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Dual Density Masks for Photoresist

IP.com Disclosure Number: IPCOM000088824D
Original Publication Date: 1977-Aug-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Abolafia, OR: AUTHOR [+3]

Abstract

A tri-level optical mask can be used to selectively expose photoresist with either full intensity light or partial intensity light. When fabricating printed circuitry on chrome-copper-chrome metallized ceramic substrates with a positive photoresist, a tri-level mask can be used to expose the photoresist completely in areas where one desires circuit lines and partially in areas where one desires lands or interconnecting pads.

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Dual Density Masks for Photoresist

A tri-level optical mask can be used to selectively expose photoresist with either full intensity light or partial intensity light. When fabricating printed circuitry on chrome-copper-chrome metallized ceramic substrates with a positive photoresist, a tri-level mask can be used to expose the photoresist completely in areas where one desires circuit lines and partially in areas where one desires lands or interconnecting pads.

After the photoresist is exposed through the tri-level mask, the completely exposed portion is removed during development. The circuit lines and land areas remain covered. The chrome-copper-chrome would then be etched from all of the uncovered areas. Next, the photoresist which was partially exposed is removed from the land-areas with further development, and the chrome is etched from these areas, thereby exposing the copper.

The process described below takes advantage of the inherently binary exposure characteristics of diazo film. The binary characteristics of diazo film contrasts to the gray scale characteristics of silver halide film. Utilizing the binary exposure characteristics of diazo film, one is certain to obtain the proper level of gray scale in the mask. The process for making a mask consists of the following steps: 1. Produce a silver halide personality negative plate by the normal manner. The pattern includes lines and lands. (A negative plate has a black background with clear "transparent" lan...