RC Variability of Short-Range Interconnects

Line edge roughness (LER) in end-of-the-roadmap integrated circuit interconnects causes variability in their resistance R, capacitance C and hence also their RC delay. We present an analysis of LER-induced variability of resistance, capacitance and delay of short-range interconnects within standard cells at the 32, 22 and 18 nm technology nodes using both a commercial RC extraction tool as well as a fast quasi-analytical (QA) method. Our QA method includes size dependent resistivity which, when coupled with LER, reveals increased resistance variability and total resistance in interconnects at these technology nodes. For example, the QA method predicts variability of 52% in resistance, 16% in capacitance and 36% in RC delay. When LER is the dominant source of variability there is a correlation of -0.8 between resistance and capacitance. Our results indicate interconnect variability is a significant and worsening problem, which should be included in statistical models of standard cells.