Fabrication of Ge-MOS capacitors with high quality interface by ultra-thin SiO2/GeO2 bi-layer passivation combined with the subsequent SiO2-depositions using magnetron sputtering

Ge-MOS capacitors were fabricated by a novel method of ultra-thin SiO2/GeO2 bi-layer passivation (BLP) for Ge surface combined with the subsequent SiO2-depositions using magnetron sputtering. For the Ge-MOS capacitors fabricated by BLP with O2, to decrease oxygen content in the subsequent SiO2 deposition is helpful for improving interface quality. By optimizing process parameters of the Ge surface thermal cleaning, the BLP, and the subsequent SiO2 deposition, interface states density of 4 × 1011 cm−2 eV−1 at around mid-gap was achieved, which is approximately three times smaller than that of non-passavited Ge-MOS capacitors. On the contrary, for the Ge-MOS capacitors fabricated by BLP without O2, interface quality could be improved by an increase in oxygen contents during the subsequent SiO2 deposition, but the interface quality was worse compared with BLP with O2.

Research highlights
► We fabricated Ge-MOS capacitors by SiO2/GeO2 bi-layer passivation for Ge surface.
► We obtained good C–VG and J–E characteristics for typical Ge-MOS capacitors.
► We obtained Dit of 4 × 1011 cm−2 eV−1 at around mid-gap for Al-gate Ge-MOS capacitor.
► Bi-layer passivation with O2 improves interface quality for Ge-MOS gate stack.