Reliability issues and design solutions in advanced CMOS design

Over decades, scientists have been scaling devices to increasingly smaller feature sizes for ever better performance of complementary metal-oxide semiconductor (CMOS) technology to meet requirements on speed, complexity, circuit density, power consumption and ultimately cost required by many advanced applications. However, going to these ultra-scaled CMOS devices also brings some drawbacks. Aging due to bias-temperature-instability (BTI) and Hot carrier injection (HCI) is the dominant cause of functional failure in large scale logic circuits. The aging phenomena, on top of process variations, translate into complexity and reduced design margin for circuits. Such issues call for “Design for Reliability”. In order to increase the overall design efficiency, it is important to (i) study the impact of aging on circuit level along with the transistor level understanding (ii) calibrate the theoretical findings with measurement data (iii) implementing tools that analyze the impact of BTI and HCI reliability on circuit timing into VLSI design process at each stage. In this work, post silicon measurements of a 28nm HK-MG technology are done to study the effect of aging on Frequency Degradation of digital circuits. A novel voltage controlled ring oscillator (VCO) structure, developed by NIMO research group is used to determine the effect of aging mechanisms like NBTI, PBTI and SILC on circuit parameters. Accelerated aging mechanism is proposed to avoid the time consuming measurement process and extrapolation of data to the end of life thus instead of predicting the circuit behavior, one can measure it, within a short period of time. Finally, to bridge the gap between device level models and circuit level aging analysis, a System Level Reliability Analysis Flow (SyRA) developed by NIMO group, is implemented for a TSMC 65nm industrial level design to achieve one-step reliability prediction for digital design.