Thermally induced modifications on bonding configuration and density of defects of plasma deposited SiOx : H films

Abstract

The bonding configuration, hydrogen evolution, and defect content of rapid thermally annealed (RTA) SiOx:H films of different compositions were studied. Infrared absorption measurements showed that all the hydrogen present in the films is lost at annealing temperatures below 600 degreesC without any change in the oxygen to silicon ratio of the films. The activation energy of the hydrogen release is in the 0.21-0.41 eV range independently of film composition, suggesting that the process occurs via network bond reactions. For annealing temperatures higher than 700 degreesC, a change in the Si-O-Si stretching wave number from the initial unannealed value to the 1070-1080 cm(-1) range was promoted, independently of the initial film composition. Electron spin resonance measurements showed that all the films contain two type of bulk paramagnetic defects: the E-' center (.Si=O-3) and the silicon dangling bond center (.Si=Si-3). The RTA process promotes a general decrease of defect concentration for annealing temperatures below 400 degreesC. At higher temperatures, E' center disappears, and the .Si=Si-3 center increases its concentration up to the 10(17)-10(18) cm(-3) range. This suggests that the RTA at higher temperatures promotes the formation of a high-quality, almost defect-free, SiO2 matrix in which highly defective Si nanocrystals are also formed, where the .Si=Si-3 centers are located.