XPS investigation of aluminum and silicon surfaces nitrided by a distributed electron cyclotron resonance nitrogen plasma

Aluminum and silicon samples were nitrided by a distributed electron cyclotron resonance nitrogen plasma. The plasma conditions used for the treatment correspond to a maximum N2+ concentration in the sample position, determined by optical emission spectroscopy. The substrates were always polarized by a DC bias voltage at −120 V and were externally heated or not. Nitrided samples were characterized by X-ray photoelectron spectroscopy (XPS) after an exposure to ambient air. A depth profile of the treated substrates was achieved by Ar+ etching sequences in the XPS spectrometer. When the samples are polarized and heated at 500°C during the plasma treatment, the nitride layer (dense AlN or Si3N4 and diffusion layers) obtained on aluminum (∼0.3 μm) is much thicker than on silicon (∼30 Å).