Method of detecting position of a mark

Details Method of detecting position of a mark Method of detecting position of a mark

1989-01-25

1990-06-12

Hayes, Monroe H.

Photocopying

Projection printing and copying cameras

Step and repeat

355 77, G03B 2742

Patent

active

049337157

ABSTRACT:
A mark detecting method and device suitably applicable to the alignment of a reticle in a semiconductor device manufacturing exposure apparatus, called a stepper, is disclosed. A mark is provided by repeated patterns having specific pitches. These patterns are set so that at least one pitch of the patterns differs, on a light-receiving surface of an image sensor which receives an image of the mark, from a multiple, by an integral number, of the sampling pitch (pitch of picture elements) of the image sensor. In one preferred form, the mark is formed by repeated patterns of a number N (.gtoreq.2), wherein at least one pitch Pp of the patterns satisfies, on the light-receiving surface of the image sensor, a relationship Pp=(m+n/N).times.Pix where m is an arbitrary number, n is an integral number which satisfies 1.ltoreq.n.ltoreq.N, and Pix is the sampling pitch of the image sensor. The image of such a mark is photoelectrically converted to thereby determine the position of the mark. With the proposed concept, any error which might be caused upon quantization of the mark image by the picture elements of the image sensor can be canceled or compensated at the time of calculation of the mark center. Therefore, the precision of the mark center detection can be improved.

REFERENCES:
patent: 4704020 (1987-11-01), Murakami et al.
patent: 4704027 (1987-11-01), Phillips
patent: 4711567 (1987-12-01), Tanimoto
patent: 4814829 (1989-03-01), Kosugi et al.

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