Inductively-coupled BCI ₃/O ₂ plasma etching of germanium

We have investigated the etch rates and the surface morphologies of Ge samples as a functions of the oxygen concentration in the BCI ₃/O ₂ gas mixture, the inductively coupled plasma (ICP) power, and working pressure. The etch rate of Ge was found to have a peak etch rate at ̃15 % O ₂. The etch rate of Ge decreases from 3700 to 1050 Å/min as the O ₂ concentration increases from 15 to 40 %. The etch rate of Ge increases as the ICP power increases, whereas the etching rate of Ge decreases as the working pressure increases. The Ge surface has a very rough surface morphology, which is due to the self-masking effect by the deposition of chlorine and oxygen-related materials in the form of micro particles. The etched surface has a very smooth appearance at a 400-W ICP power, a 200-W bias power, and a 10-mTorr working pressure. The compositions of the reaction layers on Germanium due to BCI ₃/O ₂ plasmas were obtained by using X-ray photoelectron spectroscopy (XPS). Chlorine and oxygen were detected on the surfaces of the etched Ge samples, and an analysis of the reactive layer showed the presence of Ge-Cl and Ge-0 bonds.