Microscopic Understanding of PBTI and NBTI Mechanisms in High-k / Metal Gate Stacks

We have established a comprehensive understanding of the PBTI and NBTI reliability of high-k/metal gate stacks. PBTI is found to exhibit a universal relationship, in terms of fast transient carrier traps and stress voltage, due to the formation of positive oxygen vacancies. The use of metal gates for Tinv scaling is promising for the improvement of drain current without PBTI lifetime degradation. However, in the case of NBTI, interface state degradation becomes more serious with Tinv scaling. Thus, the use of a high quality interfacial layer, such as a wet oxide interface, is a promising solution for the improvement of NBTI lifetime.