CN2819212Y - Fast elliptical polarized light measuring equipment - Google Patents

Abstract

The utility model relates to fast elliptical polarized light measuring equipment. In a structure of traditional luminosity type elliptical polarized light measuring equipment, a mechanical rotating mode is used for controlling a polarizer or an analyzer to carry out the azimuth sweep of light polarization. As the mechanical rotating speed is limited, the detecting speed of the traditional luminosity type elliptical polarized light measuring equipment is limited. The utility model adopts an elliptical polarized test system with the structural arrangement of a combining analyzer and a two-dimensional CCD array detector to fast obtain optics parameters of material. As the utility model uses the combining analyzer to replace a traditional rotary analyzer to obtain the number of sampling points required by fourier analysis and uses the two-dimensional CCD array detector to detect light signals of each polarization state in parallel, during a testing process, any mechanical part does not need to be rotated in a system. Thus, the measuring speed of optical parameters of different material is raised substantially.

Description

A kind of novel quick-speed elliptical polarized light measurement instrument

Technical field

The utility model belongs to optical electron device technology field, is specifically related to a kind of novel quick-speed elliptical polarized light measurement instrument.

Background technology

The measurement of elliptically polarized li instrument is a kind of optical gauge, and it is one of the most effective and reliable method of the optical property, optical constant and the film thickness that obtain various information functional materials.As the preparation technology with high performance Pentium chip is example, in its complete technological process, detect through more than 40 times elliptically polarized light.The development of optical communication technology, depend on the high-performance optical waveguide, photoswitch, optical amplifier, the research and development of a series of optical elements such as narrow band filter slice, in the R﹠D process of optical element, need carry out fast the various optical constants and the optical characteristics of various optical materials, high-acruracy survey and analysis, in addition to some devices of optical film, need be in the optical thin film growth course, optical constant and thickness to each rete are accurately measured and are controlled, and also very need research and development quick, the advanced method of testing and the means of precise material optical property.

The optical property and the optical constant of the various information functional materials of the elliptic polarization technology highly sensitive acquisition of energy, and then can analyze in the characteristic that different spectrum segment had material, understand its physical essence, thereby make material obtain important application.Developed multiple ellipsometry pattern at present, as delustring formula and luminosity formula etc.The ellipse inclined to one side system of delustring formula is by regulating the position angle of optical elements such as phase delayer, the polarizer and analyzer, the output intensity that makes system is zero, read the position angle of each optical element with this understanding, just can calculate and try to achieve ellipsometric parameter, but the detection speed of this method is slower.The ellipse inclined to one side system of luminosity formula has adopted light intensity with rising partially or the analyzing azimuthal variation is made the method for Fourier analysis, and by computing machine measuring process is controlled automatically, but specific extinction formula ellipsometry records ellipsometric parameter more fast and exactly.But because the ellipse inclined to one side system of common luminosity formula adopts the polarizer scan mode to obtain ellipsometric parameter, though the test to the ordinary optical parameter is enough quick, but if be applied to some specific occasion, quick real-time optical monitoring as microelectronic technique or high vacuum film growth system, certain difficulty is just arranged, and application will be restricted.For this reason, the utility model will adopt the elliptic polarization light detection method of combination analyzer and 2 dimension CCD area array detector combinations, obtain the optical parametric of material fast.[list of references: D.E.Aspnes, 8,222 (1973); D.E.Aspnes, J.Opt.Soc.Am., 64,812 (1974)].

Summary of the invention

The purpose of this utility model is, on existing structure pattern basis, its shortcoming is improved, and proposes a kind of system that need not any mechanical rotation, can carry out measurement of elliptically polarized li fast that (do not comprise and measure preceding light path adjusting) in measuring process.

The measurement of elliptically polarized li instrument concrete structure that the utility model proposes is connected to form through light path successively by light source, the polarizer, specimen holder, combination analyzer, two-dimensional CCD detector and computer control and analytic system shown in figure one; Wherein, the position angle of the polarizer between light source and the specimen holder is fixed, and cavity is arranged in the specimen holder, and is connected with vacuum pump, make sample through negative-pressure adsorption on specimen holder; Combination analyzer between specimen holder and the two-dimensional CCD detector is made up of m miniature sub-analyzer, and the position angle of this m miniature sub-analyzer roughly evenly distributes between 0-π; Computer control is made up of with relevant control and analytical calculation software a computing machine with analytic system, be used for the selection of light path adjusting and incident angle before the measurement, electric signal to ccd detector during measurement carries out data acquisition, various optical parametrics to detected materials calculate, and the result exports result of calculation.

