Radiant energy – Photocells; circuits and apparatus – Photocell controls its own optical systems
Patent
1994-08-17
1995-12-19
Westin, Edward P.
Radiant energy
Photocells; circuits and apparatus
Photocell controls its own optical systems
250557, 356401, G01N 2186
Patent
active
054770572
ABSTRACT:
The invention described herein is an alignment system used in semiconductor manufacturing. It is the core component used to align a mask containing a circuit pattern to a wafer during a scanning sequence. The alignment system images an alignment reticle pattern onto a wafer which contains alignment marks. During scanning, the light from the alignment reticle image is reflected and scattered by the wafer and its alignment marks. Multiple detectors are placed at a pupil plane of the alignment system to collect the reflected and scattered light in the bright-field and dark-field regions. The resulting signals and their analysis results in determination of accurate alignment of a wafer. The alignment system does not use or "look through" the projection optics of the scanning photolithographic device. The broadband spectrum used for alignment illumination cannot be used in the projection optics designed for the deep UV wavelengths without undesirable results. The broadband spectrum illumination utilized in the alignment system results in improved detection of wafer alignment marks independent of the various process wafer structures that can be encountered.
REFERENCES:
patent: 4504148 (1985-03-01), Kuroki et al.
patent: 4545683 (1985-10-01), Markle
patent: 4549084 (1985-10-01), Markle
patent: 4578590 (1986-03-01), Wu
patent: 4579453 (1986-04-01), Makita
patent: 4697087 (1987-09-01), Wu
Angeley David
Drazkiewicz Stan
Gallatin Gregg
Fattibene Paul A.
Steady Jacqueline M.
SVG Lithography Systems, Inc.
Westin Edward P.
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