Grabado anisotrópico de silicio para aplicación en micromaquinado usando plasmas de SF$_{\pmb 6}$/CH$_{\pmb 4}$/O$_{\pmb 2}$/Ar y SF$_{\pmb 6}$/CF$_{\pmb 4}$/O$_{\pmb 2}$/Ar

Abstract

We investigated the reactive ion etching of silicon using S$F_{6}$/C$H_{4}$(C$F_{4}$)/$O_{2}$/Ar gas mixtures containing fluorine for MEMS applications. Etch rates and anisotropy of etch profiles were examined as a function of gas composition, material of electrode, and RF power. Etch depths were measured using a profilometer, and etch profiles were analyzed by scanning electron microscope. As a mask material, an aluminium film deposited by evaporation, was used. High anisotropy of etching of ~0.95 was achieved at etch depths up to 20-30 micrometers and etch rates of approximately 0.3-0.6 $\mu$m/min. Highly anisotropic etching is based on a mechanism that enhance the ion bombarding and protects the sidewalls due to polymerization and/or oxidation mechanisms in order to avoid the lateral etch. However, under the anisotropic etching conditions, considerable damages of the etched surfaces (roughness formation), were observed. After etching experiments, wet / dry cleaning procedures were applied to remove surface residues resulting from the reactive ion etching and to improve the etched surface morphology.