Optical: systems and elements – Diffraction – Using fourier transform spatial filtering
Patent
1995-04-24
1996-03-12
Lerner, Martin
Optical: systems and elements
Diffraction
Using fourier transform spatial filtering
355 53, 355 71, G02B 2746, G03B 2742, G03B 2772
Patent
active
054991374
ABSTRACT:
In an exposure method of illuminating a pattern formed on a mask with illumination light from an illumination optical system, and projecting/exposing an image of the pattern on a photosensitive substrate through a projection optical system, the pattern includes a transmission portion having a transmittance of about 1 with respect to the illumination light and a phase shift transmission portion which provides a phase difference of about (2n+1).pi. (n is an integer) with respect to the light transmitted through the transmission portion, and has a pattern width not more than a resolving limit of the projection optical system. The illumination light passing through a predetermined plane which is substantially coincident with a Fourier transform plane of the mask in the illumination optical system or a conjugate plane thereto, is limited to at least one local region having the center at a position shifted from an optical axis of the illumination optical system, thereby inclining the illumination light radiated on the mask at an angle corresponding to fineness of the pattern in a predetermined direction.
REFERENCES:
patent: 4947413 (1990-08-01), Jewell et al.
patent: 4952815 (1990-08-01), Nishi
patent: 5126220 (1992-06-01), Tokitomo et al.
patent: 5307207 (1994-04-01), Ichihara
patent: 5335044 (1994-08-01), Shiraishi
Lerner Martin
Nikon Corporation
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