PLASMA ANODIC-OXIDATION AND NITRIDATION OF GE(111) SURFACE

Plasma anodic oxidation/nitridation of Ge(111) wafer was carried out in a plasma atmosphere of oxygen or an ammonia/nitrogen mixture. The plasma was excited by a high-frequency (0.5 MHz) electromagnetic field. The chemical and physical properties of the grown films were analysed using Auger electron spectroscopy, x-ray photoelectron spectroscopy, infrared spectrophotometry and high-frequency C-V characterization. The results show that the refractive index (1.60 +/- 0.02), chemical composition (O/Ge almost-equal-to 2.1) and infrared absorption peaks (560 cm-1 and 870 cm-1) of the oxygen plasma anodized films are very similar to those of vitreous GeO2, and that an oxygen plasma anodized film on a germanium substrate has excellent insulating and interface-state properties. It is also shown that after the nitridation processing of an oxygen plasma anodized film, the solubility of the film was greatly diminished due to the formation of the germanium oxynitride overlayer. For plasma anodic nitrided films on Ge, the refractive index is 2.10 +/- 0.02 at the growth temperature of 540-700-degrees-C and the bulk composition is N/Ge almost-equal-to 1.26. There is a broad absorption band (730-780 cm-1) and a weak peak (910 cm-1) in the IR spectrum of the plasma anodic nitrided film. These absorption peaks are associated with the alpha-phase germanium nitride and beta-phase germanium nitride in the film.