CN-116124742-B - Polarization reflectivity measuring method and device

CN116124742BCN 116124742 BCN116124742 BCN 116124742BCN-116124742-B

Abstract

The invention relates to a method and a device for measuring polarization reflectivity, which comprise the steps of measuring a reference sample by using an ellipsometer, collecting light intensity signals, carrying out ellipsometer system calibration to obtain calibrated system parameters and a reference sample film thickness, calculating to obtain a measurement Mueller matrix of the reference sample by using the calibrated system parameters and the light intensity signals, simulating to obtain the reflectivity of the reference sample by using the calibrated system parameters and the reference sample film thickness, calculating to obtain equivalent light source light intensity according to the measurement Mueller matrix of the reference sample and the reflectivity of the reference sample, collecting light intensity signals by using the ellipsometer for any sample to be measured, calculating to obtain a measurement Mueller matrix of the sample to be measured by using the calibrated system parameters, and calculating to obtain the polarization reflectivity of the sample to be measured by using the equivalent light source light intensity and the measurement Mueller matrix of the sample to be measured.

Inventors

SHI YATING
GUO CHUNFU
LIU YADING
LI WEIQI
HE YONG
XUE XIAORU
ZHANG CHUANWEI

Assignees

武汉颐光科技有限公司

Dates

Publication Date: 20260508
Application Date: 20221228

Claims (8)

1. A method for measuring polarization reflectivity, comprising the steps of: S101, measuring a reference sample by using an ellipsometer, collecting light intensity signals, and calibrating an ellipsometer system to obtain calibrated system parameters and the film thickness of the reference sample; s102, calculating to obtain a measurement Mueller matrix of the reference sample by using the calibrated system parameters and the light intensity signals; S103, simulating to obtain the reflectivity of the reference sample by using the calibrated system parameters and the film thickness of the reference sample; S104, calculating to obtain the equivalent light source light intensity according to the measured Mueller matrix of the reference sample and the reflectivity of the reference sample; S105, aiming at any sample to be detected, acquiring light intensity signals by using an ellipsometer, and calculating by using calibrated system parameters to obtain a measurement Mueller matrix of the sample to be detected; S106, calculating to obtain the polarization reflectivity of the sample to be measured by using the equivalent light source light intensity and the measured Mueller matrix of the sample to be measured; the measuring the reflectivity of the Mueller matrix and the reference sample according to the reference sample, calculating to obtain the equivalent light source light intensity comprises the following steps: the equivalent light source light intensity satisfies the following formula: ; Wherein, the The muller matrix is measured for the reference sample, For the reference sample to be reflective, Measuring a Mueller matrix for a reference sample Normalizing the resulting normalized measurement muller matrix with respect to the first element; Step S106 includes: measuring Mueller matrix based on sample to be measured And equivalent light intensity of light source Using the formula: Calculating to obtain non-normalized measurement Mueller matrix of sample to be measured : ; By means of Calculating s-polarization reflectivity and p-polarization reflectivity of the sample to be measured: Wherein, the Representation matrix Elements of row i and column j.
2. The method of claim 1, wherein the system model of the ellipsometer system is as follows: Wherein t represents time, S in is Stokes vector of light emitted by a light source, I out represents light intensity output by a system model, P, A, C 1 、C 2 is a polarizer azimuth angle, a polarization analyzer azimuth angle, a first rotation wave plate initial azimuth angle and a second rotation wave plate initial azimuth angle respectively, delta 1 and delta 2 are phase delay amounts of the first rotation wave plate and the second rotation wave plate respectively, M A and M P are polarizer characteristic Mueller matrixes, M C is a phase delay characteristic Mueller matrix, R is a rotation matrix, M s is a normalized Mueller matrix corresponding to a sample, the matrix depends on an ellipsometer incident angle AOI, a sample thickness and a sample material refractive index, and omega 1 and omega 2 are angular frequencies of the first rotation wave plate and the second rotation wave plate respectively.
3. The method according to claim 1, wherein the calibration procedure in step S101 is as follows: converting the periodic light intensity measured by the ellipsometer into a Fourier coefficient; Writing a function based on an ellipsometer system model, wherein the input of the function is a system parameter and a reference sample film thickness THK, and the output of the function is a Fourier coefficient of the simulated output light intensity of the system model; And adjusting input parameter values of the system model function through a nonlinear fitting algorithm, so that the output analog Fourier coefficient is matched with the actually measured Fourier coefficient.
4. The method of claim 2, wherein the measured mueller matrix of the reference sample is calculated using the calibrated system parameters and the light intensity signal to satisfy the following equation: Wherein, the For the light intensity of the reference sample, For the measurement mueller matrix of the reference sample, a represents the polarization arm system matrix and G represents the polarization arm system matrix.
5. The method according to claim 1, wherein the simulation method in step S103 includes a thin film transmission matrix method, a thin film optical characteristic modeling algorithm.
6. A polarization reflectivity measuring mechanism, comprising: The calibration module is used for measuring a reference sample by using an ellipsometer, collecting light intensity signals, and carrying out ellipsometer system calibration to obtain calibrated system parameters and the film thickness of the reference sample; The first calculation module calculates and obtains a measurement Mueller matrix of the reference sample by using the calibrated system parameters and the light intensity signals; the simulation module is used for obtaining the reflectivity of the reference sample by simulation by using the calibrated system parameters and the film thickness of the reference sample; the second calculation module is used for calculating the equivalent light source light intensity according to the measured Mueller matrix of the reference sample and the reflectivity of the reference sample; the third calculation module is used for collecting light intensity signals by using an ellipsometer aiming at any sample to be detected, and calculating by using calibrated system parameters to obtain a measurement Mueller matrix of the sample to be detected; The reflectivity calculation module calculates the polarization reflectivity of the sample to be measured by using the equivalent light source light intensity and the measurement Mueller matrix of the sample to be measured; the measuring the reflectivity of the Mueller matrix and the reference sample according to the reference sample, calculating to obtain the equivalent light source light intensity comprises the following steps: the equivalent light source light intensity satisfies the following formula: ; Wherein, the The muller matrix is measured for the reference sample, For the reference sample to be reflective, Measuring a Mueller matrix for a reference sample Normalizing the resulting normalized measurement muller matrix with respect to the first element; The method for calculating the polarization reflectivity of the sample to be measured by utilizing the equivalent light source light intensity and the measured Mueller matrix of the sample to be measured comprises the following steps: measuring Mueller matrix based on sample to be measured And equivalent light intensity of light source Using the formula: Calculating to obtain non-normalized measurement Mueller matrix of sample to be measured : ; By means of Calculating s-polarization reflectivity and p-polarization reflectivity of the sample to be measured: Wherein, the Representation matrix Elements of row i and column j.
7. An electronic device, comprising: A memory for storing a computer software program; a processor for reading and executing the computer software program to implement a method for measuring polarization reflectivity as claimed in any one of claims 1 to 5.
8. A non-transitory computer readable storage medium having stored therein a computer software program for implementing a method of polarization reflectivity measurement according to any one of claims 1 to 5.

