In-situ deposited HfO2 and Y2O3 on epi-Si/p-Ge-a comparative study of the interfacial properties and reliability

Single-crystal Si films six-monolayers in thickness were epitaxially grown on Ge(001) surface to minimize the formation of undesirable GeOx with subsequent deposition of HfO2 and Y2O3. The interfacial properties and reliability of the in-situ deposited high-kappa oxides on epi-Si/p-Ge(001) were compared. We have achieved interface trap density (D-it) values of (1-3) x 10(11) eV(-1) cm(-2) in the Y2O3/epi-Si/p-Ge(001), which are two times lower than those of the HfO2/epi-Si/p-Ge(001). The capacitance-equivalent-thicknesses under different annealing conditions were extracted to analyze the interdiffusion in the gate stacks under various thermal treatments. Y2O3/epi-Si/Ge exhibited higher thermal stability than HfO2/epi-Si/Ge. In both high-kappa's gate stacks, the effective charge sheet densities (Delta N-eff) are lower than the targeted value of 3 x 10(10) cm(-2). Compared to the Y2O3 gate stacks, attainment of a high acceleration factor of 11 in the HfO2 gate stacks suggested an improved defect-carrier decoupling in the latter stacks. (C) 2022 The Japan Society of Applied Physics