CN104880161A - Method for measuring solid material surface roughness by using elliptical polarization parameter - Google Patents

Abstract

A method for measuring the surface roughness of a solid material by using ellipsometric parameters, the invention relates to a method for measuring the surface roughness of a solid material. The purpose of the present invention is to solve the problems of slow speed of the atomic force microscope in the prior art measurement method, the need for the measurement sample of the scanning electron microscope to be able to conduct electricity, and the low precision of the optical section microscope. It is realized through the following technical solutions: Step 1, simulate and calculate the characteristic parameters of rough surfaces of different solid materials, that is, obtain the spatial electromagnetic field distribution of the near field of the rough surface of the solid materials through the three-dimensional time-domain finite difference method; Step 2, through the near-far Obtaining the complex electric field in the far field by field transformation , calculate the radiation polarization characteristics in the mirror reflection direction, and establish a database; Step 3, after the production of the solid material is completed, measure the optical ellipsometric parameters of the surface of the solid material, and compare with the database to obtain the root mean square roughness and autocorrelation length. The invention is applied to the field of measuring surface roughness.

Description

A Method for Measuring the Surface Roughness of Solid Materials Using Ellipsometric Parameters

technical field

The invention relates to a method for measuring the surface roughness of solid materials.

Background technique

Surface roughness refers to the small pitch and small peak-to-valley irregularities that the machined surface has. The actual surface is rough, and the surface roughness of the material has a direct impact on the wear resistance, sealing performance, and fatigue resistance of the sample, and also affects the assembly quality, vibration and noise, power consumption, and service life of the parts. Not only that, surface roughness also plays an important role in the fields of material optical properties and infrared target imaging. The measurement of surface roughness has become an important task in the quality inspection of parts. It can be characterized by root-mean-square roughness (root-mean-square, σ) and autocorrelation length (correlation length, τ). The definition of root mean square roughness is:

$\mathrm{<span\; class="notranslate">\; \&sigma;</span>}<span\; class="notranslate">\; =</span>\sqrt{<span\; class="notranslate">\; \&lang;</span>\mathrm{<span\; class="notranslate">\; \&zeta;</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&rang;</span>}$

Among them, ζ(r) is the surface height at r, which satisfies the following conditions:

<ζ(r)>=0

In reality, the root mean square roughness of many material surfaces satisfies the Gaussian distribution:

$<span\; class="notranslate">\; \&lang;</span>\mathrm{<span\; class="notranslate">\; \&zeta;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; r</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; \&zeta;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; r</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rang;</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; \&lsqb;</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\frac{{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span><span\; class="notranslate">\; (</span>\frac{{<span\; class="notranslate">\; |</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; the\; y</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&rsqb;</span>$

τ is the autocorrelation length.

Optical ellipsometry was first proposed by Rothen in 1945. He designed and manufactured the first ellipsometer, and used the ellipsometer to measure a film thickness of 0.3A, which is at least ten times more accurate than interferometric light measurement. The measurement parameters used are optical ellipsometric parameters. The existing measurement methods, such as atomic force microscopes, probe profilers and other contact measurement methods, are slow; scanning electron microscopes need to measure the constraints such as the ability of the sample to conduct electricity; optical methods such as optical sectioning Microscopes, the existing instruments generally can only measure the roughness with an average precision of 0.5 microns and above, and the precision is not high.

Contents of the invention

The purpose of the present invention is to solve the problems of low speed of the prior art measurement method, the need to measure the sample to be able to conduct electricity, and the roughness with an average precision of 0.5 microns and above, and the accuracy is not high. method of surface roughness.

