EP0420113A2
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EP
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Apparatus for and method of evaluating multilayer thin films
Assignee: Jasco Corp
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Filing: 1990-09-24
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Granted: —
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Expires: 2010-09-24
Abstract
Abstract According to an apparatus for and a method of evaluating a multilayer thin film of the present invention, an interference light beam in a predetermined wave number region is projected as a parallel beam onto a multilayer thin film sample (11) and the interference light beam reflected by the sample (11) is detected to find an interferogram. The interferogram is subjected to a Fourier transform, filtering and a reverse Fourier transform so that a spatialgram is provided. Thereby the variation of the incident angle of the light beam impinging on the sample and the incident surface is reduced, and the spatialgram can be provided with accurate information of the multilayer thin film. According to the apparatus and the method of the present invention, the reverse Fourier transform is performed by means of complex power reverse Fourier transform. As a result, compared with the case of performing cosine reverse Fourier transform, more information can be introduced in the same photometrical wave number range and a thin film measuring limit is improved.
Inventors
- 👤 Seizi Nishizawa
- 👤 Ryoichi Fukazawa
- 👤 Tokuzi Takahashi
- 👤 Ryo C/O Mitsubishi Denki K.K. Hattori
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 18:39
CPC Classifications
G; G01; G01B; G01B11/00; G01B11/02; G01B11/06; G01B11/0616; G01B11/0675
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
154 words
An apparatus for evaluating a multilayer thin film, comprising: - a first optical system (A1) for synthesizing two light beams in a predetermined wave number region while continuously varying optical path differences thereof to produce an interference light beam; - a second optical system (A2) for projecting onto a multilayer thin film sample (11) the interference light beam emitted from the first optical system (A1) as a parallel beam having a predetermined beam diameter and detecting the interference light beam reflected by the sample (11) to provide an interferogram; - Fourier transform means (B) for performing a Fourier transform on the interferogram to provide a reflection spectrum; - filtering means (C) for filtering the reflection spectrum; - reverse Fourier transform means (D) for performing a reverse Fourier transform on the filtered reflection spectrum to provide a spatialgram; and - evaluating means (E) for evaluating the multilayer thin film on the basis of the spatialgram.
Claim 2
Independent Claim
154 words
An apparatus for evaluating a multilayer thin film, comprising: - a first optical system (A1) for synthesizing two light beams in a predetermined wave number region while continuously varying optical path differences thereof to produce an interference light beam; - a second optical system (A2) for projecting onto a multilayer thin film sample (11) the interference light beam emitted from the first optical system (A1) as a parallel beam having a predetermined beam diameter and detecting the interference light beam reflected by the sample (11) to provide an interferogram; - Fourier transform means (B) for performing a Fourier transform on the interferogram to provide a reflection spectrum; - filtering means (C) for filtering the reflection spectrum; - reverse Fourier transform means (D) for performing a reverse Fourier transform on the filtered reflection spectrum to provide a spatialgram; and - evaluating means (E) for evaluating the multilayer thin film on the basis of the spatialgram.
Claim 3
Dependent Claim
104 words
The apparatus according to claim 1, wherein the second optical system (A1) comprises: - an aperture mask (27) for transforming the interference light beam emitted from the first optical system (A1) into a parallel beam having a predetermined beam diameter; - a first plane mirror (28) for reflecting and leading the parallel beam to the multilayer thin film sample (11); - a second plane mirror (29) for reflecting the interference light beam reflected by the multilayer thin film sample (11); and - an aspherical mirror (30) for converging the interference light beam reflected by the second plane mirror (29) on a photo detector (21).
Claim 4
Dependent Claim
161 words
The apparatus according to claim 1, wherein the second optical system (A2) comprises: - a first plane mirror (32) for reflecting the interference light beam emitted from the first optical system (A1); - a first aspherical mirror (33) for converging the interference light beam reflected by the first plane mirror (32); - an aperture mask (34) disposed in a converging position of the interference light beam; - a second aspherical mirror (35) for transforming the interference light beam passing through the aperture mask (34) into a parallel beam; - a first plane mirror group (36, 37) for sequentially reflecting and leading the parallel beam to the multilayer thin film sample (11); - a second plane mirror group (38, 39) for sequentially reflecting the interference light beam reflected by the multilayer thin film sample (11); and - a third aspherical mirror (40) for converging the interference light beam emitted from the second plane mirror group (38, 39) on a photo detector (21).
Claim 5
Dependent Claim
159 words
The apparatus according to claim 1, wherein the second optical system (A2) comprises: - a first aspherical mirror (42) for converging the interference light beam emitted from the first optical system (A1); - an aperture mask (43) disposed in a converging position of the interference light beam; - a converging mirror (44) having an elliptic reflecting surface for reflecting the interference light beam having passed through the aperture mask (43) on its reflecting surface to converge the interference light beam in one focus position with respect to the reflecting surface; - a hyperboloidal mirror (45) disposed in one focus position of the converging mirror (44) for transforming the interference light beam reflected by the converging mirror (44) into a parallel beam to lead the parallel beam to the multilayer thin film sample (11); and - a second aspherical mirror (46) for converging the interference light beam reflected by the multilayer thin film sample (11) on a photo detector (21).
