Amorphous silicon nitrides ($Si_3N_4$) have been deposited by a chemical vapor deposition technique using $SiCl_4, NH_3$ and $H_2$ gaseous mixtures onto silicon single crystal. The effects of deposition time, substrate temperature, gas flow rate, total pressure and partial pressure of reactant gases on the deposition rate have been studied.
In initial growth stage, amorphous silicon nitride deposit is grown by the coalescence of clusters. The growth of $Si_3N_4$ is a thermally activated process with the activation energy of 16.5 Kcal/mole. With an increase of the total pressure, homogeneous reactions in the gas phase are promoted by the collision of reactant gases. Therefore, the depletion of reactant gases makes deposition rate decrease above the maximum deposition rate.
The kinetic model of the heterogeneous reaction for $SiCl_4 -NH_3-H_2$ system is compared with the experimental results and shows a good agreement between them.
