Amorphous SiNx: H films with a low density of Si–H bonds

Abstract

Amorphous SiN_x:H films have been prepared by r.f. glow discharge of SiH₄-N₂–H₂mixtures at 300°C using a new decomposition technique, and investigated by means of Si–H vibrational absorption. The stretching absorption arising from Si–H bonds disappears for x > 0˙9, in contrast to conventional glow discharge films containing a large number of Si–H bonds. The absorption profiles are reproduced by a superposition of two components with Gaussian shapes at around 2000 and 2100 cm⁻¹. The intensity of the 2000 cm⁻¹ component decreases monotonically with x. By contrast, the intensity of the 2100 cm⁻¹ component, strongly correlated to the incorporated H content, increases with x up to x = 0˙5 keeping a fixed peak wavenumber ω_p(= 2095 cm⁻¹), and the density of Si–H bonds derived from it agrees with the density of N atoms. Above x = 0˙5 the intensity rapidly decreases, in good correspondence with an increase in ω_p up to 2200 cm⁻¹. The increase and subsequent decrease in the 2100 cm⁻¹ component are interpreted as indicating increased formation of N–SiH bonds and further replacement of Si neighbours (H and Si) in N–SiH bonds by N atoms, respectively. The absorption from N–H bonds was observed after Si–H absorption cease.