Measuring instrument of the present utility model, the monochromatic light that is sent by light source becomes the monochromatic line polarized light through the fixing polarizer, and this fixedly becomes the α angle in the initial orientation angle of the polarizer with the plane of incidence.Generally make α=45 °.Light is through fixedly shining testing sample with certain incident angle Φ behind the analyzer, and after the sample reflection, reflected light is generally elliptically polarized light.Reflected light is equipped with several miniature sub-analyzers by the combination analyzer in this combination analyzer, the position angle of each sub-analyzer has different orientation.Reflected light is behind the combination analyzer, and emergent light has different polarization states, and the light intensity of each polarization state correspondence is detected by two-dimensional CCD detector zones of different.After each the polarization state light intensity that is detected by ccd detector became electric signal, conversion was carried out signal analysis and data processing by computing machine through AD, obtains the various optical constants of material at last.

In the utility model, definite method of the optical parametric of testing sample is as follows.

The polarizer is fixed in suitable position angle, as makes α=45 °.From the light intensity of analyzer outgoing be with analyzer azimuthal variation pass

I＝I ₀+I ₁cos2A+I ₂sin2A (1)

I wherein ₀Be DC component, I ₁, I ₂Be AC compounent, A is the position angle of analyzer.Can get through calculating,

I ₀＝η(1+ρ ₀ ²)+I _B (2a)

I ₁＝η(1-ρ ₀ ²) (2b)

I ₂＝2ηρ ₀cosΔ (2c)

η is the constant relevant with light intensity, DC component I ₀In I _BBe background signal, come from the dark current of detector.(2) in the formula, ρ ₀, Δ is two ellipsometric parameters, be defined as follows:

If after light reflected through sample, the complex index of reflection of s, p polarized light was respectively ${\tilde{r}}_s=r_s{e}^{{\′\mathrm{\Δ}}_1},{\tilde{r}}_p=r_p{e}^{{\′\mathrm{\Δ}}_2}.$ R wherein _s, r _pBe respectively the mould of s, p polarized light complex index of reflection, Δ ₁, Δ ₂Be the phase differential of the relative incident light of reflected light of s, p polarization state, then ρ ₀, two parameters of Δ are defined as ρ respectively ₀=r _p/ r _s, Δ=Δ ₂-Δ ₁

Can calculate ellipsometric parameter ρ according to three coefficients in (2) formula ₀With the cos Δ,

${\mathrm{\&rho;}}_0={\left[\frac{(I_0-I_1)}{({\mathrm{<figure-callout\; id="0"\; label="I"\; filenames="Y20052004020100101.png"\; state="\{\{state\}\}">I</figure-callout>}}_0+I_1)}\right]}^{\frac{1}{2}}---\left(3\right)$

$\cos \mathrm{\&Delta;}=\frac{I_2}{{[{{\mathrm{<figure-callout\; id="0"\; label="I"\; filenames="Y20052004020100101.png"\; state="\{\{state\}\}">I</figure-callout>}}_0}^2-{I_1}^2]}^{\frac{1}{2}}}---\left(4\right)$

Light intensity I in (1) formula is made the numerical value Fourier transform to analyzer position angle A, and transform is:

$I_0=\frac{1}{n}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}(I_i-I_{\mathrm{bi}})---\left(5a\right)$

$I_1=\frac{2}{n}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{I}_i\cos \left(2A_i\right)---\left(5b\right)$

$I_2=\frac{2}{n}\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{I}_i\sin \left(2A_i\right)---\left(5c\right)$

I in the formula _iBe that the analyzer position angle is A _iThe time ccd detector received light intensity signal, λ is corresponding wavelength, n is the twice of analyzer group neutron analyzer number, makes the number of times of data collection in the one-period by Ai value.From (3), (4) formula, obtain ellipsometric parameter ρ ₀Behind Δ, can obtain parameter

$\mathrm{\&rho;}={\mathrm{\&rho;}}_0{e}^{\mathrm{i\&Delta;}}---\left(6\right)$

The multiple dielectric function ε=ε of material ₁+ i ε ₂And satisfy following relation between the parameter ρ:

