A fiber scanning based mueller matrix imaging spectroscopic ellipsometry device and method

Abstract

The application discloses a Mueller matrix imaging ellipsometry device and method based on optical fiber scanning. In view of the problem that existing equipment is difficult to consider wide spectrum, high precision and high spatial resolution, reflected light of the device is imaged to an intermediate image plane by a microscopic imaging system; a two-dimensional scanning mechanism drives a receiving optical fiber to move point by point on the intermediate image plane, and a light intensity time sequence signal is synchronously collected; a control unit carries out Fourier analysis and Mueller matrix inversion on the signal, and obtains a two-dimensional distribution diagram of sample thickness and optical constants through optical model fitting. The scheme realizes consideration of high precision and high resolution, and has flexible structure and low cost.

Description

Technical Field

[0001] This invention relates to the field of optical precision measurement technology, and specifically to a device and method for measuring spectral ellipsometrics based on Mueller matrix imaging using fiber optic scanning. Background Technology

[0002] Ellipsometry is an important optical instrument for measuring the change in polarization state of polarized light before and after incident on a sample, and is widely used to characterize the thickness and optical constants of thin films. Traditional single-point spectroscopic ellipsometers can achieve an accuracy of 0.1 nm in film thickness measurement, but they cannot acquire two-dimensional distribution information of the film surface, only measuring the average optical parameters of the area covered by the light spot. This can easily lead to measurement distortion when dealing with samples with inhomogeneities. Existing imaging ellipsometers mainly suffer from limited wavelength measurement ranges, typically a single wavelength or a narrow band, failing to capture the complete dispersive characteristics of the material. Furthermore, due to the inherent noise of the array detector, the measurement accuracy of thickness and optical constants of existing imaging devices is generally lower than that of traditional single-point spectroscopic ellipsometers, and inevitably comes with higher equipment procurement costs and extremely complex data processing algorithms. Therefore, there is an urgent need in this field for a low-cost measurement technology that maintains the high accuracy and wide spectral range advantages of single-point ellipsometers while also possessing microscopic spatial resolution capabilities. Summary of the Invention

[0003] To overcome the existing problems and shortcomings, this invention proposes a Mueller matrix imaging spectral ellipsometric measurement device based on fiber scanning, characterized by comprising:

[0004] An incident arm is used to generate illumination light with controllable polarization and irradiate the surface of the sample to be tested. The incident arm includes, in sequence, a broadband light source, a collimation system, a polarizer, and a rotation compensator.

[0005] A sample stage, used to hold and adjust the position of the sample to be tested;

[0006] The receiving arm is used to receive reflected light carrying sample information and perform demodulation, detection and imaging. The receiving arm includes a microscope objective, a rotation compensator II, an analyzer, an imaging lens and a receiving optical fiber in sequence. The microscope objective and the imaging lens constitute a microscope imaging system to image the sample area to be tested onto the intermediate image plane.

[0007] The fiber optic scanning detection system includes the receiving fiber and a two-dimensional scanning mechanism. The two-dimensional scanning mechanism drives the end face of the receiving fiber to perform a micrometer-level two-dimensional moving scan on the intermediate image plane to collect light intensity signals point by point.

[0008] A spectral analyzer is coupled to the output end of the receiving optical fiber to synchronously acquire the light intensity timing signal at each scanning position.

[0009] The control and data processing unit is communicatively connected to the two-dimensional scanning mechanism and the spectrometer. It is used to synchronously control the fiber optic two-dimensional scanning and spectral acquisition, and to perform Fourier analysis and Mueller matrix inversion calculation on the acquired light intensity time-series signal, thereby fitting and obtaining a two-dimensional distribution map of parameters such as the sample thickness and optical constants.

[0010] Furthermore, the intermediate image plane, the sample under test, and the microscopic imaging system together satisfy the Scheimpflug condition to achieve clear imaging of the sample across the entire field of view; the first and second rotary compensators employ wide-spectrum achromatic 1 / 4 waveplates to maintain a constant phase delay within the measurement wavelength range.

[0011] Furthermore, the two-dimensional scanning mechanism is a two-dimensional scanning platform driven by piezoelectric ceramics, with a positioning accuracy of 1μm; the receiving optical fiber is a single-mode optical fiber or a multi-mode optical fiber, and different lateral spatial resolutions can be matched by changing the receiving optical fiber with different core diameters.

