Infrared spectroscopic study of hydrogenated and deuterated silicon nitride films prepared from plasma-enhanced deposition

Abstract

The infrared spectroscopic studies were carried out for plasma-enhanced chemical vapor deposition amorphous silicon nitride films prepared from gas systems which contain deuterosilane (SiD4) or deuteroammonia (ND3). The stretch-mode frequencies of N–H, N–D, Si–H, and Si–D bonds were observed at 3340, 2480, 2180, and 1585 cm−1, respectively. The absorption cross section of Si–D bond has been determined considering ratios of reduced masses and dipole moment derivatives for Si–H and Si–D bonds. As a result of the calculation of Si–H and Si–D bond concentrations using the respective absorption cross sections, the isotope effect on introduction ratio of H and D atoms bonded to Si atoms was not observed. Assuming that the isotope effect does not also affect the introduction ratio between N–H and N–D bond concentrations, the absorption cross section of N–D bonds is determined. It is also found that 80–90% of the total hydrogen atoms in the films are introduced from ammonia gas.