Role of nitridation/reoxidation of NH₃-nitrided gate dielectrics on the hot-carrier resistance of CMOS transistors

Abstract

The effect of nitriding and reoxidizing conditions are examined on the hot-carrier (HC) properties of p-channel and n-channel transistors with reoxidized nitrided oxide gate dielectrics. Nitrogen was introduced into the gate dielectric by performing cyclical nitridation and reoxidation steps (one cycle versus four cycles of nit./reox.), keeping the same overall oxidation and nitridation times constant. It was found that there were considerable differences in hot-carrier hardness, of up to three orders of magnitude for p-channel transistors, but much less for n-channel devices. Nitrogen-content variations (a factor of 2) for these very similar conditions explain the n-channel hot-carrier results. In the case of the p-MOS transistors, it is suggested that changes in hydrogen concentration might be responsible for their hot-carrier behavior.

Nitrogen Effects on the Integrity of Silicon Dioxide Grown on Polycrystalline Silicon

“…[14][15][16][17] This is due to the nitrogen incorporation at gate oxide/silicon interface, which can avoid hot-carrier damages, prevent boron penetration and improve interface endurance to Fowler-Nordheim ͑FN͒ stress. [18][19][20][21][22][23] But normal nitridation with NO or N 2 O ambient introduces a small amount of nitrogen at Si/SiO 2 interface, which is insufficient to prevent boron penetration when the oxide is thinner than 3.0 nm. Increasing the temperature or time to increase the nitrogen concentration in oxides will result in a thicker oxide and redistribution of channel doping profile.…”