CN116297227A - Spectrum ellipsometry method, system and storage medium - Google Patents

Spectrum ellipsometry method, system and storage medium Download PDF

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CN116297227A
CN116297227A CN202310325048.9A CN202310325048A CN116297227A CN 116297227 A CN116297227 A CN 116297227A CN 202310325048 A CN202310325048 A CN 202310325048A CN 116297227 A CN116297227 A CN 116297227A
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measured
ellipsometry
light
incident angle
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韩景珊
王瑜
杨峰
吕彤欣
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Raintree Scientific Instruments Shanghai Corp
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/21—Polarisation-affecting properties
    • G01N21/211—Ellipsometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/21—Polarisation-affecting properties
    • G01N21/211—Ellipsometry
    • G01N2021/213—Spectrometric ellipsometry
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
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Abstract

The invention provides a spectroscopic ellipsometry method, a spectroscopic ellipsometry system and a storage medium. The method comprises the following steps: obtaining a plurality of groups of measured spectrum data which are based on different incident angles and irradiate a sample to be measured and are reflected and collected by the sample to be measured; substituting each group of measured spectrum data into a pre-established theoretical spectrum model to respectively determine measured ellipsometry function values based on each incident angle; changing film layer thickness parameters of the theoretical spectrum model to respectively obtain theoretical ellipsometry function values corresponding to the incidence angles and various candidate film layer thicknesses; comparing and performing error analysis on the theoretical ellipsometry function value of each incident angle with the corresponding actually measured ellipsometry function value to determine a spectrum fitting error; and determining the film information on the surface of the sample to be detected according to the spectrum fitting error.

Description

Spectrum ellipsometry method, system and storage medium
Technical Field
The invention relates to a semiconductor measurement technology, in particular to a spectrum ellipsometry method, a spectrum ellipsometry system and a computer readable storage medium.
Background
With the continued decrease in semiconductor process nodes, wafer manufacturers are increasingly demanding performance levels for metrology equipment. The conventional spectroscopic ellipsometry technique is a non-contact measurement technique used in semiconductor manufacturing to monitor and control the fabrication process of one or more layers. The main information parameters monitored and controlled in the measurement process include information such as thickness of the film layer, refractive index of the material, extinction coefficient, optical critical dimension, etc.
The technical principle of the spectroscopic ellipsometer mainly uses a polarizer to form a beam of light with a known polarization state, and the polarization state of reflected light of the beam is changed when the beam is incident on the surface of a sample (such as a wafer). Then, the spectrum ellipsometer can receive reflected light through a polarization detector and a photoelectric conversion device, and inversion of information of a film layer is achieved through processing of light polarization state information. At present, most of the light incidence optical axis and the light emergence optical axis of the spectrum ellipsometry system at home and abroad in the market are single constant values, and the light incidence and receiving are performed by symmetrically distributing a light range of a light cone angle by taking the single constant value as the center of the optical axis. Different angles of incidence (Angle of incidence, AOI) change the polarization state of the outgoing light according to Fresnel reflectance calculations. The larger the light cone angle of the actual light beam focusing incident on the wafer is, the more inconsistent the polarization state information of the emergent light beam is, and the more unfavorable the algorithm inversion is. Conversely, if the cone angle of the light is smaller, the larger the spot size focused on the wafer will be due to diffraction effects. That is, the larger incidence Angle (AOI) range of the angle of the light cone of the light beam on the wafer easily causes aliasing of the polarization state information of the received light, thereby affecting inversion accuracy of information such as film thickness and optical critical dimension. However, if the beam cone angle is reduced, focusing of a smaller spot cannot be achieved.
In order to solve the above problems, a split multi-angle receiving optical path architecture is adopted in the prior art, that is, an off-axis two-objective architecture is used to split the incident angle at both the left and right sides of the incident end and the exit end. However, this architecture results in an uneven polarization distribution on the one hand and an increased tuning sensitivity of the system on the other hand. Moreover, the asymmetric optical path arrangement requires different apodization filters for each angle, and is relatively complex in design and engineering implementation.
In order to solve the above-mentioned problems in the prior art, there is a need in the art for a spectroscopic ellipsometry technique that can split the total incident cone angle into multiple sub-angles, and determine the film information on the surface of the wafer to be measured based on the multiple sub-beams, so as to solve the contradiction between the spot size and the incident cone angle. In addition, the coaxial reflecting projection objective is formed by adopting the convex reflecting mirror and the concave reflecting mirror with the light through hole, and the aperture stop with the symmetrical holes is combined.
Disclosure of Invention
The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.
In order to overcome the defects in the prior art, the invention provides a spectroscopic ellipsometry method, a spectroscopic ellipsometry system and a computer readable storage medium, wherein the total incident light cone angle can be split into a plurality of sub-angles, and the thin film information of the surface of the wafer to be measured is respectively determined based on the plurality of sub-beams, so that the contradiction between the light spot size and the incident light cone angle is solved.
Specifically, according to an aspect of the present invention, there is provided a spectroscopic ellipsometry method comprising the steps of: obtaining a plurality of groups of measured spectrum data which are based on different incident angles and irradiate a sample to be measured and are reflected and collected by the sample to be measured; substituting each group of measured spectrum data into a pre-established theoretical spectrum model to respectively determine measured ellipsometry function values based on each incident angle; changing film layer thickness parameters of the theoretical spectrum model to respectively obtain theoretical ellipsometry function values corresponding to the incidence angles and various candidate film layer thicknesses; comparing and performing error analysis on the theoretical ellipsometry function value of each incident angle with the corresponding actually measured ellipsometry function value to determine a spectrum fitting error; and determining the film information on the surface of the sample to be detected according to the spectrum fitting error.
Optionally, in some embodiments of the present invention, the step of obtaining a plurality of sets of measured spectrum data that irradiates the sample to be measured based on different incident angles and is collected via reflection of the sample to be measured includes: converging incident light in a polarization state provided by a light source to the surface of the sample to be detected through a first reflective projection objective lens to form a detection light spot, wherein the first reflective projection objective lens is positioned in a light path between the light source and the sample to be detected; obtaining reflected light of the light spot from the surface of the sample to be detected through a second reflective projection objective, and performing collimation treatment on the reflected light, wherein the second reflective projection objective is symmetrically arranged on an optical path between the sample to be detected and a beam splitter by the first reflective projection objective; obtaining reflected light output by the second reflective projection objective through the beam splitter, and splitting the reflected light about an incident angle to output a plurality of split light beams based on a part of the incident angle; and
and acquiring a plurality of beam splitting beams output by the beam splitter through at least one detector.
