A dual dielectric approach for performance aware gate tunneling reduction in combinational circuits

With continued and aggressive scaling, using ultra-low thickness SiO₂ for the transistor gates, tunneling current has emerged as the major component of leakage in CMOS circuits. In this paper, we propose a new approach called dual dielectrics of dual thicknesses (DKDT) for the reduction of both ON and OFF state gate tunneling currents. We claim that the simultaneous utilization of SiON and SiO₂ each with multiple thicknesses is a better approach for gate leakage reduction than the conventional one that uses a single gate dielectric, SiO₂, of multiple thicknesses. We develop an algorithm for the corresponding assignment of dual dielectric and dual thickness cells that minimizes the overall tunneling current for a circuit without compromising its performance. We performed extensive experiments on ISCAS´85 benchmarks using 45 nm technology which demonstrate that our approach can reduce the tunneling current by as much as 98.7% (on average 94.8%), without performance degradation.