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

Abstract

Silicon nitride films (Sil.xNx) have been deposited on silicon by simultaneous evaporation of silicon and bombardment of nitrogen ions. Films approximately I pin thick were deposited in an ambient nitrogen pressure of 50 pTorr. The substrate temperature (Tsua) 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 FTIR 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 Tsu. Refractive index depends upon X and Tsm. XRD found evidence of the presence of amorphous structure, poly-crystalline silicon and (101) oriented P3-Si3N 4 depending on X and Tsu,. The Si-N absorption signal increases with X and shows some structure at high Ts..