Tetragonal $\hbox {ZrO}_{2}/\hbox {Al}_{2}\hbox {O}_{3}$ Stack as High- $\kappa$ Gate Dielect

Abstract-The combination of tetragonal ZrO₂ (t-ZrO₂) and amorphous Al₂O₃ was explored as the gate dielectric for Si-based MOS devices. Because of the absence of a ZrSiO₄ and/or ZrSi interfacial layer, the thermally stable t-ZrO₂/Al₂O₃/Si stack is more eligible than the Al₂O₃/t-ZrO₂/Si stack for the gate dielectric since it demonstrates larger capacitance, smaller hysteresis, better frequency dispersion, lower leakage current, and more robust reliability. By employing additional NH₃ plasma nitridation to well passivate the grain boundaries of the t-ZrO₂ film, without compromising its κ-value, a greatly reduced leakage current of 2.9 × 10^-8 A/cm² can be achieved at gate bias of flatband voltage (V_fb)-1 V with an effective oxide thickness of 1.64 nm, which paves a new way to develop a high-performance crystalline gate dielectric for advanced MOS devices.