A new optimized process for low pressure nitridation of thin thermal gate oxide

In this paper, a new process is proposed for low pressure nitridation of thin thermal gate oxide (8 nm) that does not produce interface degradation as it is generally observed by conventional NH3 nitridation. Electrical characteristics of thin oxides nitrided in NH3 from 1/2-h to 3-h at 5 torr and 900°C have been studied. Fixed positive charge and interface state densities in the 10¹⁰ cm^-2 range have been measured. Remarkable improvements of the interface state generation and charge trapping have been obtained after a 1/2-h nitridation, without using any reoxidation step. Under this condition, Qbd values are superior or comparable to those classically obtained on such very thin oxide.