Compact reticle/wafer alignment system

Details Compact reticle/wafer alignment system Compact reticle/wafer alignment system

1991-05-23

1993-03-16

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

356401, G01N 2186

Patent

active

051947447

ABSTRACT:
A reticle/wafer alignment system provided with a laser beam source for emitting laser beams, a first optical system portion for a reticle/wafer alignment which consists of a first optical sub-system for receiving laser beams from the laser beam source and projecting the received laser beams onto alignment marks formed on a substrate and made up of diffraction gratings and a second optical sub-system for gathering laser beams diffracted by the alignment marks to form an image thereof, a photoelectric detection portion for performing a photoelectric conversion of the gathered laser beams, a position detecting portion for measuring the position of the substrate based on a signal outputted from the photoelectric detection portion, a second optical system portion for an image processing which consists of a third optical sub-system for illuminating the alignment marks and a fourth optical sub-system having a television camera for observing the image of the alignment marks, and an image processing portion for performing an image processing of video signals outputted from the television camera. The first and second optical system portions are made in such a manner to have a common part thereof. Thereby, an entire alignment system can be made to be compact. Consequently, a position measurement accuracy can be improved.

REFERENCES:
patent: 4262208 (1981-04-01), Suzuki et al.
patent: 4631416 (1986-12-01), Trutna, Jr.
patent: 4664524 (1987-05-01), Hattori et al.
patent: 4697087 (1987-09-01), Wu
patent: 4962318 (1990-10-01), Nishi
"Alignment System in a Stepper Apparatus" by Uchida et al; Semicon News 1989. 5; pp. 98-104.
"Holographic Nanometer Alignment for a Wafer Stepper" by N. Nomura et al; SDM87-149; pp. 31-36 (no publication date).
"Direct-Referencing Automatic Two-Points Reticle-to-Wafer Alignment Using a Projection Column Servo System" by Brink et al; SPIE vol. 633 Optical Microlithography V(1986); pp. 60-71.

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