[0012] Furthermore, the control and data processing unit includes the following logical functions:

[0013] The collaborative control layer is used to synchronously control the movement and displacement of the receiving optical fiber and the data acquisition actions of the spectrum analyzer.

[0014] The data acquisition layer is used to receive data from each measurement point at different wavelengths. Light intensity timing signal ;

[0015] The core solution layer is used to perform discrete Fourier transform on the light intensity time-series signal to extract harmonic coefficients, and to obtain the 16 Mueller matrix elements at that point through the Mueller matrix inversion algorithm, thereby extracting the experimental measurement of spectral ellipsometric parameters. and ;

[0016] The model optimization layer is used to calculate the theoretical ellipsometry parameters based on the constructed material optical model. It iteratively minimizes the error between the theoretical and experimental values ​​through a nonlinear optimization algorithm, and outputs the optimal film thickness. Refractive index and extinction coefficient ;

[0017] The imaging reconstruction layer will output the thickness. Refractive index and extinction coefficient By associating the coordinates of the corresponding intermediate image plane position, a two-dimensional parameter distribution map is reconstructed and output.

[0018] A method for measuring spectral ellipsometrics based on fiber optic scanning in Mueller matrix imaging, applied to any of the measurement devices described above, includes the following steps:

[0019] S100: Align the optical axis of the system so that the area of ​​the sample to be tested can be clearly imaged onto the central image plane by the microscopic imaging system;

[0020] S200: The two-dimensional scanning mechanism drives the end face of the receiving optical fiber to move point by point within the two-dimensional scanning area set in the intermediate image plane.

[0021] S300: At each measurement point, the spectral analyzer collects the light intensity time-series signal at each wavelength, and the control and data processing unit records the spectral data and the current position coordinates of the measurement point;

[0022] S400: The light intensity time series signal is processed by Fourier analysis and Mueller matrix inversion algorithm to obtain the Mueller matrix and spectral ellipsometry parameters of the measurement point;

[0023] S500: Based on the measured sample structure, an optical model of the material is constructed, theoretical data is calculated and compared with the measured spectral ellipsometry parameters, the optical model is optimized to minimize the fitting error, and the film thickness and refractive index at the measurement point are determined. and optical constants ;

[0024] S600: While processing data in the background, control the fiber end face to move to the next measurement point and repeat steps S300 to S500 until the measurement of the entire set area is completed. Link the parameters resolved from all measurement points with the position coordinates to reconstruct the two-dimensional ellipsoidal parameter distribution map of the sample.

[0025] Furthermore, the specific calculation steps for obtaining the Mueller matrix in step S400 include: for each wavelength Light intensity timing signal Perform a discrete Fourier transform to extract the complex amplitude at a specific frequency point, and obtain the Fourier coefficients corresponding to the real and imaginary parts. and Establish a linear relationship between the Fourier coefficients and the elements of the Mueller matrix: ,in It is a column vector composed of Fourier coefficients. Given the known system constant matrix, For the sample The Mueller matrix is ​​expanded by rows into a 16-dimensional column vector; the Mueller matrix column vector is obtained by solving the linear equations using the least squares method. This allows for the reconstruction of the Mueller matrix of the sample. .

[0026] Furthermore, for isotropic samples, after obtaining the normalized Mueller matrix, the elements in the Mueller matrix are extracted. , and And according to the formula:

[0027] ;

[0028] as well as

[0029] ;

[0030] Calculate the experimentally measured values ​​of the spectral ellipsometric parameters at each wavelength. and .

[0031] Furthermore, the specific derivation steps of the theoretical data mentioned in step S500 include: based on the established environment / thin film / substrate optical model, combined with the complex refractive index of the thin film, the complex refractive index of the substrate, and the incident angle, calculating the values ​​at each interface using Fresnel's formula. Polarization complex reflection coefficient and Polarization complex reflection coefficient Combined with thin film phase thickness Calculate the total reflection coefficient after considering multiple reflections; based on the ratio of the total reflection coefficients:

[0032]

[0033] Calculate the theoretical ellipsometric parameters at each wavelength. and .

