Electrodeposition of Gold from a Thiosulfate-Sulfite Bath for Microelectronic Applications

Abstract

The feasibility of using a thiosulfate-sulfite bath to electrodeposit soft gold for microelectronic applications has been investigated. This bath is stable at near-neutral pH. shows good compatibility with positive photoresists, and does not contain any additives. It was found that the bath produced gold bumps with straight sidewalls, flat top surfaces, and a good reproduction of the resist pattern was achieved. The thickness uniformity, roughness, stress, hardness, adhesion, and shape of the plated structures were found to be compatible with the requirements for a wide range of microelectronic applications, including wafer bumping.