Defect detection system

Details Defect detection system Defect detection system

1979-01-04

1982-02-09

Corbin, John K.

Optics: measuring and testing

Inspection of flaws or impurities

Having predetermined light transmission regions

250224, 356342, G01N 2188

Patent

active

043147631

ABSTRACT:
A laser beam projected through a prism in a direction normal to the surface of a circular wafer is focused into a spot area and scanned along a spiral path on this surface. The focusing means comprises a relatively large aperture lens and the prism is on the lens axis. The retroreflected specular light passes through the lens and is prevented from reaching a light detector in the image plane of the lens by the prism. When the beam illuminates a microscopic surface defect on the wafer, the light is diffracted and reflected therefrom, and the lens captures that portion of the reflected light within the solid angle subtended by the lens, and passes that portion thereof not blocked by the prism, to the light detector. The output of the detector may be employed to intensity modulate the beam of a cathode-ray tube display, the beam of which is spirally scanned in synchronism with the scanning of the light beam.

REFERENCES:
patent: 2913568 (1959-11-01), Kates
patent: 3176306 (1965-03-01), Burns
patent: 3229564 (1966-01-01), Meltzer
patent: 3561876 (1971-02-01), Hoffman
patent: 3565568 (1971-02-01), Hock
patent: 4002827 (1977-01-01), Nevin et al.
patent: 4128834 (1978-12-01), Katagi
Conference on Laser and Electrooptical Systems, 7-9, Feb. 1978, OSA/IEE San Diego, Calif., pp. 90, 91, 92.
Electronics, Mar. 16, 1978 pp. 48, 50.
Patrick, W. J. and Patzner, E. J., "The Detection of Surface Detects on Silicon Wafers by Scattered Light Measurements," Semi-conductor, Silicon 1973.

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