Quantitation of airborne chemical contamination of chemically amplified resists using radiochemical analysis

Abstract

Many chemically amplified resists based on acid catalysis exhibit extreme sensitivity to trace quantities of airborne organic contaminants. This sensitivity is manifested as a rapid degradation in lithographic properties upon standing in clean room air. In this work we have studied the absorption of one such airborne contaminant, N-methylpyrollidone (NMP), by thin polymer films. NMP labeled with radioactive 14C was introduced at a concentration of 10 ppb into a stream of purified air, and the film of interest was immersed in that airstream for a predetermined time under controlled conditions. This method provides an ideal means for determining rates of NMP uptake, correlating resist lithographic performance with absorbed NMP content, and for examining the effects of film thickness and composition on rates of absorption.