Thickness measurement method based on overlapping signal decomposition of spectral confocal measurement system

Abstract

The present invention proposes a thickness measurement method based on the decomposition of overlapping signals of a spectral confocal measurement system. The method decomposes the overlapping peak spectral signal curve data of the object to be measured using a calibrated single-peak signal curve of the spectral confocal measurement system, and calculates the thickness of the object to be measured based on the decomposed single-peak spectral signal curve data of the upper and lower surfaces. The thickness measurement method provided by the present invention achieves accurate measurement of thin films with micron-level thickness through an algorithm without the need for any additional optical elements, thereby expanding the measurement range and application scenarios of the spectral confocal measurement system. The method solves the technical problem that when the thickness of the object to be measured is too small, the single-peak spectral signals of the upper and lower surfaces overlap, making it impossible to measure the thickness of the object to be measured with micron-level thickness.

Description

Technical Field

[0001] The present invention relates to the technical field of optical detection, and in particular to a thickness measurement method based on overlapping signal decomposition of a spectral confocal measurement system. Background Art

[0002] Thickness is one of the most widely used parameters related to length. It is defined as the distance between the top and bottom, or front and back, of an object with parallel sides. Thickness measurement is required in various research and industrial fields, such as automotive, shipbuilding, aviation, nanotechnology, and biotechnology. With the advent of the Fourth Industrial Revolution, the demand for thickness measurement in the semiconductor and display industries has steadily increased. For example, in the manufacture of smart semiconductor devices, the physical thickness of various layers, such as substrates and thin films, must be monitored and controlled to ensure performance. Depending on the test conditions, such as the material properties and shape of the sample, the thickness range, and the degree of measurement accuracy, different types of thickness measurement methods have been proposed and implemented for different applications. Thickness measurement methods can be broadly categorized as contact and non-contact. In recent years, non-contact measurement methods have attracted widespread attention due to their practical advantages in non-destructive testing and measurement. Non-contact methods are categorized as optical and non-optical.

[0003] Laser spectral confocal microscopy (LSCM) uses the spectral axial response signal from a spectrometer to identify two central wavelengths corresponding to the upper and lower surfaces of a transparent material. The thickness of the object being measured is then determined from the wavelength-displacement mapping relationship and the refractive index. LSM is an emerging technology among existing non-contact optical methods. It offers advantages such as absolute measurement and focus tracking, which can improve focus sensitivity, sensor linearity, and signal-to-noise ratio.

[0004] However, when using existing laser spectral confocal microscopy techniques on thin objects, the two wavelength-centered spectral axis response spectral signal curves cannot be independent of each other and are coupled and superimposed. This causes the peak wavelength of the spectral signal curve to drift, leading to inaccurate thickness measurements. Summary of the Invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and propose a thickness measurement method based on overlapping signal decomposition of a spectral confocal measurement system.

[0006] To achieve the above objectives, the present invention adopts the following specific technical solutions:

[0007] A thickness measurement method based on overlapping signal decomposition of a spectral confocal measurement system, the thickness measurement method comprising the following steps:

[0008] S1. Calibrate the single peak signal curve of the spectral confocal measurement system;

[0009] S2. placing the object to be measured in the spectral confocal measurement system to obtain overlapping peak spectral signal curve data of the object to be measured;

[0010] S3. Decomposing the overlapping peak spectrum signal curve data into single-peak spectrum signal curve data of the upper surface and single-peak spectrum signal curve data of the lower surface of the object to be tested according to the single-peak spectrum signal curve data;

[0011] S4. Calculate the thickness of the object to be measured based on the single-peak spectrum signal curve data of the upper and lower surfaces.

[0012] Furthermore, the specific steps of the calibration in step S1 are:

[0013] S101, placing a calibration reflective surface at a measurement position of the spectral confocal measurement system, and moving the position of the calibration reflective surface on the optical axis of the dispersive objective lens of the spectral confocal measurement system with a preset step size;

[0014] S102, collecting single-peak spectrum signal curve data of light beams of different wavelengths corresponding to different position information;

[0015] S103, obtaining single-peak signal curve data for calibrating the spectral confocal measurement system, wherein the single-peak signal curve data is as shown in formula (1):

[0016] When the calibration reflective surface moves d m At, and d m In d i and d i+1 When , the single peak signal curve data is expressed as:

[0017]

[0018] Wherein, i represents the movement of the calibration reflection surface for the i-th time; i+1 represents the movement of the calibration reflection surface for the i+1-th time; d i Indicates the position information of the calibration reflection surface moving for the i-th time; d i+1 Indicates the position information of the calibration reflection surface moving for the i+1th time; Represents the single-peak signal curve data corresponding to the ith movement of the calibration reflection surface; represents the single peak signal curve data corresponding to the movement of the calibration reflective surface for the i+1th time; △d represents the preset step size; d m Indicates the position information of the calibration reflective surface at any time; Indicates the single-peak signal curve data corresponding to the calibration reflection surface at any time.

