Photocopying – Projection printing and copying cameras – Identifying – composing – or selecting
Patent
1987-06-10
1989-03-21
Hix, L. T.
Photocopying
Projection printing and copying cameras
Identifying, composing, or selecting
355 53, G03B 2752, G03B 2770
Patent
active
048148296
ABSTRACT:
A projection exposure apparatus for projecting a pattern of a reticle upon a wafer by use of a projection lens system, is disclosed. The apparatus is arranged so that a mark illuminating light is projected upon the wafer from between the projection lens system and the wafer and not by way of the projection lens system. The light diffracted by an edge of a wafer alignment mark is photoelectrically detected by way of the projection lens system, whereby an electrical signal corresponding to an image of the alignment mark is obtained. On the basis of the detected signal, the wafer is aligned with the reticle. This arrangement allows detection of the alignment mark without being affected by a photoresist applied to the wafer surface. Thus, the reticle-to-wafer alignment can be made accurately. Also, a novel and unique alignment method is disclosed. The disclosed method assures high-accuracy reticle-to-wafer alignment.
REFERENCES:
patent: 4441250 (1984-04-01), Imhashi
patent: 4558949 (1985-12-01), Uehara et al.
patent: 4699515 (1987-10-01), Tanimoto et al.
Ina Hideki
Kosugi Masao
Ogawa Shigeki
Outsuka Kazuhito
Sakai Fumio
Canon Kabushiki Kaisha
Hix L. T,.
Rutledge D.
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