Method and apparatus for aligning mask and wafer

Details Method and apparatus for aligning mask and wafer Method and apparatus for aligning mask and wafer

1975-03-07

1976-11-09

Corbin, John K.

Optics: measuring and testing

Refraction testing

Prism engaging specimen

350 14, 350175DR, 356114, G01B 1127, G02B 310

Patent

active

039907988

ABSTRACT:
In a semiconductor photolithographic mask alignment system, a unique bifocus element is included in the microscope for permitting simultaneous focusing on the mask and semiconductor wafer surface, even though the mask and wafer separation is greater than the microscope depth of field. The bifocus element is preferably located at the rear focal plane of the microscope objective and is designed to image, at the same location, light from the mask polarized in a first direction and light from the wafer polarized at right angles to the first direction.

REFERENCES:
patent: 2601175 (1952-06-01), Smith
patent: 3488104 (1970-01-01), Doherty
patent: 3520592 (1970-07-01), Leib et al.
patent: 3558210 (1971-01-01), Smith
patent: 3751170 (1973-08-01), Hidaka

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