CN104677833A

CN104677833A - Method for carrying out optical measurement by utilizing full-Mueller matrix ellipsometer

Info

Publication number: CN104677833A
Application number: CN201310611400.1A
Authority: CN
Inventors: 崔高增; 刘涛; 李国光; 温朗枫; 熊伟
Original assignee: Bei Optics Technology Co ltd; Institute of Microelectronics of CAS
Current assignee: Bei Optics Technology Co ltd; Institute of Microelectronics of CAS
Priority date: 2013-11-26
Filing date: 2013-11-26
Publication date: 2015-06-03

Abstract

The invention discloses a method for carrying out optical measurement by using an all-Mueller matrix ellipsometer, and belongs to the technical field of optical measurement. The optical measurement method includes the steps of setting up an experimental light path of the full-Mueller matrix ellipsometer, carrying out local regression calibration on the full-Mueller matrix ellipsometer, placing a sample to be measured on a sample table to obtain an experimental Fourier coefficient of the sample to be measured, and obtaining information of the sample to be measured according to the experimental Fourier coefficient of the sample to be measured. The calibration method of the full-Mueller matrix ellipsometer is simple in operation process, fully utilizes the same measurement data of the full-Mueller matrix ellipsometer, introduces relatively small errors, obtains more accurate parameters through calibration, and further obtains more accurate measurement results when a sample to be measured is measured. Therefore, the process of the optical measuring method is simplified.

Description

Method for carrying out optical measurement by utilizing full-Mueller matrix ellipsometer

Technical Field

The invention relates to the technical field of optical measurement, in particular to a method for performing optical measurement by using an all-Mueller matrix ellipsometer.

Background

An ellipsometer (ellipsometer for short) is an optical measuring instrument that obtains information of a sample to be measured by using polarization characteristics of light. The corresponding working principle is that the surface of a sample to be measured, which is incident through polarizer light, is measured by the change (amplitude ratio and phase difference) of the front and back polarization states of the incident light and the reflected light on the surface of the sample, so that the information of the sample to be measured is obtained. The ellipsometer rotating the polarizer and rotating the single compensator obtains 12 parameters of the sample in one measurement at most; with the progress of integrated circuit technology and the complexity of device structure, the unknown quantity to be measured is increasing, so that the traditional ellipsometer has certain limitations on the film thickness measurement of ultrathin films, the measurement of anisotropic material optical constants, the depolarization analysis of surface features, the measurement of critical dimensions and morphological features in integrated circuits, and the like. The full-Mueller matrix ellipsometer (generalized ellipsometer) can obtain 16 parameters of a 4 x 4-order Mueller matrix in one measurement, and the information of a sample is richer than that obtained by a traditional ellipsometer. The ellipsometer breaks through the technical limitation of the traditional ellipsometer, and can realize the rapid and nondestructive accurate measurement of the thickness, the optical constant, the critical dimension, the three-dimensional morphology and the like of the thin film in a wide spectral range.

