Preparation of dense, smooth and homogeneous amorphous silicon nitride films by nitrogen-ion-beam assisted evaporation

Amorphous silicon-rich silicon nitride films were deposited by ion-beam-assisted evaporation onto silicon substrates maintained at 100 °C without substrate bias or with a substrate bias of −250 V. The structure, the composition of the films and the effect of the substrate bias were studied by x-ray photoelectron spectroscopy, infrared absorption measurements, chemical etch rate experiments, atomic force and scanning electron microscopies. While the films prepared without bias are nanoporous and columnar, it is shown that accelerating the nitrogen ions by biasing the substrate enables us to produce homogeneous, dense and smooth amorphous Si-rich silicon nitride (a-SiNx) films free of oxygen and hydrogen.