Optionally, in some embodiments of the invention, the beam splitter is a beam splitter prism. The step of obtaining the reflected light output by the second reflective projection objective through the beam splitter and splitting the reflected light with respect to an incident angle to output a plurality of split light beams based on a part of the incident angle includes: the reflected light is spatially split with respect to an incident angle via the splitting prism to simultaneously output a plurality of split light beams based on a part of the incident angle. The step of acquiring the plurality of split light beams output by the beam splitter via at least one detector includes: and simultaneously acquiring a plurality of beam splitting beams through a plurality of detectors arranged in a plurality of light emitting directions of the beam splitting prism.
Optionally, in some embodiments of the invention, the beam splitter uses an aperture stop wheel. The step of obtaining the reflected light output by the second reflective projection objective through the beam splitter and splitting the reflected light with respect to an incident angle to output a plurality of split light beams based on a part of the incident angle includes: and driving the aperture diaphragm wheel to rotate, and carrying out time splitting on the reflected light about the incident angle so as to output a plurality of split light beams based on part of the incident angle in a time-sharing way. The step of acquiring the plurality of split light beams output by the beam splitter via at least one detector includes: and acquiring a plurality of split light beams in a time-sharing manner through a detector arranged in one light emitting direction of the aperture diaphragm wheel.
Optionally, in some embodiments of the present invention, the beam splitter uses an aperture stop sheet, where the aperture stop sheet includes a plurality of beam splitting channels that block different incident angles. The step of obtaining the reflected light output by the second reflective projection objective through the beam splitter and splitting the reflected light with respect to an incident angle to output a plurality of split light beams based on a part of the incident angle includes: and driving the aperture diaphragm to displace, and performing time splitting on the reflected light with respect to an incident angle through each splitting channel so as to output a plurality of split light beams based on part of the incident angle in a time-sharing manner. The step of acquiring the plurality of split light beams output by the beam splitter via at least one detector includes: and acquiring a plurality of split beams in a time-sharing manner through a detector arranged in one light emitting direction of the aperture diaphragm sheet.
Optionally, in some embodiments of the present invention, the step of obtaining a plurality of sets of measured spectrum data that irradiates the sample to be measured based on different incident angles and is collected via reflection of the sample to be measured further includes: based on first relative angles of a polarizer and a polarization detector, respectively obtaining a plurality of groups of first actually measured spectrum data based on different incidence angles, wherein the polarizer is positioned between the light source and the first reflective projection objective, and the polarization detector is positioned between the second reflective projection objective and the beam splitter; adjusting the installation angle of the polarizer and/or the polarization detector to form a second relative angle; and respectively acquiring a plurality of groups of second actually measured spectrum data based on different incidence angles based on the second relative angles.
Optionally, in some embodiments of the invention, the film information includes film thickness. The theoretical spectral model is expressed as
ρ model1 (thickness)＝tanψ 1 *exp(iΔ 1 )
ρ model2 (thickness)＝tanψ 2 *exp(iΔ 2 )
Wherein, psi is 1 、Δ 1 、ψ 2 、Δ 2 Ellipsometric variables, ρ, in the spectral data, respectively model1 (. Cndot.) and ρ model2 (. Cndot.) is the function of the theoretical ellipsometry function value with respect to the thickness parameter thickness of the film in the theoretical spectral model of each incident angle number i.
Optionally, in some embodiments of the invention, the step of substituting each set of the measured spectrum data into a pre-established theoretical spectrum model to determine measured ellipsometry function values based on each of the incident angles respectively includes: determining measured ellipsometry parameters related to each incident angle according to a plurality of groups of measured spectrum data acquired based on different incident angles; substituting the measured ellipsometry parameters into the theoretical spectral model to respectively determine measured ellipsometry function values based on the incident angles
Figure BDA0004152999850000041
Figure BDA0004152999850000042
Wherein,,
Figure BDA0004152999850000043
and->
Figure BDA0004152999850000044
Is the measured ellipsometry parameter theta relative to the first incident angle 1 Is measured as ellipsometric parameter,/->
Figure BDA0004152999850000045
And->
Figure BDA0004152999850000046
Is the measured ellipsometry parameter theta relative to the second incident angle 2 Is used for measuring ellipsometry parameters.
Optionally, in some embodiments of the invention, the step of comparing and performing error analysis on the theoretical ellipsometry function value for each incident angle with the corresponding measured ellipsometry function value to determine a spectrum fitting error includes: determining the corresponding Brewster angle according to the film material on the surface of the sample to be detected; determining the spectral weight corresponding to each incidence angle according to the Brewster angle; determining the spectrum fitting error according to the spectrum weight, the theoretical ellipsometry function value of each incident angle and the corresponding measured ellipsometry function value
Figure BDA0004152999850000051
Wherein w is θ1 And w θ2 Respectively corresponding to the incident angle theta 1 And theta 2 Spectral weight, w θ1 +w θ2 =1, m is the number of data points.
Optionally, in some embodiments of the invention, the step of determining film information of the surface of the sample to be measured according to the spectrum fitting error includes: comparing the spectrum fitting error with a preset error threshold; and responding to the comparison result that the spectrum fitting error is smaller than the error threshold value, and determining the film thickness of the surface of the sample to be detected according to the film thickness parameter of the theoretical spectrum model.
Optionally, in some embodiments of the invention, the thin film information of the surface of the sample to be measured includes at least one of a refractive index of a material, an extinction coefficient, and an optical plane critical dimension.
In addition, the spectroscopic ellipsometry system provided in accordance with the second aspect of the present invention includes a memory and a processor. The memory has stored thereon computer instructions. The processor is connected to the memory and configured to execute computer instructions stored on the memory to implement the above-mentioned spectroscopic ellipsometry method provided by the first aspect of the present invention.
Further, the above-described computer-readable storage medium according to the third aspect of the present invention has stored thereon computer instructions. The above-described spectroscopic ellipsometry method provided in the first aspect of the present invention is implemented when the computer instructions are executed by a processor.
