Substrate Temperature Effects on Properties of Silicon Nitride Films Deposited by Ion Beam Assisted Deposition

Silicon nitride films (Si1−xNx) have been deposited on silicon by simultaneous evaporation of silicon and bombardment of nitrogen ions. Films approximately 1 µm thick were deposited in an ambient nitrogen pressure of 50 µTorr. The substrate temperature (TSUB) ranged from nominally room temperature to 950°C for films with X between 0 and 0.6. Nitrogen atom fraction, X, was measured with Rutherford backscattering spectrometry (RBS). Refractive index was measured with near-IR reflection spectroscopy. Differences in film structure were measured by FT1R on the Si-N bond bending absorption mode, and by x-ray diffraction (XRD). X was found to depend upon the incident flux ratio of energetic nitrogen atoms to vapor silicon, and upon TSUB. Refractive index depends upon X and TSUB. XRD found evidence of the presence of amorphous structure, poly-crystalline silicon and (101) oriented β-Si3N4 depending on X and TSUB. The Si-N absorption signal increases with X and shows some structure at high TSUB.