Double-focus measurement apparatus utilizing chromatic aberratio

Details Double-focus measurement apparatus utilizing chromatic aberratio Double-focus measurement apparatus utilizing chromatic aberratio

1992-02-07

1993-06-08

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Photocell controls its own optical systems

356401, G01J 120

Patent

active

052181936

ABSTRACT:
A double-focus detector utilizing a lens system having axial chromatic aberration vertically illuminates a mask and a wafer disposed at a minute interval in the direction of the optical axis of the lens system. The mask is illuminated with a single ray of wavelength 500 nm or more and the wafer is illuminated with a given band flux or a plurality of rays of wavelength larger than that selected for the mask and one of focus planes of the lens system is an image forming plane of the single ray and the other focus plane of the lens system is the same image forming plane of the given band ray or the plurality of rays so that the relative position between the mask and the wafer can be detected.

REFERENCES:
patent: 5004348 (1991-04-01), Magome
patent: 5114236 (1992-05-01), Matsugu et al.

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