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The above features and advantages of the present invention will be better understood after reading the detailed description of embodiments of the present disclosure in conjunction with the following drawings. In the drawings, the components are not necessarily to scale and components having similar related features or characteristics may have the same or similar reference numerals.
Fig. 1 is a schematic diagram of a spectroscopic ellipsometry system according to some embodiments of the present invention.
Fig. 2A is a schematic structural diagram of a first reflective projection objective in the spectroscopic ellipsometry system shown in fig. 1.
Fig. 2B is a schematic structural diagram of a second reflective projection objective in the spectroscopic ellipsometry system shown in fig. 1.
Fig. 3 is a schematic diagram of the combination of a polarizer and a reflective projection objective in the spectroscopic ellipsometry system of fig. 1.
Fig. 4A and 4B are schematic diagrams showing two design architecture lengths and a shielding ratio of a reflective projection objective in a spectroscopic ellipsometry system according to some embodiments of the present invention.
Fig. 5 is a schematic diagram showing the collection of two incident angles and their corresponding cone angles of light for a reflective projection objective in a spectroscopic ellipsometry system, according to some embodiments of the present invention.
Fig. 6 is a schematic diagram illustrating a distribution of different incident angles acquired by a spectroscopic ellipsometry system according to some embodiments of the present invention.
Fig. 7A and 7B are schematic structural diagrams of a spectroscopic ellipsometry system according to other embodiments of the present invention.
Fig. 8A and 8B are schematic structural diagrams of an aperture stop wheel in a spectroscopic ellipsometry system according to other embodiments of the present invention.
Fig. 9 is a schematic flow chart of measuring film thickness based on a spectroscopic ellipsometry method according to some embodiments of the present invention.
Detailed Description
Further advantages and effects of the present invention will become apparent to those skilled in the art from the disclosure of the present specification, by describing the embodiments of the present invention with specific examples. While the description of the invention will be presented in connection with a preferred embodiment, it is not intended to limit the inventive features to that embodiment. Rather, the purpose of the invention described in connection with the embodiments is to cover other alternatives or modifications, which may be extended by the claims based on the invention. The following description contains many specific details for the purpose of providing a thorough understanding of the present invention. The invention may be practiced without these specific details. Furthermore, some specific details are omitted from the description in order to avoid obscuring the invention.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
In addition, the terms "upper", "lower", "left", "right", "top", "bottom", "horizontal", "vertical" as used in the following description should be understood as referring to the orientation depicted in this paragraph and the associated drawings. This relative terminology is for convenience only and is not intended to be limiting of the invention as it is described in terms of the apparatus being manufactured or operated in a particular orientation.
It will be understood that, although the terms "first," "second," "third," etc. may be used herein to describe various elements, regions, layers and/or sections, these elements, regions, layers and/or sections should not be limited by these terms and these terms are merely used to distinguish between different elements, regions, layers and/or sections. Accordingly, a first component, region, layer, and/or section discussed below could be termed a second component, region, layer, and/or section without departing from some embodiments of the present invention.
As described above, in the prior art, the conventional spectroscopic ellipsometer system has a problem in that the optical axis of the incident light and the optical axis of the outgoing light are both single constant values. According to the incidence principle, the spot size soptsize is approximately 1.22 λ/NA, where λ is the wavelength, the numerical aperture na=n×sin θ, n is the refractive index of air, and θ is the cone angle of the beam. If the angle of incidence (AOI) of the beam cone on the wafer is large, aliasing of the polarization state information of the received light is easily caused, thereby affecting inversion accuracy of information such as film thickness, optical critical dimension, and the like. On the contrary, if the beam cone angle is reduced, the focusing of smaller light spots cannot be realized. Although the prior art can adopt a split type multi-angle receiving light path architecture to solve the problems, the left and right sides of the incident end and the emergent end of the architecture adopt an off-axis two-anti-objective architecture, so that on one hand, uneven polarization state distribution can be caused, and on the other hand, the adjustment sensitivity of the system can be improved. In addition, the asymmetric optical path arrangement requires different apodization filters for each angle, and the design and engineering implementation are relatively complex.
In order to solve the problems in the prior art, the invention provides a spectrum ellipsometry system, which can split the total incident light cone angle into a plurality of sub-angles and respectively determine the film information on the surface of a wafer to be measured based on a plurality of sub-beams, thereby solving the contradiction between the light spot size and the incident light cone angle. In addition, the coaxial reflecting projection objective is formed by adopting the convex reflecting mirror and the concave reflecting mirror with the light passing hole, and the light diaphragm with the symmetrical holes is combined, so that the spectroscopic ellipsometry system can ensure that the polarization state of light rays is uniformly distributed, an apodization filter is not required, the design structure can be simplified, and the adjustment sensitivity of the system is reduced.
In some non-limiting embodiments of the present invention, a spectroscopic ellipsometry system consists essentially of: a light source for providing incident light in a polarization state; the first reflection type projection objective is positioned in a light path between the light source and the sample to be detected and is used for converging incident light to the surface of the sample to be detected so as to form a detection light spot; the second reflective projection objective is symmetrically arranged on the optical path between the sample to be detected and the beam splitter, and is used for acquiring reflected light of light spots from the surface of the sample to be detected and carrying out collimation treatment on the reflected light; the beam splitter acquires reflected light output by the second reflective projection objective and splits the reflected light about an incident angle to output a plurality of split light beams based on a part of the incident angle; and at least one detector for acquiring the multiple beam-splitting beams output by the beam splitter and determining the film information on the surface of the sample to be detected according to the polarization state parameters of the multiple beam-splitting beams.
Referring to fig. 1, fig. 1 is a schematic diagram illustrating a spectroscopic ellipsometry system according to some embodiments of the present invention.
As shown in fig. 1, in some embodiments of the present invention, the spectroscopic ellipsometry system 100 may be comprised of a light source 110, a reflective collimation module 170, a polarizer 150, a first reflective projection objective 121, a second reflective projection objective 122, a polarizer 160, a splitting prism 130, and at least one detector 141, 142.
Specifically, the light source 110 is configured to provide incident light in a polarization state. The incident light can be selected from a broad band light with a wave band of 190nm-2200nm, or a broad band light with partial bandwidth. The light source 110 may include a halogen lamp, a xenon lamp, a mercury xenon lamp, a laser excited plasma light source (Laser Driven Light Source, LDLS for short), a multi-color LED combined light source, and the like.
