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Method for making photomasks having regions of different light transmissivities

  • US 5,718,991 A
  • Filed: 12/27/1996
  • Issued: 02/17/1998
  • Est. Priority Date: 12/27/1996
  • Status: Expired due to Term
First Claim
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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.

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