Understanding and Optimization of Hot-Carrier Reliability in Germanium-on-Silicon pMOSFETs

In this paper, a comprehensive study of hot- carrier injection (HCI) has been performed on high-performance Si-passivated pMOSFETs with high-k metal gate fabricated on n-type germanium-on-silicon (Ge-on-Si) substrates. Negative bias temperature instability (NBTI) has also been explored on the same devices. The following are found: (1) Impact ionization rate in Ge-on-Si MOSFETs is approximately two orders higher as compared to their Si counterpart; (2) NBTI degradation is a lesser concern than HCI for Ge-on-Si pMOSFETs; and (3) increasing the Si-passivation thickness from four to eight monolayers provides a remarkable lifetime improvement.