In addition, in order to shorten the optical path and to achieve miniaturization of the entire spectroscopic ellipsometry system 100, a reflective collimation module 170 may be preferably disposed between the light source 110 and the polarizer 150. The reflective collimation module 170 may be composed of a spherical mirror 171 and a planar mirror 172. Specifically, the divergent light beam output from the light source 110 may be reflected by the spherical mirror 171 to the plane mirror 172, and then the parallel light beam obtained after the collimation treatment may be transmitted to the polarizer 150 via the plane mirror 172. Compared with the conventional refractive projection lens element, the reflective collimation module adopted in the embodiment can couple the light beam emitted by the light source 110 into the polarizer 141 with maximum efficiency, so that the light-emitting efficiency and the light-emitting intensity are higher in the application of broadband light projection, and the detection precision of the film information is improved.
Furthermore, a polarizer 150 may be arranged between the light source 110 and the first reflective projection objective 121. Further, the polarizer 150 may be preferably disposed between the reflective collimating module 170 and the first reflective projection objective 121, so as to polarize the parallel light beam collimated by the reflective collimating module 170, thereby providing the incident light with linear polarization to the reflective projection objective 121.
Correspondingly, a polarization detector 160 may be disposed between the second reflective projection objective 122 and the beam splitter prism 130, for performing polarization processing on the reflected light output by the second reflective projection objective 122, so as to provide output light reflecting the polarization state change to the detector via the beam splitter prism 130. Here, the polarizer 150 and the polarization detector 160 in the present invention may be rochon prisms or gram thompson prisms, which are symmetrically distributed and have consistent polarization parameters. In principle of ellipsometry for film thickness, the polarizer 150 and the polarization detector 160 are not limited to the above two types, and may filter light via rotation-polarizer ellipsometry (RPE) and rotation-analyzer ellipsometry (RAE).
In some preferred embodiments, to make the polarization distribution of the light uniform, two apodization filters, i.e., gaussian progressive filters, are preferably included in the spectroscopic ellipsometry system 100 to further reduce the spot size. Here, a first apodization filter may be arranged between polarizer 150 and first reflective projection objective 121, while a second apodization filter may be arranged between second reflective projection objective 122 and beam splitter 130. The first and second apodization filters may be of identical design, e.g. having identical optical parameters. Because the spectroscopic ellipsometry system 100 of the present invention adopts a symmetrical architecture of focusing and collimation by using the two on-axis reflective projection objectives 121 and 122, compared with the off-axis structure adopted in the prior art, the present invention does not need to design apodization filters with different structures, and can realize the filtering only by arranging the same apodization filters on an input light path and a reflected light path, thereby simplifying the design structure, making the engineering implementation simpler and the system has lower adjustment sensitivity.
Alternatively, in the present invention, at least one of the polarizer 150 and the polarization detector 160 may be mounted on a motor that rotates 360 ° around the optical axis. Thereafter, the polarizer 150 and the polarization detector 160 may be rotated relatively by the rotation of the motor, and the spectral polarization signal is collected. When the motor rotates at angular velocity ω, the detector 130 can acquire the following periodic modulated signals:
I(t)＝I0·(1+αcos2ωt+βsin2ωt)
Further, in order to be able to transmit 190nm to 2500nm broadband ultraviolet to near infrared spectrum, the materials of the polarizer 150 and the polarization detector 160 may preferably be magnesium fluoride (MgF 2 )。
Furthermore, in the embodiment shown in FIG. 1, the first reflective projection objective 121 and the second reflective projection objective 122 may be symmetrically disposed on both sides of the sample (e.g., wafer) 10 to be measured, respectively. The first reflective projection objective 121 is coaxially disposed in the optical path between the light source 110 and the sample 10 to be tested, and is used for converging the incident light to the surface of the sample 10 to be tested to form a detection light spot. The second reflective projection objective 122 is coaxially disposed in the optical path between the sample to be measured 10 and the beam splitter prism 130, and is used as a reflective receiving objective to obtain the reflected light of the detection light spot from the surface of the sample to be measured 10, and collimate the reflected light to form parallel light for emission. By employing coaxial reflective projection objectives 121, 122, the spectroscopic ellipsometry system 10 can provide uniform polarization distribution of light, thereby simplifying design and reducing system tuning sensitivity.
In this embodiment, the first reflective projection objective 121 and the second reflective projection objective 122 have the same structure and are symmetrical in position. The structure of the first reflective projection objective 121 will be described in detail below. Referring to fig. 2A and 2B, fig. 2A and 2B are schematic structural diagrams of a reflective projection objective in the spectroscopic ellipsometry system shown in fig. 1.
As shown in fig. 2A, the first reflective projection objective 121 may consist of a first convex mirror 1211 and a first concave mirror 1212 with a first light-passing aperture 1210. The polarized incident light emitted by the polarizer 150 passes through the first concave mirror 1212 through the first light-passing hole 1210, reaches the first convex mirror 1211 in front of the first concave mirror 1212, is divergently reflected by the first convex mirror 1211 to return to the first concave mirror 1212, and is converged and reflected by the first concave mirror 1212, so that the light is converged at the focal point of the first reflective projection objective 121. Ideally, the light passing through the first reflective projection objective 121 can be converged to the region to be measured on the surface of the sample to be measured 10, and form a detection light spot with an adaptive size.
As shown in fig. 2B, the reflected light reflected from the surface of the sample 10 to be measured is converged and reflected to the second convex mirror 1221 by the second concave mirror 1222 of the second reflective projection objective 122, and then collimated and reflected by the second convex mirror 12221, so as to output the second reflective projection objective 122 through the second light through hole 1220.
Referring further to fig. 3, fig. 3 is a schematic structural diagram showing a combination of a polarizer and a first reflective projection objective in the spectroscopic ellipsometry system shown in fig. 1.
