Analysis of ion energy impact on the refractive index of silicon nitride films by use of neural network model

Physical ion bombardment plays a crucial role in determining refractory properties of silicon nitride films. The duty ratio is also a critical parameter that controls the amount of radio frequency power delivered to a plasma. In this study, impacts of duty ratio-induced ion energy on the refractive index are investigated. Silicon nitride films are deposited using a pulsed-plasma enhanced chemical vapor deposition. Ion energy variables and their relationship with the refractive index are studied. We report a decrease of the refractive index with decreasing duty ratio as well as a strong relationship of the refractive index with the ratio of high (or low) ion energy to high ion energy flux. A neural network model is developed to predict the effect of ion energy parameters.

► Silicon nitride films were deposited using a pulsed, plasma-enhanced chemical vapor deposition system at room temperature. ► The impact of ion energy variables on a refractive index was studied experimentally as well as using a neural network model. ► The refractive index decreased with a decrease in the duty ratio and strongly related to the ratios of high (or low) ion energy to high ion energy flux.