Effects of fluorine incorporation and forming gas annealing on high-k gated germanium metal-oxide-semiconductor with GeO_2 surface passivation

摘要

Effective pregate surface passivation and postgate treatments are very important to optimize the germanium metal-oxide-semiconductor (MOS) interface quality. In this work, pregate GeO_2 surface passivation and postgate treatments including CF_4-plasma treatment and forming gas annealing are employed to make high quality HfO_2 gated germanium MOS capacitors. Excellent electrical characteristics with negligible capacitance-voltage stretch-out and frequency dispersion are achieved. The interface trap density of TaN/HfO_2/GeC_xGe MOS structure is as low as 2.02 × 10~(11) cm~(-2) eV~(-1) at the minimum. Comparing to the forming gas annealing, it is found that CF_4-plasma treatment is more effective to passivate interface states located in the upper half of Ge bandgap.