[0034] Furthermore, the comparison and optimization steps in step S500 include:

[0035] Using theoretical elliptic parameters , Compared with experimental measurements , Based on the difference at corresponding wavelengths, a weighting term is introduced incorporating the standard deviation to construct the root mean square error function. As the objective function;

[0036] The Levenberg-Marquardt algorithm is used as the nonlinear least squares optimization algorithm to iteratively adjust the parameter vector of the model to be optimized. until the root mean square error function The convergence condition is met;

[0037] The parameter vector corresponding to the minimum error That is, the optimal film thickness at that measurement point. Refractive index Dispersion curve and extinction coefficient Dispersion curve.

[0038] Furthermore, in step S200, when controlling the movement of the receiving optical fiber, the movement interval between the previous measurement point and the next measurement point is consistent with the core diameter value of the selected receiving optical fiber; the lateral spatial resolution of the sample under test is determined by equal-interval dense sampling in conjunction with the magnification of the microscopic imaging system.

[0039] The beneficial effects of this invention are as follows:

[0040] The present invention provides a device and method for measuring spectral ellipsometrics in Mueller matrix imaging based on fiber scanning, which has the following advantages compared with the prior art:

[0041] This invention combines single-point high-precision detection with fiber optic spatial scanning technology. By using a single fiber to detect point by point on the intermediate image plane instead of the traditional array detector, it not only inherits the high precision and wide spectrum measurement advantages of the traditional spectroscopic ellipsometer, but also achieves high lateral resolution at the micrometer level, which can intuitively present the two-dimensional microscopic distribution information of the sample surface.

[0042] The device provided by this invention has a flexible spatial structure design. This solution matches the step size of the optical fiber movement with the core diameter of the receiving optical fiber. By replacing the receiving optical fiber with different core diameters, a variety of different lateral spatial resolutions can be flexibly adjusted and obtained to adapt to different testing needs.

[0043] Since this invention still uses the data processing logic of a single-point spectral ellipsometer in its detection, it avoids the complex image pixel processing process brought about by array detectors. Its system algorithm is simpler and more direct, effectively reducing the hardware cost and manpower processing cost of the equipment. Attached Figure Description

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

[0045] Figure 1 This is a schematic diagram of the overall structure of the Mueller matrix imaging spectral ellipsometry measurement device based on fiber scanning in an embodiment of the present invention.

[0046] Figure 2 This is a schematic diagram of the optical path principle of the sample surface to be imaged to the intermediate image plane by the microscopic imaging system in an embodiment of the present invention.

[0047] Figure 3 This is a schematic diagram of the trajectory of the receiving optical fiber end face performing two-dimensional region scanning movement on the intermediate image plane in an embodiment of the present invention.

[0048] Explanation of reference numerals in the attached figures: 1-Broadband light source, 2-Collimation system, 3-Polarizer, 4-Rotation compensator one, 5-Sample stage, 51-Sample to be tested, 6-Microscope objective, 7-Rotation compensator two, 8-Analyzer, 9-Imaging lens, 10-Receiving fiber, 101-Intermediate image plane, 102-Two-dimensional scanning area, 11-Two-dimensional scanning mechanism, 12-Spectrum analyzer, 13-Control and data processing unit, 14-Alignment system. Detailed Implementation

[0049] The present application will be described below with reference to specific embodiments:

[0050] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] Example 1:

[0052] Please see Figures 1 to 3 This embodiment provides a Mueller matrix imaging spectral ellipsometric measurement device based on fiber optic scanning. The device mainly includes an incident arm, a sample stage 5, a receiving arm, and an alignment system 14. Through the physical spatial cooperation and signal transmission of each component, it realizes two-dimensional spatial resolution measurement of the microstructure and optical parameters of the surface of the sample 51 to be measured.

