Varying Etch Rates Simultaneously Across a Single Surface
Original Publication Date: 1988-Mar-01
Included in the Prior Art Database: 2005-Feb-14
This article describes a procedure for obtaining different etch rates at different locations on a common surface while subtractively etching that surface. The disclosed procedure permits the etching of composite structures of varying metal thicknesses from one side while using a single etchant. The procedure to be described is based on obtaining a reduced etch rate in selected areas of a common surface by use of a porous membrane, such as a metal mesh or screen, placed between such areas and the source of etchant agitation, e.g., spray nozzles. The controlled obstruction of etchant flow in such areas acts to slow the normal flow of etchant across them, resulting in a build-up of reaction products due to the slower renewal of spent etchant. This contributes to a reduced etch rate in such areas as are screened. Fig.