Recent advances in EM and BTI induced reliability modeling, analysis and optimization (invited)

Abstract

In this article, we will present recent advances in reliability effects such as electromigration on interconnects and Negative/Positive Bias Temperature Instability (N/P BTI) effects on CMOS devices, which are the most important reliability concerns for VLSI systems specifically at the nanometer regime. We will start with the grand reliability challenges facing the semi-conductor and computing industry. Then, we will first present recent advances in the electromigration (EM) modeling and assessment techniques at the circuit level, the full-chip level and the system level. We will focus on the recently proposed advanced EM modeling techniques including stress-oriented physic-based EM models, EM modeling considering the time-varying temperature and current density changes, EM recovery effect modeling, the more general physics-based 3-phase EM models and the finite-difference-method based numerical analysis technique for dynamic EM stress analysis. Then we will present recent developments for dynamic reliability management at the system level, where EM-induced lifetime and performance can be traded off and the EM recovery effects can be leveraged for a longer lifetime on different computing platforms.For BTI effects, we will briefly explain the key mechanisms behind it first. Then, we will demonstrate how to bring aging-awareness to EDA tool flows based on our so-called degradation-aware cell libraries. Afterwards, we will present the impact of BTI effects on the leakage and dynamic power showing that BTI impact not only affects circuits’ delay over time (as in the traditional view), but also the overall power of circuits. Towards removing guard-bands and hence increase the efficiency, we will present how aging-induced stochastic timing errors can be translated into deterministic and controlled approximations in which aging effects are suppressed with a minimum loss in quality. Finally, we will demonstrate short-term aging effect which is a recent discovery that is hardly explored until now. In fact, short-term aging effects are a paradigm shift in BTI from sole long-term reliability degradation, which is observable in the order of months and years as in the traditional view, to an emerging reliability degradation, which is observable in a significantly smaller time domain in the order of milliseconds and even microseconds. Some of the developed EM models and assessment programs can be downloaded at https://github.com/sheldonucr/physics_based_em_assessment_analysis. The developed aging models, degradation-aware cell libraries, reliability framework, etc. are publicly available at: http://ces.itec.kit.edu/dependable-hardware.php. They are ready to be directly used with existing EDA tool flows like Synopsys without requiring any modifications.