[0053] The incident arm, arranged sequentially along the beam propagation direction, comprises a broadband light source 1, a collimation system 2, a polarizer 3, and a rotation compensator 4. The broadband light source 1 can be a tungsten lamp or a halogen tungsten lamp, filtered by a filter, preferably with a wavelength range of 400-1000 nm. The collimation system 2 uses an off-axis parabolic mirror or an achromatic lens group to collimate the light emitted from the broadband light source 1 to output a parallel beam. The polarizer 3 is a high extinction ratio linear polarizer, capable of obtaining linearly polarized light with an extinction ratio greater than 10^6. The rotation compensator 4 uses a broadband achromatic quarter-wave plate to reduce the influence of wavelength on the phase delay, keeping the phase delay constant within the measurement wavelength range. During measurement, the rotation compensator 4 rotates continuously at a constant angular velocity ω1, thereby modulating the phase of the emitted linearly polarized light, generating polarization-controllable illumination light that illuminates the surface of the sample 51 on the sample stage 5. The sample stage 5 has five-dimensional adjustment functions, including XYZ axis displacement adjustment, pitch adjustment, and yaw adjustment. It works in conjunction with the alignment system 14 to ensure that the sample 51 under test can be accurately aligned with the system's optical axis. The alignment system 14 consists of an autocollimating telescope and a microscope. It adjusts the sample stage 5 in real time to keep the optical axis of the alignment system 14 perpendicular to the surface of the sample 51 under test.

[0054] The receiving arm receives reflected light carrying information about the surface of the sample 51 under test, and performs demodulation, detection, and imaging processing. Along the optical path, the receiving arm sequentially includes a microscope objective 6, a rotation compensator 7, a polarizer 8, an imaging lens 9, and a receiving fiber optic cable 10. The microscope objective 6 is an apochromatic infinity-corrected objective with a field-of-view diameter of, for example, 2 mm and a magnification of 5x. The imaging lens 9 uses an aspherical lens or an achromatic lens group to achieve wide-band achromatic aberration. The microscope objective 6 and the imaging lens 9 together constitute a microscopic imaging system used to clearly image the area of ​​the sample 51 under test point-to-point onto the intermediate image plane 101. To ensure clear imaging of the entire field of view under non-perpendicular reflection paths, the intermediate image plane 101, the sample 51 under test, and the microscopic imaging system together satisfy the Scheimpflug condition. Rotary compensator 7 also employs a broadband achromatic quarter-wave plate and rotates continuously at a constant angular velocity ω2, wherein a constant rotational speed ratio is maintained between rotary compensator 4 and rotary compensator 7. Analyzer 8 is a high extinction ratio linear polarizer used to detect polarized light after phase demodulation.

[0055] The receiving optical fiber 10 and the two-dimensional scanning mechanism 11 together constitute an optical fiber scanning detection system. The input detection end face of the receiving optical fiber 10 is fixed on the two-dimensional scanning mechanism 11, which employs a high-precision piezoelectric ceramic driven two-dimensional scanning platform with a positioning accuracy of 1μm, and is equipped with a precision five-dimensional adjustment frame to ensure efficient coupling of the light beam into the optical fiber. The two-dimensional scanning mechanism 11 drives the detection end face of the receiving optical fiber 10 to perform micrometer-level two-dimensional moving scans on the intermediate image plane 101, thereby collecting the optical signal on the intermediate image plane 101 point by point. Depending on the required spatial resolution, the receiving optical fiber 10 can be selected from visible light single-mode fiber with a core diameter of 3-5μm, standard single-mode fiber with a core diameter of 9μm, or conventional multimode fiber with a core diameter of 50μm. The output end of the receiving optical fiber 10 is directly coupled to the input of the spectrometer 12, which is used to synchronously acquire the spectral information of the receiving optical fiber 10 at the corresponding scanning position to obtain the light intensity signal at each wavelength.

[0056] Both the spectral analyzer 12 and the two-dimensional scanning mechanism 11 are communicatively connected to the control and data processing unit 13. The control and data processing unit 13 is divided from bottom to top in its background logic into a collaborative control layer, a data acquisition layer, a core calculation layer, a model optimization layer, and an imaging reconstruction layer. The collaborative control layer is electrically connected to both the two-dimensional scanning mechanism 11 and the spectral analyzer 12 to synchronously control the scanning motion timing and spectral acquisition actions of the receiving fiber optic cable 10. The data acquisition layer is unidirectionally connected to the spectral analyzer 12 to receive and record in real-time the light intensity time-series signals of each measurement point at different wavelengths λ over time t. The core solution layer extracts the light intensity time-series signal through discrete Fourier transform. The harmonic coefficients in the sample were obtained, and the 16 Mueller matrix elements at the measurement point were obtained by solving a system of linear equations. This allowed for the reconstruction of the experimentally measured values ​​of the sample's spectral ellipsometric parameters. and The model optimization layer calculates the theoretical elliptic parameters based on the preset sample multilayer structure model and material dispersion model, and performs iterative fitting using a nonlinear least squares optimization algorithm until the root mean square error function reaches the convergence condition, thereby outputting the optimal film thickness d, refractive index n dispersion curve, and extinction coefficient k dispersion curve at the measurement point; the imaging reconstruction layer maps and associates the physical parameters resolved by the model optimization layer with the spatial coordinates recorded by the collaborative control layer, and finally reconstructs and generates a two-dimensional elliptic parameter distribution map of the sample surface.

