AN AREA SELECTIVE AND ANISOTROPIC ETCHING OF SI BY SYNCHROTRON RADIATION EXCITATION - EFFECTS OF INTRODUCING O-2 MOLECULES

Single crystalline silicon was photochemically etched by synchrotron radiation (SR) in the presence of reactive species produced by microwave discharge. The etching gases were a mixture of SF6 and Ar. We attempted to introduce O2 gas in order to increase the area selectivity by protecting the nonirradiated area. It was found that the introduction of O2 molecules was very effective in depressing the etching of a nonirradiated area resulting in high area selectivity. Also an anisotropic feature of c-Si was obtained by addition of O2 molecules and submicron patterning was successfully performed using a stencil mask. The effect Of O2 molecules was investigated by the measurement of the spectra of total electron yield and Auger electrons. It seems that the formation of an oxide layer on c-Si surface played an important role in the area-selective etching.