Impact of Bias temperature instability on reconfigurable field effect transistors and circuits

Abstract

Assessing the reliability of emerging device technologies is of fundamental importance to facilitate their adoption in larger scale electronic circuits and systems. This is even more true for all those devices whose unique behavior paves the way towards innovative circuit solutions, but also poses new reliability concerns that are not well known as in established technologies such as CMOS. In this paper, we thoroughly discuss the bias temperature instability (BTI) reliability features of three-independent-gate reconfigurable field effect transistors (RFETs). This multi-gate transistor technology is characterized by the unique feature of providing volatile polarity and threshold control within an individual device. While these devices are subjected to positive and negative BTI in alternating fashion during circuit operation, we identified negative BTI to be the worst-case condition with respect to performance degradation of RFETs in terms of threshold voltage shift and sub-threshold slope reduction. In addition we could reveal clear phenomenological differences in the degradation if the stress profiles are applied to the gates that turn on and off the transistors, rather than when they are applied to the ones that program their polarity. Positive BTI generally produces negligible effects on the threshold voltage shifts, while it has a certain impact on the sub-threshold slope degradation of one of the operational modes of the considered transistors.