[0057] Example 2:

[0058] Based on the fiber optic scanning-based Mueller matrix imaging spectral ellipsometric measurement device described in Embodiment 1, this embodiment provides a fiber optic scanning-based Mueller matrix imaging spectral ellipsometric measurement method. This method combines spatial scanning with polarization spectral calculation, specifically including the following steps: First, a system calibration and alignment step is performed. The alignment system 14 is adjusted, and the sample stage 5 is controlled to move in five dimensions, so that the optical axis of the alignment system 14 is perpendicular to the surface of the sample 51 to be measured. This allows the area of ​​the sample 51 to be clearly imaged point-to-point onto the intermediate image plane 101 by the microscopic imaging system composed of the microscope objective 6 and the imaging lens 9. The two-dimensional scanning area 102 of the fiber end face on the intermediate image plane 101 is set by the control and data processing unit 13.

[0059] During the scanning and data acquisition phase, as the rotary compensators 4 and 7 rotate continuously at a constant speed ratio, the collaborative control layer drives the two-dimensional scanning mechanism 11 to control the detection end face of the receiving optical fiber 10 to move to the current measurement point. The spectrometer 12 synchronously responds to the trigger command and acquires the light intensity time-series signal at that measurement point as a function of time t. The light intensity timing signal is recorded by the data acquisition layer. And the two-dimensional position coordinates of the current measurement point on the intermediate image plane 101. Then, the core calculation layer performs Fourier analysis and Mueller matrix inversion calculations on the acquired spectral data. For each wavelength... Light intensity timing signal Perform Discrete Fourier Transform to extract the frequency points of the time-series signal. The complex amplitude at a given point is used to obtain the Fourier coefficients corresponding to the real and imaginary parts. and The known model of the light intensity signal received by the detector is:

[0060]

[0061] in The DC component, and The harmonic order. Based on the instrument matrix determined by pre-system calibration. Construct a column vector composed of Fourier coefficients. With the sample 16-dimensional Mueller matrix vector The relationship between the linear equations: The Mueller matrix vector of the sample is obtained by solving the system of linear equations using the least squares method. And reconstruct it by expanding it line by line. Muller matrix For isotropic samples, the normalized Mueller matrix elements ( Based on ), extract elements , and And calculate each wavelength directly according to the following formula. Experimental measurements of spectral ellipsometric parameters and :

[0062]

[0063]

[0064] Subsequently, the model optimization layer performs analytical fitting of optical constants and thickness. Based on the actual physical layering of the sample under test, a multilayer structure model of "environmental medium / monolayer thin film / substrate" is constructed, and a dispersion model describing the variation of optical constants with wavelength is selected. Based on thin film optics theory and Fresnel formulas, combined with the complex refractive index of the thin film... Complex refractive index of the substrate and the incident angle of the light beam in the thin film. Angle of refraction in the substrate The computing interface Polarization complex reflection coefficient and Polarization complex reflection coefficient :

[0065]

[0066]

[0067] And combined with the phase thickness of the thin film The total reflection coefficient after considering multiple reflections between interfaces was further calculated. and Based on the ratio of total reflectance:

[0068]

[0069] Theoretical ellipsometric parameters at each wavelength are derived. .

[0070] Based on this, the model optimization layer constructs the root mean square error function. As the objective function for optimization:

[0071]

[0072] in Number of wavelength points The number of fitting parameters, and The standard deviation of the experimental data is given. The Levenberg-Marquardt algorithm is used as the nonlinear least squares optimization rule, utilizing the current parameter vector during the iteration process. Calculate the theoretical value and update the error function until the successive iterations. The change is less than a preset threshold or the maximum number of iterations has been reached. At this point, the parameter vector output by convergence is... That is, it contains the optimal film thickness. Refractive index Curve and extinction coefficient curve.

