Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Radiation mask
Patent
1996-12-27
1998-02-17
Rosasco, S.
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Radiation mask
430 7, G03F 900
Patent
active
057189919
ABSTRACT:
An improved method for preparing multiple-exposure photomasks having at least three levels of transmissivity is disclosed. A conventional bi-exposure photomask is first formed which contains a macroscopically exposed area, a microscopically exposed area, and a masked area on a transparent substrate. Then a diffractive-refractive light-scattering optical element is formed above the microscopically exposed area so as to provide an exposure area with an intermediate light transmissivity. In a preferred embodiment, the diffractive-refractive light-scattering optical element above the microscopically exposed area is formed by first forming a transparent positive photoresist above the bi-exposure photomask. The transparent positive photoresist is exposed to an irradiation from the bottom of the transparent substrate, and is developed. Finally, the transparent positive photoresist is heated to cause a melt-flow thereof which forms a concave optical element above the microscopically exposed area. The transmissivity of the intermediate exposure area can be adjusted by adjusting the dimensions of the microscopical openings provided therein and the distance between the microscopic openings. More than one microscopic pattern can be provided on the same substrate so as to allow two or more intermediate transmissitivities to be obtained.
REFERENCES:
patent: 4415262 (1983-11-01), Koyama et al.
Cheng Hua-Chi
Cheng Wen-Tung
Lee Rong-Jer
Lin Dhei-Jhai
Industrial Technology Research Institute
Liauh W. Wayne
Rosasco S.
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