Method for making photomasks having regions of different light transmissivities
First Claim
1. A method for preparing multiple-exposure photomasks having at least three levels of transmissivity comprising the steps of:
- (a) forming a hi-exposure photomask containing a microscopically exposed area and a masked area on a transparent substrate, wherein said microscopically exposed area comprises a plurality of through holes surrounded by a portion of said masked area; and
(b) forming a refractive light-scattering optical element above said microscopically exposed area so as to cause a light ray through said microscopically exposed area to be uniformly distributed.
3 Assignments
0 Petitions
Accused Products
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.
-
Citations
20 Claims
-
1. A method for preparing multiple-exposure photomasks having at least three levels of transmissivity comprising the steps of:
-
(a) forming a hi-exposure photomask containing a microscopically exposed area and a masked area on a transparent substrate, wherein said microscopically exposed area comprises a plurality of through holes surrounded by a portion of said masked area; and (b) forming a refractive light-scattering optical element above said microscopically exposed area so as to cause a light ray through said microscopically exposed area to be uniformly distributed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. A multiple-exposure photomask having at least three levels of transmissivity comprising:
-
(a) a masked area for low light transmissivity and an area of partial light transmissivity, formed on a transparent substrate; (b) wherein said partial light transmissivity area comprises a refractive light-scattering optical element formed above a microscopically exposed area, which comprises a plurality of through holes surrounded by a portion of said masked area. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
-
-
20. A method for making color filters including the steps of exposing a photoresist to a light irradiation via a multiple-exposure photomasks wherein said multiple-exposure photomasks comprises:
-
(a) a masked area for low light transmissivity and an area of partial light transmissivity, formed on a transparent substrate; (b) further wherein said partial light transmissivity area comprises a refractive light scattering optical element formed above a microscopically exposed area, which comprises a plurality of through holes surrounded by a portion of said masked area.
-
Specification