[0019] Furthermore, the specific steps of step S3 are:

[0020] S301, establishing a model of the overlapping peak spectrum signal curve data of the analyte to be decomposed, the model is shown in formula (2):

[0021]

[0022] in, Represents the overlapping peak spectrum signal curve data; d up Indicates the position information of the upper surface of the object to be measured; d down Indicates the position information of the lower surface of the object to be measured; Indicates that the calibration reflective surface is at position d on the surface of the object to be measured up Single peak signal curve data when Indicates that the calibration reflective surface is at position d below the object under test down k1 represents the refractive index compensation factor of the upper surface of the object to be measured; k2 represents the refractive index compensation factor of the lower surface of the object to be measured;

[0023] S302, initializing the position information of the upper surface of the object to be measured, the position information of the lower surface of the object to be measured, and the refractive index compensation factor of the lower surface of the object to be measured;

[0024] S303, fixing the refractive index compensation factor of the lower surface of the object to be measured and the position information of the lower surface of the object to be measured, calculating the minimum value of formula (3) according to the first preset condition, and then obtaining the updated refractive index compensation factor of the upper surface of the object to be measured and the updated position information of the upper surface of the object to be measured; the formula (3) is as follows:

[0025]

[0026] Among them, loss up (k, d) represents the loss function of the upper surface of the object to be tested;

[0027] S304: Fix the refractive index compensation factor of the upper surface of the object to be measured and the position information of the upper surface of the object to be measured, calculate the minimum value of formula (4) according to the first preset condition, and then obtain the updated refractive index compensation factor of the lower surface of the object to be measured and the updated position information of the lower surface of the object to be measured; the formula (4) is as follows:

[0028]

[0029] Among them, loss down (k, d) represents the loss function of the lower surface of the object to be tested;

[0030] S305. Determine whether a second preset condition is met. If the second preset condition is not met, repeat steps S303 and S304 to perform iterative updating. If the second preset condition is met, stop the iterative updating and obtain the iteratively updated position information of the upper surface of the object to be measured, the position information of the lower surface of the object to be measured, the refractive index compensation factor of the upper surface of the object to be measured, and the refractive index compensation factor of the lower surface of the object to be measured. The second preset condition is that the value of the total loss value function does not change. Formula (5) is as follows:

[0031]

[0032] Among them, loss all Represents the total loss function value.

[0033] Furthermore, in step S302, initialization is specifically as follows: assigning the position information of the upper surface of the object to be measured and the position information of the lower surface of the object to be measured to the position information of the first movement of the calibration reflective surface, and assigning the refractive index compensation factor of the lower surface of the object to be measured to 0.

[0034] Furthermore, the first preset condition is: calculating k={0, Δk e ,…,k max}, d={d1, d 1+ △d e ,…,d N}, the values of k and d at which the loss function takes the minimum value;

[0035] Wherein k represents the refractive index compensation factor of the upper surface of the object to be measured or the refractive index compensation factor of the lower surface of the object to be measured; Δk e represents the optimization step size of the refractive index compensation factor; k max represents the maximum optimization step size of the refractive index compensation factor; d1 represents the position information of the first movement of the calibration reflective surface; △d e represents the optimized step length of the surface position of the object to be measured; d N Indicates the maximum optimization step size of the surface position of the object to be measured.

[0036] Furthermore, the formula (6) for calculating the thickness of the object to be measured in step S4 is specifically:

[0037]

[0038] Wherein, thickness represents the thickness of the object to be measured; n represents the refractive index of the object to be measured; and NA represents the numerical aperture of the dispersion objective lens of the spectral confocal measurement system.

