ETCHING OF SILICON WITH XEF2 VAPOR

It is shown that silicon is isotropically etched by exposure to XeF 2(gas) at T=300 K. Si etch rates as large as 7000 Å/min were observed for P (XeF2) <1.4×10-2 Torr and the etch rate varies linearly with P (XeF2). There was no observable etching of SiO2, Si3N4, or SiC, demonstrating an extremely large selectivity between silicon and its compounds. Therefore, thin masks constructed from silicon compounds can be used for pattern delineation. The implication of these experimental results for understanding mechanisms associated with plasma etching (including RIE) will be discussed.