Position detector employing a sector Fresnel zone plate

Details Position detector employing a sector Fresnel zone plate Position detector employing a sector Fresnel zone plate

1989-08-04

1991-12-24

Evans, F. L.

Optics: measuring and testing

By alignment in lateral direction

With registration indicia

2504911, 378 34, G01B 1100

Patent

active

050746677

ABSTRACT:
A position detector for use with an X ray exposure apparatus and the like includes sector Fresnel zone plates (SFZP) which are provided on a mask and a wafer minutely spaced in position in the direction of the optical axis of an exposure X ray, as alignment marks. A laser ray of at least one of wavelength is applied to the surfaces of the SFZPs at an angle with respect to the surfaces. The SFZPs are designed such that the principal focal planes of Fesnel diffraction images of the SFZPs to a single wavelenth laser ray agree with each other. In the case of illumination rays of a plurality of wavelengths, an objective lens is provided in a detection optical system which objective has such an axial chromatic aberration that focal planes of the objective lens to the plural wavelength rays agree with respective Fresnel diffraction focal planes of the SFZPs to the rays. The image formed on the superposed focal plane of the objective lens is converted into an electric signal, which is handled to detect a relative position between the mask and wafer in the direction perpendicular to the surface thereof.

REFERENCES:
patent: 4326805 (1982-04-01), Feldman et al.
patent: 4600309 (1986-07-01), Fay
patent: 4815854 (1989-03-01), Tanaka et al.
patent: 4918301 (1990-04-01), Miyatake

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