[0039] The thickness measurement method based on the decomposition of overlapping signals of a spectral confocal measurement system provided by the present invention can be applied to an existing spectral confocal measurement system, and the overlapping peak signals of the upper and lower surfaces of the object to be measured are decomposed, and when the upper and lower surface loss functions are obtained by an algorithm to obtain the minimum value, the single-peak spectral signal curve data of the upper surface of the object to be measured and the single-peak spectral signal curve data of the lower surface of the object to be measured are obtained, thereby achieving the purpose of making the difference between the decomposed spectral signal and the real spectral signal smaller, thereby improving the accuracy of the thickness measurement method. According to the decomposed single-peak spectral signal curve data, the thickness of the object to be measured is obtained. The embodiment of the present invention achieves accurate measurement of thin films with micron-level thickness only through an algorithm without any additional optical elements, thereby expanding the measurement range and application scenarios of the spectral confocal measurement system. It solves the technical problem that when the thickness of the object to be measured is too small, the single-peak spectral signals of the upper and lower surfaces overlap with each other, and the thickness of the object to be measured with micron-level thickness cannot be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a first schematic diagram of a spectral confocal measurement system according to an embodiment of the present invention;

[0041] Figure 2 is a second schematic diagram of a spectral confocal measurement system according to an embodiment of the present invention;

[0042] Figure 3 4 is a flow chart of a thickness measurement method based on overlapping signal decomposition of a spectral confocal measurement system according to an embodiment of the present invention.

[0043] Reference numerals include:

[0044] White point light source assembly 1, beam splitter 2, dispersive objective lens 3, calibration reflective surface 4, electric displacement platform 5, pinhole 6, spectrometer 7, object to be measured 8. DETAILED DESCRIPTION

[0045] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, identical modules are denoted by identical reference numerals. In the case of identical reference numerals, their names and functions are also identical. Therefore, their detailed description will not be repeated.

[0046] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0047] The specific working mode of the present invention is described in detail below with reference to the accompanying drawings:

[0048] In order to illustrate the embodiment of the present invention in detail, the spectral confocal measurement system in the prior art is described in detail. The spectral confocal measurement system used in the embodiment of the present invention is as follows: Figure 1 and Figure 2 As shown, Figure 1 The calibration reflective surface 4 is placed at the middle measurement position, and the single-side calibration reflective surface 4 obtained by the spectrometer 7 is a single-peak signal curve; Figure 2 The object to be measured 8 is placed at the middle measurement position. When the object to be measured 8 is relatively thin, the data obtained by the spectrometer 7 will show the overlap of two sets of single-peak signal curves. In the embodiment of the present invention, the calibration reflection surface 4 adopts a plane reflector. The spectral confocal measurement system includes a white point light source component 1, a beam splitter 2, a dispersive objective lens 3, an electric displacement platform 5 capable of driving the object to be measured 8 or the calibration reflection surface 4 to move back and forth, a pinhole 6, and a spectrometer 7, which are arranged in sequence along the optical path. The white point light source component 1 emits a white laser beam, which is split by the beam splitter 2. The transmitted beam is dispersed by the dispersive objective lens 3 and reaches the surface of the object to be measured 8. The beam reflected back from the surface of the object to be measured 8 is reflected by the dispersive objective lens 3 and the beam splitter 2. The reflected beam is incident on the spectrometer 7 through the pinhole 6. The thickness information of the object to be measured 8 is obtained by analyzing the data of the spectrometer 7. The thickness measurement method provided by the present invention can be applied to different differential confocal measurement systems in the prior art. Therefore, the spectral confocal measurement system may have other forms of changes, which are subject to actual usage. The present invention is not limited to this, and only gives examples to illustrate the embodiments of the present invention in detail.

