Importance

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Abstract

A semiconductor wafer placed on a table is rotated by a stepper motor stepwise by a broad pitch. At this time, a CCD line sensor transmits output signals to comparators. A CPU monitors output signals of the comparators and detects a notch formed in the wafer. After the notch is detected, the wafer is rotated stepwise by a fine pitch, and outer peripheral positional data of a notched region (outputs of an analog-to-digital converter) are sampled and stored in a RAM. The CPU computes a notch position from the outer peripheral positional data stored in the RAM. In this way, a V-shaped notch formed in a semiconductor wafer is detected speedily and with high precision.

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First Claim