Infrared studies of room temperature deposition of hydrogenated silicon oxide films in rf magnetron discharges

Abstract

The properties of a-SiOx:H thin films deposited at low temperature (∼ 50 °C) in a low energy magnetron rf plasma system with Ar/SiH4/O2 gas mixtures are investigated. In the low pressure regime (about 5 mTorr reactive gases), the surface reaction dominates in the film formation process. As the partial pressure ratio (ROS) of oxygen to silane increases, the Si-H related vibrational modes gradually disappear, and the film becomes stoichiometric SiO2 for ROS≥1. High quality oxide film can be deposited due to the low pressure environment and the plasma promoted surface process. In the high pressure regime (tens of mTorr) the deposited SiO2 films contain fine particles (tens of nanometer in size) and are porous (15% void) due to the gas phase homogeneous reaction and aggregation. The infrared absorbance spectra with normal and oblique incidence imply different origins of the half width and the shoulder intensity of the 1070 cm−1 Si-O(s) mode. In comparison with the low pressure dense films, the narrow half width of the high pressure film may be caused by the more ordered local structure which has a narrower distribution of bond angle and length, while the large shoulder intensity may be dominated by the larger (fine particle size) scale disorder.