Etching of silicon and silicon dioxide by halofluorocarbon plasmas

Abstract

The etching of silicon and silicon dioxide by halofluorocarbon (CF4, CF3Cl, CF3Br) discharges has been studied using discharge-sensitive techniques (actinometry, mass spectroscopy) and surface-sensitive techniques (in situ Auger electron spectroscopy, quartz crystal microbalances). The effect of low-energy ion bombardment has also been assessed by the application of bias voltages on samples used for surface analysis. The chemistry of the discharge has been shown to be affected by the etching reactions. Enrichments in chlorine- and bromine-containing species, due to the consumption of fluorine in etching, were observed. Plasma treatments induced the formation of a layer of silicon oxyfluoride with a stable composition on top of silicon dioxide, independent of the gas or the ion bombardment energy. Silicon halide layers were formed on the silicon surface. The increase in the energy of impinging ions led to thicker and more chlorine- and bromine-rich layers. In both cases low-energy ion bombardment induced steady increases in etch rate. © 1989 IOP Publishing Ltd.