US4744660A
Expired / Lapsed
US
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Apparatus for measuring difference in shallow level
Assignee: Hitachi Ltd
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Filing: 1986-04-11
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Granted: 1988-05-17
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Expires: 2006-04-11
Abstract
Abstract An apparatus for measuring a difference in level in a sample comprises a light source section which provides illumination light of a variable-wavelength. The illumination light is irradiated onto the sample. A group of filters is provided for shielding diffraction light rays of O-order or other than O-order of the light reflected from the sample. The intensity of interference light of the light rays not shielded by the filter group is detected by a light detector which in turn converts it into an electric signal. An arithmetic operation unit receives the electric signal while the wavelength of the illumination light from the light source section is continuously varied. In the arithmetic unit, wavelengths at which the electric signal or detected light intensity takes extreme values are determined, and the level difference in the sample is determined on the basis of those wavelengths.
Inventors
- 👤 Minori Noguchi
- 👤 Toru Otsubo
- 👤 Susumu Aiuchi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 09:22
CPC Classifications
G; G01; G01B; G01B11/00; G01B11/22
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
204 words
A level difference measuring apparatus comprising: light source means for projecting coherent light onto a rugged portion of a sample, said light source means including wavelength varying means for varying a light wavelength λ of the projected light and for providing a signal indicative of the light wavelength λ; a spatial filter, arranged at a position in an imaging relation with said light source, for shielding 0-order diffraction light of the light reflected from the rugged portion of the sample or diffraction light from the rugged portion of the sample other than the 0-order diffraction light; an imaging optical system for imaging the light image reflected from the rugged portion of the sample; detection means, having an opening for passing only the light image reflected from the rugged portion at a position where the imaging by said imaging optical system is effected, for detecting the intensity of the light passing said spatial filter and said opening and for providing a detection signal (I) indicative thereof; and arithmetic means for calculating the depth of the rugged portion of the sample from the detection signal (I) from the detection means and the signal indicative of the light wavelength λ as varied by said wavelength varying means.
Claim 2
Dependent Claim
204 words
A level difference measuring apparatus comprising: light source means for projecting coherent light onto a rugged portion of a sample, said light source means including wavelength varying means for varying a light wavelength λ of the projected light and for providing a signal indicative of the light wavelength λ; a spatial filter, arranged at a position in an imaging relation with said light source, for shielding 0-order diffraction light of the light reflected from the rugged portion of the sample or diffraction light from the rugged portion of the sample other than the 0-order diffraction light; an imaging optical system for imaging the light image reflected from the rugged portion of the sample; detection means, having an opening for passing only the light image reflected from the rugged portion at a position where the imaging by said imaging optical system is effected, for detecting the intensity of the light passing said spatial filter and said opening and for providing a detection signal (I) indicative thereof; and arithmetic means for calculating the depth of the rugged portion of the sample from the detection signal (I) from the detection means and the signal indicative of the light wavelength λ as varied by said wavelength varying means.
Claim 3
Dependent Claim
30 words
A level difference measuring apparatus according to claim 1, wherein said light source means includes a xenon lamp and a diffraction grating for spectroscopically dispersing light from said xenon lamp.
Claim 4
Dependent Claim
44 words
A level difference measuring apparatus according to claim 1, wherein said light source means includes a dye laser using a 2nd harmonic wave of one laser excitation source selected from a group consisting of He-Cd laser, N 2 laser, Ar laser and YAG laser.
Claim 5
Dependent Claim
54 words
A level difference measuring apparatus according to claim 1, wherein an illumination optical system for introducing the light from the light source means onto the sample includes an objective lens having an F value which is greater than 4.0 and the upper limit of which is determined by a sensitivity of said detection means.
Claim 6
Dependent Claim
46 words
A level difference measuring apparatus according to claim 1, further comprising a sample table for mounting the sample thereon and provided with an optical system for observing said sample, said optical system including a graduated plate in interlocking relation with said opening of said detection means.
Claim 7
Dependent Claim
27 words
A level difference measuring apparatus according to claim 5, wherein said graduated plate is provided with a mark of the same shape as that of the opening.
