Integration of Amorphous and Crystalline as Gate Stack for Aggressively Scaled MOS Devices

Because of a higher permittivity than Al2O3, a large conduction band offset and high thermal stability, a thin amorphous Yb2O3 layer was integrated with a ZrTiO4 film as the gate stack for advanced Si MOS devices. With 800 °C annealing, the ZrTiO4 film can be crystallized in orthorhombic phase with permittivity of 45.9 and a gate stack with equivalent oxide thickness of 0.86 nm can be achieved. This crystalline ZrTiO4/Yb2O3 gate stack demonstrates negligible frequency dispersion in capacitance, low interface trap density of 1.86 × 1011 cm-2 eV-1, leakage current of 6.7 × 10-6 A/cm2 at gate bias of Hatband voltage (VFB) -1 V, and high extrapolated 10-year lifetime operating voltage of -2.9 V. These promising electrical characteristics suggest that the crystalline ZrTiO4/Yb2O3 gate stack holds great potential to be applied to aggressively scaled CMOS technology.