$\mathrm{\&epsiv;}={\mathrm{\&epsiv;}}_a[{\sin }^2\mathrm{\&phi;}+{\sin }^2\mathrm{\&phi;}{\tan }^2\mathrm{\&phi;}{\left(\frac{1-\mathrm{\&rho;}}{1+\mathrm{\&rho;}}\right)}^2]---\left(7\right)$

Wherein Φ is the incident angle of light, ε _aBe the dielectric function of environment medium, if environment is air, then ε _a=1.Multiple dielectric function and other optical constant as the pass of complex index of refraction N, absorption coefficient and reflectivity R etc. are:

$\mathrm{\&epsiv;}=N^2,N=n+\mathrm{ik},{\mathrm{\&epsiv;}}_1=n^2-k^2,{\mathrm{\&epsiv;}}_2=2\mathrm{nk},\mathrm{\&alpha;}=\frac{4\mathrm{\&pi;k}}{\mathrm{\&lambda;}},R=\frac{{(n-1)}^2+k^2}{{(n+1)}^2+k^2}---\left(8\right)$

(8) in the formula, N=n+ik is the complex index of refraction of specimen material, and its real part n is a refractive index, and imaginary part k is an extinction coefficient.Therefore in case measure ellipsometric parameter ρ ₀Behind Δ, can obtain the multiple dielectric function of material by (7) formula, and then calculate other optical constant of sample, as complex index of refraction N, absorption coefficient and reflectivity R etc. by (8) formula.

Above-mentioned calculating formula all realizes at software section----the Computer Analysis calculating section of measuring instrument.

The utility model adopts the ellipsometric measurement system of combination analyzer and the combination of two-dimensional CCD array detector, need not to rotate any mechanism components in test process, has increased substantially the measuring speed of various material optical parametrics.

Description of drawings

Fig. 1 is the utility model measuring instrument structural representation.

Fig. 2 is a kind of structural diagrams of the utility model measuring instrument.

Fig. 3 is a kind of combination analyzer structural diagrams in the utility model measuring instrument.

Number in the figure: 1 is LASER Light Source, and 2 is laser beam expanding camera lens group, and 3 are the fixing polarizer, 4 is specimen holder, and 5 is the specimen holder turntable, and 6 is reflected light arm turntable, 7 are the combination analyzer, 8 is ccd detector, and 9 is reflected light arm turntable motor driver, and 10 is the sample rotary table motor driver, 11 is computer data acquiring and analysis process system, 12 are the output result, and 13 is the incident light arm, and 14 is the reflected light arm.

Embodiment

The novel quick-speed elliptical polarized light measurement instrument of the utility model design shows in figure one, provides a special case here.In this example, light source adopts LASER Light Source., incided the polarizer 3, and then incide on the sample after expanding bundle by the light of LASER Light Source outgoing, reflexed to combination analyzer 7 by sample, the light by 7 outgoing of combination analyzer is received by the zones of different of two-dimensional CCD planar array detector 8 respectively.

Combination analyzer 7 is made up of m miniature sub-analyzer.The general desirable 5-20 of m.The azimuth angle theta of each sub-analyzer ₁, θ ₂θ _m, in 0～180 °, roughly evenly distribute.Specific practice combination analyzer is the aperture (as square hole) of m number of processing (as more than ten) in a hard material, the orientation of square hole is different, deflection roughly evenly distributes in 0～180 ° of scope, each miniature sub-analyzer is processed into the size that is complementary with orifice size, again by the direction of shaking thoroughly of sub-analyzer, they are put into each aperture, make the direction difference of shaking thoroughly of the sub-analyzer in each hole, and its position angle also roughly evenly distributes in 0～180 ° of scope.Fig. 3 provides a special case of this combination analyzer: in this example, it is 9.5mm that 12 square miniature analyzers of 1.5mm * 1.5mm are installed in a diameter, on the stainless steel stent of thick about 2mm, the position angle of these 12 miniature analyzers is followed successively by 0 °, 16 °, 33 °, 49 °, 66 °, 82 °, 90 °, 98 °, 114 °, 131 °, 147 °, 164 °.

The utility model measuring instrument further describes as follows:

System comprises parts such as optics, electron device, mechanical part and control analysis software.

