Silicon Nitride Ultra Thin Film Formation by Electron Cyclotron Resonance Plasma and its Application to Gate-Insulator

The silicon nitride film attracts much attention as scaled gate dielectric films, because of low gate leakage current. In this study, we have investigated the properties of the silicon nitride ultra thin films produced by ECR-PECVD method employing SiH₄ and N₂ gases, and ECR N₂ plasma nitridation on silicon substrates. The silicon nitride films were formed by ECR plasma nitridation on silicon substrates at 300W, 0.5Pa, a N₂ flow of 100sccm. The bias and temperature of the substrate were floating and 350 degree C. The film properties were studied by Fourier Transform Infrared Spectroscopy(FT-IR), ellipsometry and in-situ X-ray Photoelectron Spectroscopy(XPS). In-situ XPS analysis showed that the peaks of Si2p and N1s were saturated in 60 min. N₂ plasma duration. The silicon nitride layer was 3.5nm in thickness and the stoichiometric composition(Si_3N_4) without hydrogen content. The films synthesized by ECR-PECVD indicated the nearly stoichiometric composition(SiN_1) without hydrogen content. These results suggest that those nitride films are applicable for the gate insulator in next generations ULSI.