The key link of the elliptical polarization spectrometer for ensuring the measurement accuracy and maintaining the equipment state is the calibration of the instrument. As the ellipsometer is used and time goes on, system deviation can be generated gradually, and especially the thickness of the wave plate is susceptible to temperature and pressure changes and environmental deliquescence; therefore, the calibration method capable of quickly and accurately correcting the ellipsometer is a key technology for ensuring the effectiveness of equipment and the production efficiency. In the calibration process of the conventional ellipsometer (as shown in fig. 1), as shown in chinese patent 201210375771.X, when the polarization direction of the polarizer is calibrated, the polarizer is generally fixed at a position P1 near 0 °, the analyzer a is rotated, and the light intensity I is measured₁Obtaining I in this state₁(t) curve; then changing the angle of the polarizer P to make the polarizer P at the position P2, measuring the light intensity I₂To obtain I₂(t) curve; and repeating the steps, and respectively measuring the light intensity when the polarizer P is at different angles to obtain the I (t) curve when the polarizer P is at different angles. Respectively carrying out Fourier expansion on the curves I (t) to obtain Fourier coefficients of the polarizer P at different angles; constructing a function that is related to the Fourier coefficient and has a minimum value when the polarization angle of the polarizer P is 0; by data analysis, the position of the polarizer P that minimizes this function is found, and the angle of the polarizer P can be considered to be 0 (see in particular Spectroscopic Ellipsometry Principles and Applications, Hiroyuki Fujiwara,2007). Then, the value of the polarization direction As of the initial position of the analyzer is calculated through Fourier coefficients. In this calibration method, not only the rotation of the analyzer but also the electric or manual rotation of the polarizer P and the manual or electric adjustment of the angle of the polarizer after the polarization direction of the polarizer is determined are required, in which case, due to the instability of the mechanical structure and/or the error of manual operation, an error between the actual angle and the angle to be set is caused, which easily results in the inaccuracy of the measurement of the reference sample. Therefore, the angular calibration accuracy of the polarizer is low when this method is used, and the measurement accuracy of the ellipsometer is limited. The light incident angle in the ellipsometer can be obtained by a manual measurement method, but because the manual measurement precision is limited, and some measurements need to measure the reference sample at different incident angles to obtain more information of the reference sample, the manual measurement is prone to cause error in the result of data analysis due to manual adjustment error or reading error, chinese patent 201010137774.0 discloses an apparatus for automatically detecting the incident angle in the ellipsometer, which can achieve automatic detection of the incident angle, but the apparatus needs to install position detection devices at multiple places in the system, which makes the system structure of the apparatus complex, and the calibration of the position detection device itself is a relatively complex process, thereby limiting the application of the automatic detection device in the ellipsometer.

In the calibration of the conventional full-muller matrix ellipsometer system, for example, in US patent US005956147, a photoelastic modulator (PEM) is used as a phase compensator, when the PEM is calibrated for phase delay, the PEM is set up in a through ellipsometer for measurement, the PEM needs to be taken down from the original equipment for measuring the corresponding phase delay, and the PEM is re-installed on the equipment after calibration is completed, and cannot be guaranteed to be the same as the previously-installed position in the mechanical loading and unloading process, so that the system error is increased, and the through ellipsometer is re-set up to increase the workload. In the literature (Harland G. Tompkins, Eugene A. Irene, Handbook of ellipsometry,7.3.3.4 Calibration)7) In the Mueller ellipsometer, a wave plate is used as a phase compensator, a straight-through type measuring platform is built on an experimental platform, Fourier coefficients obtained in the experiment are measured, and the Fourier coefficients are utilized

And

whereinWhen the calibration is performed, the two phase compensators need to be removed and then put back, so that the system error is increased. If not removed for calibration, the oblique incidence measurement arms on both sides of the sample must be rotated to a horizontal position (e.g., Woo)llam, fig. 3, with the entrance arm rotated from position 1 to position 3 and the exit arm rotated from position 2 to position 4) during calibration, adding to the complexity of the system.

In summary, the current technology must test the retardation line of the phase compensator used before the equipment is assembled, and the phase retardation of the phase compensator must be calibrated using a straight-through ellipsometric system. The systems are required to have a design in which the adjustable incident angle is straight-through, and there is a process of changing the incident angle in the calibration process, which increases the complexity of the system, and the calibration process is also more complicated.

Since the method for performing optical measurement by using the full-muller matrix ellipsometer is performed after the full-muller matrix ellipsometer is calibrated, the calibration process of the full-muller matrix ellipsometer is complicated, and the method for performing optical measurement by using the full-muller matrix ellipsometer is inevitably complicated.

Disclosure of Invention

In order to solve the above problems, the present invention provides a simplified method for performing optical measurement using an all-muller matrix ellipsometer, which is implemented by simplifying a calibration process of the all-muller matrix ellipsometer.