Above-mentioned purpose of the invention is achieved through the following technical solutions:

A method for measuring the surface roughness of a solid material by using ellipsometric parameters is specifically carried out according to the following steps:

Step 1. Simulating and calculating the characteristic parameters of the rough surface of different solid materials, that is, obtaining the spatial electromagnetic field distribution of the near field of the rough surface of the solid material through the three-dimensional time domain finite difference method;

Wherein, the near field is an electromagnetic field within a range of less than 10 wavelengths;

The space electromagnetic field refers to the complex electric field and magnetic field

Rough surface characteristic parameters refer to root mean square roughness and autocorrelation length;

Step 2. Obtain the complex electric field of the far field by transforming the near and far fields Extract the complex electric field component in the mirror reflection direction from the far-field space electromagnetic field to calculate the radiation polarization characteristics in the mirror reflection direction. The radiation polarization characteristics are expressed by optical ellipsometric parameters, and a database is established;

Wherein, the far field generally refers to an electromagnetic field that is 105 wavelengths away from the sample ^;

Step 3. After the production of the solid material is completed, the optical ellipsometric parameters of the surface of the solid material are measured with an instrument for measuring the polarization characteristics of the surface radiation, and compared with the optical ellipsometric parameters in the database to obtain the ellipsometric parameters of the solid material surface RMS roughness and autocorrelation length.

A method for measuring the surface roughness of a solid material by using ellipsometric parameters is specifically carried out according to the following steps:

Step 1. Simulate and calculate the characteristic parameters of the rough surface of different solid materials, that is, obtain the spatial electromagnetic field distribution of the near field of the rough surface of the solid material through the three-dimensional finite difference time domain method (FDTD);

Wherein, the near field is an electromagnetic field within a range of less than 10 wavelengths;

The space electromagnetic field refers to the complex electric field and magnetic field

Rough surface characteristic parameters refer to root mean square roughness and autocorrelation length;

Step 2. Obtain the complex electric field of the far field by transforming the near and far fields Extract the complex electric field component in the mirror reflection direction from the far-field space electromagnetic field to calculate the radiation polarization characteristics in the mirror reflection direction. The radiation polarization characteristics are expressed by optical ellipsometric parameters, and a database is established;

Wherein, the far field generally refers to an electromagnetic field that is 105 wavelengths away from the sample ^;

Step 3. After the production of the solid material is completed, the optical ellipsometric parameters are measured sequentially through the scanning area of the instrument for measuring the surface radiation polarization characteristics, and compared with the optical ellipsometric parameters in the database to obtain the root mean square of the surface of the solid material Roughness and autocorrelation length, the error range of the corresponding optical ellipsometric parameters should be set in the computer according to the accuracy of the solid material;

The error range is: |Ellipsometric parameters calculated in the database-measured optical ellipsometric parameters|≤accuracy value set according to the accuracy of solid materials;

If the measured optical ellipsometric parameters are within the allowable range of error, the surface roughness of the solid material meets the requirements;

If the measured optical ellipsometric parameters are not within the allowable range of error, the surface roughness of the solid material does not meet the requirements;

Use the computer to record the number of the solid material with errors or directly use the mechanical arm to take out the solid material, and monitor the surface roughness of the solid material in real time.

Invention effect

Adopt a kind of method of utilizing ellipsometric parameters of the present invention to measure the surface roughness of solid material,

The present invention uses the FDTD numerical simulation method to obtain the spatial electromagnetic field distribution of the near-field of the rough surface; the far-field electromagnetic field is obtained by the transformation of the near-far field, and then the complex electric field in the mirror reflection direction is extracted from the far-field spatial electromagnetic field Calculate the radiation polarization characteristics of the complex electric field component in the mirror reflection direction. The radiation polarization characteristics are represented by optical ellipsometric parameters and a database is established; In contrast, the roughness is obtained, which is represented by root mean square roughness and autocorrelation length. Combining Figures 3 and 4, it can be seen that the ellipsometric parameters will change regularly with the root mean square roughness σ and the autocorrelation length τ, and the ellipsometric parameters will change regularly with the root mean square height and the autocorrelation length. This regularity ensures the feasibility of obtaining solid parameter roughness by measuring ellipsometric parameters.