1) optics

A) light source 1: adopting wavelength is the He-Ne gas laser of 632.8nm;

B) expander lens 2: expander lens is made up of confocal lens, expands the bundle multiplying power and is about 5～10 times;

C) the fixing polarizer 3: the Glan-Foucault polarizing prism that adopts the kalzit material;

D) combination analyzer 7: as shown in Figure 3, be the miniature sub-analyzer that 12 1.5mm * 1.5mm are installed on the stainless steel stent of 9.5mm, thick about 2mm at diameter, the position angle of this a little analyzer is roughly evenly distribution in 0～180 ° of scope;

E) ccd detector 8: adopt the two-dimensional CCD planar array type detector with 1024 * 1024 pixels, each pixel is of a size of 24 * 24 μ m ²

2) electron device

A) driving circuit of specimen holder 4 and emergent light arm: be made of stepper motor drives and computer interface circuit, gating pulse is produced by software mode;

B) data collecting card: by finishing the vision signal that receives by ccd detector transmission course to the computer system input with the supporting video data acquiring card of ccd detector.

3) mechanical part

A) incidence angle variable rotary table base: comprise specimen holder rotary table base and emergent light arm rotary table base; The specimen holder turntable can rotate between 0～90 °, be mainly used in each measurement before, beam path alignment and the light path measured are regulated; Emergent light arm turntable can rotate in 30～180 ° of scopes, is used to select suitable incident angle;

B) negative-pressure adsorption-type sample holder: specimen holder is to be processed into cavity in the middle of will the flat brass material and to make, and cavity one end is connected with vacuum pump, and cavity has a plurality of apertures to link to each other with flat surface, and when the vacuum pump work, sample is by the negative-pressure adsorption in the vacuum chamber; Specimen holder is contained on the multidimensional adjustable support;

C) incident light arm and emergent light arm: the incident light arm is the wire chamber of aluminum, in expander lens, fixing assembly such as polarizer are housed; The emergent light arm also is the wire chamber of aluminum, in ccd detector and assemblies such as combination analyzer etc. are housed; The incident light arm maintains static, and the emergent light arm links to each other with emergent light arm rotary table base, can rotate according to the incident angle of measuring.

4) control analysis software

A) control section: the light path that is mainly used in before measuring is regulated, and the selection of incident angle, as driving sample rotary table, with the calibration light path, drives emergent light arm turntable to select suitable incident angle.

B) data acquisition: read the electric signal that comes from ccd detector in real time by data collecting card by software control.

C) data processing section: the different polarization states signal that collects is carried out Fourier transform, obtain the coefficient of light intensity AC and DC component, and then obtain two ellipse inclined to one side constant ρ ₀, Δ.Calculate the various optical constants that can obtain detected materials by two ellipse inclined to one side constants by foregoing a series of formula again.

D) data output: data can be presented on the screen in real time or output to data file.

2,, after expanding bundle, form the parallel beam of diameter 9.5mm, again by becoming the linearly polarized light of diameter 9.5mm behind the polarizer by the 623.8nm monochromatic light of LASER Light Source outgoing.This monochromatic line polarized light incides on the sample with 60 ° incident angle

3, sample is installed on the specimen holder with vacuum suction structure, has realized harmless optical detection.

4, by the combination analyzer, the combination analyzer is made of 12 miniature sub-analyzers light through sample reflection back, and the plane of polarization of these miniature analyzers is evenly configuration in 0～180 ° of scope.

5, surveyed by the zones of different of two-dimensional CCD face array respectively through the light of 12 miniature analyzers, deliver to computing machine by the signal of ccd detector output through data collecting card, and it is analyzed, with regard to the readable intensity level that gets each corresponding polarization state.

6, the intensity level of each polarization state is carried out analyzing and processing after, promptly obtain corresponding optical constant.

The enforcement of native system also comprises calibration and debugging two parts, the calibration of first ccd detector and combination analyzer, and it two is comprehensive debuggings of system.After the calibration of combination analyzer, obtain the variation of light through intensity behind the different miniature analyzers, and the variation of polarization state, these running parameters write instrument control procedure after demarcating, and consider these factors when data processing, thereby obtain accurate result.The pixel of ccd detector zones of different and the corresponding relation between the different polarization states light intensity are promptly determined in the calibration of ccd detector.This corresponding relation also will enroll computer analysis program.The comprehensive debugging of system comprises that light path system aims at, and the azimuthal adjustment of polarizer polarization and make system hardware and the software integration running solves a series of problems in aspect such as mechanical, optics and electronics.In the middle of design of the present utility model, the incident angle continuous variable, resolution is better than 0.01 °.Automatic data collection, analysis and calculating.System has realized the characteristics of measuring real-time.

