CN103575661A - Optical measurement system with vertical and oblique incidence measurement functions - Google Patents

Abstract

The application discloses an optical measurement system with vertical and oblique incidence measurement functions. The optical measurement system comprises a light source, an optical fiber bundle, a refection focusing system, a first light focusing unit, a second light focusing unit, a third light focusing unit, a fourth light focusing unit, a first polarizer, a second polarizer and an optical spectrometer. The optical measurement system provided by the application comprises an oblique incidence measurement device and a vertical incidence measurement device; the measurement accuracy of a sample is improved.

Description

The optical measuring system that comprises vertical incidence and oblique incidence

Technical field

The application relates to optical technical field, particularly a kind of optical measuring system that comprises vertical incidence and oblique incidence.

Background technology

Along with the fast development of semicon industry, critical dimension (Critical Dimension), space pattern and the material behavior of utilizing optical measuring technique accurately to measure the three-dimensional structure that on wafer, single or multiple lift film forms become very important.In order to make measurement result effective, measuring system used should be able to be measured thickness and/or film formation in pinpoint accuracy ground.In well-known non-destructive detection technique, be photometry and ellipsometric measurement method, they obtain reflectivity data by measuring the electromagnetic radiation of sample reflection.In spectroscopic ellipsometers, there is the incident light of definite polarization state by sample reflection (general with larger incident angle), by analyzing catoptrical polarization state, can obtain the characteristic of sample.Because incident light comprises multi-frequency, form, can obtain spectral curve.Particularly, the polarization state of incident light has time dependence (making incident light pass through the polarizer of a rotation), or analyzes catoptrical method and have time dependence (making reflected light pass through the analyzer of a rotation).

Generally, semiconductive thin film need to measure the thickness d of film, refractive index n and extinction coefficient k.And Ellipsometric can only be measured two ellipsometric parameters, that is: ψ and Δ, only cannot accurately provide the optical parametric (Acta Physica Sinica Vol.59, No.4) of sample thin film according to two ellipse folk prescription journeys, can only solve by the method for computer fitting.In order to increase measuring accuracy, obtain the additional information of target sample, researcher in this field has proposed a kind of spectroscopic ellipsometers (VASE, variable angle spectroscopic Ellipsometry) of variable-angle.This measurement mechanism can provide the ellipse folk prescription journey under a plurality of angles in theory, can increase measuring accuracy to a certain extent.Yet, in fact so often produce effects little, as Critical Reviews of Optical Science and Technology Volume CR72, described in 14-16 page, discovery when film thickness is carried out to data fitting, film thickness is at 330-

scope in can obtain basic the same matched curve.For the film thickness of a hypothesis, thus the optical constant of film thereupon compensatory change obtain a same good fitting result, this is because the thickness of film and the optical constant of membraneous material are relevant often in matching.Therefore want only by Ellipsometric, accurately to measure film thickness and optical constant can be more difficult.In order accurately to measure sample, for example, measure thickness and the optical parametric of sample thin film, conventionally integrated a plurality of optical measuring devices in a compound optical measuring system, utilize two optical measuring systems of vertical incidence and oblique incidence to measure sample (referring to US Patent No. 5608526, US6713753) simultaneously.In general, the measuring system more complicated of integrated a plurality of optical measuring devices, and need a plurality of wideband light sources and sniffer, cost is higher.If as described in US Patent No. 6713753, adopt beam splitter to carry out coupling optical path, although also can reach minimizing light source, the requirement reducing costs, but in actual applications, optical path adjusting is also difficult for realizing, and, by beam splitter, carry out light splitting and close the light time, the logical efficiency of its light is lower, light beam for vertical incidence, at least need to pass through spectroscope twice, its theoretical throughput is only up to 25%, the light beam of oblique incidence, also need by a spectroscope, can reduce the accuracy of systematic survey, therefore this optical measuring system that comprises vertical incidence and oblique incidence is not extensively promoted in actual applications.

On the other hand, those skilled in the art is known, and it is favourable that broadband detecting light beam is focused into relatively undersized hot spot on sample surfaces, because small size can be measured micro structured pattern, and broadband detecting light beam can improve measuring accuracy.In this case, a key link in optical measurement is that broadband detecting light beam is focused on sample surfaces, while adopting lens, conventionally can have aberration, thereby causes the light focal position of different wave length different, increases error.And for achromat, although reduce within the specific limits the aberration that the index of refraction in lens causes, color difference eliminating completely, in addition, this lens are due to complex structure, and cost is higher.Also there is the non-spherical reflector of employing this area as toroidal reflectors, the scheme of off-axis parabolic mirror, although they utilize reflect focalization, can within the scope of whole wide spectral wavelength, realize no color differnece, and can in wider wavelength coverage, all there is high reflectance, but non-spherical reflector processing technology is complicated, and price is also more expensive.And processing is simple, low-cost spherical reflector, although the paraxial directional light that is parallel to spherical reflector main shaft can be converged to its focus, its focus is positioned on main shaft, for focusing on and inconvenience.In actual applications, generally make incident light depart from a little main shaft, but because its focus adjustment range is very limited, and general sample general size is larger, is hundreds of millimeter, therefore directly utilize it that broad band light beam is focused on to sample surfaces, is difficult for realizing.

Summary of the invention

The application's technical matters to be solved is to provide a kind of simple in structure, measures accurately the vertical incidence that integrated level is high and the optical measuring system of oblique incidence.

For solving the problems of the technologies described above, the application provides a kind of optical measuring system, comprises light source, spectroscopic ellipsometers and spectrophotometer; Described light source, launches the first detecting light beam and the second detecting light beam; Described spectroscopic ellipsometers, measures the polarization variations after the first detecting light beam is reflected by sample; Described spectrophotometer, the light intensity after measuring the second detecting light beam that vertical or near vertical incides sample surfaces and being reflected by sample changes.

