Stochastic Buffering for Bundled SWCNT Interconnects Considering Unidimensional Fabrication Variation

Abstract

The heterogeneous system architecture which leverages multicore computing paradigm has become increasingly popular. Nevertheless, timing minimization is still a critical design challenge. Buffer insertion for bundled single-walled carbon nanotubes (SWCNTs) is capable of significantly improving circuit timing of signal nets with limited buffer deployment. However, due to the imperfection of fabricating long straight carbon nanotubes, there exist significant variations on the critical CNT geometric parameters such as the diameter and density, which will affect the circuit performance. On the other hand, the prevailing CNT fabrication uses Chemical Vapor Deposition, where the unidimensional spatial correlation manifests strongly. In this work, a unidimensional variation aware stochastic SWCNT interconnects buffering algorithm is developed to handle fabrication variations of CNTs in buffer insertion. To improve its time complexity, a novel importance sampling based timing evaluation technique is proposed considering unidimensional correlations of variations. The simulation results demonstrate that the unidimensional variation aware importance sampling based stochastic SWCNT interconnects buffering algorithm on average saves more than 30 percent buffer area over copper buffering while satisfying timing constraints. In addition, our proposed stochastic algorithm achieves much better performance than the best case design and the worst case design in terms of timing and buffer cost.