Effects of Annealing Atmosphere on the Characteristics and Optical Properties of SiON Films Prepared Plasma Enhanced Chemical Vapor Deposition

摘要

SiON thin films were deposited by plasma-enhanced chemical vapor deposition method at 350°C using N{sub}2O/SiH{sub}4 gas mixtures as precursors. As-deposited SiON films were annealed in different gas atmospheres (air, N{sub}2, and O{sub}2) and at different annealing temperatures (800°C～1100°C). Effects of annealing atmosphere on the Si-O, Si-N, Si-H, and N-H bonding characteristics in SiON films and their structural and optical properties have been investigated. Cross-sectional and planar microstructures were characterized by scanning electron microscopy and atomic force microscopy, and crystallinity was investigated by X-ray diffraction. Chemical bonding characteristics and optical properties SiON films were studied using fourier transform infrared spectroscopy and prism coupler. X-ray diffractions showed no evidence of any crystals in all SiON films. The deposition rate strongly depended on the processing parameters such as radio frequency (rf) power, N{sub}2O/SiH{sub}4 flow ratio, and SiH{sub}4 flow rate. Deposition rate increased as N{sub}2O/SiH{sub}4 flow ratio increased and SiH{sub}4 flow rate increased. It was possible to obtain SiON films with surface roughness of about 1 nm and a high deposition rate of about 4 μm/h when the processing parameters were optimized as rf power of 200 W, N{sub}2O/SiH{sub}4 flow ratio of 3, SiH{sub}4 flow rate of 100 sccm. It was observed that the intensity and the shift of the Si-O stretch and Si-N peaks depended on the annealing atmosphere as well as the annealing temperature. The intensity of Si-O peaks increased in the samples annealed in oxygen atmosphere, but it decreased in the samples annealed in nitrogen atmosphere. The intensity of Si-N peak decreased in the samples annealed in oxygen atmosphere, but it increased in the samples annealed in nitrogen atmosphere. The position of Si-O peaks shifted from 1030 nm to 1140 nm in the samples annealed both in oxygen and in nitrogen atmosphere. It was also observed that the intensities of Si-H (～2250 cm{sup}(-1)) and N-H (～3550 cm{sup}(-1)) peaks decreased apparently as the annealing temperature increased in all annealed samples.