Leakage power reduction using stress-enhanced layouts

In recent years, process-induced mechanical stress has emerged as a useful manufacturing technique that enhances carrier transport and increases drive currents. This improvement in current has helped to compensate the decline of device scaling factors in parameters such as t_ox, V_th, and V_dd. In this work, we propose stress as a means to achieve optimal power-performance trade-off by combining stress-based, performance-enhanced standard cell assignment with dual-V_th, assignment. We study how stress-induced performance enhancements are affected by layout properties and improve standard cell layouts so that performance gains are maximized. We then develop a circuit-level, block-based, stress-enhanced optimization algorithm that includes all layout-dependent sources of mechanical stress. By combining the two performance enhancement techniques (stress-based and dual-V_th) for a set of benchmark circuits, we find that our stress-aware optimization, decreases leakage by ~24% on average, for iso-delay, when compared to dual-V_th assignment. Similarly, for iso-leakage, our optimization algorithm reduces delay on average by 5%. In both cases, the proposed method only incurs a small area penalty (< 0.5%).