Etching of xerogel in high-density fluorocarbon plasmas

Abstract

The etching of various xerogel films has been studied in high-density fluorocarbon plasmas. The xerogel etch rate is in part enhanced by the porosity. In discharges resulting in low surface polymerization, such as CF4 or oxygen-rich fluorocarbon plasmas, an additional enhancement up to 60% is observed. When the polymerization of the discharge is increased, this additional enhancement disappears and the xerogel etch rate becomes more suppressed. The suppression is more pronounced for xerogel films with a higher porosity and a larger pore size. X-ray photoelectron spectroscopy analysis on partially etched samples shows that the suppression in etch rate is accompanied by an increasing amount of fluorocarbon material at the xerogel surface, especially in the pores of the xerogel structure. Finally, a 30% porous xerogel film was patterned using CHF3 as an etching gas. Slight bowing of the sidewalls was observed.