Description

Polarization reflectivity measuring method and device Technical Field The invention relates to the technical field of optical scattering measurement, in particular to a method and a device for measuring polarization reflectivity. Background As one of electromagnetic waves, a light wave can be characterized in three dimensions, intensity, phase, and polarization. When a light wave propagates from one medium to another, not only does the propagation direction of the light wave change at the medium interface, but also its phase and polarization changes. Therefore, the reflected light and the transmitted light generated after the light irradiates the sample to be measured carry the characteristic information of the sample to be measured, and the reflected light and the transmitted light can be used for analyzing the characteristic information of the sample to be measured, such as the refractive index of a material, the thickness of a film layer and the like. The ellipsometer is used as a precise optical measuring instrument, and can measure the change of a sample piece to an s-polarized component and a p-polarized component of the light wave, and specifically, can measure the amplitude ratio and the phase difference value of the two polarized components. It is readily understood that the amplitude ratio and the phase difference are both relative changes. However, in some applications, such as polarization device optimization design, it is desirable to obtain absolute changes in the sample for the s-and p-polarization components of the light wave, i.e., to measure the polarization reflectivity of the sample. Disclosure of Invention Aiming at the technical problems in the prior art, in a first aspect, the invention provides a method for measuring the polarization reflectivity based on an ellipsometer, which comprises the following steps: S101, measuring a reference sample by using an ellipsometer, collecting light intensity signals, and calibrating an ellipsometer system to obtain calibrated system parameters and the film thickness of the reference sample; s102, calculating to obtain a measurement Mueller matrix of the reference sample by using the calibrated system parameters and the light intensity signals; S103, simulating to obtain the reflectivity of the reference sample by using the calibrated system parameters and the film thickness of the reference sample; S104, calculating to obtain the equivalent light source light intensity according to the measured Mueller matrix of the reference sample and the reflectivity of the reference sample; S105, aiming at any sample to be detected, acquiring light intensity signals by using an ellipsometer, and calculating by using calibrated system parameters to obtain a measurement Mueller matrix of the sample to be detected; S106, calculating to obtain the polarization reflectivity of the sample to be measured by using the equivalent light source light intensity and the measured Mueller matrix of the sample to be measured. Further, the system model of the ellipsometer system is as follows: Iout＝[MAR(A)]×[R(-ω2t+C2)MC(δ2)R(ω2t-C2)]×MS ×[R(-ω1t+C1)MC(δ1)R(ω1t-C1)]×[R(-P)MP]×Sin Wherein t represents time, S in is Stokes vector of light emitted by a light source, I out represents light intensity output by a system model, P, A, C 1、C2 is a polarizer azimuth angle, a polarization analyzer azimuth angle, a first rotation wave plate initial azimuth angle and a second rotation wave plate initial azimuth angle respectively, delta 1 and delta 2 are phase delay amounts of the first rotation wave plate and the second rotation wave plate respectively, M A and M P are polarizer characteristic Mueller matrixes, M C is a phase delay characteristic Mueller matrix, R is a rotation matrix, M s is a normalized Mueller matrix corresponding to a sample, the matrix depends on an ellipsometer incident angle AOI, a sample thickness and a sample material refractive index, and omega 1 and omega 2 are angular frequencies of the first rotation wave plate and the second rotation wave plate respectively. Further, the calibration procedure in step S101 is as follows: converting the periodic light intensity measured by the ellipsometer into a Fourier coefficient; Writing a function based on an ellipsometer system model, wherein the input of the function is a system parameter and a reference sample film thickness THK, and the output of the function is a Fourier coefficient of the simulated output light intensity of the system model; And adjusting input parameter values of the system model function through a nonlinear fitting algorithm, so that the output analog Fourier coefficient is matched with the actually measured Fourier coefficient. Further, the method for calculating the measurement muller matrix of the reference sample by using the calibrated system parameters and the light intensity signals comprises the following steps: The system model is converted into a matrix form I out＝AMS G, wherein A repres