Claim 8
Dependent Claim
26 words
A level difference measuring apparatus according to claim 5, wherein said graduated plate is provided with a mark of a non-specified shape indicating a closed area.
Claim 9
Dependent Claim
205 words
A level difference measuring apparatus comprising: a light source means for projecting coherent light onto a rugged portion of a sample; a first spatial filter, arranged at a position in an imaging relation with said light source means, for shielding 0-order diffraction light of the light reflected from the rugged portion of the sample or diffraction light of the light reflected from the rugged portion of the sample other than the 0-order diffraction light; an imaging optical system for imaging the light image reflected from the rugged portion of the sample; detection means, having an opening for passing only the light image reflected from the rugged portion of the sample at a position where the imaging by said imaging optical system is effected, for detecting the intensity of the light passing said first spatial filter and said opening and for providing a detection signal (I) indicative thereof; wavelength varying means for varying a light wavelength λ and for providing a signal indicative of the light wavelength λ, and arithmetic means for calculating the depth of the rugged portion of the sample from the detection signal (I) from the detection means and the signal indicative of light wavelength λ as varied by said wavelength varying means.
Claim 10
Dependent Claim
205 words
A level difference measuring apparatus comprising: a light source means for projecting coherent light onto a rugged portion of a sample; a first spatial filter, arranged at a position in an imaging relation with said light source means, for shielding 0-order diffraction light of the light reflected from the rugged portion of the sample or diffraction light of the light reflected from the rugged portion of the sample other than the 0-order diffraction light; an imaging optical system for imaging the light image reflected from the rugged portion of the sample; detection means, having an opening for passing only the light image reflected from the rugged portion of the sample at a position where the imaging by said imaging optical system is effected, for detecting the intensity of the light passing said first spatial filter and said opening and for providing a detection signal (I) indicative thereof; wavelength varying means for varying a light wavelength λ and for providing a signal indicative of the light wavelength λ, and arithmetic means for calculating the depth of the rugged portion of the sample from the detection signal (I) from the detection means and the signal indicative of light wavelength λ as varied by said wavelength varying means.
Claim 11
Dependent Claim
69 words
A level difference measuring apparatus according to claim 8, further comprising a half mirror arranged so that the light emitted from said light source means is illuminated onto the rugged portion of the sample along an axis perpendicular to the rugged portion and the light image reflected from the rugged portion of the sample is imaged by said imaging optical system having a light axis along said perpendicular axis.
Claim 12
Dependent Claim
26 words
A level difference measuring apparatus according to claim 8, wherein said light source means directs the light to a spatial filter having an annular diaphragm shape.
Claim 13
Dependent Claim
18 words
A level difference measuring apparatus according to claim 8, wherein said light source means comprises a laser oscillator.
Claim 14
Dependent Claim
27 words
A level difference measuring apparatus according to claim 8, wherein said light source means emits substantially parallel light and said first spatial filter has a circular shape.
Claim 15
Dependent Claim
28 words
A level difference measuring apparatus according to claim 12, wherein said light wavelength varying means varies the light wavelength in the range of 250 nm to 800 nm.
Claim 16
Dependent Claim
21 words
A level difference measuring apparatus according to claim 8, wherein said wavelength varying means is provided in said light source means.
Claim 17
Dependent Claim
27 words
A level difference measuring apparatus according to claim 14, wherein said value of l is calculated either by fast Fourier transformation (FET) or maximum entropy method (MEM).
Claim 18
Dependent Claim
68 words
A level difference measuring apparatus according to claim 8, whwerein said arithmetic means calculates the depth h of the rugged portion from the relation of h=1/2nl=1/2n (λ j+2 λj/λj-λ j+2 ) where λj and λ j+2 represent the wavelengths providing peak values of the detected signal I, l is a distance between the peak values of the detected signal I, and n is a refraction index of light.
Claim 19
Dependent Claim
21 words
A level difference measuring apparatus according to claim 8, wherein said wavelength varying means selects any wavelength through a diffraction grating.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-05-17 | 1991-11-16 | 1992-05-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-05-17 | 1995-11-16 | 1996-05-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-05-17 | 1999-11-16 | 2000-05-17 | $7700.00 | Window Closed / Lapsed |