Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Patent
1991-02-27
1992-12-08
Howell, Janice A.
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
356347, 359564, G01B 9021
Patent
active
051700638
ABSTRACT:
An inspection device for detecting defects in a periodic pattern on a semiconductor wafer includes a laser oscillator. In the exposure process, light emitted from the laser oscillator is divided into a subject beam and a reference beam. The subject beam is guided to a semiconductor wafer having a periodic pattern thereon by mirrors and a beam expander. The light scattered from the specimen is collected by a lens on a photographic plate. The reference beam is guided to the photographic plate via a second beam expander and another mirror. The intensity of the reference beam is adjusted to a level at which the reference beams interferes on the photographic plate with the light scattered from defects in the periodic pattern and collected by the lens. Thus, a hologram of the defects in the pattern is recorded on the photographic plate. After development, the photographic plate is returned to its original position and used to form a holographic image of the defects with a transmitted regeneration light beam.
REFERENCES:
patent: 4674824 (1987-06-01), Goodman et al.
patent: 4857425 (1989-08-01), Phillips
patent: 4929081 (1990-05-01), Yamamoto et al.
D. L. Cavan et al., "Patterned Wafer Inspection Using Laser Holography And Spatial Frequency Filtering", Journal of Vacuum Science Technology B6 (6), Nov./Dec. 1988, pp. 1934-1939.
Kosaka Nobuyuki
Miyazaki Yoko
Tanaka Hitoshi
Tomoda Toshimasa
Hanig Richard
Howell Janice A.
Mitsubishi Denki & Kabushiki Kaisha
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