Charge trapping and reliability characteristics of sputtered Y2O3 high-k dielectrics on N- and S-passivated germanium

Abstract

We demonstrate the potential of sulfur passivation to improve the interface characteristics between germanium (Ge) and Y2O3 high-k gate dielectric. Effects of nitrogen (N) and sulfur (S) passivation of the Ge surface on the charge trapping and reliability properties of Y2O3/Ge gate stacks are studied in detail and the results are compared. Sulfur passivation of the Ge surface has been performed using both the wet sulfidation technique with aqueous ammonium sulfide and plasma sulfidation with H2S gas. N-passivation of Ge substrates has been performed in NO plasma for comparison. Ultrathin (∼15 nm) Y2O3 films are deposited on both the N- and S-passivated p-Ge (1 0 0) wafers. Y2O3 films on the S-passivated Ge surface show low fixed oxide charge and interface state density than what is achieved with N-passivation. The electrical characterization results of MOS capacitors with Y2O3 films reveal the potential of S-passivation for the fabrication of Y2O3/Ge gate stacks for Ge MOSFETs.