Claim 6
Independent Claim
132 words
An apparatus for evaluating a multilayer thin film, comprising: - an optical system (A) for projecting onto a multilayer thin film sample (11) an interference light beam obtained by synthesizing two light beams in a predetermined wave number region while continuously varying optical path differences thereof and detecting the interference light beam reflected by the sample (11) to provide an interferogram; - Fourier transform means (B) for performing a Fourier transform on the interferogram to provide a reflection spectrum; - filtering means (C) for filtering the reflection spectrum; - complex power reverse Fourier transform means (F) for performing a complex power reverse Fourier transform on the reflection spectrum filtered to provide a spatialgram; and - evaluating means (E) for evaluating the multilayer thin film sample (11) on the basis of the spatialgram.
Claim 7
Independent Claim
132 words
An apparatus for evaluating a multilayer thin film, comprising: - an optical system (A) for projecting onto a multilayer thin film sample (11) an interference light beam obtained by synthesizing two light beams in a predetermined wave number region while continuously varying optical path differences thereof and detecting the interference light beam reflected by the sample (11) to provide an interferogram; - Fourier transform means (B) for performing a Fourier transform on the interferogram to provide a reflection spectrum; - filtering means (C) for filtering the reflection spectrum; - complex power reverse Fourier transform means (F) for performing a complex power reverse Fourier transform on the reflection spectrum filtered to provide a spatialgram; and - evaluating means (E) for evaluating the multilayer thin film sample (11) on the basis of the spatialgram.
Claim 8
Dependent Claim
38 words
The apparatus according to claim 5, wherein the reverse Fourier transform is expressed by the following formula: where R(σ): reflected light intensity, f(σ): filtering function, σ: wave number (1/cm), X: distance (cm), and σs/σe: photometrical wave number limits.
Claim 9
Independent Claim
145 words
A method of evaluating a multilayer thin film, comprising: - a first step of synthesizing two light beams in a predetermined wave number region while continuously varying optical path differences thereof to produce an interference light beam; - a second step of projecting onto a multilayer thin film sample (11) the interference light beam produced in the first step as a parallel beam having a predetermined beam diameter and detecting the interference light beam reflected by the sample (11) to provide an interferogram; - a third step of performing a Fourier transform on the interferogram to provide a reflection spectrum; - a fourth step of filtering the reflection spectrum; - a fifth step of performing a reverse Fourier transform on the reflection spectrum filtered to provide a spatialgram; and - a sixth step of evaluating the multilayer thin film on the basis of the spatialgram.
Claim 10
Independent Claim
145 words
A method of evaluating a multilayer thin film, comprising: - a first step of synthesizing two light beams in a predetermined wave number region while continuously varying optical path differences thereof to produce an interference light beam; - a second step of projecting onto a multilayer thin film sample (11) the interference light beam produced in the first step as a parallel beam having a predetermined beam diameter and detecting the interference light beam reflected by the sample (11) to provide an interferogram; - a third step of performing a Fourier transform on the interferogram to provide a reflection spectrum; - a fourth step of filtering the reflection spectrum; - a fifth step of performing a reverse Fourier transform on the reflection spectrum filtered to provide a spatialgram; and - a sixth step of evaluating the multilayer thin film on the basis of the spatialgram.
Claim 11
Independent Claim
124 words
A method of evaluating a multilayer thin film, comprising: - a first step of projecting onto a multilayer thin film sample (11) an interference light beam obtained by synthesizing two light beams in a predetermined wave number region while continuously varying optical path differences thereof and detecting the interference light beam reflected by the sample (11) to provide an interferogram; - a second step of performing a Fourier transform on the interferogram to provide a reflection spectrum; - a third step of filtering the reflection spectrum; - a fourth step of performing a complex power reverse Fourier transform on the reflection spectrum filtered to provide a spatialgram; and - a fifth step of evaluating the multilayer thin film on the basis of the spatialgram.
Claim 12
Independent Claim
124 words
A method of evaluating a multilayer thin film, comprising: - a first step of projecting onto a multilayer thin film sample (11) an interference light beam obtained by synthesizing two light beams in a predetermined wave number region while continuously varying optical path differences thereof and detecting the interference light beam reflected by the sample (11) to provide an interferogram; - a second step of performing a Fourier transform on the interferogram to provide a reflection spectrum; - a third step of filtering the reflection spectrum; - a fourth step of performing a complex power reverse Fourier transform on the reflection spectrum filtered to provide a spatialgram; and - a fifth step of evaluating the multilayer thin film on the basis of the spatialgram.
References Cited (Backward Citations)
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