Influence of helium dilution on physico-chemical and defect properties of PECVD silicon oxynitride films

Abstract

We have prepared oxynitride films by PECVD at 380°C using N 2O, NH 3 and SiH 4 as reactive gases without and with helium dilution. In both cases, the hydrogen detected by infra-red spectroscopy is mainly incorporated as NH bonds coming from ammonia. For the same O/O + N ratios, helium dilution results in a slower growth rate and in a lower total hydrogen incorporation. The spin densities measured by ESR experiments decrease and the lineshape is affected by the He dilution. The characteristics of the dark ESR signals measured at 40 K on samples grown without helium dilution ( g = 2.0047, ΔH pp = 15 G for the largest linewidths) are discussed; we also detect narrow signals (2.001, 2–3 G) for the more oxidized samples which are attributed to the E' center SiO 3 observed in a previous ESR study of PECVD silicon oxynitride prepared with only two gases SiH 4 and N 2O. With helium dilution, the characteristics of the broadest signals are shifted (2.0025, 12 G).