Local atomic structure in thin films of silicon nitride and silicon diimide produced by remote plasma-enhanced chemical-vapor deposition

Abstract

We have grown thin films of silicon nitride by remote plasma-enhanced chemical-vapor deposition and have studied the chemical bonding by infrared absorption, x-ray photoelectron spectroscopy, Rutherford backscattering, and Auger-electron spectroscopy. Films were grown using two different gases as the source of nitrogen, ${\mathrm{N}}_2$ and ${\mathrm{NH}}_3$. We have found that films grown from ${\mathrm{N}}_2$ and deposited at substrate temperatures in excess of 350 °C have a composition corresponding to stoichiometric ${\mathrm{Si}}_3$ ${\mathrm{N}}_4$, whereas films deposited from ${\mathrm{NH}}_3$ require substrate temperatures in excess of about 500 °C to eliminate bonded H and yield the same stoichiometric composition. In contrast films grown from ${\mathrm{NH}}_3$ at temperatures in the range of 50 to 100 °C have a chemical composition corresponding to silicon diimide, Si(NH${)}_2$. Films grown from ${\mathrm{NH}}_3$ at intermediate substrate temperatures are solid solutions of ${\mathrm{Si}}_3$ ${\mathrm{N}}_4$ and Si(NH${)}_2$.