The optical measuring system that the application provides comprises spectroscopic ellipsometers and two measurement mechanisms of spectrophotometer, improved the precision of sample measurement, simultaneously, this optical measuring system is carried out light splitting and is closed light by fibre bundle, can make two cover optical measuring device common light source and spectrometers, greatly reduce the cost of system, simultaneously, optical splitter, uses the logical efficiency of system light of fiber bundle coupling higher relatively.In addition, the spectrophotometer in this optical measuring system adopts cheap, processes simple spherical reflector and focuses on, and can reach the effect of broadband no color differnece, does not increase equipment cost simultaneously.

Accompanying drawing explanation

The structural representation of the focusing system that Fig. 1 provides for the embodiment of the present application;

Fig. 2 is the principle schematic that the application's optics no color differnece focuses on;

The structural representation of the W-type fiber bundle that Fig. 3 provides for the application;

Fig. 4 a is the structural representation that in Fig. 3, I sub-optical fibre and II sub-optical fibre are arranged at fibre bundle port 2;

Fig. 4 b is the structural representation that in Fig. 3, II sub-optical fibre and III sub-optical fibre are arranged at fibre bundle port 3;

Fig. 4 c is the structural representation that in Fig. 3, III sub-optical fibre and IV sub-optical fibre are arranged at fibre bundle port 4;

The light beam that Fig. 5 provides for the application enters the light path schematic diagram of III sub-optical fibre;

Fig. 6 is the periodically structural drawing of shallow trench of monocrystalline silicon.

Fig. 7 is the spectrogram of the phase differential between TM and TE reflectivity amplitude ratio and TM and TE.

The structural representation of the optical measuring system that Fig. 8 provides for the application;

Another structural representation of the optical measuring system that Fig. 9 a provides for the application.

Fig. 9 b by Fig. 9 a the III sub-optical fibre of use fibre bundle, IV sub-optical fibre and V sub-optical fibre are in the preferred arrangement at port 4 places.

Embodiment

The no color differnece that the application realizes detecting light beam by cheap spherical reflector focuses on.As shown in Figure 1, this focusing system consists of two spherical reflectors and a plane mirror.Preferably, curved reflector SPR1 and curved reflector SPR2 have identical radius-of-curvature, pointolite S0 is positioned at the focus place of spherical reflector SPR1, the divergent beams that send through pointolite are through the reflection of spherical reflector SPR1, after deflection angle α, form parallel beam, this parallel beam is incident to plane mirror M post deflection angle beta, is then incident to curved reflector SPR2, and curved reflector SPR2 makes after this parallel beam deflection α vertical incidence and focuses to sample surfaces.Above-mentioned curved reflector SPR1, SPR2, the normal of plane mirror M is in same plane.As can be seen from Figure 1, by the structure of this particular design, can make the incident beam of small angle deflection on spherical reflector impinge perpendicularly on sample surfaces, and obtain under the precondition of suitable operating distance, each optical element does not block light path.In addition, the key light of above-mentioned incident beam also can be different from curved reflector SPR1 at the deflection angle of curved reflector SPR2.

As shown in Figure 2, the main beam of the detecting light beam of incident and the angle of surface level are t, and from geometric knowledge, the main beam of the convergent beam being reflected by curved reflector SPR2 if will make, perpendicular to directive sample surfaces, should meet: 2 alpha+betas-t=90 °.

For spherical reflector, the angle that parallel incident light direction departs from its main shaft is larger, its focusing effect is poorer, therefore, the deflection angle α of above-mentioned light beam is unsuitable excessive, and in the application, the incident angle of light beam on spherical reflector is for being preferably 5-15 degree, can make the system of above-mentioned two spherical reflectors and a plane mirror formation detecting light beam can be focused on to suitable spot size, obtain comparatively suitable operating distance simultaneously.In addition, from 2 alpha+betas-t=90 °, β=90 °-2 α+t, the deflection angle β of incident light on above-mentioned plane mirror M can determine according to the α angle of the direction of incident beam and setting.

If the position of above-mentioned thrihedral reflector immobilizes, only change the incident direction of incident beam, for example, make the angle of incident beam and surface level become t+ Δ t, the deflection angle of light beam on curved reflector SPR1 is α+2 Δ t, deflection angle on M is β-2 Δ t, deflection angle on curved reflector SPR2 is by α-2 Δ t, by above formula, can know 2 α '+β '-t=90 °+2 Δ t, the angle that the key light of the convergent beam being reflected by curved reflector SPR2 departs from vertical direction is 2 Δ t.Therefore, from above-mentioned conclusion is counter, push away, if what incide incident beam on sample SA departs from vertical direction 2 Δ t, can be by the incident direction that incides the main beam of the divergent beams on SPR1 be changed to Δ t, can adjust the direction of the convergent beam being reflected by SPR2, make it again impinge perpendicularly on sample surfaces.The application's focusing system can, by fine setting incident direction of light, change the exit direction of emergent light.

Spherical reflector makes to utilize reflection to focus on, irrelevant with Refractive Index of Material, can reach the effect of broadband no color differnece, in addition, spherical reflector is easy to processing, so therefore low price realizes the focusing of broad band light beam by the system of such spherical reflector, not only can color difference eliminating, can reduce costs simultaneously.

The application can realize the light beam coupling in the optical measuring system of vertical incidence and oblique incidence by fibre bundle, reaches the structure that two measurement mechanisms share a light source and spectrometer, reduces the effect of system cost when improving measuring accuracy.Introduce in the application " W " shape fibre bundle for light beam coupling below.

As shown in Figure 3, this fibre bundle is by fibre bundle sub-optical fibre I, II, III, IV, and fibre bundle port one, 2,3,4,5 form the profile of likeness in form W type, and every two fibre bundle sub-optical fibres share a port, specific as follows: fibre bundle sub-optical fibre I and fibre bundle sub-optical fibre II common optical fiber beam port 2; The other end of fibre bundle sub-optical fibre II and fibre bundle sub-optical fibre III common optical fiber beam port 3, the other end of fibre bundle sub-optical fibre III and fibre bundle sub-optical fibre IV common optical fiber beam port 4, in addition, the other end of fibre bundle sub-optical fibre I is connected with fibre bundle port one, and the other end of fibre bundle sub-optical fibre IV is connected with fibre bundle port 5.Wherein, the length of every section of fibre bundle sub-optical fibre is about 1m.