As shown in fig. 3, two refracted rays, an ordinary ray (also called o ray) and an extraordinary ray (extraordinary ray, also called e ray), are generated due to the incident light passing through the polarizer 150. The o light fully satisfies the law of refraction and propagates in the plane of incidence, whereas the e light rays do not satisfy the law of refraction and the ratio of the sine of the angle of incidence to the sine of the angle of refraction is not constant and does not normally propagate in the plane of incidence. To increase the stray light suppression level, in some embodiments, the present invention may preferably adjust the distance L between the polarizer 150 and the first reflective projection objective 121 to be L+.D/2 tan θ, where D is the diameter of the light-passing hole 1210 of the concave mirror 1212 and θ is the angle between the o-light and e-light separated by the polarizer 150. Thus, the first reflective projection objective 121 can ensure that the e-light emitted from the polarizer 150 does not enter the projection objective 121.
It will be appreciated by those skilled in the art that the above-mentioned scheme of suppressing incident stray light by making the spacing L between the polarizer 150 and the projection objective 121 satisfy L.gtoreq.D/2. Tan. Theta. Is merely a non-limiting embodiment provided by the present invention, and is intended to clearly illustrate the main concept of the present invention and to provide a specific scheme for public implementation, not to limit the scope of the present invention.
Furthermore, the first reflective projection objective 121 in this embodiment may adopt a coaxial two-reflection structure, i.e. the two mirrors may be a combination of a coaxial convex spherical mirror and a concave spherical mirror, or a combination of a coaxial convex ellipsoidal mirror and a concave spherical mirror.
Please refer to fig. 2A, fig. 4A and fig. 4B in combination. Fig. 4A shows the trend of the combined length and center shielding ratio of the coaxial convex spherical mirror and concave spherical mirror combination 410. Fig. 4B shows the trend of the combined length and center shielding ratio of the coaxial convex ellipsoidal mirror and concave spherical mirror combination 420. In fig. 2A and 4A, curve 411 represents the combined length of the convex spherical mirror and concave spherical mirror combination 410 as a function of the central obscuration ratio, while curve 412 represents the working distance of the convex spherical mirror 1211 to the focal point of the reflective projection objective 121 as a function of the central obscuration ratio. Accordingly, in fig. 2A and 4B, the curve 421 represents the combined length of the convex ellipsoidal mirror and concave spherical mirror combination 420 as a function of the central obscuration ratio, while the curve 422 represents the working distance of the convex ellipsoidal mirror 1211 to the focal point of the reflective projection objective 121 as a function of the central obscuration ratio.
The two reflective projection objectives are different in that the coaxial convex spherical mirror and concave spherical mirror combination 410 has loose tolerance sensitivity, easy assembly and adjustment, and the coaxial convex ellipsoidal mirror and concave spherical mirror combination 420 has relatively tight tolerance sensitivity, and has large assembly and adjustment difficulty. In contrast, the overall length of the coaxial convex ellipsoidal mirror and concave spherical mirror combination 420 is more compact when the parameters are the same and the center obscuration ratio is the same as the coaxial convex spherical mirror and concave spherical mirror combination 410 solution.
With continued reference to fig. 1, in some embodiments of the present invention, the beam splitter prism 130 may receive the collimated and polarized reflected light with a changed polarization state from the second reflective projection objective 122 and the polarization detector 160, and split the reflected light with respect to an incident angle to output a plurality of split beams based on a part of the incident angle. The beam splitter prism 130 may then output each of the split beams to the plurality of detectors 141, 142, respectively, for determining film information on the surface of the sample 10 to be measured according to the polarization state parameters of the plurality of split beams.
Specifically, in the embodiment shown in fig. 1, the beam splitter prism 130 may be a triangular beam splitter prism, which is used to spatially split the light reflected by the polarization detector 160 with respect to the incident angle, so as to output two split beams based on the partial incident angle. The detectors 141 and 142 may be optical spectrometers, and are respectively disposed in two light-emitting directions of the beam-splitting prism 130, for simultaneously acquiring two beam-splitting beams, and determining film information on the surface of the sample 10 to be measured according to the polarization state parameters of the two beam-splitting beams. Compared with an embodiment in which a CCD (Charge-coupled Device) array or a PD (Photo-Diode) array is directly adopted to receive reflected light, the spectrometer can perform spectrum light splitting on the received output light, so that film information such as material refractive index, extinction coefficient and the like of a film under detection light with different wavelengths is analyzed, and the analysis requirement of broadband light is met.
Further, please refer to fig. 5 and 6. Fig. 5 is a schematic diagram showing the collection of two incident angles and their corresponding cone angles of light for a reflective projection objective in a spectroscopic ellipsometry system, according to some embodiments of the present invention. Fig. 6 is a schematic diagram illustrating a distribution of different incident angles acquired by a spectroscopic ellipsometry system according to some embodiments of the present invention.
In the embodiment shown in fig. 5 and 6, the angle range θ of the first reflective projection objective 121 incident on the surface of the sample 10 to be measured is between 54.6 ° and 62 ° and 72 ° and 79.4 °, and the numerical aperture (Numerical aperture, NA for short) is 0.215. The second reflective projection objective 122 receives the reflected light rays of the two incident angles using sub-aperture separation and outputs them to the beam splitting prism 130 to perform spatial beam splitting with respect to the incident angles, and outputs two split light beams of which the incident Angles (AOI) are 54.6 ° to 62 ° and 72 ° to 79.4 °. The detectors 142 and 141 may receive the two split beams at positions θ1=58.3° and θ2=75.7°, respectively, and determine film information on the surface of the sample 10 to be measured according to the polarization state parameters of the two split beams. Here, since the incident light maintains an incident Angle (AOI) of 24.8 °, the light spot focused on the sample 10 to be measured is controlled to be smaller in size, so as to facilitate improving the detection accuracy of the spectroscopic ellipsometry system 100. In addition, the angle range of the separation angle light cone of each beam splitting light beam is 7.4 degrees, namely NA is 0.065, so that the consistency of polarization state information is obviously improved, and the algorithm inversion accuracy of information such as film thickness, optical critical dimension and the like is improved.
Alternatively, please refer to fig. 7A, 7B and 8A. Fig. 7A and 7B are schematic structural diagrams of a spectroscopic ellipsometry system according to other embodiments of the present invention. Fig. 8A shows a schematic structural diagram of an aperture stop wheel in a spectroscopic ellipsometry system provided according to further embodiments of the present invention.
