Amorphous silicon nitride deposited by hot-wire chemical vapor deposition

Abstract

High-quality amorphous silicon nitrides were deposited by hot-wire chemical vapor deposition using SiH4, NH3, and H2 gases. These films show a high deposition rate of 5Å∕s, a low processing temperature of 300°C, an excellent conformal coverage, a low etching rate of 7Å∕min, an index of refraction of 2.1, an optical band gap of 4.0eV, and a high breakdown field of 3MV∕cm. The effects of hydrogen dilution, substrate temperature, chamber pressure, and filament temperature on silicon nitride film property were studied to optimize the process. We found that adding H2 to the processing significantly enhances the silicon nitride films’ properties. The N content in the film increased significantly based on the infrared measurement. Hydrogen dilution is believed to play a key role for the conformal silicon nitride film. Hydrogen dilution also improves the process in that the gas ratio of NH3∕SiH4 has been greatly reduced with the assistance of the H2 gas. With substrate temperatures varying from 23°to400°C, this study showed a best film at near 300°C. However, a good-quality silicon nitride can be grown even if starting with a substrate at room temperature. Furthermore, we found that increasing chamber pressure and a high filament temperature result in higher deposition rate and better quality in the films. The optimized films were grown with hydrogen dilution at about 300°C substrate temperature, 83mTorr pressure, and 2100°C filament temperature.