Alignment pattern detecting apparatus
First Claim
1. An alignment pattern detecting apparatus comprising an image pick-up device for scanning and picking up an optical image of a registration pattern formed on a wafer, the direction of the scanning being in a direction transverse to the lengthwise direction of the pattern, and means for symmetrically returning a video signal obtained from said image pick-up device to determine the degree of matching of said video signal with the video signal returned and for determining a return point associated with the best matching to detect said return point as the center of said alignment pattern.
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Abstract
An alignment pattern detecting apparatus comprises an image pick-up device for scanning and picking up an optical image of alignment pattern formed on a wafer to produce a time-base video signal, and means for sampling at predetermined intervals and converting from analog to digital form the video signal produced by the image pick-up device so that the video signal is returned symmetrically at a predetermined point to determine the degree of matching between the two signals thereby to obtain a point where the degree of matching is the best. This best matching degree point is detected as the center position of the alignment pattern.
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Citations
5 Claims
- 1. An alignment pattern detecting apparatus comprising an image pick-up device for scanning and picking up an optical image of a registration pattern formed on a wafer, the direction of the scanning being in a direction transverse to the lengthwise direction of the pattern, and means for symmetrically returning a video signal obtained from said image pick-up device to determine the degree of matching of said video signal with the video signal returned and for determining a return point associated with the best matching to detect said return point as the center of said alignment pattern.
Specification