Laser-assisted plasma-enhanced chemical vapor deposition of silicon nitride thin film

Hydrogenated amorphous silicon-nitride (a-Si-N(x):H) films with low hydrogen content were deposited using a CO₂ laser-assisted PECVD, or LAPECVD system. This system was based upon a conventional capacitive RF (13.56 MHz) discharge to dissociate both ammonia and silane, but the substrate could be irradiated by a CO₂ laser beam as well. Whether the substrates were heated or not, irradiation with a CO₂ laser beam without wavelength selection effectively reduced the amount of hydrogen bonds in the films. These films were proved to have a larger index of refraction and better surface flatness. Besides, their resistance to corrosion was considerably improved as compared to films grown under a conventional PECVD process. While the resistive heating was replaced by appropriate CO₂ laser irradiation, the absorption of laser beam raised the substrate-thin film temperature up to 50-60°C only. This non-thermal process represented another advantage of our LAPECVD method.