Continuous alignment target pattern and signal processing

Details Continuous alignment target pattern and signal processing Continuous alignment target pattern and signal processing

1983-05-02

1986-03-25

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

356400, G01N 2186

Patent

active

045785902

ABSTRACT:
The present invention is directed to a combination of elements for use in an alignment system for a scanning mask aligner, which include a viewing system having an optical grid, apparatus for moving the mask and wafer alignment patterns across the optical grid, each pattern having front edge portions displaced with respect to rear edge portions in the direction of scanning so that only light corresponding to a plurality of said front edge portions is transmitted through the grid at one time and only light corresponding to a plurality of the rear edge portions being transmitted through the grid at a second later period of time, the grid corresponding to the directions and spacing of the pattern so that light transmitted through the grid is strongly modulated, and circuitry responsive to the transmitted light operative to output alignment signal errors.

REFERENCES:
patent: 4252442 (1981-02-01), Dandliker et al.
patent: 4301363 (1981-11-01), Suzuki et al.
patent: 4408885 (1983-10-01), Johannsmeier et al.

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