The method for carrying out optical measurement by using the full-Mueller matrix ellipsometer is characterized by comprising the following steps of:

the method comprises the following steps of building an experimental light path of the full-Mueller matrix ellipsometer, wherein the experimental light path of the full-Mueller matrix ellipsometer comprises a light source, a polarizer, a first phase compensator, an analyzer, a second phase compensator, a spectrometer and a sample table;

performing local regression calibration on the full-Mueller matrix ellipsometer;

placing a sample to be tested on the sample table, and obtaining an experimental Fourier coefficient of the sample to be tested by using the full-Mueller matrix ellipsometer;

obtaining the information of the sample to be detected according to the experimental Fourier coefficient of the sample to be detected;

the method for calibrating the full-Mueller matrix ellipsometer comprises the following steps:

setting the rotational speeds of the first and second phase compensators;

setting the frequency of the light intensity data measured by the spectrograph, so that the spectrograph measures the light intensity data once every T/N time, and collecting N groups of light intensity data in total, wherein N is more than or equal to 25, and T is a measurement period;

collecting light intensity data measured by the spectrometer;

obtaining each experimental Fourier coefficient alpha 'according to the light intensity data acquired by the spectrometer data acquisition module and N light intensity data-experimental Fourier coefficient relational expressions formed by the N times of light intensity data'_2n，β′_2n；

According to the experimental Fourier coefficients, the initial polarization angle C of the calibrated first phase compensator_s1Initial polarization angle C of the second phase compensator_s2To obtain each theoretical Fourier coefficient alpha_2n，β_2n；

Based on isotropy and uniformity of the reference sample, the phase delay amount operation module of the first phase compensator calculates the polarization angle P of the calibrated polarizer according to the theoretical Fourier coefficients_sPolarization angle A of polarization analyzer_sObtaining the phase delay amount of the first phase compensator₁；

Based on the isotropy and uniformity of the reference sample, the second phase compensator phase retardation operation module calculates the polarization angle P of the polarizer according to the theoretical Fourier coefficients and the calibrated polarization angle P of the polarizer_sPolarization angle A of polarization analyzer_sObtaining the phase delay amount of the second phase compensator₂；

Will have been calibrated toAn initial polarization angle C of the phase compensator_s1Initial polarization angle C of the second phase compensator_s2Polarizing angle P of polarizer_sPolarization angle A of polarization analyzer_sThe phase delay amount of the first phase compensator₁And phase delay amount of the second phase compensator₂And (3) as an accurate value, obtaining the accurate value of the residual working parameter (d, theta) of the full-Mueller matrix ellipsometer by using a least square fitting method and taking (d, theta) as a variable through a relation between a theoretical Fourier coefficient and the working parameter, wherein d is the thickness of the reference sample, and theta is the angle of light incidence to the reference sample.

The method for performing optical measurement by using the full-Mueller matrix ellipsometer provided by the invention utilizes an isotropic and uniform reference sample, and is based on the light intensity data-experimental Fourier coefficient relation formula acquired by the spectrometer data acquisition module and the polarization angle P of the calibrated polarizer_sPolarization angle A of polarization analyzer_sObtaining the phase delay amount of the first phase compensator₁And phase delay amount of the second phase compensator₂Then, the initial polarization angle C of the first phase compensator obtained by calibration is used_s1Initial polarization angle C of the second phase compensator_s2Polarizing angle P of polarizer_sPolarization angle A of polarization analyzer_sThe phase delay amount of the first phase compensator₁And phase delay amount of the second phase compensator₂And (3) as an accurate value, obtaining the accurate value of the residual working parameters (d, theta) of the full-Mueller matrix ellipsometer by using least square fitting by using (d, theta) as a variable through a relation between a theoretical Fourier coefficient and the working parameters. The full-Mueller matrix ellipsometer can fully utilize the same measurement data, the introduced error is relatively small, the calibrated parameters are more accurate, and further, when the method provided by the invention is applied to measurement of a sample to be measured, the measurement result is more accurate.