The port of W-type fiber bundle is comprised of sleeve pipe and optical fiber, and optical fiber is arranged in sleeve pipe.

Preferably, fibre bundle sub-optical fibre I, II, IV only comprises an optical fiber, and fibre bundle sub-optical fibre III comprises six roots of sensation optical fiber.In order to realize higher coupling efficiency, fiber port can arrange as follows:

At port 2 places, fibre bundle sub-optical fibre I, II xsect forms solid matter structure arranged side by side, as shown in Fig. 4 a;

At port 3 places, fibre bundle sub-optical fibre II is positioned at centre, and the six roots of sensation optical fiber that forms fibre bundle sub-optical fibre III is arranged around it symmetrically, forms a regular hexagon, as shown in Figure 4 b;

At port 4 places, the six roots of sensation optical fiber that forms fibre bundle sub-optical fibre III is yi word pattern with an optical fiber that forms fibre bundle sub-optical fibre IV and puts side by side, and fibre bundle sub-optical fibre IV is in middle, the six roots of sensation optical fiber that forms fibre bundle sub-optical fibre III is divided into two parts, its symmetria bilateralis distribute, as shown in Fig. 4 c, shape like this can coordinate the slit entrance of spectrometer, and two bundle reflected light can be entered in spectrometer with greater efficiency.

As seen from the above description, if incident beam enters fibre bundle by fibre bundle port 2, this light beam is by fibre bundle sub-optical fibre I, after II, be divided into two-beam, this two-beam is respectively from fibre bundle port one, 3 outgoing, can be respectively as the detecting light beam of different optical measuring systems, for example, detecting light beam from the light beam of fibre bundle port one outgoing as the spectroscopic ellipsometers of oblique incidence, from the light beam of fibre bundle port 3 outgoing as vertical incidence the spectrophotometric detecting light beam to sample surfaces measurement of reflectivity, port 3 is returned on the folded light beam Jiang Yanyuan road of sample surfaces, if make, by impinging perpendicularly on the detecting light beam that sample surfaces reflected by sample, by port 3, enter fibre bundle sub-optical fibre III, make to be mapped to the detecting light beam that sample surfaces reflected by sample and to enter fibre bundle sub-optical fibre IV by port 5 by spectroscopic ellipsometers is oblique simultaneously, respectively by different optical measuring devices, the two bundle detecting light beams that comprise specimen material optical characteristics information will be from same fibre bundle port 4 outgoing, only spectrometer need be aimed to optical fiber beam port 4, can realize same spectrometer and survey different detecting light beams.In order to make to impinge perpendicularly on sample surfaces, when the detecting light beam being reflected by sample surfaces returns to optical fiber beam port 3, can enter fibre bundle sub-optical fibre III with greater efficiency, generally by regulating condenser lens L or the fibre bundle port 3 before micro-regulation sample, the light beam that makes to focus on sample surfaces is slightly out of focus, the spectrophotometer that Ze Yanyuan returns on road is surveyed the optical fiber in outside in light entry port 3, be in fibre bundle sub-optical fibre III, as shown in Figure 5, concrete methods of realizing can be referring to Chinese patent application 201110005913.9 for its light path.And in the present invention, because being used (even if incident light direction departs from main shaft), the off-axis of spherical reflector can cause the hot spot focusing on sample to have spherical aberration, and the light beam of sample reflection has spherical aberration while getting back to the fiber port 3 of W-type fiber equally, can just utilize this spherical aberration, make the overwhelming majority of the folded light beam of sample surfaces can be just by W-type fiber beam port 3 enter in sub-optical fibre III rather than fibre bundle sub-optical fibre II is returned on Yan Yuan road, can make the logical efficiency of theoretical light of vertical incidence part reach more than 50%, and oblique incidence part is due to without optical splitter, it does not substantially have intensity loss in light beam coupling process, with in prior art, use the technical scheme of optical splitter and compare, greatly improved the logical efficiency of light.

In addition, fibre bundle sub-optical fibre as above, can be also the fibre bundle consisting of multiple beams of optical fiber close-packed arrays.In addition, if be coupled a root optical fiber at port 4 places, this fibre bundle can be for the reception of the detecting light beam of other optical measuring devices in system again, for example, and the reception of the transmitted light beam by sample in spectrophotometer.

Utilize the fibre bundle multi-beam that is coupled, be compared to beam splitter, because the separating end of fibre bundle is independent separately, light path is more easily calibrated.For example, if desired two-beam is closed to bundle, only the fibre bundle port 3 and 5 in Fig. 3 need be aimed at respectively to this two-beam and just can realize.

Ellipsometric measurement method:

Spectroscopic ellipsometers in the application can be the ellipsometer test of a polarizer-sample-analyzer (PSA) structure.Can be by rotation polarizer P, fixing analyzer A, or rotation analyzer A, fixing polarizer P, or polarizer P and analyzer A be by certain frequency ratio rotation, the Fourier coefficient calculating, and then by returning computation and measurement sample with Numerical Simulation Results comparison and numerical value.Concrete measuring principle can reference book HANDBOOK OF ELLIPSOMETRY, Harland G.Tompkins, 2005; Spectroscopic Ellipsometry Principles and Applications, Hiroyuki Fujiwara, 2007 and document Liang-Yao Chen, Xing-Wei Feng, Yi Su, Hong-Zhou Ma, and You-Hua Qian, " Design of a scanning ellipsometer by synchronous rotation of the polarizer and analyzer; " Appl.Opt.33, the principle formula that 1299-1305 (1994) is illustrated, below only with rotation analyzer (RAE) situation, do concise and to the point description:

