Investigation of different interface passivation on Germanium: RTO-GeO2 and nitrogen-plasma-passivation

Ge p-MOSFETs with two kinds of passivation methods, RTO-GeO₂ interfacial layer and nitrogen-plasma-passivation, were fabricated. CV and IV characteristics of both devices were measured and compared systemically. Results show that the RTO-GeO₂ interfacial layer is more efficient in passivating the donor-like interface state near the valence band edge and is also beneficial for the hole mobility enhancement, while the nitrogen-plasma-passivation is much more efficient in passivating the acceptor-like interface state near the conductance band edge and is probably more useful in improving the electron mobility. Besides, compared to the RTO-GeO₂ interfacial layer, the nitrogen-plasma-passivation is much more beneficial to improve the physical stability of the gate dielectric and suppress the degradation of the gate stack on Ge. For Ge CMOS technology, hybrid interface passivation method should be introduced.