Experimental and chemical kinetic study of silicon nitride via LPCVD at low temperature from disilane and ammonia

Silicon nitride was deposited from disilane and ammonia reactant gases under LPCVD conditions and at temperatures around 600 OC. The growth rate was studied experimentally on 4 and 5-inch silicon wafers by batch depositions in a horizontal hotwall LPCVD furnace. The kinetics of growth was found to follow a LangmuirHinshelwood mechanism and the appropriate kinetic constants were estimated using the experimental data. The theoretical results expressed in terms of deposition rate are compared with the experimental data and they are in good agreement. The film properties were assessed by ellipsometry and their composition was determined by FT-IR spectroscopy. Refractive index at 830.0 nm was correlated with the film composition Si/N and nitrogen concentration (in atom cm-3). These correlations show a linear dependency of the refractive index on the composition and on the amount of nitrogen supplied to the deposited layers.