As shown in fig. 7A, 7B and 8A, in some embodiments of the present invention, the above-described light-splitting prism 130 may also be replaced with an aperture stop wheel 181 to perform time-splitting of the reflected light output from the polarization detector 160 with respect to the incident angle. Accordingly, the spectroscopic ellipsometry system 200 in this embodiment only needs to configure one detector 140 to obtain multiple beam of spectroscopic light in a time-sharing manner, and determine the film information on the surface of the sample 10 to be measured according to the polarization state parameters of the multiple beam of spectroscopic light. The rest of the structures in the spectroscopic ellipsometry system 200 can be referred to the spectroscopic ellipsometry system 100 of the above embodiment, and will not be described herein.
Specifically, in the case of performing spectroscopic ellipsometry based on the spectroscopic ellipsometry system 200 shown in fig. 7A, 7B and 8A, the incident light in the polarization state provided by the light source 110 may be converged on the surface of the sample 10 to be measured through the first reflective projection objective 121 as described above to form a detection light spot, and the light reflected from the surface of the sample 10 to be measured is received and collimated by the second reflective projection objective 122 disposed symmetrically to form parallel light, and then passes through the polarization detector 160 to reach the aperture stop wheel 181. The aperture stop wheel 181 can be rotated by a motor. The upper beam a of the two split beams can pass through an aperture stop 1811 which is opened at the upper side and blocked at the lower side in the aperture stop wheel 181, and is transmitted to the detector 140 along the light emitting direction. The lower beam B of the two split beams can pass through an aperture stop 1812 with a top blocking and a bottom opening in the aperture stop wheel 181, and is transmitted to the detector 140 along the light emitting direction. In this way, the aperture wheel 181 can perform time-division on the reflected light with respect to the incident angle, thereby outputting a plurality of split light beams based on a part of the incident angle.
That is, in the present embodiment, the detector 140 may be disposed in one light emitting direction of the aperture wheel 181. The aperture stop wheel 181 can enable two light beams to respectively and independently enter the same detector 140 through the light outlet hole in time sequence, so that the detector 140 samples the two light beams in time sequence. Thus, the detector 140 can acquire multiple beam-splitting beams in a time-sharing manner, and determine the film information on the surface of the sample 10 to be measured according to the polarization state parameters of the multiple beam-splitting beams. In addition, by using the symmetrically apertured aperture stop wheel 181 for time-division with respect to the incident angle, the present invention can achieve uniform polarization distribution, thereby further simplifying the design structure.
Alternatively, please refer to fig. 8B. Fig. 8B is a schematic diagram illustrating the structure of an aperture stop wheel in a spectroscopic ellipsometry system according to other embodiments of the present invention. In other embodiments shown in fig. 8B, the aperture wheel 181 may be replaced by an aperture plate 182 driven by a linear motor, and the aperture plate may be switched to the corresponding open aperture by a linear cutting-in and cutting-out operation. Specifically, as shown in fig. 7A and 8B, the upper beam a of the two split beams can pass through an aperture stop 1821 that opens at the upper side and blocks at the lower side in the aperture stop plate 182, and is transmitted to the detector 140 in the light-emitting direction. As shown in fig. 7B and 8B, the lower beam B of the two split beams can pass through an aperture stop 1822 with an upper side blocked and a lower side opened in the aperture stop plate 182, and is transmitted to the detector 140 in the light-emitting direction.
By comprehensively comparing the spectral ellipsometry system 100 based on spatial light splitting shown in fig. 1 with the spectral ellipsometry system 200 based on temporal light splitting shown in fig. 7A and 7B, the throughput (throughput) of the spectral ellipsometry system 100 for reflected light is higher, and two AOI angles can be collected at the same time, but two or more detectors are required to receive, which also has a higher requirement for consistency between the detectors. In contrast, the spectroscopic ellipsometry system 200 has a low throughput (throughput) of reflected light, and needs to sample twice in time, so that the requirement on the stability of the platform environment is high, but only one detector is needed to receive the reflected light. From the viewpoint of equipment cost, the spectroscopic ellipsometry system 100 needs more detectors, and the spectroscopic ellipsometry system 200 only needs to add a motion mechanism to control the switching of the aperture stop, so in practical application, the spectroscopic ellipsometry system 200 of time-division can be used to optimize the cost.
Further, in the above embodiment of the present invention, since the spectroscopic ellipsometry systems 100 and 200 all adopt the symmetrical architecture of focusing and collimation by the coaxial two reflection type projection objective lenses 121 and 122, and the designs of the small holes 1811 and 1812 of the aperture stop wheel 181 are symmetrical, and the light beams corresponding to the separated sub-apertures are symmetrical, the light filtering can be realized only by arranging the same apodization filter on the input light path and the reflection light path, so that the design structure is simplified, the engineering implementation is simpler, and the adjustment sensitivity of the system is lower.
Furthermore, according to another aspect of the present invention, there is provided a spectroscopic ellipsometry method. The method is stored in a memory of a spectrum ellipsometry system in the form of computer instructions, and is executed by a processor connected with the memory, so that the function of determining film information such as film thickness, material refractive index, extinction coefficient, optical critical dimension and the like on the surface of a semiconductor device based on spectrum data of a plurality of different incident light cone angles is realized.
Referring to fig. 9, fig. 9 is a schematic flow chart of measuring film thickness based on a spectroscopic ellipsometry method according to some embodiments of the present invention.
As shown in fig. 9, in the process of performing the spectroscopic ellipsometry, the processor of the spectroscopic ellipsometry system may first adjust the relative angles of the polarizer 150 and the polarization detector 160 to obtain multiple sets of measured spectroscopic data collected based on different incident angles. Here, the plurality of sets of measured spectrum data may be acquired based on the above-described spatial light-splitting embodiment, or may be acquired based on the above-described temporal light-splitting embodiment, and are expressed as follows:
Figure BDA0004152999850000151
Figure BDA0004152999850000152
wherein I (θ) 1 )＝f(tanψ 1 ,cosΔ 1 ) To correspond to the first incident light cone angle theta 1 Is a first light intensity of (A), I (θ) 2 )＝f(tanψ 2 ,cosΔ 2 ) Corresponding to the second entranceCone angle theta of light beam 2 And f (·) is a function of the relation of the ellipsoids ψ, Δ and the light intensity I, P is the installation angle of the polarizer 150, a is the installation angle of the polarization detector, and a-P is the relative angle of the polarizer 150 and the polarization detector 160.
For example, a technician may fix the polarizer angle P and change the angle A of the analyzer to obtain the above-described sets based on different incident angles θ i And collecting actual measurement spectrum data.