Drawings

Fig. 1 is an experimental light path diagram of an all-muller matrix ellipsometer constructed in the method for performing optical measurement by using the all-muller matrix ellipsometer according to the embodiment of the present invention;

fig. 2 is a logic block diagram of a method for performing an optical measurement by using a full-muller matrix ellipsometer according to an embodiment of the present invention;

fig. 3 is a logic block diagram of a method for performing an optical measurement by using a full-muller matrix ellipsometer according to a second embodiment of the present invention.

Detailed Description

For a better understanding of the present invention, reference will now be made in detail to the present embodiments of the invention, examples of which are illustrated in the accompanying drawings.

Example one

The method for performing optical measurement by using the full-Mueller matrix ellipsometer provided by the embodiment of the invention comprises the following steps of:

step 1: referring to the attached drawing 1, an experimental light path for constructing an all-muller matrix ellipsometer comprises a light source 1, an annular mirror 2, a pinhole 3, a first off-axis parabolic mirror 4, a polarizer 5, a first phase compensator 6, a first plane mirror 7, a sample stage 8, a second off-axis parabolic mirror 9, a third off-axis parabolic mirror 10, a second plane mirror 11, a second phase compensator 12, an analyzer 13, a fourth off-axis parabolic mirror 14, a spectrometer 15 and a terminal 16, wherein an isotropic and uniform reference sample is loaded on the sample stage 8; the optical process of the experimental light path of the full-Mueller matrix ellipsometer capable of local regression and self calibration comprises

S_out=M_AR(A′)R(-C′₂)M_c2(₂)R(C′₂)×M_s×R(-C′₁)M_c1(₁)R(C′₁)R(-P′)M_pR(P)S_in

Namely:

step 2: performing local regression calibration on the full-Mueller matrix ellipsometer;

and 3, step 3: placing a sample to be tested on a sample table, and obtaining an experimental Fourier coefficient of the sample to be tested by using a full Mueller matrix ellipsometer;

and 4, step 4: obtaining the information of the sample to be detected according to the experimental Fourier coefficient of the sample to be detected;

experimental fourier coefficient and azimuth P of mueller element and polarizer of sample_sAzimuth angle A of the analyzer_sAzimuth angle C of two phase compensators_s1And C_s2And amount of phase delay₁And₂there is a relationship (refer to Harland G. Tompkins, Eugene A. Irene, Handbook of ellipsometry,7.3.3DualRotating Compensator 7). And the Mueller element of the sample is related to the optical constants n and k and the thickness d of the sample material, the incident angle theta and the wavelength lambda of the light beam to the sample. Therefore, after the experimental fourier coefficient of the sample is measured, the mueller element of the sample can be obtained according to the above relationship, and further the information of the sample can be obtained.

The method for carrying out local regression calibration on the full-Mueller matrix ellipsometer comprises the following steps of;

step 21: setting the rotation speed of the first phase compensator and the second phase compensator;

step 22: setting the frequency of light intensity data measured by a spectrometer, so that the spectrometer measures the light intensity data once every T/N time, and collecting N groups of light intensity data in total, wherein N is more than or equal to 25, and T is a measurement period;

step 23: collecting light intensity data measured by a spectrometer;

step 24: obtaining each experimental Fourier coefficient alpha 'according to the light intensity data acquired by the spectrometer data acquisition module and N light intensity data-experimental Fourier coefficient relational expressions formed by the N times of light intensity data'_2n，β′_2n；

Step 25: according to each experimental Fourier coefficient, the initial polarization angle C of the calibrated first phase compensator_s1Initial polarization angle C of the second phase compensator_s2To obtain each theoretical Fourier coefficient alpha_2n，β_2n；

Step 26: based on isotropy and uniformity of a reference sample, the phase delay amount operation module of the first phase compensator calculates the polarization angle P of the polarizer according to each theoretical Fourier coefficient and the calibrated polarization angle P of the polarizer_sPolarization angle A of polarization analyzer_sObtaining the phase delay amount of the first phase compensator₁；

