Surface Roughness in Plasma-Etched $\hbox {As}_{\bf 2}\hbox {S}_{\bf 3}$ Films: Its Origin and Improvement

We describe the microstructure of As₂S₃ films and its effect on the morphology of plasma-etched surfaces. The Raman spectroscopy and X-ray photoelectron spectroscopy demonstrated that the observed grainy morphology of etched As₂S₃ surfaces comes from differential chemical attack between different phases within the film. Two approaches were found to be effective for improving the smoothness of etched surfaces: a change in the plasma chemistry from CF₄-O₂ to CHF₃-O₂ and the application of a thin-conformal coating onto structures already patterned using CF₄-O₂ plasma.