Apparatus for detecting a mutual positional relationship of two

Details Apparatus for detecting a mutual positional relationship of two Apparatus for detecting a mutual positional relationship of two

1980-01-22

1982-06-01

Corbin, John K.

Optics: measuring and testing

By dispersed light spectroscopy

Utilizing a spectrometer

250237G, 356363, G01B 902

Patent

active

043324738

ABSTRACT:
An apparatus for detecting a mutual positional relationship of a semiconductor wafer and mask comprises first and second diffraction gratings formed on the wafer and mask and located parallel to each other; a laser source for radiating a coherent light vertically toward the first and second diffraction gratings; a drive mechanism for periodically varying a relative distance between the first and second diffraction gratings; a pair of photosensors for receiving a first interference beam resulting from those +n-order diffracted beams included in said diffracted beams and a second interference beam resulting from those -n-order diffracted beams included in said diffracted beams; and a differential amplifier calculating the difference between the intensities of the first and second interference lights thereby detecting a mutual positional displacement between the first and second diffraction grating.

REFERENCES:
patent: 4200395 (1980-04-01), Smith et al.

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