Ester degradation in the DESIRE process

摘要

Abstract: This paper attempts to investigate the possible degradation of the ester formed in PLASMASK 200G photoresist during extended silylation times with HMDS (hexamethyldisilazane). The breakdown of the ester results in the formation of a phenolic moiety and an amide. This may lead to silylation of this newly released phenolic OH-group in the unexposed regions, and hence a decrease in the contrast might occur. This would have a detrimental effect on critical dimension (CD) control. It was found that under higher ammonia concentrations, an ester degrades to release a phenolic group and also an amide. The silylation times involved are much greater than that used in the DESIRE process, and as such degradation of the ester in the DESIRE process is itself quite minimal. It is, however, suggested that a silylating agent that does not form a base on cleavage be used instead to reduce the degradation effect. !10