Devices and methods for reading identification marks on semicond

Image analysis – Histogram processing – For setting a threshold

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382 1, 358101, 359382, 359388, G06K 900

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052651703

ABSTRACT:
Methods and apparatus for machine reading of identification marks incised on semiconductor wafers. Preferred apparatus makes it possible to view the mark either as a dark image on a light background (which is in itself novel) or as a light image on a dark background. Using a television camera and an optical character reader, the viewing method can be changed automatically if a preset confidence level is not reached, and provides a signal if neither method (or the combination of the two methods) gives a satisfactory result. The method is particularly useful for successively reading the identification marks on a number of wafers stacked in a cassette. Preferred apparatus for such reading comprises a wafer support which can be pushed upwards from underneath the cassette so that the wafer to be identified rests on one ledge of the support and the adjacent wafer rests on another higher ledge on the support, thus exposing and precisely locating the identification mark on the first wafer.

REFERENCES:
patent: 4606616 (1986-08-01), Parker
patent: 4618938 (1986-10-01), Sandland et al.
patent: 4687304 (1987-08-01), Piller et al.
patent: 4845770 (1989-07-01), Koshida
patent: 4872052 (1989-10-01), Liudzius et al.
Patent Abstracts of Japan, 12 (224), 721, published Jun. 25, 1988, which is an abstract of Japanese Patent Application No. 63/018,209 (NEC Corp) Search Report, EP 91 90 4111, Nov. 19, 1992.
Hine Design Proofreader Trade Brochure, May 1989.

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