Based on isotropy and uniformity of the reference sample, the second phase compensator phase retardation operation module calculates the polarization angle P of the polarizer according to each theoretical Fourier coefficient and the calibrated polarization angle_sPolarization angle A of polarization analyzer_sObtaining the phase delay amount of the second phase compensator₂；

Step 27: the initial polarization angle C of the first phase compensator obtained by calibration_s1Initial polarization angle C of the second phase compensator_s2Polarizing angle P of polarizer_sPolarization angle A of polarization analyzer_sThe phase delay amount of the first phase compensator₁And phase delay amount of the second phase compensator₂And (3) as an accurate value, obtaining the accurate value of the residual working parameter (d, theta) of the full-Mueller matrix ellipsometer by using a least square fitting method and taking (d, theta) as a variable through a relation between a theoretical Fourier coefficient and the working parameter, wherein d is the thickness of the reference sample, and theta is the angle of light incidence to the reference sample.

The corresponding Mueller matrix for the isotropic and uniform reference sample is:

M_{s} = [\begin{matrix} M_{11} & M_{12} & 0 & 0 \\ M_{21} & M_{22} & 0 & 0 \\ 0 & 0 & M_{33} & M_{34} \\ 0 & 0 & M_{43} & M_{44} \end{matrix}]

taking N =36, and the rotation speed of the first phase compensator 6 and the rotation speed of the second phase compensator 12 = 5: 3 as an example, at this time, the first phase compensator 6 and the second phase compensator 12 are in a rotating state, and the rotation speed of the first phase compensator 6 and the rotation speed of the second phase compensator 12 = 5: 3, and at this time, C'₁=5(C-C_s1)，C′₂=3(C-C_s2) The time for the first phase compensator 6 to turn 5 turns or the second phase compensator 12 to turn 3 turns is a period T,

wherein,

cs1, t = the angle of the fast axis of the first phase compensator 5 at time instant 0,

cs2, the angle of the fast axis of the second phase compensator 12 at time t =0,

c = ω t, the angle by which the first compensator 5 and the second compensator 12 rotate at the fundamental physical frequency ω.

<math> <mfenced open='' close=''> <mtable> <mtr> <mtd> <msub> <mi>S</mi> <mi>j</mi> </msub> <mo>=</mo> <msubsup> <mo>&Integral;</mo> <mfrac> <mrow> <mrow> <mo>(</mo> <mi>j</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> <mi>T</mi> </mrow> <mn>36</mn> </mfrac> <mfrac> <mi>jT</mi> <mn>36</mn> </mfrac> </msubsup> <msubsup> <mi>I</mi> <mn>0</mn> <mo>′</mo> </msubsup> <mo>[</mo> <mn>1</mn> <mo>+</mo> <munderover> <mi>Σ</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>1</mn> </mrow> <mn>16</mn> </munderover> <mrow> <mo>(</mo> <msubsup> <mi>α</mi> <mrow> <mn>2</mn> <mi>n</mi> </mrow> <mo>′</mo> </msubsup> <mi>cos</mi> <mn>2</mn> <mi>nωt</mi> <mo>+</mo> <msubsup> <mi>β</mi> <mrow> <mn>2</mn> <mi>n</mi> </mrow> <mo>′</mo> </msubsup> <mi>sin</mi> <mn>2</mn> <mi>nωt</mi> <mo>)</mo> </mrow> <mo>]</mo> <mi>dt</mi> </mtd> </mtr> <mtr> <mtd> <mo>=</mo> <mfrac> <msubsup> <mi>πI</mi> <mn>0</mn> <mo>′</mo> </msubsup> <mrow> <mn>36</mn> <mi>ω</mi> </mrow> </mfrac> <mo>+</mo> <munderover> <mi>Σ</mi> <mrow> <mi>n</mi> <mo>=</mo> <mn>1</mn> </mrow> <mn>16</mn> </munderover> <mfrac> <msubsup> <mi>I</mi> <mn>0</mn> <mo>′</mo> </msubsup> <mi>nω</mi> </mfrac> <mrow> <mo>(</mo> <mi>sin</mi> <mfrac> <mi>nπ</mi> <mn>36</mn> </mfrac> <mo>)</mo> </mrow> <mo>[</mo> <msubsup> <mi>α</mi> <mrow> <mn>2</mn> <mi>n</mi> </mrow> <mo>′</mo> </msubsup> <mi>cos</mi> <mfrac> <mrow> <mrow> <mo>(</mo> <mn>2</mn> <mi>j</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> <mi>nπ</mi> </mrow> <mn>36</mn> </mfrac> <mo>+</mo> <msubsup> <mi>β</mi> <mrow> <mn>2</mn> <mi>n</mi> </mrow> <mo>′</mo> </msubsup> <mi>sin</mi> <mfrac> <mrow> <mrow> <mo>(</mo> <mn>2</mn> <mi>j</mi> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> <mi>nπ</mi> </mrow> <mn>36</mn> </mfrac> <mo>]</mo> </mtd> </mtr> <mtr> <mtd> <mrow> <mo>(</mo> <mi>j</mi> <mo>=</mo> <mn>1,2</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mn>36</mn> <mo></mo> <mo>)</mo> </mrow> <mo>·</mo> <mo>·</mo> <mo>·</mo> <mn>2.1</mn> </mtd> </mtr> </mtable> </mfenced> </math>

