Room-temperature deposition of low H-content SiNx/SiNxOy thin films using a specially designed PECVD system

Low-temperature deposition of amorphous silicon nitride/oxynitride (a-SiNx/a-SiNxOy) is of significance for many industrial applications. In this work, low H-content a-SiNx/a-SiNxOy films were prepared at room temperature by a specially designed plasma enhanced chemical vapor deposition (PECVD) system using Ar-diluted SiH4 and pure N2 as the reactant gases. The plasmas for the deposition of a-SiNx/a-SiNxOy films were studied as a function of discharge power and working pressure. It was found that the density of N atoms in plasma plume was found to have significant impacts on the compositions and optical properties of a-SiNx/a-SiNxOy films and the correlations between the plasma discharge and the as-deposited films were explored. With the increase of N atoms in the plasma, the growth rate of a-SiNx/a-SiNxOy films was increased and the refractive index was gradually reduced, and thus the value of refractive index at 633 nm was tuned from 2.20 to 1.64 due to the increase of the atomic ratio of N to Si in the films. In addition, the O and H contents were increased with the increase of N density in the plasma and have contributions to the variation in the refractive index of a-SiNxOy films as well. The low-temperature deposition of a-SiNx/a-SiNxOy films with tunable refractive index exhibited a great potential in practical applications, especially in flexible electronics.