Characteristics and Fluctuation of Negative Bias Temperature Instability in Si Nanowire Field-Effect Transistors

In this letter, negative bias temperature instability (NBTI) in silicon nanowire field-effect transistors (SNWFETs) is investigated and found to exhibit some new characteristics that are probably due to the structural nature of nanowires. In long-channel SNWFETs, a fast degradation and a quick saturation of NBTI are observed and discussed. In short-channel SNWFETs, a large fluctuation of NBTI is observed, which mainly originates from the ultrasmall gate areas of the short-channel SNWFETs and the statistical nature of randomly trapped charges in the oxide and at the Si/SiO₂ interface. Techniques to suppress the fluctuation and characterize the intrinsic NBTI in ultrasmall SNWFETs are proposed and discussed. A recently developed online gate current method is demonstrated, which effectively alleviates this NBTI fluctuation in SNWFETs.