Analyzing crosstalk-induced effects in rough on-chip copper interconnects

Abstract

Aggressive scaling of on-chip interconnects results in significantly higher coupling capacitance, which results in crosstalk effects as we enter the end-of-the-roadmap era. Moreover, surface roughness is seen as a major contributor to conductor losses that further exacerbates these crosstalk-induced effects. This article reports an exhaustive analysis of crosstalkinduced effects, considering interconnect surface roughness at current and future technology nodes (i.e., 13 and 7 nm), for on-chip global copper interconnects. The role of repeater insertion in rough interconnects is also presented in our work. For our analysis, we have used an aggressor-victim-aggressor three-line bus architecture and FINFET-based driver circuits with binary input logic. Our results show that surface roughness degrades typical interconnect performance metrics i.e., worst case delay, bandwidth density (BWD), power consumption, and powerdelay product. At a 7-nm technology node, average worst case crosstalk delay and power consumption increase by 17× and 9×, respectively, when compared to smooth interconnects. Similarly, due to surface roughness, BWD reduces by nearly 17× for 7-nm global interconnects. For data rates of 0.2 Mb/s, eye height and eye width are reduced by 73% and 54%, respectively, in the worst case scenario for 7-nm global lines. Finally, we showcase the role of repeater insertion in enhancing performance metrics, in which crosstalk delay and power delay products are significantly improved (by 85% and 99%, respectively) at a 7-nm technology node.