Improving the quality of sub-1.5-nm-thick oxynitride gate dielectric for FETs with narrow channel and shallow-trench isolation using radical oxygen and nitrogen

We have demonstrated that oxynitridation using radical-oxygen (radical-O) and radical-nitrogen (radical-N) improves reverse narrow channel effects (RNCE) and reliability in sub-1.5-nm-thick gate-SiO₂ FETs with narrow channel and shallow-trench isolation (STI), suitable for high-density SRAM and logic devices. The STI formation followed by oxidation for the gate-dielectric causes various orientations of the Si surface, and thus, thermal oxidation forms the partial thin SiO₂ and causes RNCE and reliability degradation. Oxidation using radical-O forms uniform SiO₂ on Si[100] and Si[111] surfaces and suppresses RNCE in a sub-1.5 nm-thick gate-SiO₂ FET with STI. Nitrifying the SiO₂ using radical-N increases the physical thickness while maintaining the oxide equivalent thickness on both Si[111] and Si[100] surfaces, thus producing a low-leakage and highly reliable sub-1.5 nm-thick gate-SiON.