Standard cell library optimization for leakage reduction

Scaling device geometries have caused leakage-power consumption to be one of the major challenges of deep sub-micron design and a major source for parametric yield loss. We propose a library optimization approach involving generation of additional variants for each cell master, by biasing gate-lengths of devices. We employ transistor-level gate-length assignment to exploit asymmetries in standard cell circuit topology as well slack distribution of the design. The enhanced library is used by a power optimizer to reduce design leakage without violating any timing constraints. Such transistor-level optimization of cell libraries offers significantly better leakage-delay tradeoff than simple cell-level biasing (CLB) proposed previously. Experimental results on benchmarks show transistor-level biasing (TLB) can improve the CLB leakage optimization results by 8-17%. There is a corresponding improvement in design leakage distribution as well.