Optical ellipsometry is an indirect measurement method, which has the advantages of fast speed and non-destructive. It is faster than atomic force microscope and probe type profiler, and its ellipsometric parameters have high sensitivity; compared with scanning electron microscope, the present invention does not need to measure samples to be able to Conduction; According to the calculations in this paper, using an incident wave with a wavelength of 4 μm, the accuracy of detecting rough silicon surfaces can reach 10 nm, while the accuracy of most light-section microscopes is about 0.5 μm, and the accuracy of ellipsometry has increased by an order of magnitude. If the material whose optical constant is more different from air, such as metal, etc., the detection accuracy of ellipsometry can be further improved. When other conditions are the same, if the incident wave with shorter wavelength is used, the detection accuracy of ellipsometry can be further improved.

Description of drawings

Fig. 1 is a flowchart of the present invention;

Fig. 2 is a schematic diagram of a rough surface with a root mean square roughness of σ=0.05 μm and an autocorrelation length τ=0.5 μm;

Fig. 3 is the incident wave wavelength is 4 microns, when τ = 0.05 μm and τ = 1 μm, the variation trend diagram of ellipsometric parameters with σ;

Fig. 4 shows the variation trend of ellipsometric parameters with τ when the wavelength of the incident wave is 4 microns, σ=0.1 μm and σ=0.2 μm.

Detailed ways

Embodiment 1: This embodiment is described in conjunction with FIG. 1. A method for measuring the surface roughness of a solid material using ellipsometric parameters is specifically carried out in accordance with the following steps:

Step 1. Simulate and calculate the characteristic parameters of the rough surface of different solid materials, that is, obtain the spatial electromagnetic field distribution of the near field of the rough surface of the solid material through the three-dimensional finite difference time domain method (FDTD);

Wherein, the near field is an electromagnetic field within a range of less than 10 wavelengths;

The space electromagnetic field refers to the complex electric field and magnetic field

Rough surface characteristic parameters refer to root mean square roughness and autocorrelation length;

Step 2. Obtain the complex electric field of the far field by transforming the near and far fields Extract the complex electric field component in the mirror reflection direction from the far-field space electromagnetic field to calculate the radiation polarization characteristics in the mirror reflection direction. The radiation polarization characteristics are expressed by optical ellipsometric parameters, and a database is established;

Wherein, the far field generally refers to an electromagnetic field that is 105 wavelengths away from the sample ^;

Step 3. After the production of the solid material is completed, the optical ellipsometric parameters of the surface of the solid material are measured with an instrument for measuring the polarization characteristics of the surface radiation, and compared with the optical ellipsometric parameters in the database to obtain the ellipsometric parameters of the solid material surface. RMS roughness and autocorrelation length.

Specific embodiment 2: The difference between this embodiment and specific embodiment 1 is that in the step 2, the complex electric field of the far field is obtained by transforming the near and far fields Extract the complex electric field component in the mirror reflection direction from the far-field space electromagnetic field to calculate the radiation polarization characteristics in the mirror reflection direction. The radiation polarization characteristics are expressed by optical ellipsometric parameters, and a database is established;

The specific process is:

Calculating the radiation polarization characteristics in the specular reflection direction is calculated using the following formula:

Radiation polarization characteristics are represented by optical ellipsometric parameters; optical ellipsometric parameters are divided into: optical ellipsometric parameter reflection coefficient ratio real part Ψ and optical ellipsometric parameter reflection coefficient ratio imaginary part △; complex electric field Divided into and and is set during calculation;

$\mathrm{<span\; class="notranslate">\; \&rho;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; \&Psi;</span>}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}<span\; class="notranslate">\; =</span>\frac{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}<span\; class="notranslate">\; /</span>\frac{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}}}$

In the formula: is the complex reflection coefficient in the p direction, is the complex reflection coefficient in the s direction, is the reflected electric field vector in the p direction, is the incident electric field vector in the p direction, is the reflected electric field vector in the s direction, is the incident electric field vector in the s direction, r refers to the reflection, and i refers to the incident.