Sample Jones matrix can be expressed as $J_s=\left[\begin{array}{cc}{r}_{\mathrm{pp}}& r_{\mathrm{ps}}\\ r_{\mathrm{sp}}& r_{\mathrm{ss}}\end{array}\right]=r_{\mathrm{ss}}\left[\begin{array}{cc}{\mathrm{\&rho;}}_{\mathrm{pp}}& {\mathrm{\&rho;}}_{\mathrm{ps}}\\ {\mathrm{\&rho;}}_{\mathrm{<figure-callout\; id="1"\; label="sp"\; filenames="DEST\_PATH\_HDA00002411083300023.png,HDA00001990131200013.png"\; state="\{\{state\}\}">sp</figure-callout>}}& 1\end{array}\right],$

By L _out=AR (A) J _sr (P) PL _incan obtain,

$\left[\begin{array}{c}{E}_A\\ 0\end{array}\right]=E_{\mathrm{in}}\left[\begin{array}{cc}1& 0\\ 0& 0\end{array}\right]\left[\begin{array}{cc}\cos A& \sin A\\ -\sin A& \cos A\end{array}\right]\left[\begin{array}{cc}{r}_{\mathrm{pp}}& r_{\mathrm{ps}}\\ r_{\mathrm{sp}}& r_{\mathrm{ss}}\end{array}\right]\left[\begin{array}{cc}\cos P& -\sin P\\ \sin \mathrm{<figure-callout\; id="1"\; label="P\; cos\; P"\; filenames="DEST\_PATH\_HDA00002411083300023.png,HDA00001990131200013.png"\; state="\{\{state\}\}">P</figure-callout>}& \cos P\end{array}\right]\left[\begin{array}{cc}1& 0\\ 0& 0\end{array}\right]\left[\begin{array}{c}1\\ 0\end{array}\right].$

Ignore proportionality constant wherein, can draw:

E _A＝(ρ _pp+ρ _pstanP)cosA+(ρ _sp+tanP)sinA，

The light intensity of surveying:

I＝|E _A| ²＝I _O(1+αcos2A+βsin2A)

Wherein, α, β are the Fourier coefficient of light intensity I, and empirical value can be by calculating.Its corresponding expression formula is

$\mathrm{\&alpha;}=\frac{{|{\mathrm{\&rho;}}_{\mathrm{pp}}+{\mathrm{\&rho;}}_{\mathrm{ps}}\tan P|}^2-{|{\mathrm{\&rho;}}_{\mathrm{sp}}+\tan P|}^2}{{|{\mathrm{\&rho;}}_{\mathrm{pp}}+{\mathrm{\&rho;}}_{\mathrm{ps}}\tan P|}^2+{|{\mathrm{\&rho;}}_{\mathrm{sp}}+\tan P|}^2};$

$\mathrm{\&beta;}=\frac{2\mathrm{Re}\left[({\mathrm{\&rho;}}_{\mathrm{pp}}+{\mathrm{\&rho;}}_{\mathrm{ps}}\tan P){({\mathrm{\&rho;}}_{\mathrm{sp}}+\tan P)}^{*}\right]}{{|{\mathrm{\&rho;}}_{\mathrm{pp}}+{\mathrm{\&rho;}}_{\mathrm{ps}}\tan P|}^2+{|{\mathrm{\&rho;}}_{\mathrm{sp}}+\tan P|}^2}.$

Work as r _ps=r _sp=0, i.e. ρ _ps=ρ _sp=0 o'clock, the computing formula of isotropy film sample that can be conventional:

$\mathrm{\&alpha;}=\frac{{\left|{\mathrm{\&rho;}}_{\mathrm{pp}}\right|}^2-{\left|\tan P\right|}^2}{{\left|{\mathrm{\&rho;}}_{\mathrm{pp}}\right|}^2+{\left|\tan P\right|}^2}=\frac{{\mathrm{<figure-callout\; id="2"\; label="tan"\; filenames="HDA00001990131200042.png"\; state="\{\{state\}\}">tan</figure-callout>}}^2\mathrm{\&psi;}-{\tan }^2\mathrm{<figure-callout\; id="2"\; label="P\; tan"\; filenames="HDA00001990131200042.png"\; state="\{\{state\}\}">P</figure-callout>}}{{\tan }^{}};$

$\mathrm{\&beta;}=\frac{2\mathrm{Re}\left({\mathrm{\&rho;}}_{\mathrm{pp}}\tan P\right)}{{\left|{\mathrm{\&rho;}}_{\mathrm{pp}}\right|}^2+{\left|\tan P\right|}^2}=\frac{2\tan \mathrm{\&psi;}\cos \mathrm{\&Delta;}\tan P}{{\tan }^2\mathrm{\&psi;}+{\tan }^{2}P}.$

Wherein, tan ψ is r _pp, r _ssthe amplitude of ratio, Δ is r _pp, r _ssthe phase differential of ratio.

By ellipsometric measurement method, can calculate the spectral line of α, two Fourier coefficients of β, this spectral line is directly related with sample ellipsometric parameter Ψ and Δ.

The concrete operations of ellipsometric measurement method comprise following three key steps: 1), due to the existence of rotary system, system need to calibrate to get rid of the measurement light intensity deviation that polarizer rotation causes.Bearing calibration is the even sample of use standard, and for example silicon chip, measures the light intensity of even sample under different polarization device angle; In theory, light intensity should be identical; The variation relation of this light intensity and angle can be used as reference value, and by ratio, removing system affects in the light intensity of different polarization device angle.Specifically can be, every rotation 1 degree of polarizer, records the reflective light intensity spectrum of each angle lower silicon slice, and completes the whole scanning of 360 degree, and these data are as preserving with reference to value.2) while measuring, the reflective light intensity of all angles is compared with reference value, obtained light intensity at the relative actual value of all angles.3) by calculated with mathematical model and curvilinear regression matching, obtain result.