[0049] The principle of the thickness measurement method provided by the present invention is as follows: the refractive index changes with the change of wavelength in the same medium. Therefore, the image point of the light beam after passing through the dispersion objective lens has different focusing positions on the optical axis, forming a series of continuous focusing spots on the optical axis, forming axial dispersion in the aberration, so that not all wavelengths of light beams can be focused on the surface of the object to be measured. When the measurement point on the surface of the object to be measured coincides with the point where the surface of the object to be measured is focused, the point where the light source component emits the light beam, the point where it can be focused on the surface of the object to be measured, and the point where it enters the spectrometer are conjugated to each other to form three confocal points. Therefore, the thickness information of the object to be measured can be obtained by analyzing the single-peak signal curve corresponding to the peak wavelength of the spectrometer. When the thickness of the object to be measured is very thin, the data obtained by the spectrometer will show the overlap of two sets of single-peak signal curves, and the thickness signal of the object to be measured cannot be directly extracted from the peak positions of the two sets of single-peak signals. The thickness measurement method provided by the present invention first calibrates the single-peak signal curve of the spectral confocal measurement system, obtains the single-peak signal curves obtained by the spectrometer when the single reflective surface is at different axial positions of the spectral confocal measurement system, and establishes an estimation model for the single-peak signal curve when the single reflective surface is at any position. Based on the proposed overlapping peak signal decomposition method, the overlapping peak signal of the spectrometer is decomposed when measuring an object to be measured that has reflective surfaces on both the upper and lower surfaces. The position information of the decomposed single-peak signal is used, combined with the refractive index of the object to be measured and the numerical aperture of the dispersion objective lens, to calculate the thickness information of the object to be measured.

[0050] The embodiment of the present invention provides a thickness measurement method based on the decomposition of overlapping signals of a spectral confocal measurement system, and the method flow chart is as follows: Figure 3 The thickness measurement method includes the following steps:

[0051] S1. First, calibrate the single-peak signal curve of the spectral confocal measurement system to obtain the single-peak signal curve data when the calibration reflection surface 4 is at different axial positions of the dispersion objective lens 3, that is, establish an estimation model of the single-peak signal curve when the single reflection surface is at any position in the spectral confocal measurement system.

[0052] The specific steps of calibration in step S1 are:

[0053] S101. Place the calibration reflective surface 4 at the measurement position of the spectral confocal measurement system. The motorized displacement platform 5 drives the calibration reflective surface 4 to move it in preset step sizes to different axial positions on the optical axis of the focusing end of the dispersive objective lens 3. In this embodiment of the present invention, the calibration reflective surface is a calibration plane reflector, the preset step size Δd is 1 μm, the number of movements N is 2000, and the operating range of the spectral confocal measurement system is 3700 μm.

[0054] S102 , collecting single-peak spectrum signal curve data of light beams of different wavelengths corresponding to different position information, and collecting single-peak signal curve data corresponding to the spectrometer 7 each time the electric displacement platform 5 moves.

[0055] S103, obtaining single-peak signal curve data for calibrating the spectral confocal measurement system, wherein the single-peak signal curve data is as shown in formula (1), and the position of the electric displacement platform 55 when the electric displacement platform 5 moves for the i-th time is recorded as d i , the obtained single peak signal curve data is recorded as Where i∈(1,N).

[0056] When the calibration reflective surface 4 moves to d m At, and d m In d i and d i+1 When , the single peak signal curve data is expressed as:

[0057]

[0058] Wherein, i represents the movement of the calibration reflection surface 4 for the i-th time; i+1 represents the movement of the calibration reflection surface 4 for the i+1th time; d i Indicates the position information of the calibration reflective surface 4 moving for the i-th time; d i+1 Indicates the position information of the calibration reflective surface 4 moving for the i+1th time; Represents the single-peak signal curve data corresponding to the ith movement of the calibration reflective surface 4; represents the single peak signal curve data corresponding to the movement of the calibration reflective surface 4 for the i+1th time; △d represents the preset step size; d m Indicates the position information of the calibration reflective surface 4 at any time; It represents the single-peak signal curve data corresponding to the calibration reflection surface 4 at any time.

[0059] S2. Measure the thickness of the object 8 by placing the object 8 horizontally in the spectral confocal measurement system, ensuring that both the upper and lower surfaces of the object 8 are within the working range of the spectral confocal system, and obtain overlapping peak spectral signal curve data of the object 8.

[0060] S3. Decompose the overlapping peak spectrum signal curve data into single-peak spectrum signal curve data of the upper surface and single-peak spectrum signal curve data of the lower surface of the object to be tested 8 according to the single-peak spectrum signal curve data.

[0061] S301, establishing a model of the overlapping peak spectrum signal curve data of the analyte 8 to be decomposed, the model is shown in formula (2):

[0062]

[0063] in, Represents the overlapping peak spectrum signal curve data; d up Indicates the position information of the upper surface of the object to be measured 8; d down Indicates the position information of the lower surface of the object to be measured 8; Indicates that the calibration reflective surface 4 is at position d on the surface of the object to be measured 8 up Single peak signal curve data when Indicates that the calibration reflective surface 4 is at position d on the lower surface of the object to be measured 8 down k1 represents the refractive index compensation factor of the upper surface of the object to be measured 8; k2 represents the refractive index compensation factor of the lower surface of the object to be measured 8.