Specific embodiment three: a method for measuring the surface roughness of a solid material using ellipsometric parameters is specifically carried out in accordance with the following steps:

Step 1. Simulate and calculate the characteristic parameters of the rough surface of different solid materials, that is, obtain the spatial electromagnetic field distribution of the near field of the rough surface of the solid material through the three-dimensional finite difference time domain method (FDTD);

Wherein, the near field is an electromagnetic field within a range of less than 10 wavelengths;

The space electromagnetic field refers to the complex electric field and magnetic field

Rough surface characteristic parameters refer to root mean square roughness and autocorrelation length;

Step 2. Obtain the complex electric field of the far field by transforming the near and far fields Extract the complex electric field component in the mirror reflection direction from the far-field space electromagnetic field to calculate the radiation polarization characteristics in the mirror reflection direction. The radiation polarization characteristics are expressed by optical ellipsometric parameters, and a database is established;

Wherein, the far field generally refers to an electromagnetic field that is 105 wavelengths away from the sample ^;

Step 3. After the production of the solid material is completed, the optical ellipsometric parameters are measured sequentially through the scanning area of the instrument for measuring the surface radiation polarization characteristics, and compared with the optical ellipsometric parameters in the database to obtain the root mean square of the surface of the solid material Roughness and autocorrelation length, the error range of the corresponding optical ellipsometric parameters should be set in the computer according to the accuracy of the solid material;

The error range is: |Optical ellipsometric parameters calculated in the database-measured optical ellipsometric parameters|≤Accuracy value that needs to be set according to the accuracy of solid materials

If the measured optical ellipsometric parameters are within the allowable range of error, the surface roughness of the solid material meets the requirements;

If the measured optical ellipsometric parameters are not within the allowable range of error, the surface roughness of the solid material does not meet the requirements;

Use the computer to record the number of the solid material with errors or directly use the mechanical arm to take out the solid material, and monitor the surface roughness of the solid material in real time.

Embodiment 4: The difference between this embodiment and Embodiment 3 is that in the step 2, the complex electric field of the far field is obtained by transforming the near and far fields Extract the complex electric field component in the mirror reflection direction from the far-field space electromagnetic field to calculate the radiation polarization characteristics in the mirror reflection direction. The radiation polarization characteristics are expressed by optical ellipsometric parameters, and a database is established; the specific process is as follows:

Calculating the radiation polarization characteristics in the specular reflection direction is calculated using the following formula:

Radiation polarization characteristics are represented by optical ellipsometric parameters; optical ellipsometric parameters are divided into: optical ellipsometric parameter reflection coefficient ratio real part Ψ and optical ellipsometric parameter reflection coefficient ratio imaginary part △; complex electric field Divided into and and is set during calculation;

$\mathrm{<span\; class="notranslate">\; \&rho;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; t</span>}\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; no</span>}\mathrm{<span\; class="notranslate">\; \&Psi;</span>}\mathrm{<span\; class="notranslate">\; exp</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; \&Delta;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}}_{\mathrm{<span\; class="notranslate">\; p</span>}}}{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; r</span>}}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}}<span\; class="notranslate">\; =</span>\frac{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; p</span>}}}<span\; class="notranslate">\; /</span>\frac{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}}_{\mathrm{<span\; class="notranslate">\; r</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}}}{{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; E.</span>}}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; the\; s</span>}}}$

In the formula: is the complex reflection coefficient in the p direction, is the complex reflection coefficient in the s direction, is the reflected electric field vector in the p direction, is the incident electric field vector in the p direction, is the reflected electric field vector in the s direction, is the incident electric field vector in the s direction, r refers to the reflection, and i refers to the incident.

Embodiment 1: In the first case, when τ is constant, the variation of ellipsometric parameters with σ is calculated. Figure 3 shows the variation of ellipsometric parameters with σ when τ=0.05μm and τ=1μm. The abscissa is σ, and the ordinate is the value of the ellipse parameter. In Fig. 3, the data of σ = 0.05 μm and τ = 0.05 μm are the ellipsometric calculation results of the surface shown in Fig. 2 . In Figure 2, the root mean square roughness σ affects the level of roughness fluctuations, and the autocorrelation length τ affects the density of fluctuations.

