Interface Structure and Charge Trapping in Hf-Incorporated Y2O3 Gate Dielectrics on Germanium

Abstract

Y2O3 and HfYOx (~12nm) high dielectric constant films, with RF sputtering, have been prepared and studied with respect to their chemical bonding and electrical properties. The rapid thermal annealing after high-k dielectric deposition in N2 ambient showed major impacts on crystalinity properties. The incorporation of Hf into Y2O3 causes reduction in generation of positive oxide charge and leakage current density. The mechanism of leakage current reduction is considered to be due to Hf-induced compensation of existing oxygen vacancies. Moreover, HfYOx films exhibit superior electrical performances in terms of charge trapping induced flatband voltage instability and gate leakage current compared to directly deposited Y2O3 high-k dielectric films on Germanium. The density of interface traps (Dit) and border traps (Nbt) estimated from high-frequency CV curves (1 MHz) indicates that incorporation of Hafnium can improve the interfacial defects.The breakdown field in MIS capacitor with Y2O3 gate dielectric was significantly enhanced by incorporating Hf.