[0064] In the embodiment of the present invention, by obtaining d up and d down , combined with the refractive index of the object 8 to be measured and the data aperture of the dispersive objective lens 3, the thickness of the object 8 to be measured can be obtained.

[0065] S302, initializing the position information d of the upper surface of the object to be measured 8 up , the position information d of the lower surface of the object to be measured 8 down and the refractive index compensation factor k2 of the lower surface of the object to be measured 8, in the embodiment of the present invention, d up =d1,d down =d1, k2=0, where d1 represents the position information corresponding to the curve data collected when the calibration reflective surface 4 moves to the first position point.

[0066] S303, fixing the refractive index compensation factor k2 of the lower surface of the object to be measured 8 and the position information d of the lower surface of the object to be measured 8 down Calculate the minimum value of formula (3) according to the first preset condition, and then obtain the updated refractive index compensation factor of the upper surface of the object to be measured 8 and the updated position information of the upper surface of the object to be measured 8. That is, calculate k={0, △k e ,…,k max}, d={d1, d 1+ △d e ,…,d N}, make loss up (k, d) takes the minimum value of k and d as k1 and d up The updated value of . The formula (3) is as follows:

[0067]

[0068] Among them, loss up(k, d) represents the loss function of the upper surface of the object to be tested 8;

[0069] S304: Fix the refractive index compensation factor of the upper surface of the object to be measured 8 and the position information of the upper surface of the object to be measured 8, calculate the minimum value of formula (4) according to the first preset condition, and then obtain the updated refractive index compensation factor k2 of the lower surface of the object to be measured 8 and the updated position information d of the lower surface of the object to be measured 8. down . That is, calculate k={0,△k e ,…,k max}, d={d1, d 1+ △d e ,…,d N}, so that the loss function loss down (k, d) takes the minimum value of k and d as k2 and d down The updated value of . Among them, the first preset condition is: calculate k={0, △k e ,…,k max}, d={d1, d 1+ △d e ,…,d N}, the loss function achieves the minimum value.

[0070] Wherein, k represents the refractive index compensation factor of the upper surface of the object to be measured 8 or the refractive index compensation factor of the lower surface of the object to be measured 8; Δk e Indicates the optimization step size of the refractive index compensation factor. The smaller the optimization step size is, the higher the thickness measurement accuracy will be, but the calculation time will take longer. max represents the maximum optimization step size of the refractive index compensation factor; d1 represents the position information of the calibration reflective surface 4 when it moves for the first time; △d e represents the optimized step length of the surface position of the object to be measured 8; d N Indicates the maximum optimization step length of the surface position of the object to be measured 8.

[0071] Formula (4) is as follows:

[0072]

[0073] Among them, loss down (k, d) represents the loss function of the lower surface of the object to be tested 8;

[0074] S305: Determine whether the second preset condition is met. If the value of the total loss value function still changes, repeat steps S303 and S304 to iteratively update. If the value of the total loss value function does not change, stop iterative updating, obtain the refractive index compensation factor k1 of the upper surface of the object to be tested 8 and the refractive index compensation factor k2 of the lower surface of the object to be tested 8; and combine formula (1) to obtain the position information d of the upper surface of the object to be tested 8 after iterative update. up , the position information d of the lower surface of the object to be measured 8 down The second preset condition is that the value of the total loss function does not change, and formula (5) is as follows:

[0075]

[0076] Among them, loss all Represents the total loss function value.

[0077] In the embodiment of the present invention, the loss value is iteratively calculated according to the formula, and the position information of the upper surface of the object to be measured 8, the position information of the lower surface of the object to be measured 8, the refractive index compensation factor of the upper surface of the object to be measured 8, and the refractive index compensation factor of the lower surface of the object to be measured 8 are obtained after the value of the total loss value function does not change. The difference between the value obtained by the above algorithm and the true value is minimized, so that the difference between the thickness value obtained by subsequent calculation and the true thickness value of the object to be measured 8 is minimized, thereby improving the accuracy of thickness measurement.

[0078] S4. Calculate the thickness of the object to be measured 8 according to the single-peak spectrum signal curve data of the upper and lower surfaces.

