Electrical properties of 1.5-nm SiON gate-dielectric using radical oxygen and radical nitrogen

We have developed a low-leakage and highly reliable 1.5-nm SiON gate-dielectric by using radical oxygen and nitrogen. In this development, we introduce a new method for determining an ultrathin SiON gate-dielectric thickness based on the threshold voltage dependence on the substrate bias in MOSFETs. It was found that oxidation using radical oxygen followed by nitridation using radical nitrogen provides the 1.5-nm (oxide equivalent thickness) SiON, in which leakage current is two orders of magnitude less than that of 1.5-nm SiO₂ without degrading device performance in NMOSFETs. The 1.5-nm (oxide equivalent thickness) SiON was also found to be ten times more reliable than 1.5-nm SiO₂.