Pure germanium nitride formation by atomic nitrogen radicals for application to Ge metal-insulator-semiconductor structures

We have investigated the nitridation of germanium using atomic nitrogen radicals generated by a remote rf plasma source. Pure amorphous Ge3N4 films without oxygen are obtained by the direct nitridation of clean Ge substrates. The conformal growth with smooth surface and sharp interface can be achieved in the Ge3N4 films grown at 100°C, where the maximum thickness of the Ge3N4 films is approximately 3nm. While the surfaces of the Ge3N4 films are partially oxidized by the exposure to air, the Ge3N4 films exhibit the high resistance against oxygen diffusion. The Ge3N4 films are water insoluble and soluble in HF. These results demonstrate that pure direct nitridation of Ge substrates has a possibility to be used not only as a passivation layer but also as a diffusion barrier layer against oxygen for Ge metal-insulator-semiconductor field effect transistor applications.