Phosphorous ion implantation into NiGe layer for Ohmic contact formation on n-type Ge

摘要

Low-resistivity Ohmic contacts on n-type germanium (Ge) together with ideal rectifying characteristics for p-type Ge were achieved using phosphorous-ion-implanted nickel germanide (NiGe). A pre-germanidation process prior to ion implantation was employed, and subsequent drive-in annealing at low temperature was used to precisely control the phosphorous profile and optimize the process conditions. Very low contact resistance on n-type Ge was demonstrated by using low-temperature drive-in annealing at 300 ℃. Further process optimization (ion dose of 2 × 10~(15) cm~(-2); drive-in annealing at 400 ℃ for 30 min) resulted in an effective electron Schottky barrier height as low as 0.09 eV for n-type Ge and an on/off current ratio of five orders of magnitude for p-type Ge. The proposed low-temperature contact formation process offers a significant advantage in source/drain contact formation for Ge-based high mobility n-channel transistors.