Etch Rate Retardation of Ga[sup +]-Ion Beam-Irradiated Silicon

Surface chemistry during wet chemical etching in alkaline KOH solution and dry etching in plasma of high-dose -implanted Si has been investigated by means of secondary ion mass spectroscopy (SIMS) and X-ray photoelectron spectroscopy (XPS). During wet chemical etching in a solution a thin layer of of thickness is formed, which has been investigated in more detail by angle-resolved XPS. In the case of dry reactive ion etching (RIE) the surface chemistry is quite different. In this case a more enhanced oxidation of Ga takes place due to the high reactivity of atomic oxygen from the plasma. SIMS results show that during RIE a Ga-rich surface layer forms, and therefore an enhanced Ga oxidation takes place, leading to a thicker layer compared to wet chemical treatment. XPS depth profiling reveals a stoichiometry of almost completely oxidized Ga layer free from Si with a thickness of about . The etch rate lowering in as-implanted silicon is ascribed to the formation of gallium oxide at the Si surface during the etch processes.