Buffering Carbon Nanotube Interconnects Considering Inductive Effects

While copper interconnect scaling is approaching its fundamental physical limit, increasing wire resistivity and delay have greatly limited the circuit miniaturization. The emerging carbon nanotube (CNT) interconnects, especially single-walled CNTs (SWCNTs) bundle interconnects, have become a promising replacement material. Nevertheless, physical design optimization techniques are still needed to allow them achieving the desired performances. While the preliminary conference version of this work [L. Liu, Y. Zhou and S. Hu, Proc. IEEE Computer Society Annual Symp. on VLSI (IS VLSI), 2014] designs the first timing driven buffer insertion technique for SWCNT interconnects, it only considers resistive and capacitive effects but not inductive effects. Although inductance could be negligible for prevailing CNT-based circuit designs, it becomes important when designing ultra-high performance chips in the future. Thus, this paper considers buffering inductive bundled SWCNTs interconnects through developing a dynamic programming algorithm for buffer insertion using the RLC tree delay model. Our experiments demonstrate that bundled SWCNTs interconnect-based buffering can effectively reduce the delay by over 3 x when inductive effects are considered. With the same timing constraint, bundled SWCNTs interconnect-based buffering can save over 20% buffer area compared to copper interconnect based buffering, while still running about 2 x faster.