First-principles investigations of the dielectric properties of crystalline and amorphous Si3N4 thin films

We have investigated the dielectric properties of silicon nitride thin films with thickness below 6 nm, by using density functional theory calculations. We find a substantial decrease in the static dielectric constant of crystalline films, as their size is reduced. The variation in the response in proximity of the surface plays a key role in the observed decrease. In addition, amorphization of the films may bring further reduction of both the static and optical dielectric constants.