[0073] Finally, while the control and data processing unit 13 performs the aforementioned data processing in the background, the collaborative control layer synchronously drives the two-dimensional scanning mechanism 11 to move the fiber end face to the next measurement point at equal intervals. The movement interval between the previous and next measurement points is strictly consistent with the core diameter of the currently selected receiving fiber 10; for example, when using a 5μm core diameter fiber, the movement step is 5μm. The spectral signal acquisition, Mueller matrix inversion, and model optimization calculation are repeated until the entire set area 102 has been traversed. After scanning, the imaging reconstruction layer resolves the thickness from all measurement points. Refractive index Extinction coefficient By performing matrix correlation with the corresponding spatial coordinates, a two-dimensional ellipsometric parameter distribution map of the sample surface across the entire field of view is finally reconstructed, specifically including the thickness distribution map, refractive index distribution map, and extinction coefficient distribution map. Since the microscopic imaging system has a magnification of 5x, when used with a 5μm core diameter single-mode fiber for equidistant dense sampling, the actual lateral spatial resolution of the reconstructed sample surface reaches 1μm.

[0074] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A Mueller matrix imaging spectral ellipsometric measurement device based on fiber optic scanning, characterized in that, include: An incident arm is used to generate illumination light with controllable polarization state and irradiate the surface of the sample to be tested (51). The incident arm includes, in sequence, a broadband light source (1), a collimation system (2), a polarizer (3), and a rotation compensator (4). The sample stage (5) is used to support and adjust the position of the sample to be tested (51); The receiving arm is used to receive reflected light carrying sample information and perform demodulation, detection and imaging. The receiving arm includes a microscope objective (6), a rotation compensator (7), an analyzer (8), an imaging lens (9) and a receiving fiber (10). The microscope objective (6) and the imaging lens (9) constitute a microscope imaging system to image the sample area to be tested onto the intermediate image plane (101). The fiber optic scanning detection system includes the receiving fiber (10) and a two-dimensional scanning mechanism (11). The two-dimensional scanning mechanism (11) drives the end face of the receiving fiber (10) to perform a micron-level two-dimensional moving scan on the intermediate image plane (101) to collect light intensity signals point by point. The spectrometer (12) is coupled to the output end of the receiving optical fiber (10) and is used to synchronously acquire the light intensity timing signal at each scanning position; The control and data processing unit (13) is connected in communication with the two-dimensional scanning mechanism (11) and the spectrometer (12) to synchronously control the fiber optic two-dimensional scanning and spectral acquisition, and to perform Fourier analysis and Mueller matrix inversion calculation on the acquired light intensity time-series signal, thereby fitting and obtaining a two-dimensional distribution map of parameters such as the thickness and optical constants of the sample.

2. The measuring device according to claim 1, characterized in that, The intermediate image plane (101), the sample to be tested (51), and the microscopic imaging system together satisfy the Scheimpflug condition to achieve clear imaging of the sample across the entire field of view; the first rotary compensator (4) and the second rotary compensator (7) use a wide-spectrum achromatic 1 / 4 waveplate to keep the phase delay constant within the measurement wavelength range.

3. The measuring device according to claim 1, characterized in that, The two-dimensional scanning mechanism (11) is a two-dimensional scanning platform driven by piezoelectric ceramics, with a positioning accuracy of 1μm; the receiving optical fiber (10) is a single-mode optical fiber or a multi-mode optical fiber, and different lateral spatial resolutions can be matched by changing the receiving optical fiber with different core diameters.

4. The measuring device according to claim 1, characterized in that, The control and data processing unit (13) includes the following logical functions: The collaborative control layer is used to synchronously control the movement and displacement of the receiving optical fiber and the data acquisition actions of the spectrum analyzer. The data acquisition layer is used to receive data from each measurement point at different wavelengths. Light intensity timing signal ; The core solution layer is used to perform discrete Fourier transform on the light intensity time-series signal to extract harmonic coefficients, and to obtain the 16 Mueller matrix elements at that point through the Mueller matrix inversion algorithm, thereby extracting the experimental measurement of spectral ellipsometric parameters. and ; The model optimization layer is used to calculate the theoretical ellipsometry parameters based on the constructed material optical model. It iteratively minimizes the error between the theoretical and experimental values ​​through a nonlinear optimization algorithm, and outputs the optimal film thickness. Refractive index and extinction coefficient ; The imaging reconstruction layer will output the thickness. Refractive index and extinction coefficient By associating the coordinates of the corresponding intermediate image plane position, a two-dimensional parameter distribution map is reconstructed and output.

