Ammonia plasma immersion ion implantation into silicon: Composition and structure of the resulting silicon-nitrogen-hydrogen system

Silicon nitride phases are of technological interest for example as gate di electric in thin film and field effect transistors. The present study compa res nitrogen with ammonia plasma immersion ion implantation (PIII) of silic on before and after an annealing step. Nitrogen, silicon and hydrogen depth profiles were obtained by Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA). For ammonia plasma immersion implantation significantly higher nitrogen concentrations are obtained than for nitroge n implantation as well as the maximum of the nitrogen profile is buried. It turns out that despite the excess of H compared to N in the plasma only a maximum of 2.5 at.% of H is incorporated in a stoichiometric Si3N4 film in the as implanted state. Upon annealing, hydrogen-free silicon nitride films are obtained. The structure has been examined by transmission electron mic roscopy (TEM). XTEM shows that the initially amorphous SixNyH films are con verted into crystalline alpha-Si3N4 after the annealing step. (C) 2000 Else vier Science B.V. All rights reserved.