Where ω = π/T. Using the collected S1, S2, S3.. S36, 36 equations (n =9, 12, 14, 15 with a prime fourier coefficient α ') including 25 unknowns can be obtained from the above equation'_2n=0 and β'_2n= 0), the fourier coefficient with a prime α 'can be solved by a nonlinear least squares method'_2nAnd beta'_2nAnd 24 in total.

Theoretical fourier coefficient α_2nAnd beta_2nAnd Fourier coefficient alpha 'obtained by experiment'_2nAnd beta'_2nConversion relation (equations 2.7 and 2.8)

α_2n=α′_2ncosφ_2n+β′_2nsinφ_2n…2.7

β_2n=-α′_2nsinφ_2n+β′_2ncosφ_2n…2.8

Wherein:

φ₂=12C_s2-10C_s1; φ₄=10C_s1-6C_s2;

φ₆=6C_s2; φ₈=20C_s1-12C_s2;

φ₁₀=10C_s1; φ₁₂=12C_s2;

φ₁₄=20C_s1-6C_s2; φ₁₆=10C_s1+6C_s2;

φ₂₀=20C_s1; φ₂₂=10C_s1+12C_s2;

φ₂₆=20C_s1+6C_s2; φ₃₂=20C_s1+12C_s2

the theoretical fourier coefficient α can be obtained from the equations (equations 2.7 and 2.8)_2nAnd beta_2n。

Due to the isotropic and homogeneous sample, M₁₃=M₃₁=M₁₄=M₄₁=M₂₃=M₃₂=M₂₄=M₄₂=0, and the theoretical fourier coefficient α can be known from the theoretical principle of the Mueller ellipsometer₂、β₂、α₁₀、β₁₀、α₆、β₆、α₁₄、β₁₄、α₂₂、β₂₂、α₂₆、β₂₆The theoretical expression of (1):

from the equations 2.10 and 2.12

Wherein

<math> <mrow> <mrow> <mo>(</mo> <msub> <mi>P</mi> <mi>s</mi> </msub> <mo>+</mo> <msub> <mi>A</mi> <mi>s</mi> </msub> <mo>)</mo> </mrow> <mo>&NotEqual;</mo> <mfrac> <mi>nπ</mi> <mn>2</mn> </mfrac> </mrow> </math>

And is

<math> <mrow> <msub> <mi>P</mi> <mi>s</mi> </msub> <mo>&NotEqual;</mo> <mfrac> <mi>nπ</mi> <mn>2</mn> </mfrac> </mrow> </math>