[0079] The formula (6) for calculating the thickness of the object to be measured 8 is specifically:

[0080]

[0081] Wherein, thickness represents the thickness of the object to be measured 8; n represents the refractive index of the object to be measured 8; and NA represents the numerical aperture of the dispersion objective lens 3 of the spectral confocal measurement system.

[0082] The present invention provides a thickness measurement method based on decomposing overlapping signals from a spectral confocal measurement system. The method can be applied to existing spectral confocal measurement systems. The method decomposes the overlapping peak signals resulting from the superposition of the upper and lower surface reflections of an object 8 to be measured. The method first calibrates the single-peak signal curve of the spectral confocal measurement system, obtains single-peak signal curves obtained by the spectrometer 7 when the single reflective surface is at different axial positions of the spectral confocal measurement system, and establishes an estimation model for the single-peak signal curve when the single reflective surface is at any position. The calibrated model is used to decompose the upper and lower surfaces of the object 8 to be measured. The difference between the decomposed single-peak signal curve data for the upper and lower surfaces and the actual single-peak signal curve data is minimized by estimating the model and iteratively calculating the loss value, thereby improving the accuracy of thickness measurement. The overlapping peak signal decomposition method proposed in the present invention decomposes the overlapping peak signal of the spectrometer 7 when measuring the object to be measured 8 with reflection surfaces on both the upper and lower surfaces. The position information of the decomposed single peak signal is used, and the thickness information of the object to be measured 8 is obtained by combining the refractive index of the object to be measured 8 and the numerical aperture of the dispersion objective lens 3. The thickness measurement method provided by the present invention has a fast measurement speed. It does not require axial scanning and does not require any additional optical elements. It can achieve accurate measurement of micron-level thickness films by building a model and coordinating the algorithm, thereby expanding the measurement range and application scenarios of the spectral confocal measurement system. It solves the technical problem that when the thickness of the object to be measured 8 is too small, the spectral data of the upper and lower surfaces will produce overlapping peaks, making it impossible to measure the thickness of the object to be measured at the micron level.

[0083] The embodiment of the present invention verifies the effectiveness of the thickness measurement method of the technical solution of the present invention through experiments. The system parameters of the selected spectral confocal measurement system are as follows: the data aperture NA of the dispersive objective lens 3 is 0.4, the measurement range of the spectral confocal measurement system is 3700 μm, and the object to be measured 8 is a glass sheet with a refractive index of 1.52.

[0084] Table 1 shows the thickness of the object 8 measured by the thickness measurement method of the present invention and the actual thickness of the object 8. The actual thickness of the object 8 was measured using an optical interferometer with a resolution of 0.01 μm. Five sets of measurement experiments were conducted using five objects 8 of different thicknesses. The results are as follows:

[0085] Table 1

[0086] Serial number True thickness Technical solution of the present invention 1 180.35μm 179.78μm 2 172.78μm 171.97μm 3 147.26μm 147.59μm 4 131.85μm 131.04μm 5 99.74μm 100.48μm

[0087] Using the thickness measurement method provided by the technical solution of the present invention, the spectral confocal measurement system has a range of more than 2.7%, and the thickness of the object to be measured with a thickness of more than 100 μm is measured with a measurement error within 1 μm.

[0088] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0089] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art may make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