The one-dimensional grating as shown in Figure 6 of take is example, and when measurement parameter φ=0, θ=60 o'clock, at this angle r _ps=r _sp=0, its amplitude ratio and phase differential are as shown in Figure 7.

Spectroscopic ellipsometers in the application can also, for comprising a phase compensator, form the ellipsometer test of the polarizer-compensator-sample-analyzer (PCSA) structure or the polarizer-sample-compensator-analyzer (PSCA) structure.Can pass through rotatable phase compensator C, fixedly polarizer P and analyzer A or rotation analyzer A, fixedly polarizer P and phase compensator C, the spectrum measuring, and by calculating Fourier coefficient, and then obtain ellipsometric parameter ψ and the Δ of sample, and then by returning computation and measurement sample with Numerical Simulation Results comparison and numerical value.With the situation of whirl compensator (RCE) under PSCA structure, do concise and to the point description below:

L _out＝AR(A)R(-C)CR(C)J _sR(-P)PL _in，

That is: supposing the system P=45 ° and A=0 °, that is:

$\left[\begin{array}{c}{E}_A\\ 0\end{array}\right]=E_{\mathrm{in}}\left[\begin{array}{cc}1& 0\\ 0& 0\end{array}\right.s\left[\begin{array}{cc}\cos C& -\sin C\\ \sin \mathrm{<figure-callout\; id="1"\; label="C\; cos\; C"\; filenames="DEST\_PATH\_HDA00002411083300023.png,HDA00001990131200013.png"\; state="\{\{state\}\}">C</figure-callout>}& \cos C\end{array}\right]\left[\begin{array}{cc}1& 0\\ 0& \exp (-\mathrm{i\&delta;})\end{array}\right]\left[\begin{array}{cc}\cos C& \sin C\\ -\sin C& \cos C\end{array}\right]\left[\begin{array}{cc}\sin \mathrm{\&psi;exp}\left(\mathrm{i\&Delta;}\right)& 0\\ 0& \cos \mathrm{\&psi;}\end{array}\right]$

$\&times;\left[\begin{array}{cc}\cos 45& -\sin 45\\ \sin 45& \cos 45\end{array}\right]\left[\begin{array}{cc}1& 0\\ 0& 0\end{array}\right]\left[\begin{array}{c}1\\ 0\end{array}\right]$

Can draw when δ=90 are spent:

$E_A=\frac{\sqrt{2}}{2}{E}_{\mathrm{in}}[({\cos }^{2}C-i{\sin }^{2}C)\sin \mathrm{\&psi;exp}\left(\mathrm{i\&Delta;}\right)+(1+i)\cos C\sin C\cos \mathrm{\&psi;}]$

The light intensity of surveying:

I=|E _a| ²=I _oin the case, the Stokes Vector corresponding expression formula of detection light after sample reflection is in (2-cos2 ψ+2sin2 ψ sin Δ sin2C-cos2 ψ cos4C+sin2 ψ cos Δ sin4C)/2:

S ₀＝1

S ₁＝-cos2ψ

S ₂＝sin2ψcosΔ

S ₃＝-sin2ψsinΔ

The detection light intensity of expressing with Stokes Vector:

$I=I_0(1+\frac{{\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="DEST\_PATH\_HDA00002411083300023.png,HDA00001990131200013.png"\; state="\{\{state\}\}">S</figure-callout>}}_1}{2}-{\mathrm{<figure-callout\; id="3"\; label="S"\; filenames="DEST\_PATH\_HDA00002411083300023.png,HDA00001990131200013.png"\; state="\{\{state\}\}">S</figure-callout>}}_3\sin 2C+\frac{{\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="DEST\_PATH\_HDA00002411083300023.png,HDA00001990131200013.png"\; state="\{\{state\}\}">S</figure-callout>}}_1\cos 4\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA00001990131200042.png"\; state="\{\{state\}\}">C</figure-callout>}}{2}+\frac{{\mathrm{<figure-callout\; id="2"\; label="S"\; filenames="HDA00001990131200042.png"\; state="\{\{state\}\}">S</figure-callout>}}_2\sin 4C}{2})$

By ellipsometric measurement method, can calculate S by empirical value ₁, S ₂, S ₃the spectral line of three Fourier coefficients, this spectral line is in directly related with sample ellipsometric parameter Ψ and Δ, and compares with the above-mentioned ellipsometer that does not comprise compensator, can calculate the concrete angle of Δ, increased measuring accuracy.

Because reflectivity R and the transmissivity T of sample is decided by film thickness equally, optical constant, the features such as three-dimensional appearance, thereby the spectroscopic ellipsometers by oblique incidence is when measuring sample ellipsometric parameter, utilize the spectrophotometer of vertical incidence to measure reflectivity R and/or the transmissivity T of sample, the more relevant information of Multi-example can be provided, be conducive to calculating and the regression fit of mathematical model, get a more accurate measurement result.Or the optical measuring system of the spectroscopic ellipsometers by comprising oblique incidence and vertical incidence, also can obtain more Fourier coefficient spectral line, gets a more accurate measurement result.

Measure the ellipsometric parameter of sample, and after reflectivity and/or transmissivity, by calculated with mathematical model spectral line and curvilinear regression matching, optical constant that can calculation sample material, film thickness and/or for critical dimension (CD) or the three-dimensional appearance of the sample of analytical cycle structure.

Embodiment mono-

The optical measuring system of the first embodiment of the application shown in Fig. 8.Optical parameter measurement system comprises light source SO, curved reflector CM, fibre bundle FB, spherical reflector SPR1, SPR2, plane mirror M, achromat L1, L2, L3, L4, polarizer P, analyzer A, and spectrometer SP, formed the spectroscopic ellipsometers SPE of oblique incidence and these two different optical measuring devices of the spectrophotometer SPM of vertical incidence with upper-part.

