Water Absorption and Densification of Phosphosilicate Glass Films

Abstract

The interaction between phosphosilicate glass films and water vapour has been studied at the temperature range 70-100degC, using infrared spectroscopy. The films were deposited at 640degC using low pressure chemical vapour deposition. The infrared spectra change significantly during the exposure of the films to water vapor. In spite of the observed decrease in the intensity of the P=O band it has been found that phosphorus ions do not outflow from glasses that contain less than 8 m/o phosphorus oxide. The diffusion of water in the films can be described by a single activation energy, which increases with increasing phosphorus oxide concentration. Densification of the glass by means of heat-treatment substantially increases the film resistance to water absorption. The densification of the phosphosilicate glass has been studied by infrared spectroscopy and etch rate measurements. The efficiency of the densification increases with increasing the temperature and time of the heat-treatment. The effectiveness of the ambients used in this study can be ranked in the order: steam>O2>Ar, N2.