And is

<math> <mrow> <msub> <mi>A</mi> <mi>s</mi> </msub> <mo>&NotEqual;</mo> <mfrac> <mi>π</mi> <mn>4</mn> </mfrac> <mo>+</mo> <mfrac> <mi>nπ</mi> <mn>2</mn> </mfrac> </mrow> </math>

(n is an integer) (it must be ensured that the Fourier coefficient is not zero)

Similarly, the phase delay amount of the compensator can be calculated by equations 2.9 and 2.12, equations 2.9 and 2.11, equations 2.10 and 2.11, equations 2.9 and 2.13, 2.9 and 2.14, equations 2.10 and 2.13, and equations 2.10 and 2.14₁。

The amount of phase delay of the second compensator is calibrated₂。

From equations 2.16 and 2.18:

wherein

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And is

<math> <mrow> <msub> <mi>A</mi> <mi>s</mi> </msub> <mo>&NotEqual;</mo> <mfrac> <mi>nπ</mi> <mn>2</mn> </mfrac> </mrow> </math>

(n is an integer) (it must be ensured that the Fourier coefficient is not zero)

Similarly, the phase delay amount of the compensator can be calibrated by equations 2.16 and 2.19, equations 2.17 and 2.18, equations 2.17 and 2.19, equations 2.18 and 2.20, 2.18 and 2.21, equations 2.19 and 2.20, and equations 2.19 and 2.21₂。

The transformation of the experimental Fourier coefficient and the theoretical Fourier coefficient can be realized by the formulas 2.7 and 2.8, and the theoretical Fourier coefficient, the Mueller element of the sample and the azimuth angle P of the polarizer_sAzimuth angle A of the analyzer_sAzimuth angle C of two phase compensators_s1And C_s2And amount of phase delay₁And₂(see Harland g. tompkins, Eugene a. irene, Handbook of ellipsometry,7.3.3dual rolling comparator 7). And the Mueller element of the sample is related to the optical constants n and k and the thickness d of the sample material, the incident angle theta and the wavelength lambda of the light beam to the sample. Experimental Fourier coefficient alpha'_2nAnd beta'_2nAnd (n, k, d, θ, λ, P)_s，A_s，C_s1，C_s2，₁，₂) In this regard, the angle at which the beam is incident on the sample. Alpha 'obtained in the experiment for a reference sample with known optical constants n, k at one wavelength'_2nAnd beta'_2n24, a total, 24 corresponding equations can be obtained,only with (d, theta, lambda, P)_s，A_s，C_s1，C_s2，₁，₂) It is related. P from the above calibration_s，A_s，C_s1，C_s2，₁，₂As initial values, and the corresponding wavelengths measured experimentally are known, 24 equations from experimental fourier coefficients are derived, with (d, θ, P)_s，A_s，C_s1，C_s2，₁，₂) And (4) performing correlation, namely fitting the residual working parameters (d, theta, P) of the muller ellipsometer by using a least square method_s，A_s，C_s1，C_s2，₁，₂). The reference sample may be a silicon dioxide thin film sample with silicon as a substrate, and optical constants n and k of the silicon dioxide thin film sample can be referred to from the literature, and the optical constants of the silicon dioxide thin film sample are n =1.457 and k =0, taking a wavelength of 632.8nm as an example.

When N =25, the experimental Fourier coefficient calculation module directly obtains each experimental Fourier coefficient alpha 'according to N light intensity data-experimental Fourier coefficient relational expressions formed by the N times of light intensity data'_2n，β′_2n。

When N is more than 25, the experimental Fourier coefficient calculation module obtains each experimental Fourier coefficient alpha 'through a least square method according to an N light intensity data-experimental Fourier coefficient relation formed by the N times of light intensity data'_2n，β′_2n。

The light source may be a broad spectrum light source, the number of wavelengths of light that the light source is capable of producing is N ', and the number of relations between theoretical fourier coefficients and operating parameters is 24 × N'.

The number of isotropic and homogeneous reference samples may be m, the number of relations between theoretical fourier coefficients and operating parameters being 24 × N' × m.