Main measuring process:

1. with system's each several part power connection;

2. by vacuum suction, sample is contained on the specimen holder;

3. adjusting light path, selected suitable incident angle;

4. measure and read output data.

Measure illustration: if to certain material, measurement data as shown in Table 1:

Table one analyzer position angle and corresponding light intensity output

Analyzer position angle (radian) light intensity

0.8409 23.3853

0.9718 19.8025

1.1027 15.8922

1.2336 11.7324

1.3645 7.4318

1.4954 3.3058

1.6263 2.7852

1.7572 6.7775

1.8881 11.0842

2.0190 15.2738

2.1499 19.2275

2.2808 22.8645

(5a)-(5c) can get according to formula:

I ₀＝13.2969，I ₁＝12.8590，I ₂＝-0.6312

Ignore dark current I _BiInfluence, according to (3), (4) Shi Kede:

ρ ₀＝7.7283，Δ＝79.2572°

Here incident angle is Φ=60 °, lambda1-wavelength λ=632.8nm, according to (7) Shi Kede:

ε ₁＝2.264，ε ₂＝1.377，n＝1.567，k＝0.439，a＝8.713μm ^-1，R＝0.0760

Can obtain the optical constants such as specific inductive capacity, refractive index, extinction coefficient, absorption coefficient and reflectivity of this kind material thus.

Claims (4)

1, a kind of measurement of elliptically polarized li instrument is characterized in that being connected to form through light path successively by light source, the polarizer, specimen holder, combination analyzer, two-dimensional CCD detector and computer control and analytic system; Wherein, the position angle of the polarizer between light source and the specimen holder is fixed, and cavity is arranged in the specimen holder, and is connected with vacuum pump, make sample through negative-pressure adsorption on specimen holder; Combination analyzer between specimen holder and the two-dimensional CCD detector is made up of m miniature sub-analyzer, and the position angle of this m miniature sub-analyzer roughly evenly distributes between 0-π.

2, measuring instrument according to claim 1 is characterized in that in each optics,

(1) light source (1): adopting wavelength is the He-Ne gas laser of 632.8nm;

(2) expander lens (2): expander lens is made up of confocal lens, expands the bundle multiplying power and is about 5～10 times;

(3) the fixing polarizer (3): the Glan-Foucault polarizing prism that adopts the kalzit material;

(4) combination analyzer (7): be the miniature sub-analyzer that 12 1.5mm * 1.5mm are installed on the stainless steel stent of 9.5mm, thick about 2mm at diameter, the position angle of this a little analyzer is roughly evenly distribution in 0～180 ° of scope;

(5) ccd detector (8): adopt the two-dimensional CCD planar array type detector with 1024 * 1024 pixels, each pixel is of a size of 24 * 24 μ m ²

3, measuring instrument according to claim 1 is characterized in that also comprising electron device, and electron device comprises:

(1) driving circuit of specimen holder 4 and emergent light arm: constitute by stepper motor drives and computer interface circuit;

(2) data collecting card: by finishing the vision signal that receives by ccd detector transmission course to the computer system input with the supporting video data acquiring card of ccd detector.

4, measuring instrument according to claim 1 is characterized in that also comprising mechanical part, and these mechanical parts comprise:

(1) incidence angle variable rotary table base: comprise specimen holder rotary table base and emergent light arm rotary table base; The specimen holder turntable can rotate between 0～90 °, be mainly used in each measurement before, beam path alignment and the light path measured are regulated; Emergent light arm turntable can rotate in 30～180 ° of scopes, is used to select suitable incident angle;

(2) negative-pressure adsorption-type sample holder: specimen holder is to be processed into cavity in the middle of will the flat brass material and to make, and cavity one end is connected with vacuum pump, and cavity has a plurality of apertures to link to each other with flat surface, and when the vacuum pump work, sample is by the negative-pressure adsorption in the vacuum chamber; Specimen holder is contained on the multidimensional adjustable support;

(3) incident light arm and emergent light arm: the incident light arm is the wire chamber of aluminum, in expander lens, fixing assembly such as polarizer are housed; The emergent light arm also is the wire chamber of aluminum, in ccd detector and assemblies such as combination analyzer etc. are housed; The incident light arm maintains static, and the emergent light arm links to each other with emergent light arm rotary table base, can rotate according to the incident angle of measuring.

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