Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1992-09-18
1994-12-13
Evans, F. L.
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
356369, G01J 3447, G01N 2121
Patent
active
053733592
ABSTRACT:
To sense characteristics of a sample, an ellipsometer includes a pivotal diffraction grating positioned to receive white light from the analyzer without further focusing of the light after the light leaves the sample. The diffraction grating is focused on the sensor at a predetermined angle with a precision of at least plus or minus one-half degree using an alignment-sensing means positioned between the analyzer and diffraction grating. The sensor includes an aperture through which the incident beam of light is transmitted, light-sensitive areas on opposite sides of said sensor and a comparator for comparing the signal from said light-sensitive areas. Equality of the light from the light-sensitive areas indicates that the incident beam of light is perpendicular to the diffraction grating. A second diffraction grating and a second sensing means may receive the specularly reflected white light from a first diffraction grating and reflect it to another diffraction grating to investigate another spectrum of light. A spectroscopic ellipsometer uses a stacked photodiode in which the first photodiode and second photodiode have overlapping spectral ranges.
REFERENCES:
patent: 2837959 (1958-06-01), Saunderson et al.
patent: 3846024 (1974-11-01), Turner
patent: 4227079 (1980-10-01), Dukes et al.
patent: 4571074 (1986-02-01), Thevenon
patent: 4606641 (1986-08-01), Yamada et al.
Christenson Reed A.
Doerr David W.
Johs Blaine D.
Woollam John A.
Carney Vincent L.
Evans F. L.
J. A. Woollam Co.
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