Characterization of plasma-deposited silicon nitride films by Auger electron spectroscopy and electron energy loss spectroscopy

Abstract

Valence and core electron excitation spectra for amorphous Si nitride films prepared in a glow discharge plasma were measured by low energy electron energy loss spectroscopy (ELS). For comparision, the corresponding spectra were measured on hydrogenated amorphous silicon (a-Si:H). The elemental composition of these films was analyzed using Auger electron spectroscopy (AES). In order to evaluate the influence of hydrogen upon the spectra, comparison of the as-deposited plasma films was made (i) with plasma films annealed at 900 °C, (ii) with pyrolytic Si nitride, and (iii) with ion-bombarded crystalline silicon. Significantly different ELS spectra were obtained for the plasma-deposited films compared to the hydrogen free samples. For plasma Si nitride a new energy loss peak at 8.6 eV was detected and related to the presence of chemically bonded hydrogen. The interband excitations at high energies (EL ≳10 eV) due to Si-N bonds were found to be less pronounced compared to chemical vapor deposited (CVD)Si nitride. For plasma silicon a new energy loss at 8.5 eV was measured which could be attributed to Si-H bonds. The AES experiments revealed a pronounced gettering effect for impurities in plasma Si nitride.