Impacts of non-negligible electron trapping/detrapping on the NBTI characteristics in silicon nanowire transistors with TiN metal gates

Impacts of electron trapping/detrapping on the negative bias temperature instability (NBTI) characteristics in silicon nanowire transistors (SNWTs) with metal gates are experimentally studied in this paper. It is demonstrated that large amounts of as-grown defects, including both electron traps and hole traps, are induced by nanowire structure due to multiple surface crystal orientations of the cylinder nanowires. Quite different from conventional planar devices, both stress and recovery of NBTI in SNWTs are evidently impacted by electron trapping/detrapping behavior, due to the enhanced electrical field with cylinder surrounded gate, increased electron traps in the gate dielectrics and electron injection from metal gates. The generation of new-born trap-precursors in the gate dielectrics of SNWTs was also observed and the generation kinetics is discussed. These new-born precursors can be converted into traps after experiencing a grounded recovery phase and a pulse state, leading to additional unexpected reliability degradation of SNWTs.