NBTI: What we know and what we need to know a tutorial addressing the current understanding and challenges for the future

In advanced CMOS technologies, the Negative Bias Temperature Instability (NBTI) phenomenon in pMOSFETs is a major reliability concern as well as a limiting factor in future device scaling. Recently, much effort has been expended to further the basic understanding of this mechanism. This tutorial will give an overview of the physics of NBTI. Discussion will include such topics as the impact of NBTI on the observed changes in the device characteristics as well as the impact of gate oxide processes on the physics of NBTI. Current experimental results exploring various NBTI effects such as frequency dependence and relaxation will also be discussed. Since some of the recent work on the various NBTI effects seems contradictory, focus will be placed on highlighting our current understanding, our open questions and our future challenges.