Modeling stress development and hydrogen diffusion in plasma enhanced chemical vapor deposition silicon nitride films submitted to thermal cycles

Abstract

We conducted isochronal stress hysteresis measurements coupled with thermal desorption spectroscopy on silicon nitride thin films obtained by performing plasma enhanced chemical vapor deposition on (001) silicon wafers. Above the deposition temperature, we observed irreversible stress build-up in parallel to substantial hydrogen effusion out of the films. We confirmed that the hydrogen dissociation and stress build-up can be modeled with similar kinetic equations. The hydrogen dissociation and stress development activation energies as well as the hydrogen diffusion coefficients were determined by fitting the experimental data with solutions to the kinetics and Fickian diffusion equations obtained with the finite difference method. A first order correlation was found between the hydrogen diffusion coefficients calculated between 400 and 800 °C and the silicon nitride film density.