Study of Dry Photoresist Stripping Processes for Hydrogen Silsesquioxane Thin Films

Abstract

AbstractThe impact of dry stripping process chemistries on the selective removal DUV photoresist (PR) in the presence of hydrogen silsesquioxane (HSQ) have been studied along with HSQ film properties in order to develop a new, effective process to minimize changes in HSQ during the PR stripping processes. The results show that oxygen-free gas mixtures, specifically H2/N2 gas mixtures, have the best combination of PR:HSQ ash selectivity and minimized changes in HSQ films. However, gas mixtures containing CF4 or O2 greatly reduce PR/HSQ ash selectivity. The process temperature is another parameter that strongly influences ash selectivity. While the higher ash temperature greatly enhances selectivity in oxygen-free gas mixtures, the ash selectivity is only marginally enhanced with increasing ash temperature in the presence of O2. Furthermore, the k-value of HSQ suffers in the presence of O2 due to the oxidization of HSQ films. The data also shows that lower pressure will help to increase ash selectivity. In this study, processes have been demonstrated, which yield a PR:HSQ selectivity greater than 150, while maintaining the dielectric constant of HSQ at 2.8.