It can be seen from Figure 3 that among the ellipsometric parameters, when τ=0.05μm, the reflection coefficient ratio real part Ψ increases with the increase of σ, and the reflection coefficient ratio imaginary part Δ decreases with the increase of σ. When τ=1μm, the reflection coefficient ratio real part Ψ decreases with the increase of σ, and the reflection coefficient ratio imaginary part △ decreases with the increase of σ.

In the second case, when σ is constant, the variation of ellipsometric parameters with τ is calculated. Figure 4 shows the variation of ellipsometric parameters with τ when σ=0.1μm and σ=0.2μm. It can be seen from the figure that among the ellipsometric parameters, when σ=0.1μm, the reflection coefficient ratio real part Ψ increases and then decreases with the increase of τ, and the reflection coefficient ratio imaginary part △ increases with the increase of τ . When σ=0.2μm, the reflection coefficient ratio real part Ψ decreases with the increase of τ, and the reflection coefficient ratio imaginary part △ increases with the increase of τ.

From Figure 3 and Figure 4, it can be seen that the ellipsometric parameters will change regularly with the root mean square roughness σ and the autocorrelation length τ. This change makes it possible to invert roughness by measuring ellipsometric parameters. When the sample passes through the instrument for measuring ellipsometric parameters, the ellipsometric value of the sample is measured and compared with the above calculation results. The roughness value corresponding to the ellipsometric parameters is the roughness of the sample.

Claims (4)

1. utilize ellipsometric parameter to measure a method for solid material surface roughness, it is characterized in that: a kind of method utilizing ellipsometric parameter to measure solid material surface roughness is specifically carried out according to following steps:

Step one, analog computation is carried out to different solid material rough surface features parameter, namely tried to achieve the spatial electromagnetic field distribution in this solid material rough surface near field by Three-dimensional Time Domain method of finite difference;

Wherein, described near field is be less than the electromagnetic field in 10 wavelength coverages;

External electromagnetic field refers to telegram in reply field and magnetic field

Rough surface features parameter refers to r.m.s. roughness and auto-correlation length;

Step 2, tried to achieve the telegram in reply field in far field by Near-far fields transfer extract the radiation polarisation characteristic of the telegram in reply field component calculating specular reflection direction of specular reflection direction from far field space elect magnetic field, radiation polarisation characteristic uses optics ellipsometric parameter to represent, and building database;

Wherein, described far field is often referred to distance sample is 10 ⁵electromagnetic field outside individual wavelength;

Step 3, after solid material has been produced, the optics ellipsometric parameter of the instrument of measured surface radiation polarisation characteristic to this solid material surface is utilized to measure, and compare with the optics ellipsometric parameter in database, obtain r.m.s. roughness and the auto-correlation length of this solid material surface.

2. a kind of method utilizing ellipsometric parameter to measure solid material surface roughness according to claim 1, be is characterized in that: the telegram in reply field of being tried to achieve far field in described step 2 by Near-far fields transfer extract the radiation polarisation characteristic of the telegram in reply field component calculating specular reflection direction of specular reflection direction from far field space elect magnetic field, radiation polarisation characteristic uses optics ellipsometric parameter to represent, and building database; Detailed process is:

The radiation polarisation characteristic calculating specular reflection direction adopts following formula to calculate:

Radiation polarisation characteristic uses optics ellipsometric parameter to represent; Optics ellipsometric parameter is divided into: optics ellipsometric parameter reflectance ratio real part Ψ and optics ellipsometric parameter reflectance ratio imaginary part △; Telegram in reply field be divided into with with set when calculating;

$\mathrm{\&rho;}=tan\mathrm{\&Psi;}\exp \left(i\mathrm{\&Delta;}\right)=\frac{{\stackrel{\&RightArrow;}{r}}_p}{{\stackrel{\&RightArrow;}{r}}_s}=\frac{{\stackrel{\&RightArrow;}{E}}_{rp}}{{\stackrel{\&RightArrow;}{E}}_{ip}}/\frac{{\stackrel{\&RightArrow;}{E}}_{rs}}{{\stackrel{\&RightArrow;}{E}}_{is}}$

In formula: for p direction complex reflection coefficient, for s direction complex reflection coefficient, for p direction reflected field vector, for p direction incident electric field vector, for s direction reflected field vector, for s direction incident electric field vector, r digital reflex, i refers to incidence.

