Effects of post-deposition anneal on the electrical properties of Si3N4 gate dielectric

Effects of postdeposition anneal of chemical vapor deposited silicon nitride are studied. The Si3N4 films were in situ annealed in either H-2(2%)/O-2 at 950 degreesC or N2O at 950 degreesC in a rapid thermal oxidation system. It is found that an interfacial oxide was grown at the Si3N4/Si interface by both postdeposition anneal conditions. This was confirmed by thickness measurement and X-ray photoelectronic spectroscopy (XPS) analysis. The devices with H-2(2%)/O-2 anneal exhibit a lower gate leakage current and improved reliability compared to that of N2O anneal. This improvement is attributed to a greater efficiency of generating atomic oxygen in the presence of a small amount of hydrogen, leading to the elimination of structural defects in the as-deposited Si3N4 film by the atomic oxygen. Good drivability is also demonstrated on a 0.12 mum n-MOSFET device.