[0090] The above specific embodiments of the present invention do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A thickness measurement method based on overlapping signal decomposition of a spectral confocal measurement system, characterized in that: The thickness measurement method comprises the following steps: S1. Calibrate the single peak signal curve of the spectral confocal measurement system; S2. placing the object to be measured in the spectral confocal measurement system to obtain overlapping peak spectral signal curve data of the object to be measured; S3. Decomposing the overlapping peak spectrum signal curve data into single-peak spectrum signal curve data of the upper surface and single-peak spectrum signal curve data of the lower surface of the object to be tested according to the single-peak spectrum signal curve data; S301, establishing a model of the overlapping peak spectrum signal curve data of the analyte to be decomposed, the model is shown in formula (2): in, Represents the overlapping peak spectrum signal curve data; d up Indicates the position information of the upper surface of the object to be measured; d down Indicates the position information of the lower surface of the object to be measured; Indicates that the calibration reflective surface is at position d on the surface of the object to be measured up Single peak signal curve data when Indicates that the calibration reflective surface is at position d below the object under test down k1 represents the refractive index compensation factor of the upper surface of the object to be measured; k2 represents the refractive index compensation factor of the lower surface of the object to be measured; S302, initializing the position information of the upper surface of the object to be measured, the position information of the lower surface of the object to be measured, and the refractive index compensation factor of the lower surface of the object to be measured; S303, fixing the refractive index compensation factor of the lower surface of the object to be measured and the position information of the lower surface of the object to be measured, calculating the minimum value of formula (3) according to the first preset condition, and then obtaining the updated refractive index compensation factor of the upper surface of the object to be measured and the updated position information of the upper surface of the object to be measured; the formula (3) is as follows: Among them, loss up represents the loss function of the upper surface of the object to be tested; S304: Fix the refractive index compensation factor of the upper surface of the object to be measured and the position information of the upper surface of the object to be measured, calculate the minimum value of formula (4) according to the first preset condition, and then obtain the updated refractive index compensation factor of the lower surface of the object to be measured and the updated position information of the lower surface of the object to be measured; the formula (4) is as follows: Among them, loss down represents the loss function of the lower surface of the object to be tested; S305. Determine whether a second preset condition is met. If the second preset condition is not met, repeat steps S303 and S304 to perform iterative updating. If the second preset condition is met, stop the iterative updating and obtain the iteratively updated position information of the upper surface of the object to be measured, the position information of the lower surface of the object to be measured, the refractive index compensation factor of the upper surface of the object to be measured, and the refractive index compensation factor of the lower surface of the object to be measured. The second preset condition is that the value of the total loss value function does not change. Formula (5) is as follows: Among them, loss all Represents the numerical value of the total loss function; S4. Calculate the thickness of the object to be measured based on the single-peak spectrum signal curve data of the upper surface and the lower surface.

2. The thickness measurement method according to claim 1, characterized in that: The specific steps of the calibration in step S1 are: S101, placing a calibration reflective surface at a measurement position of the spectral confocal measurement system, and moving the position of the calibration reflective surface on the optical axis of the dispersive objective lens of the spectral confocal measurement system with a preset step size; S102, collecting single-peak spectrum signal curve data of light beams of different wavelengths corresponding to different position information; S103, obtaining single-peak signal curve data for calibrating the spectral confocal measurement system, wherein the single-peak signal curve data is as shown in formula (1): When the calibration reflective surface moves to d m At, and d m In d i and d i+1 When , the single peak signal curve data is expressed as: Wherein, i represents the movement of the calibration reflection surface for the i-th time; i+1 represents the movement of the calibration reflection surface for the i+1-th time; d i Indicates the position information of the calibration reflection surface moving for the i-th time; d i+1 Indicates the position information of the calibration reflection surface moving for the i+1th time; Represents the single-peak signal curve data corresponding to the ith movement of the calibration reflection surface; represents the single peak signal curve data corresponding to the movement of the calibration reflective surface for the i+1th time; △d represents the preset step size; d m Indicates the position information of the calibration reflective surface at any time; Indicates the single-peak signal curve data corresponding to the calibration reflection surface at any time.

3. The thickness measurement method according to claim 2, characterized in that: In step S302 , the initialization specifically includes: assigning the position information of the upper surface of the object to be measured and the position information of the lower surface of the object to be measured to the position information of the first movement of the calibration reflective surface, and assigning the refractive index compensation factor of the lower surface of the object to be measured to 0.

4. The thickness measurement method according to claim 3, characterized in that: The first preset condition is: obtain k={0, Δk e ,…,k max }, d={d1, d1+△d e ,…,d N }, the loss function loss up or loss down The values of k and d when the minimum value is obtained; Wherein, k represents the refractive index compensation factor of the upper surface of the object to be measured or the refractive index compensation factor of the lower surface of the object to be measured; Δk e represents the optimization step size of the refractive index compensation factor; k max represents the maximum optimization step size of the refractive index compensation factor; d1 represents the position information of the first movement of the calibration reflective surface; △d e represents the optimized step length of the surface position of the object to be measured; d N represents the maximum optimization step length of the surface position of the object to be measured; d represents the set of surface position information of the object to be measured.

5. The thickness measurement method according to claim 4, characterized in that: The formula (6) for calculating the thickness of the object to be measured in step S4 is specifically: Wherein, thickness represents the thickness of the object to be measured; n represents the refractive index of the object to be measured; and NA represents the numerical aperture of the dispersion objective lens of the spectral confocal measurement system.

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