Spatial charge distribution in the plasma-enhanced chemical vapor deposited nitrogen-rich silicon nitride

Abstract

Gate quality N-rich silicon nitride films, with low bulk dangling bond densities, have been prepared by plasma-enhanced chemical vapor deposition at a substrate temperature of 400°C. Films of different thicknesses, ranging from 200 to 10 500 Å, were obtained by varying the deposition time. The dielectric constant was found to be around 6.6 for this material, independent of the film thickness. The flatband voltage shift was also found to be proportional to the silicon nitride thickness, which suggests that a centroid of the trapped charge is located close to (within a region narrower than 200 Å) the silicon/nitride interface. For films thicker than 200 Å, the effective charge and effective trapped carrier density were found to be Q eff≅2×10-7 C cm-2 and Neff≅1×1012 cm -2.