Method for aligning photomasks

Details Method for aligning photomasks Method for aligning photomasks

1987-07-06

1989-05-30

Dees, Jose G.

Radiation imagery chemistry: process, composition, or product th

Registration or layout process other than color proofing

430311, 430394, 250548, 356400, G03F 900

Patent

active

048350788

ABSTRACT:
Photomasks (11,12) are aligned on opposite sides of a wafer by directing light beams through zone plates (13 A-C) in one photomask and through aligned transparent slits (14 A-C) on the other photomask. Simultaneous detection of the beams by photodetectors (18 A-C) indicates alignment. A method for obtaining precise centering by scanning the slits with the beams, sampling light transmitted through the slits, and fitting the samples to a parabola by the use of a computer (27) is also described.

REFERENCES:
patent: 3264105 (1966-08-01), Houtz
patent: 3759767 (1973-09-01), Walls
patent: 3963489 (1976-06-01), Cho
patent: 4109158 (1978-08-01), Blitchington et al.
patent: 4311389 (1982-01-01), Fay et al.
patent: 4545683 (1985-10-01), Markle et al.

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