Method of protecting a solder ball during an etch process, by applying a resist around the base of the solder ball.

摘要

A method for forming a metallic contact on an integrated circuit consists of: (a) depositing first (13) and second (14) layers of metal; (b) plating and patterning a layer of solder (15) thereon; (c) reflowing the solder to form a set of spheroidal contacts having a bottom diameter in contact with the second metal layer; (d) etching the second metal layer using the solder balls as a mask; (e) applying a positive photoresist having a viscosity, and a solvent having a chemical compsn. such that the solvent wets the solder at the bottom dia., (f) exposing and stripping the photoresist using the solder balls as a self-aligned exposure mask, thereby forming a protective ring (16) about the bottom dia.; and (g) etching the first layer of metal so that the solder is resting on a shoulder of the first metal layer which forms a disc larger than the disc formed by the second metal layer.