The light beam that broadband pointolite SO sends through one for entering the port 2 of W-type fiber bundle after the curved reflector CM focusing on, by fibre bundle sub-optical fibre I and fibre bundle sub-optical fibre II, be divided into two-beam, respectively as the detecting light beam of optical measuring device spectroscopic ellipsometers SPM and spectrophotometer SPE.The light path of this two bundles detecting light beam is described respectively below:

(1) enter fibre bundle sub-optical fibre II, from the light beam of fibre bundle port 3 outgoing as the detecting light beam spectrophotometer, this detecting light beam is incident to spherical reflector SPR1, after spherical reflector SPR1 reflection, form parallel beam, and deflect, this parallel beam incides on plane mirror M, there is again a deflection, then be incident to spherical reflector SPR2, spherical reflector makes this parallel beam deflection certain angle, the only key light being reflected by spherical reflector is perpendicular to the convergent beam of sample, this convergent beam vertical incidence also focuses on the O point on sample surfaces, the reflected light of sample surfaces, pass through successively spherical reflector SPR2, level crossing M, after spherical reflector SPR1, form convergent beam, and enter fibre bundle sub-optical fibre III by fibre bundle port 3, by the transmission of fibre bundle sub-optical fibre III, by 4 outgoing of fibre bundle port, then enter in spectrometer luminosity SP.

(2) enter fibre bundle sub-optical fibre I, detecting light beam from the light beam of fibre bundle port one outgoing as spectroscopic ellipsometers, this light beam is incident to achromat L1, fiber port 1 is positioned at the focus place of this achromat L1, these divergent beams become parallel beam after lens L1, it is upper that this parallel beam incides achromat L2 after polarizer P, after achromat L2 assembles this parallel beam for example, with (, the 70 degree) incident of larger incident angle and focus to sample surfaces.The reflected light of sample surfaces, passes through achromat L3 successively, and analyzer A enters in fibre bundle sub-optical fibre IV by fibre bundle port 5 after achromat L4, then, by 4 outgoing of fibre bundle port, enters in spectrometer SP.

Spectrometer SP is connected with processor or computing machine, analyzes the signal that spectrometer SP detects, thereby the curve fitting process returning by numerical value calculates thickness and the optical parametric of sample thin film, the features such as three-dimensional appearance.

In the present embodiment, in vertical incidence optical system, the off-axis of spherical reflector is used (incident light direction departs from main shaft) although can not cause aberration, but can cause the hot spot focusing on sample to have spherical aberration, in this example, just utilize this spherical aberration, make the overwhelming majority in the folded light beam of sample surfaces can be just by W-type fiber beam port 3 enter in sub-optical fibre III rather than fibre bundle sub-optical fibre II is returned on Yan Yuan road, use spectrometer to compare with prior art, improved the logical efficiency of light.

The embodiment of the present application also comprises that one for carrying adjustable example platform of sample, and the example of this example platform comprises the sample stage of X-Y-Z-Theta or R-Theta-Z coordinate.At semicon industry, the size of sample is the wafer of diameter 8 inches (200 millimeters) or 12 inches (300 millimeters) normally.In flat-panel monitor industry, sample has 1 meter of above size conventionally.For wafer, due to the reasons such as thin layer stress on wafer, surface may be uneven.For large scale sample, the distortion of sample surfaces possibility, or example platform may be uneven.Therefore,, when sample is detected, in order to realize the measurement of pinpoint accuracy and the Quick Measurement of assurance semiconductor production line output, can again focus on each measurement point.

In actual measurement process, in order to make detecting light beam and the detecting light beam in spectrophotometer SPM in spectroscopic ellipsometers SPE accurately focus on same point on sample, can realize by example platform movably, by spectroscopic ellipsometers, measure after experimental data, mobile example platform, makes the detecting light beam in spectrophotometer SPM also aim at the same point on sample.

Preferably, the present embodiment can also comprise phase compensator, as shown in Figure 8, this compensator C can polarizer P and analyzer A in spectroscopic ellipsometers SPE light path between, spectroscopic ellipsometers of the application etc. is all the ellipsometer test of a polarizer-compensator-sample-analyzer (PCSA) or the polarizer-sample-compensator-analyzer (PSCA) structure.Under this structure, 1) by rotation analyzer A, fixedly polarizer P and compensator C form PSCA _ror PCSA _rmetering system, 2) by whirl compensator C, fixedly analyzer A and polarizer P form PSC _ra or PC _rsA metering system.By above ellipsometric measurement method, calculate the spectral line of Fourier coefficient, this spectral line is directly related in ellipsometric parameter Ψ and Δ with sample.

In addition,, in the present embodiment, the spectroscopic ellipsometers of oblique incidence can be also the projection polariscope (polarimeter) of oblique incidence.

In addition, the present embodiment can also comprise for controlling the polarizer rotating control assembly of polarizer polarization direction and/or for controlling the wave plate rotating control assembly of wave plate optical axis direction.

In addition, the achromat L1 in the present embodiment, L2, L3, L4 can be also curved reflector, as off-axis parabolic mirror, the spectroscopic ellipsometers in the present embodiment can be realized the effect of broadband no color differnece.

In the present embodiment, also can comprise imaging system, this imaging system comprises lighting unit and image-generating unit.By one movably plane mirror cut in half light path, the measurement of sample surfaces uses the folded light beam of folded light beam and lighting unit after movably plane mirror reflects, be imaged elements capture, then pass through movably example platform, will survey hot spot and aim at the tested pattern of sample.

In the application, spectrophotometer SPM and spectroscopic ellipsometers SPE share a spectrometer, and the measurement of sample ellipsometric parameter and the measurement of reflectivity can not be carried out simultaneously, and diaphragm can be set in light path, as diaphragm D1 and the D2 in figure.During measurement, first load sample, aims at after measurement point by example platform, opens diaphragm D1, closes diaphragm D2, by the reflectivity of photometric measurement sample; Then, close diaphragm D1, open diaphragm D2, by Ellipsometric, measure sample, after having measured, by the data input processor measuring, digital simulation can obtain the optical constant of specimen material, film thickness, three-dimensional appearance etc. feature.

