Influence of stoichiometry of direct plasma-enhanced chemical vapor deposited SiN _x films and silicon substrate surface roughness on surface passivation

In this article, we report on the use of direct plasma-enhanced chemical vapor deposited silicon nitride (SiNx) films deposited at low excitation frequency (440 kHz) on low-resistivity (1.5 Ω cm) p-type Czochralski silicon substrate surfaces with different textures, to elucidate the influence of microroughness of the substrate surface on the surface-passivating properties of thin SiNx films. Whereas flat surfaces get the best passivation from Si-rich SiNx films, the optimum passivation shifts towards stoichiometric nitride as the microroughness increases, which points to the increasing relative importance of a charge-induced field effect. When short high-temperature (firing) treatments are applied upon passivation layer deposition, the process window to yield good surface passivation broadens, although very Si-rich films tend to suffer from blistering.