Dependence of short channel length on negative/positive bias temperature instability (NBTI/PBTI) for 3D FinFET devices

A comprehensive study of the negative and positive bias temperature instability (NBTI/PBTI) of 3D FinFET devices with different small channel lengths is presented. It is found while with the channel lengths shrinking from 100 nm to 30 nm, both the NBTI characteristics of p-FinFET and PBTI characteristics of n-FinFET turn better. Moreover, the channel length dependence on NBTI is more serious than that on PBTI. Through the analysis of the physical mechanism of BTI and the simulation of 3-D stress in the FinFET device, a physical mechanism of the channel length dependence on NBTI/PBTI is proposed. Both extra fluorine passivation in the corner of bulk oxide and stronger channel stress in p-FinFETs with shorter channel length causes less NBTI issue, while the extra nitrogen passivation in the corner of bulk oxide induces less PBTI degradation as the channel length decreasing for n-FinFETs. The mechanism well matches the experimental result and provides one helpful guide for the improvement of reliability issues in the advanced FinFET process.