The negative bias temperature instability in MOS devices: A review

Negative bias temperature instability (NBTI), in which interface traps and positive oxide charge are generated in metal–oxide–silicon (MOS) structures under negative gate bias, in particular at elevated temperature, has come to the forefront of critical reliability phenomena in advanced CMOS technology. The purpose of this review is to bring together much of the latest experimental information and recent developments in theoretical understanding of NBTI. The review includes comprehensive summaries of the basic phenomenology, including time- and frequency-dependent effects (relaxation), and process dependences; theory, including drift–diffusion models and microscopic models for interface states and fixed charge, and the role of nitrogen; and the practical implications for circuit performance and new gate-stack materials. Some open questions are highlighted.