Effects of Vacuum-Ultraviolet-Light-Induced Surface Reaction on Selective and Anisotropic Etching of Silicon Dioxide Using Anhydrous Hydrogen Fluoride Gas

Vacuum-ultraviolet (VUV) light induced etching of thermally grown silicon dioxide films was investigated near room temperature. We used synchrotron radiation as a VUV light source and anhydrous-hydrogen-fluoride as an etching gas. The silicon dioxide is etched only in the VUV light irradiated area, and etched selectively with respect to (100) oriented singlecrystalline silicon, which is not etched even under the irradiation. Moreover, we have found anisotropic etching with the patterned polycrystalline silicon etching mask. The ratio of the etch rate of SiO2 in the vertical direction compared to the horizontal direction of the substrate surface is about 30. From these results, the etching process is due to the photo-induced surface reaction. The excitation of the adsorbed AHF molecules or SiO2 surface would be a dominant process.