Wide-bandgap high-k Y2O3 as passivating interlayer for enhancing the electrical properties and high-field reliability of n-Ge metal-oxide-semiconductor capacitors with high-k HfTiO gate dielectric

High-k and wide-bandgap Y2O3 was proposed as an interlayer in n-Ge metal-oxide-semiconductor (MOS) capacitor with HfTiO gate dielectric for passivating its dielectric/Ge interface, and thus improving its electrical properties and high-field reliability. Results showed that as compared to the Ge MOS capacitor with HfTiO dielectric, the sample with HfTiO/Y2O3 dielectric had better electrical properties such as higher dielectric constant (k=24.4), lower interface-state density, and less frequency-dependent C-V dispersion, and also better reliability with less increases in gate leakage and interface states after high-field stressing. This should be attributed to the excellent interfacial quality of Y2O3/Ge with no appreciable growth of unstable GeOx at the interface as confirmed by transmission electron microscopy. Moreover, Y2O3 can also act as a barrier against the diffusions of Ge, Hf, and Ti, thus further improving the interface quality.