AVS 46th International Symposium
    Electronic Materials and Processing Division Monday Sessions
       Session EM-MoM

Paper EM-MoM11
Characterization of a Very Thin Film: N2 Plasma Nitridation of GaAs (110)

Monday, October 25, 1999, 11:40 am, Room 608

Session: Nitride Epitaxy
Presenter: J.E. Hulse, National Research Council of Canada
Authors: J.E. Hulse, National Research Council of Canada
D. Landheer, National Research Council of Canada
R. Krishnamurthy, National Research Council of Canada
S. Moisa, National Research Council of Canada
Correspondent: Click to Email
GaAs (110) wafers were prepared by cycles of UV-ozone/HF cleaning and inserted into an Ultra-High Vacuum processing system. Nitridation of the wafers by a remote Electron Cyclotron Resonance (ECR) nitrogen plasma produced a porous GaN film of up to about 3 nm in thickness. In situ analysis by X-ray Photoelectron Spectroscopy (XPS) revealed that the plasma both scoured the GaAs substrate surface of carbon and oxygen and produced a GaN film. Ex situ analysis by Spectroscopic Ellipsometry indicated that the GaN layer was porous. Angle-Dependent XPS demonstrated that the GaN layer contained traces of As predominantly in the outer regions of the film, and that the porous GaN can absorb water on exposure to air. A 5 second exposure of a GaAs (110) wafer to the ECR nitrogen plasma simulates the initial stage of ECR plasma deposition of silicon nitride, which exposes the substrate to a nitrogen plasma at turn-on. Such a short nitridation produced a GaN film that was 1.9 nm thick with traces of arsenic throughout and approximately 50 % voids. Longer exposures to the nitrogen plasma produced films whose thicknesses followed an inverse power law time dependence. The wafers were examined by Atomic Force Microscopy both before and after nitridation. Before plasma nitridation, the cleaned wafers showed clearly identifiable roughness features due to chemical-mechanical polishing. Plasma nitridation left the surface smooth and free of identifiable features less than 10 microns in lateral size.