Optical parameter measurement system described in the embodiment of the present application comprises two different optical measuring devices, i.e. the spectroscopic ellipsometers SPE of oblique incidence and the spectrophotometer SPM of vertical incidence, thus can accurately measure thickness and the optical constant thereof of sample thin film.This optical parameter measurement system comprises by the coupling of a W type fibre bundle, can make optical measuring device spectroscopic ellipsometers SPE and spectrophotometer SPM common light source SO and spectrometer SP, reached the effect that reduces costs and simplify light path, in addition, this fibre bundle can also be collected in spectrophotometer SPM measurement mechanism with the logical efficiency of higher light the detecting light beam that impinges perpendicularly on sample surfaces, returned by sample reflection Yan Yuan road.In addition, in the present embodiment, in measurement mechanism spectrophotometer SPM, adopt the system of two spherical reflectors and a plane mirror formation to replace achromat or non-spherical reflector (as off-axis parabolic mirror) to carry out focused beam, not only eliminate aberration, reduced the expensive expense of using aspheric mirror to bring simultaneously.

Embodiment bis-

The optical measuring system that comprises spectroscopic ellipsometers SPE and spectrophotometer SPM of the application shown in Fig. 9 a.The optical parameter measurement system of the present embodiment is on the basis of embodiment 1, port 4 at W-type fiber bundle adds a fibre bundle sub-optical fibre V, by the other end of fibre bundle sub-optical fibre V, be that port 6 is placed on detecting light beam in the sample aligned beneath spectrophotometer focal beam spot on sample, for receiving the light beam through sample, this transmitted light can be transferred to port 4 by fibre bundle sub-optical fibre V, thereby enter in spectrometer SP, surveys.The arrangement of fibre bundle port 4 each optical fiber of place as shown in the figure, can be so that the central authorities of the port of fibre bundle sub-optical fibre IV and fibre bundle sub-optical fibre V in port 4, the fiber port of fibre bundle sub-optical fibre III is divided into the both sides that two parts are arranged in them side by side, and the arrangement of fibre bundle port 4 each optical fiber of place is as shown in Fig. 9 b.

Compare with the first embodiment, the present embodiment only need increase an optical fiber, can realize when measuring the ellipsometric parameter of sample and reflectivity spectral line by spectroscopic ellipsometers SPE and spectrophotometer SPM, also utilize spectrophotometer SPM to measure the transmissivity spectral line of sample, thereby can measure more accurately thickness and the optical constant thereof of sample thin film.Be that the present embodiment can be realized three kinds of measurement approach a shared spectrometer and light source simultaneously, both simplified the structure of device, reached again the effect reducing costs.

In addition, the present embodiment also comprises a lens L5 who is arranged on sample below, and for the transmitted light beam of spectrophotometer is focused in optical fiber V, these lens can be achromat, also with curved reflector, replace.

In addition, in the present embodiment, because spectroscopic ellipsometers and spectrophotometer share spectrometer SP and light source SO, also need in each light path, diaphragm be set, the switch by controlling diaphragm is to realize different measuring methods.The setting of diaphragm is as shown in D1, D2, D3 in figure.During measurement, loaded after sample, first opened diaphragm D2, closed diaphragm D1 and D3, by Ellipsometric, measured sample, obtained spectral intensity I ₁(t); Then open diaphragm D1, close diaphragm D2 and D3, the reflectance spectrum I that spectra re-recorded meter SP measures ₂; Finally, open diaphragm D1 and D3, close diaphragm D2, the spectrum I that spectra re-recorded meter SP measures ₃, the transmitted spectrum of sample is I=I ₃-I ₂.

In the application, spectrometer SP is connected with processor, can by computing machine, calculate the optical constant that matching can obtain specimen material by the data input processor measuring, the critical dimension of film thickness, three-dimensional structure (Critical Dimension), space pattern etc.

In the application, described light source can be for comprising the light source of multi-wavelength.Specifically, the spectrum of described light source can be at vacuum ultraviolet near infrared range, that is, and and in 150nm to 2200nm wavelength coverage.Light source can be xenon lamp, deuterium lamp, tungsten lamp, Halogen lamp LED, mercury lamp, the composite broadband light source that comprises deuterium lamp and tungsten lamp, the composite broadband light source that comprises tungsten lamp and Halogen lamp LED, the composite broadband light source that comprises mercury lamp and xenon lamp or the composite broadband light source that comprises deuterium tungsten halogen, and the light beam of this type of light source is natural light conventionally.The example of this type of light source comprises the product HPX-2000 of Oceanoptics company, HL-2000 and DH2000, and the product L11034 of Hamamatsu company, L8706, L9841 and L10290.Light source also can be and utilizes depolariser that partial poolarized light or polarized light are transformed to the rear natural light forming.For example, depolariser can be Lyot depolariser (U.S. Patent No. 6667805).Described spectrometer specifically, can be to comprise grating, catoptron, with the spectrometer of charge-coupled device (CCD) or photodiode array (PDA), for example, Ocean Optics QE65000 spectrometer or B & W Teck Cypher H spectrometer.Described fibre bundle sub-optical fibre can change optical fiber (solarization resistant) for uvioresistant, and its wavelength coverage is 200-1100nm.

In addition, the application's optical measuring system can also comprise computing unit, and this computing unit is for the optical constant of calculation sample material, film thickness etc.

In addition, the optical measuring system in the application can also comprise imaging system, and figuratum sample surfaces is generated to distribution patterns, measures assigned address, and observes the focus state of described detecting light beam on sample.

In addition, in the application, while utilizing the reflectivity of spectrophotometer measurement sample or transmissivity, transmitted spectrum that also need to be when measuring the reflectance spectrum of reference sample of the known absolute reflectance of pre-test and n.s..

