Laser apparatus and method for measuring stress in a thin film u

Details Laser apparatus and method for measuring stress in a thin film u Laser apparatus and method for measuring stress in a thin film u

1991-02-13

1993-09-28

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250226, 356371, G01N 2186, G01B 1130

Patent

active

052488896

ABSTRACT:
An apparatus and a method for measuring the radius of curvature of a surface using a laser beam with a wavelength selectable from a plurality wavelengths are disclosed. The present invention avoids poor measurement due to destructive interference of the beams reflected at a thin film's upper and lower surfaces. The present invention is applicable to laser reflection stress measurement apparatuses of both scanning and beam-splitting types.

REFERENCES:
patent: 3857637 (1974-12-01), Obenreder
patent: 4425041 (1984-01-01), Nishiyama
patent: 4789237 (1988-12-01), Inoue
patent: 4865445 (1989-09-01), Kuriyama et al.
patent: 4900940 (1990-02-01), Nakamura
patent: 5072128 (1991-12-01), Hayano et al.
patent: 5118955 (1992-06-01), Cheng
patent: 5118957 (1992-06-01), Kawashima et al.
patent: 5134303 (1992-07-01), Blech et al.

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