted, determine the peak value of the peak as the main peak value; Obtain a thickness guess value; Use the thickness equation to inversely solve for the secondary peak value according to the thickness guess value and the main peak value; Use the main peak value and the secondary peak value as the initial guess values of the double-peak pseudo Voigt fitting equation to fit the current frame of spectral signal, and obtain the main peak value and the secondary peak value of the current frame of spectral signal.

2. The method according to claim 1, wherein When two peaks are extracted, determine that the peak values of the two peaks are the main peak value and the secondary peak value respectively; Use the main peak value and the secondary peak value as the initial guess values of the double-peak pseudo Voigt fitting equation to fit the current frame of spectral signal, and obtain the main peak value and the secondary peak value of the current frame of spectral signal.

3. The method according to claim 1, characterized in that The thickness equation is: ; Among them, represents the thickness, is the peak value of the main peak, is the peak value of the secondary peak, , , , , , , , are the parameter results fitted according to the measurement data of the displacement stage and the spectrometer.

4. The method according to claim 1, characterized in that, Using the main peak value and the secondary peak value as the initial guess values of the double-peak pseudo Voigt fitting equation to fit the current frame of spectral signal includes: Use the main peak value, the secondary peak value and preset parameters as the initial guess values of the double-peak pseudo Voigt fitting equation to fit the current frame of spectral signal, and the preset parameters include the intensity maximum value of the spectral signal, the proportion of the Gaussian signal in the spectral signal, and the width of the peak in the spectral signal; Wherein, the double-peak pseudo Voigt fitting equation is: ; Among them, represents the intensity at any wavelength in the current frame spectral signal, and represents the maximum intensity of the spectral signal, and represents the proportion of the Gaussian signal in the spectral signal, and represent the peak value of the main peak and the peak value of the secondary peak in the spectral signal, and represent the width of the peak in the spectral signal, is the wavelength independent variable in the current frame spectral signal.

5. The method according to claim 1, wherein Using the thickness equation to inversely solve for the secondary peak value according to the thickness guess value and the main peak value includes: Obtain the wavelength interval; Calculate the predicted secondary peak value according to the wavelength interval and the main peak value; Use the thickness equation to calculate the thickness according to the main peak value and the predicted secondary peak value, continuously update the wavelength interval according to the difference between the thickness guess value and the thickness, and then update the predicted secondary peak value until the difference between the thickness guess value and the thickness is less than the preset convergence threshold, and obtain the secondary peak value that meets the accuracy requirements.

6. The method according to claim 1, wherein Before performing peak extraction on the current frame of spectral signal according to the preset intensity threshold, it further includes: Obtain the background spectral signal originating from the measurement conditions; Subtract the background spectral signal from the current frame of spectral signal of the wafer to obtain the true spectral signal of the wafer in the current frame; Perform main peak judgment on the true spectral signal; If there is a main peak, perform smoothing processing on the true spectral signal according to the preset smoothing intensity; If there is no main peak, stop the peak extraction of the current frame of spectral signal.

7. A thickness measurement method, characterized in that, Including: Obtain the main peak value and the secondary peak value by using the method described in any one of claims 1-6; Calculate the thickness of the wafer at the current frame according to the main peak value and the secondary peak value.

8. A peak extraction device, characterized in that, Including: A processor and a memory connected to the processor; wherein, the memory stores instructions executable by the processor, and the instructions are executed by the processor to enable the processor to execute the peak extraction method described in any one of claims 1-6.

9. A thickness measuring device, characterized in that, Including: A processor and a memory connected to the processor; wherein, the memory stores instructions executable by the processor, and the instructions are executed by the processor to cause the processor to execute the thickness measurement method as recited in claim 7.

10. A thinning machine, characterized in that, For thinning a wafer and executing the method recited in any one of claims 1-7 during the thinning process.

Images