Example two

Referring to fig. 3, a difference between the local regression self-calibrated full-muller matrix ellipsometer according to the second embodiment of the present invention and the local regression self-calibrated full-muller matrix ellipsometer according to the first embodiment of the present invention is that the local regression self-calibrated method for a local regression self-calibrated full-muller matrix ellipsometer according to the second embodiment of the present invention further includes the following steps:

according to each experimental Fourier coefficient alpha'_2n，β′_2nTo obtain each theta_2nHere, θ_2nAre intermediate parameters defined for ease of operation;

according to each theta_2nObtaining an initial polarization angle C of the first phase compensator_s1；

According to each theta_2nObtaining an initial polarization angle C of the second phase compensator_s2；

According to each theta_2nObtaining the polarization angle P of the polarizer_s；

According to each theta_2nObtaining the polarization angle A of the analyzer_s。

Wherein,

θ_2n=tan^-1(β′_2n/α′_2n)…2.2

using the method already known in the literature (R.W.Collins and Joohyun Koh Dual rotating-lubricating tubular analyzer: instrument design for real-time Mueller matrix spectroscopy of surfaces andvol.16, No.8/August 1999/J.Opt.Soc.am.A1997-2006), corresponding to equations 2.3-2.6, the initial polarization angle C of the compensator can be calibrated_s1And C_s2And the polarization angle P of the polarizer and analyzer_sAnd A_s。

After P is calibrated_s、A_s、C_s1And C_s2On the basis, under the condition that the compensators are not detached from an experiment table or equipment for independent measurement, a method is provided, the phase delay amounts of the two compensators under different wavelengths can be completely calibrated through one-time experiment, and the calibration process is accurate and simple.

The above embodiments are provided to further explain the objects, technical solutions and advantages of the present invention in detail, it should be understood that the above embodiments are merely exemplary and not restrictive, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for optical measurement by using an all-Mueller matrix ellipsometer is characterized by comprising the following steps:

setting the rotational speeds of the first and second phase compensators;

collecting light intensity data measured by the spectrometer;

The initial polarization angle C of the first phase compensator obtained by calibration_s1Initial bias of the second phase compensatorVibration angle C_s2Polarizing angle P of polarizer_sPolarization angle A of polarization analyzer_sThe phase delay amount of the first phase compensator₁And phase delay amount of the second phase compensator₂And (d, theta) is used as a variable, and a least square method is used for fitting to obtain the accurate value of the residual working parameter (d, theta) of the full-Mueller matrix ellipsometer by using a relation between the theoretical Fourier coefficient and the working parameter (d, theta), wherein d is the thickness of the reference sample, and theta is the angle of light incidence to the reference sample.

2. The method of claim 1, further comprising the steps of:

according to the experimental Fourier coefficients alpha'_2n，β′_2nTo obtain each theta_2n=tan^-1(β′_2n/α′_2n)；

Each theta_2nObtaining the polarization angle P of the polarizer_s；

3. The method according to claim 1, wherein N =25, and the experimental Fourier coefficient calculation module directly obtains each experimental Fourier coefficient α 'from N intensity data-experimental Fourier coefficient relations formed by the N intensity data'_2n，β′_2n。

4. The method according to claim 1, wherein N > 25, and the experimental Fourier coefficient calculation module forms an N intensity data-experimental Fourier coefficient relation from the N intensity data by least squaresObtaining the Fourier coefficient alpha 'of each experiment'_2n，β′_2n。

5. The method of claim 1, wherein the light source is a broad spectrum light source, the number of wavelengths of light that the light source is capable of producing is N ', and the number of relationships between the theoretical fourier coefficients and the operating parameters is 24 x N'.

6. The method according to claim 5, characterized in that the number of isotropic and homogeneous reference samples is m and the number of relations between theoretical Fourier coefficients and operating parameters is 24 XN' x m.

7. The method of claim 1, wherein the reference sample is a silicon dioxide thin film of a silicon substrate.