For another example, the technician may also fix the polarizer angle A and change the polarizer angle P to obtain the above-mentioned multiple groups based on different incident angles θ i And collecting actual measurement spectrum data.
For another example, the skilled person can also change the polarizer angle P and the angle A of the analyzer simultaneously to obtain the above-mentioned multiple groups based on different incident angles θ i And collecting actual measurement spectrum data.
Then, the spectroscopic ellipsometry system may substitute the multiple sets of measured spectrum data collected based on different incident angles into a theoretical spectrum model established in advance to determine the angles θ based on the incident angles respectively i Is a function of the measured ellipsometry.
Specifically, a theoretical spectral model built based on various angles of incidence can be expressed as follows:
ρ model1 (thickness)＝tanψ 1 *exp(iΔ 1 )，
ρ model2 (thickness)＝tanψ 2 *exp(iΔ 2 )
Wherein ψ and Δ are ellipsometric variables in the spectral data, ρ model1 And ρ model2 In the theoretical spectral model of each incidence angle number i, the theoretical ellipsometry function value is a relation function of the film thickness parameter (namely, thickness).
The spectroscopic ellipsometry system can firstly collect the actual measurement spectroscopic data I (theta) based on different incidence angles according to the multiple groups 1 ) And I (theta) 2 ) Solving for the measured ellipsometry parameter (tan. Phi.) 1 ,cosΔ 1 ) And (tan. Phi.) 2 ,cosΔ 2 ) Substituting the measured ellipsometry function values into theoretical spectrum models corresponding to the serial numbers i to obtain measured ellipsometry function values corresponding to the incident angle serial numbers i, namely:
Figure BDA0004152999850000153
Figure BDA0004152999850000154
then, the spectroscopic ellipsometry system can change the film thickness parameter (i.e. thickness) of the theoretical spectroscopic model multiple times to obtain multiple theoretical ellipsometry function values ρ modeli Then the measured ellipsometry function value rho is matched with the corresponding measured ellipsometry function value rho measurementi And respectively carrying out comparison and error analysis to determine the spectrum fitting error.
Here, the spectral fitting error can be expressed as follows:
Figure BDA0004152999850000161
wherein w is θ1 ，w θ2 Respectively for the incident angle theta 1 And theta 2 Is added to the spectrum of w θ1 +w θ2 =1, and M is the number of data points.
Thus, the spectroscopic ellipsometry system can add weight in the spectrum fitting process and can calculate the error sigma 2 And when the thickness of the film layer is smaller than a preset threshold value, determining the thickness of the film layer on the surface of the semiconductor device.
Further, in some embodiments, since different thin film materials have different brewster angles, the spectroscopic ellipsometry system and system may preferably further increase the spectral weight near the brewster angle of the thin film materials to further increase the sensitivity of the film thickness measurement.
Compared with the prior art of carrying out spectroscopic ellipsometry based on a single constant incident light cone angle, the method can selectively increase or decrease the contribution of spectra of different incident angles by changing the weight, so that the method can comprehensively adapt to the measurement requirements of various different film materials.
In addition, by constructing a theoretical spectrum model for a plurality of incidence angle ranges and correspondingly introducing a plurality of groups of measured spectrum data based on different incidence angles, the invention also effectively increases the fitting point number of spectrum fitting, thereby reducing fitting errors.
It will be appreciated by those skilled in the art that the theoretical spectral model constructed based on the film thickness parameter (i.e. thickness) is merely a specific embodiment of the present invention for adapting to the film thickness measurement requirement, and is intended to clearly illustrate the main concept of the present invention, not to limit the scope of the present invention.
Optionally, in other embodiments, to adapt to the actual requirements of measuring information such as the refractive index, the extinction coefficient, the optical critical dimension, and the like of the material of the thin film on the surface of the semiconductor device, a person skilled in the art may correspondingly establish a theoretical spectral model related to parameters such as the refractive index, the extinction coefficient, the optical critical dimension, and the like of the material, and perform spectral fitting as described above to determine corresponding thin film information according to the spectral fitting error, which is not described herein again.
In summary, the spectroscopic ellipsometry system and the spectroscopic ellipsometry method provided by the invention can split the total incident light cone angle into a plurality of sub-angles, and respectively determine the film information on the surface of the sample to be measured based on the plurality of sub-beams, thereby solving the contradiction between the light spot size and the incident light cone angle. In addition, the coaxial reflecting projection objective is formed by adopting the convex reflecting mirror and the concave reflecting mirror with the light through hole, and the aperture stop with the symmetrical holes is combined.
The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (13)

1. A spectroscopic ellipsometry method, comprising the steps of:
obtaining a plurality of groups of measured spectrum data which are based on different incident angles and irradiate a sample to be measured and are reflected and collected by the sample to be measured;
substituting each group of measured spectrum data into a pre-established theoretical spectrum model to respectively determine measured ellipsometry function values based on each incident angle;
changing film layer thickness parameters of the theoretical spectrum model to respectively obtain theoretical ellipsometry function values corresponding to the incidence angles and various candidate film layer thicknesses;
comparing and performing error analysis on the theoretical ellipsometry function value of each incident angle with the corresponding actually measured ellipsometry function value to determine a spectrum fitting error; and
and determining the film information on the surface of the sample to be detected according to the spectrum fitting error.
2. A method of spectroscopic ellipsometry in accordance with claim 1, wherein the step of obtaining a plurality of sets of measured spectroscopic data based on different angles of incidence illuminating a sample to be measured and being collected via reflection from the sample to be measured comprises:
converging incident light in a polarization state provided by a light source to the surface of the sample to be detected through a first reflective projection objective lens to form a detection light spot, wherein the first reflective projection objective lens is positioned in a light path between the light source and the sample to be detected;
Obtaining reflected light of the light spot from the surface of the sample to be detected through a second reflective projection objective, and performing collimation treatment on the reflected light, wherein the second reflective projection objective is symmetrically arranged on an optical path between the sample to be detected and a beam splitter by the first reflective projection objective;
obtaining reflected light output by the second reflective projection objective through the beam splitter, and splitting the reflected light about an incident angle to output a plurality of split light beams based on a part of the incident angle; and
and acquiring a plurality of beam splitting beams output by the beam splitter through at least one detector.
