Apparatus for processing a signal for alignment

Optics: measuring and testing – By alignment in lateral direction – With light detector

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Details

356401, G02B 2106, G01B 1100

Patent

active

044875053

ABSTRACT:
An apparatus for processing a signal for aligning a mask having at least one standard mark thereon with a wafer having at least one reference mark thereon, includes a first sensor for sensing the standard mark, a second sensor for sensing the reference mark through the mask, a threshold value determining circuit for detecting a peak value from a signal stream put out by the first sensor and determining a first threshold value and for detecting a peak value from a signal stream put out by the second sensor and determining a second threshold value, a signal converting circuit for converting a signal of a higher level than the first threshold value from the signal stream put out by the first sensor into a first digital signal and for converting a signal of a higher level than the second threshold value from the signal stream put out by the second sensor into a second digital signal, and a composing circuit for composing the first digital signal and the second digital signal.

REFERENCES:
patent: 4167677 (1979-09-01), Suzki
patent: 4219719 (1980-08-01), Frosien et al.
patent: 4251129 (1981-02-01), Suzki et al.
patent: 4406546 (1983-09-01), Suzuki

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