X-ray or gamma ray systems or devices – Specific application – Lithography
Patent
1987-10-23
1989-11-14
Church, Craig E.
X-ray or gamma ray systems or devices
Specific application
Lithography
378 34, 430 5, G21K 500
Patent
active
048812579
ABSTRACT:
An X-ray exposure mask for use in a stepper in X-ray lithography is formed so that deformation of mask patterns on a surface of the X-ray mask is prevented, so that when these patterns are transferred to a semiconductor wafer substantially no deformation of the patterns will occur, allowing higher integration of patterns. The surface of the X-ray mask is divided into a centrally located first region and a surrounding second region. A layer of X-ray absorbing material is superposed on the surface of the X-ray mask and includes a first layer portion coextensive with the first central region and patterned for selectively exposing the first central region of the membrane surface in a corresponding pattern for selected transmission of an X-ray beam therethrough. A second layer portion of the layer of X-ray absorbing material, coextensive with the second, surrounding region of the membrane, is patterned for selectively exposing the second, surrounding region to reduce the density of the X-ray absorbing material on that second, surrounding region. Preferably, the respective densities of the first and second layer portions of the X-ray absorbing material are substantially the same, although a difference of up to 30% therebetween will yield satisfactory results.
REFERENCES:
patent: 3742229 (1973-06-01), Smith et al.
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patent: 4152601 (1979-05-01), Kadota et al.
patent: 4260670 (1981-04-01), Burns
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patent: 4515876 (1985-05-01), Yoshihara et al.
patent: 4522842 (1985-06-01), Levinstein et al.
"Use of Random Patterns and Grilles for Mask Alignment in X-Ray Lithography", by Hunziker, IBM Technical Disclosure Bulletin, vol. 20, No. 3, Aug. 1977.
Church Craig E.
Freeman John C.
Fujitsu Limited
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