Structural and optical properties of amorphous silicon oxynitride

Hydrogenated amorphous silicon oxynitride (a-SiOxNy:H) films have been prepared by glow discharge of silane (SiH4, 50% in H-2), nitric oxide (N2O) and hydrogen (H-2) at a substrate temperature of 250 degrees C. The properties of these films have been investigated using infrared absorption, ellipsometry, optical absorption, and photoluminescence, etc. Various molecular bonds were identified by the infrared absorption measurement. For example, the 2185, 975, 935, and 700 cm(-1) peaks are associated with the stretching, bending, wagging, and rocking modes of the Si-H-2 bond back bonded to two oxygen atoms, respectively. It was found that the water molecules H2O appear as the gas phase composition of N2O becomes larger than 0.965; they are trapped in the film by their hydrogen bonds. It is found that the low frequency (less than or equal to 1 MHz) refraction indexes of the deposited films are 0.2 higher than the high frequency (632.8 nm) values. Two peaks are observed in the photoluminescence spectra of n-SiOxNy:H when the gas phase composition is smaller than 0.8; this indicates that the a-SiOxNy:H films are inhomogeneous. (C) 1996 American Institute of Physics.