Growth competition between crystalline silicon carbon nitrides and silicon nitrides deposited on Si wafer by MPCVD

The Si–C–N films were synthesized on Si wafer by microwave plasma chemical vapor deposition with CH4, N2, 0.0–8.3 vol.% H2 and the additional Si chips, as the sources. The growth competition on Si wafer between crystalline ternary Si–C–N and binary silicon nitrides was examined. Based merely on the results of ESCA, XRD and SEM analyses on the film surface, it might often give false impression of forming ternary silicon carbon nitride crystalline films, as reported in the literature, though their volume fractions of H2 were from 35 to 77%. One of the possible reasons for a false impression is due to the fact that carbon often settles on the deposited films during cooling period. The further examinations on the cross-section of the films by TEM+EDS+ED, and on the film surface by FTIR and Raman spectroscopy clarify that the films essentially consist of ∼2 μm binary silicon nitride crystals on top of ∼100 nm ternary Si–C–N crystallites. This is in agreement with the ESCA depth profile examinations and the substrate scratching experiment by Si3N4 powders, which greatly enhance nucleation rate of binary silicon nitride crystals. Under a higher temperature and a longer deposition time, growth competition between crystalline Si–C–N and silicon nitrides will generally result in forming a film covered with silicon nitrides. The crystal structure of the silicon nitrides on the films is much close to α-Si3N4 than β-Si3N4 and tetragonal Si3N4 type structures, but silicon content is higher.