3. A spectroscopic ellipsometry method as claimed in claim 2, wherein the beam splitter is a beam splitter prism,
the step of obtaining the reflected light output by the second reflective projection objective through the beam splitter and splitting the reflected light with respect to an incident angle to output a plurality of split light beams based on a part of the incident angle includes: performing spatial light splitting on the reflected light with respect to an incident angle via the light splitting prism to simultaneously output a plurality of split light beams based on a part of the incident angle,
The step of acquiring the plurality of split light beams output by the beam splitter via at least one detector includes: and simultaneously acquiring a plurality of beam splitting beams through a plurality of detectors arranged in a plurality of light emitting directions of the beam splitting prism.
4. A spectroscopic ellipsometry method as claimed in claim 2, wherein said beam splitter is an aperture stop wheel, wherein,
the step of obtaining the reflected light output by the second reflective projection objective through the beam splitter and splitting the reflected light with respect to an incident angle to output a plurality of split light beams based on a part of the incident angle includes: driving the aperture diaphragm wheel to rotate, performing time splitting on the reflected light about an incident angle to output a plurality of split light beams based on part of the incident angle in a time-sharing manner,
the step of acquiring the plurality of split light beams output by the beam splitter via at least one detector includes: and acquiring a plurality of split light beams in a time-sharing manner through a detector arranged in one light emitting direction of the aperture diaphragm wheel.
5. A spectroscopic ellipsometry method as recited in claim 2, wherein said beam splitter is an aperture stop plate, wherein said aperture stop plate comprises a plurality of beam splitting channels that block different angles of incidence,
The step of obtaining the reflected light output by the second reflective projection objective through the beam splitter and splitting the reflected light with respect to an incident angle to output a plurality of split light beams based on a part of the incident angle includes: driving the aperture diaphragm to displace, performing time-division on the reflected light with respect to an incident angle through each of the light-dividing channels to time-division output a plurality of light-divided light beams based on a part of the incident angle,
the step of acquiring the plurality of split light beams output by the beam splitter via at least one detector includes: and acquiring a plurality of split beams in a time-sharing manner through a detector arranged in one light emitting direction of the aperture diaphragm sheet.
6. A method of spectroscopic ellipsometry in accordance with claim 2, wherein the step of obtaining a plurality of sets of measured spectroscopic data based on different angles of incidence illuminating a sample to be measured and being collected via reflection from the sample to be measured further comprises:
based on first relative angles of a polarizer and a polarization detector, respectively obtaining a plurality of groups of first actually measured spectrum data based on different incidence angles, wherein the polarizer is positioned between the light source and the first reflective projection objective, and the polarization detector is positioned between the second reflective projection objective and the beam splitter;
Adjusting the installation angle of the polarizer and/or the polarization detector to form a second relative angle; and
and respectively acquiring a plurality of groups of second actually measured spectrum data based on different incidence angles based on the second relative angles.
7. A spectroscopic ellipsometry method as recited in claim 1, wherein said film information includes film thickness and said theoretical spectroscopic model is expressed as
ρ model1 (thickness)＝tanψ l *exp(iΔ 1 )
ρ model2 (thickness)＝tanψ 2 *exp(iΔ 2 )
Wherein, psi is 1 、Δ 1 、ψ 2 、Δ 2 Ellipsometric variables, ρ, in the spectral data, respectively model1 (. Cndot.) and ρ model2 (. Cndot.) is the function of the theoretical ellipsometry function value with respect to the thickness parameter thickness of the film in the theoretical spectral model of each incident angle number i.
8. A spectroscopic ellipsometry method as recited in claim 7, wherein said step of substituting each set of said measured spectral data into a pre-established theoretical spectral model to separately determine measured ellipsometry function values based upon each said angle of incidence comprises:
determining measured ellipsometry parameters related to each incident angle according to a plurality of groups of measured spectrum data acquired based on different incident angles; and
substituting the measured ellipsometry parameters into the theoretical spectral model to respectively determine measured ellipsometry function values based on the incident angles
Figure FDA0004152999840000031
Figure FDA0004152999840000032
Wherein,,
Figure FDA0004152999840000033
and->
Figure FDA0004152999840000034
Is the measured ellipsometry parameter theta relative to the first incident angle 1 Is measured as ellipsometric parameter,/->
Figure FDA0004152999840000041
And->
Figure FDA0004152999840000042
Is the measured ellipsometry parameter theta relative to the second incident angle 2 Is used for measuring ellipsometry parameters.
9. A method of spectroscopic ellipsometry as recited in claim 8, wherein said step of comparing and error analyzing theoretical ellipsometry function values for each of said incident angles with corresponding measured ellipsometry function values, respectively, to determine a spectroscopic fitting error comprises:
determining the corresponding Brewster angle according to the film material on the surface of the sample to be detected;
determining the spectral weight corresponding to each incidence angle according to the Brewster angle; and
determining the spectrum fitting error according to the spectrum weight, the theoretical ellipsometry function value of each incident angle and the corresponding measured ellipsometry function value
Figure FDA0004152999840000043
Wherein w is θ1 And w θ2 Respectively corresponding to the incident angle theta 1 And theta 2 Spectral weight, w θ1 +w θ2 =1, m is the number of data points.
10. A method of spectroscopic ellipsometry as recited in claim 7, wherein said step of determining film information of said surface of said sample to be measured based upon said spectral fitting error comprises:
comparing the spectrum fitting error with a preset error threshold; and
And responding to a comparison result that the spectrum fitting error is smaller than the error threshold value, and determining the film thickness of the surface of the sample to be detected according to the film thickness parameter of the theoretical spectrum model.
11. The spectroscopic ellipsometry method of claim 1, wherein the thin film information of the surface of the sample to be measured comprises at least one of a refractive index of the material, an extinction coefficient, and an optical plane critical dimension.
12. A spectroscopic ellipsometry system, comprising:
a memory having stored thereon computer instructions; and
a processor connected to the memory and configured to execute computer instructions stored on the memory to implement the spectroscopic ellipsometry method of any one of claims 1-11.
13. A computer readable storage medium having stored thereon computer instructions which, when executed by a processor, implement a spectroscopic ellipsometry method according to any one of claims 1 to 11.
CN202310325048.9A 2023-03-29 2023-03-29 Spectrum ellipsometry method, system and storage medium Pending CN116297227A (en)

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