5. A method for measuring spectral ellipsometrics using Mueller matrix imaging based on fiber optic scanning, applied to the measuring device as described in any one of claims 1-4, characterized in that, Includes the following steps: S100: Align the optical axis of the system so that the area of ​​the sample to be tested is clearly imaged onto the intermediate image plane (101) by the microscopic imaging system. S200: The two-dimensional scanning mechanism (11) drives the end face of the receiving optical fiber (10) to move point by point within the two-dimensional scanning area set by the intermediate image plane (101); S300: At each measurement point, the spectral analyzer (12) collects the light intensity time-series signal at each wavelength, and the control and data processing unit (13) records the spectral data and the position coordinates of the current measurement point; S400: The light intensity time series signal is processed by Fourier analysis and Mueller matrix inversion algorithm to obtain the Mueller matrix and spectral ellipsometry parameters of the measurement point; S500: Based on the measured sample structure, an optical model of the material is constructed, theoretical data is calculated and compared with the measured spectral ellipsometry parameters, the optical model is optimized to minimize the fitting error, and the film thickness and refractive index at the measurement point are determined. and optical constants ; S600: While processing data in the background, control the fiber end face to move to the next measurement point and repeat steps S300 to S500 until the measurement of the entire set area is completed. Link the parameters resolved from all measurement points with the position coordinates to reconstruct the two-dimensional ellipsoidal parameter distribution map of the sample.

6. The measurement method according to claim 5, characterized in that, The specific calculation steps for obtaining the Mueller matrix in step S400 include: for each wavelength Light intensity timing signal Perform a discrete Fourier transform to extract the complex amplitude at a specific frequency point, and obtain the Fourier coefficients corresponding to the real and imaginary parts. and Establish a linear relationship between the Fourier coefficients and the elements of the Mueller matrix: ,in It is a column vector composed of Fourier coefficients. Given the known system constant matrix, For the sample The Mueller matrix is ​​expanded by rows into a 16-dimensional column vector; the Mueller matrix column vector is obtained by solving the linear equations using the least squares method. This allows for the reconstruction of the Mueller matrix of the sample. .

7. The measurement method according to claim 6, characterized in that, For isotropic samples, after obtaining the normalized Mueller matrix, the elements of the Mueller matrix are extracted. , and And according to the formula: ； as well as ； Calculate the experimentally measured values ​​of the spectral ellipsometric parameters at each wavelength. and .

8. The measurement method according to claim 5, characterized in that, The specific derivation steps of the theoretical data mentioned in step S500 include: based on the established environment / thin film / substrate optical model, combined with the complex refractive index of the thin film, the complex refractive index of the substrate, and the incident angle, calculating the values ​​at each interface using Fresnel's formula. Polarization complex reflection coefficient and Polarization complex reflection coefficient Combined with thin film phase thickness Calculate the total reflection coefficient after considering multiple reflections; based on the ratio of the total reflection coefficients: Calculate the theoretical ellipsometric parameters at each wavelength. and .

9. The measurement method according to claim 8, characterized in that, The comparison and optimization steps in step S500 include: Using theoretical elliptic parameters , Compared with experimental measurements , Based on the difference at corresponding wavelengths, a weighting term is introduced incorporating the standard deviation to construct the root mean square error function. As the objective function; The Levenberg-Marquardt algorithm is used as the nonlinear least squares optimization algorithm to iteratively adjust the parameter vector of the model to be optimized. until the root mean square error function The convergence condition is met; The parameter vector corresponding to the minimum error That is, the optimal film thickness at that measurement point. Refractive index Dispersion curve and extinction coefficient Dispersion curve.

10. The measurement method according to claim 5, characterized in that, In step S200, when controlling the movement of the receiving optical fiber, the movement interval between the previous measurement point and the next measurement point is consistent with the core diameter value of the selected receiving optical fiber; the lateral spatial resolution of the sample under test is determined by equal-interval dense sampling in conjunction with the magnification of the microscopic imaging system.

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