Effects of nitridation pressure on the characteristics of gate dielectrics annealed in N2O ambient

Effects of N/sub 2/O pressure during oxynitridation on the characteristics of ultrathin gate dielectrics have been investigated. Reoxidation in N/sub 2/O ambient showed three distinguished oxidation regions as a function of tube pressure; that is, enhancement at 10-40 torr, retardation at 40-100 torr, and enhancement at 100-600 torr. The N/sub 2/O-nitridation at 40 torr incorporated much less nitrogen in oxide bulk than that at near-atmospheric pressure. The 40 torr N/sub 2/O-nitridation case exhibited about 70% of nitrogen incorporation at the Si/SiO/sub 2/ interface compared to that of the 600 torr N/sub 2/O-nitridation case. The low-pressure N/sub 2/O-nitridation at 40 torr results in improvement of TDDB of gate dielectrics and the transconductance of nMOSFETs compared to the nitridation at near-atmospheric pressure. These data suggest that low pressure oxynitridation should be more recommendable for device application.