Room-Temperature Wet Etching of Polycrystalline and Nanocrystalline Silicon Carbide Thin Films with HF and HNO3

Polycrystalline 3C-SiC films deposited using low-pressure chemical vapor deposition from the precursors 1,3-disilabutane and dichlorosilane (DCS) are etched at room temperature in a mixed acid solution consisting of a 1:1 mixture of HF:HNO3. DCS flow rate fractions from 0 to 0.47. which yield a range of films with varying grain sizes. are examined. Etch rates vary from 50 angstrom/min for smaller grained films to 0.1 angstrom/min for larger grained films. A kinetic model of the etch rate with first-order dependence oil free silicon concentration and inverse power-law dependence on grain size is developed that fits the data well. The change in roughness of most polycrystalline sic films is nominal upon etching; however, films deposited with 0.16 DCS fraction exhibit an increase in roughness accompanied by the exposure of larger grains at the etched surface. Furthermore. films deposited without DCS exhibit an increase in roughness accompanied by the formation of 2-4 nm deep nanocraters on the surface of individual grains. The room temperature wet-etch capability thus presented enables new process flows for the realization of micro- and nanoelectromechanical system devices for harsh environments. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3061944] All rights reserved.