3. utilize ellipsometric parameter to measure a method for solid material surface roughness, it is characterized in that: a kind of method utilizing ellipsometric parameter to measure solid material surface roughness is specifically carried out according to following steps:

Step one, analog computation is carried out to different solid material rough surface features parameter, namely tried to achieve the spatial electromagnetic field distribution in this solid material rough surface near field by Three-dimensional Time Domain method of finite difference;

Wherein, described near field is be less than the electromagnetic field in 10 wavelength coverages;

External electromagnetic field refers to telegram in reply field and magnetic field

Rough surface features parameter refers to r.m.s. roughness and auto-correlation length;

Step 2, tried to achieve the telegram in reply field in far field by Near-far fields transfer extract the radiation polarisation characteristic of the telegram in reply field component calculating specular reflection direction of specular reflection direction from far field space elect magnetic field, radiation polarisation characteristic uses optics ellipsometric parameter to represent, and building database;

Wherein, described far field is often referred to distance sample is 10 ⁵electromagnetic field outside individual wavelength;

Step 3, after solid material has been produced, optics ellipsometric parameter is recorded successively by the scanning area of measured surface radiation polarisation characteristic instrument, and compare with the optics ellipsometric parameter in database, obtain r.m.s. roughness and the auto-correlation length of this solid material surface, in computer, need according to the precision of solid material the error range setting corresponding optics ellipsometric parameter;

Error range is: | the optics ellipsometric parameter of the optics ellipsometric parameter calculated in database-record |≤accuracy value that arranges is needed according to solid material precision;

If when the optics ellipsometric parameter recorded is in error allowed band, then this solid material surface roughness meets the requirements;

If when the optics ellipsometric parameter recorded is not in error allowed band, then this solid material surface roughness is undesirable;

Computer record is used to occur the solid material numbering of error or directly use mechanical arm to be taken out by this solid material, Real-Time Monitoring solid material surface roughness.

4. a kind of method utilizing ellipsometric parameter to measure solid material surface roughness according to claim 3, be is characterized in that: the telegram in reply field of being tried to achieve far field in described step 2 by Near-far fields transfer extract the radiation polarisation characteristic of the telegram in reply field component calculating specular reflection direction of specular reflection direction from far field space elect magnetic field, radiation polarisation characteristic uses optics ellipsometric parameter to represent, and building database; Detailed process is:

The radiation polarisation characteristic calculating specular reflection direction adopts following formula to calculate:

Radiation polarisation characteristic uses optics ellipsometric parameter to represent; Optics ellipsometric parameter is divided into: optics ellipsometric parameter reflectance ratio real part Ψ and optics ellipsometric parameter reflectance ratio imaginary part △; Telegram in reply field be divided into with with set when calculating;

$\mathrm{\&rho;}=tan\mathrm{\&Psi;}\exp \left(i\mathrm{\&Delta;}\right)=\frac{{\stackrel{\&RightArrow;}{r}}_p}{{\stackrel{\&RightArrow;}{r}}_s}=\frac{{\stackrel{\&RightArrow;}{E}}_{rp}}{{\stackrel{\&RightArrow;}{E}}_{ip}}/\frac{{\stackrel{\&RightArrow;}{E}}_{rs}}{{\stackrel{\&RightArrow;}{E}}_{is}}$

In formula: for p direction complex reflection coefficient, for s direction complex reflection coefficient, for p direction reflected field vector, for p direction incident electric field vector, for s direction reflected field vector, for s direction incident electric field vector, r digital reflex, i refers to incidence.