AUGER-ELECTRON SPECTROSCOPY AND LOW-ENERGY ELECTRON LOSS SPECTROSCOPY INVESTIGATIONS OF PLASMA-NITRIDED THIN THERMAL SIO2 AND NATIVE OXIDE ON SILICON

Auger electron spectroscopy and low energy electron loss spectroscopy in conjunction with inert gas ion sputtering are used to investigate the nitridation of thin thermal SiO2 (ca. 10-35 nm) and pure silicon wafers in an r.f. NH3 plasma. The change in the thermal oxide spectra after plasma nitridation depends on the oxide thickness, time of exposure to the plasma and substrate temperature during the plasma process. It is established that the ammonia plasma does not transform the initial oxide with thickness about 30-35 nm into oxynitride (in any of the plasma regimes used) and forms only ultrathin oxynitride film on the surface of thermal oxide. The nitrided layer contains both Si-O and Si-N bonds. It is found that plasma action at a substrate temperature of 573 K can completely nitride the thermal oxide with a thickness of 10-20 nm to an oxynitride layer. An ultrathin homogeneous oxynitride layer (ca. 4 nm) is formed after a long period of NH3 plasma action on silicon substrate at 573 K.