Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1988-10-25
1989-10-10
Nelms, David C.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
250228, 250560, 356382, G01V 500
Patent
active
048734306
ABSTRACT:
A method for optically measuring at least one characteristic of a thin film on a reflecting substrate. A p-polarized beam of collimated light of known intensity is directed through an integrating sphere onto the film at substantially the Brewster's angle of the film. All the light is reflected into the sphere, including all diffusely reflected light as well as the light specularly reflected at a region inside the sphere where the specularly reflected light is incident. A reflective surface is provided for determining the thickness of the film as a function of the total intensity of light sensed within the sphere. An absorptive surface is provided at said region for absorbing the specularly reflected light for determining the porosity or surface roughness of the film based on the intensity of the diffused light sensed within the sphere not reflected from the substrate.
REFERENCES:
patent: 3985447 (1976-10-01), Aspnes
patent: 4129781 (1978-12-01), Doyle
patent: 4626101 (1986-12-01), Ogawa et al.
patent: 4707611 (1987-11-01), Southwell
patent: 4745291 (1988-05-01), Niiya
M. L. E. Chwalow et al., "Automatic Brewster's Angle Thin Film Thickness Measurement Spectrophotometer", IBM Technical Disclosure Bulletin, vol. 20, No. 8, Jan. 1978, pp. 3313-3314.
Juliana Anthony
Leung Wai C.
Pan Victor T.
Rosen Hal J.
Strand Timothy C.
International Business Machines - Corporation
Nelms David C.
Oen William L.
Otto, Jr. Henry E.
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