Reoxidation after NH₃ plasma nitridation for multiple-thickness oxynitrides

A novel manufacturable multiple gate oxynitride thickness technology is proposed in this work. An ultrathin dielectric film (E_OT = 2.5 nm) of lower oxidation growth rate than conventional films was fabricated by NH ₃ plasma nitridation. Oxide thickness was reduced by about 80% for samples treated by NH₃ plasma nitridation. However, the thickness limitation is 1.3 nm for NH₃ plasma nitridation. This is believed to be due to nitrogen incorporated in the silicon surface to form a nitridelike thin film, which retarded oxide growth. The effects of NH₃ plasma nitridation were systematically studied, and the rapid thermal N₂O reoxidation of an NH₃ plasma sample was also demonstrated in this work. This novel process improves the gate oxide reliability, decreases bulk trap densities, provides better SILC immunity, and produces less charge trapping and a higher Q_bd.