Comparative study of thermally cured and electron-beam-exposed hydrogen silsesquioxane resists

A comparative study of the changes in the chemical structure and properties of hydrogen silsesquioxane (HSQ) resists induced by thermal curing and electron-beam exposure has been conducted. Studies using Fourier transform infrared (FTIR) spectroscopy suggested similar behavior in the redistribution of bonds for both processes. Quantitative analysis of both spectra revealed the existence of a critical temperature and electron dose for the achievement of development for pattern generation. As a complementary technique, x-ray reflectivity measurements were performed to monitor changes in the film density. Notwithstanding the similar changes in bond redistribution observed from the FTIR spectra for both thermal curing and electron-beam exposure, the film densification processes seem to occur in quite distinctive fashions. This was confirmed through dry etching experiments; the results of which were consistent for both Freon and $Cl2∕Ar$ reactive ion etching. While effective film densification occurred only at curing temperatures above $400°C$⁠, insignificant changes in density and etch durability were observed for electron-beam-exposed HSQ resists at electron doses commonly used for pattern generation. Wet etching characteristics engendered by hydrofluoric acid showed that both chemical bond redistribution and densification lead to decreases in etch rates.