Hollow Cathode Etching of Si and SiO2 Using CF 4 and H 2

Abstract

Si and films have been etched using and mixtures in a hollow cathode etching (HCE) reactor. We have measured etch rates and characterized the Si surfaces after HCE by x‐ray photoemission spectroscopy (XPS). Addition of to did not significantly enhance the etch rate ratio of to Si. The fluorocarbon film, which is responsible for the achievement of etch selectivity in reactive ion etching (RIE) reactors (1), has not been observed by XPS for Si surfaces etched in our HCE reactor at high RF power levels. This result is similar to that found in magnetron ion etching (MIE) at high power (2). C‒C and C‒H groups were the predominant species detected on Si surfaces etched in the HCE reactor; only small amounts of were present. Low fluorination of the carbonaceous film is believed to be due to high dissociation rates of the parent molecules in both the HCE and the MIE reactors. The low fluorination of the carbonaceous deposits on surfaces results in low etch rates for . When both carbon and fluorine arrive at the surface as in RIE, the oxygen in the can form volatiles by reactions with carbon, while the Si can be removed by F atoms. When mostly carbon is deposited on the surface, as in HCE and MIE, the Si in the is removed at a relatively slower rate. The thicknesses of the deposits on the Si surface were found to be smaller for the HCE reactor than for RIE reactor at high percentages. Slow deposition of carbonaceous species on Si can account for the relatively high Si etch rates. The high Si etch rates and the effect of low fluorination of the carbonaceous deposits on for can account for the low etch rate ratios of to Si in the HCE reactor.