Detrimental impact of hydrogen passivation on NBTI and HC degradation

Numerous studies have shown that the passivation of interface states by hydrogen has a significant impact on degradation mechanisms such as the bias temperature instability (BTI) and hot carrier (HC) degradation. By varying the thickness of the titanium layer at the beginning of the back-end-of-line processing we are able to change the hydrogen content near the Si-SiO₂ interface. While the precursor density for negative BTI (NBTI) defects with large time constants, typically observed as a quasi-permanent component, is dramatically increased with the hydrogen passivation degree, the distribution of activation energies is left unchanged. For PBTI, the opposite observation is made, that is, the degradation decreases with hydrogen passivation. Interestingly, the recovery activation energy for hot carrier induced degradation is fully consistent with P_b center passivation, while the recovery of the permanent component of BTI appears to be due to a different mechanism.