Remote plasma-enhanced chemical vapour deposition of silicon nitride at atmospheric pressure

Abstract

Silicon nitride films were deposited using an atmospheric pressure plasma source. The discharge was produced by flowing nitrogen and helium through two perforated metal electrodes that were driven by 13.56 MHz radio frequency power. Deposition occurred by mixing the plasma effluent with silane and directing the flow onto a rotating silicon wafer heated to between 100°C and 500°C. Film growth rates ranged from 90±10 to 1300±130 Å min^-1. Varying the N₂/SiH₄ feed ratio from 55.0 to 5.5 caused the film stochiometry to shift from SiN_1.45 to SiN_1.2. Minimum impurity concentrations of 0.04% carbon, 3.6% oxygen and 13.6% hydrogen were achieved at 500°C, and an N₂/SiH₄ feed ratio of 22.0. The growth rate increased with increasing silane and nitrogen partial pressures, but was invariant with respect to substrate temperature and rotational speed. The deposition rate also decreased sharply with distance from the plasma. These results combined with emission spectra taken of the afterglow suggest that gas-phase reactions between nitrogen atoms and silane play an important role in this process.