A study of amorphous hydrogenated silicon nitride films produced in the plasma of a high-frequency discharge

A study has been carried out of a-SiNx:H films produced by deposition from a silane+nitrogen mixture in the plasma of a 55-MHz glow discharge. It was found that, as compared with the 13.56-MHz discharge, a lower concentration of nitrogen was required to ensure that the electronic properties of the films were appreciably influenced by nitrogen. A variation was observed in the electronic properties of these films as the nitrogen concentration X=[N]/[Si] in the gas mixture was varied. Infrared spectroscopy has shown that hydrogen bonds preferentially to silicon. In films with X<8, nitrogen appears to behave as an impurity, forming chemical bonds with the silicon lattice, whereas a wide-bandgap alloy of the type a-SiNx:H is formed for X>8. (C) 1996 American Institute of Physics.