Please note, according to the instruction of this instructions, those skilled in the art will should be appreciated that, the application comprise spectroscopic ellipsometers and spectrophotometric optical measuring system is not limited to disclosed concrete form in above-described embodiment, as long as under the application's general plotting, can carry out various distortion to the application's measuring system.The application's measuring system can be applied to the thickness, optical constant of probing semiconductor film, optical mask, metallic film, thin dielectric film, glass (or plated film), laser mirror, organic film etc. and critical dimension and the three-dimensional appearance of the periodic structure that these materials form, and especially can be applied to measure whole yardsticks of the formed three-dimensional structure planar with a peacekeeping two-dimensional and periodic of multilayer film and the optical constant of layers of material.

Although the application is described with reference to exemplary embodiment, should be appreciated that the application is not limited to disclosed exemplary embodiment.The scope of appended claim should be given the explanation of maximum magnitude, thereby comprises all such modifications and equivalent structure and function.

It should be noted last that, above embodiment is only in order to the application's technical scheme to be described and unrestricted, although the application is had been described in detail with reference to example, those of ordinary skill in the art is to be understood that, can modify or be equal to replacement the application's technical scheme, and not departing from the spirit and scope of present techniques scheme, it all should be encompassed in the middle of the application's claim scope.

Claims (11)

1. an optical measuring system that comprises vertical incidence and oblique incidence, is characterized in that, comprising:

Light source, fibre bundle, reflection focusing system, the first light focusing unit, the second light focusing unit, the 3rd light focusing unit, the 4th light focusing unit, the first polarizer, the second polarizer and spectrometer;

Described reflection focusing system comprises the first reflecting element, the second reflecting element and plane reflection unit;

Wherein,

The light that described light source sends is divided into the first detecting light beam and the second detecting light beam through described fibre bundle, and wherein, the second detecting light beam is successively by impinging perpendicularly on sample surfaces after described the first reflecting element, plane reflection element, the second reflecting element; The first detecting light beam is successively by described the first light focusing unit, the first polarizer, the oblique sample surfaces that is mapped to of the second light focusing unit;

Through sample surfaces reflection and successively by the vertical incidence light of the second reflecting element, plane reflection element, the first reflecting element, with from sample surfaces reflection and successively by the oblique incident ray of the 3rd light focusing unit, the second polarizer, the 4th light focusing unit, after described fibre bundle transmission, by same port, export described spectrometer to.

2. optical measuring system according to claim 1, is characterized in that, described the first light focusing unit, the second light focusing unit, the 3rd light focusing unit, the 4th light focusing unit are achromat or curved reflector; Described the first reflecting element, the second reflecting element are spherical reflector; Described plane reflection element is plane mirror; Described the first polarizer is the polarizer, and described the second polarizer is analyzer.

3. optical measuring system according to claim 1, is characterized in that, described fibre bundle comprises:

I sub-optical fibre, II sub-optical fibre, III sub-optical fibre and IV sub-optical fibre;

Described I sub-optical fibre and described II sub-optical fibre shared input mouth;

Described III sub-optical fibre and described IV sub-optical fibre common output mouth;

Binding is connected the output port of described II sub-optical fibre with the input port of described III sub-optical fibre, forms input/output port;

The other end of described I sub-optical fibre and IV sub-optical fibre is connected respectively a fiber port.

4. optical measuring system according to claim 3, is characterized in that,

Described I sub-optical fibre, II sub-optical fibre and IV sub-optical fibre comprise an optical fiber, and described III sub-optical fibre consists of six roots of sensation optical fiber;

At the input/output port place of described fibre bundle, described II sub-optical fibre is positioned at centre, and the described six roots of sensation optical fiber that forms described III sub-optical fibre is arranged described II sub-optical fibre around symmetrically, forms a regular hexagon;

At the output port place of described fibre bundle, described III sub-optical fibre and described IV sub-optical fibre are yi word pattern and put side by side; Described IV sub-optical fibre is in middle, and the described six roots of sensation optical fiber that forms described III sub-optical fibre is divided into two parts, described IV sub-optical fibre symmetria bilateralis distribute.

5. optical measuring system according to claim 3, is characterized in that, described fibre bundle is W-type fiber bundle; Described fibre bundle is that wavelength coverage is the uvioresistant variation optical fiber of 200-1100nm; Described light source is to be xenon lamp, deuterium lamp, tungsten lamp, Halogen lamp LED, mercury lamp, the composite broadband light source that comprises deuterium lamp and tungsten lamp, the composite broadband light source that comprises tungsten lamp and Halogen lamp LED, the composite broadband light source that comprises mercury lamp and xenon lamp or the composite broadband light source that comprises deuterium tungsten halogen.

6. optical measuring system according to claim 2, is characterized in that, described optical measuring system also comprises compensator;

Described compensator is between the described polarizer and sample or between sample and described analyzer.

7. optical measuring system according to claim 3, is characterized in that, described optical measuring system also comprises the first diaphragm and the second diaphragm;

Described the first diaphragm is arranged in the light path between described II sub-optical fibre and described the first reflecting element;

Described the second diaphragm is arranged in the light path between described I sub-optical fibre and described the first light focusing unit.

8. optical measuring system according to claim 7, is characterized in that, the fibre bundle output port that described fibre bundle is connected with spectrometer also comprises V sub-optical fibre;

Described V sub-optical fibre, transfers to the part that sees through sample in described the second detecting light beam in described spectrometer.

9. optical measuring system according to claim 8, is characterized in that, described optical measuring system also comprises the 5th light focusing unit;

Described the 5th light focusing unit, focuses to the part that sees through sample in described detecting light beam in described V sub-optical fibre, and described the 5th light focusing unit is curved reflector, or achromat.

10. optical measuring system according to claim 9, is characterized in that, described optical measuring system also comprises the 3rd diaphragm;

Described the 3rd diaphragm is arranged in the light path between the 5th light focusing unit and described sample.

11. according to the optical measuring system described in claim 1-10 any one, it is characterized in that, described optical measuring system also comprises computing unit, described computing unit is for the optical constant of calculation sample material, film thickness and/or for critical dimension characteristic or the three-dimensional appearance of the periodic structure of analytic sample.

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