Comparative analysis of copper and CNT interconnects for H-tree clock distribution

Abstract

Clock distribution network is an important part of digital integrated circuits. The clock signal carried by the distribution network has to reach every end node at the same time to ensure synchronized switching. Due to mismatches among different nodes of the H-tree, the clock transitions among the final nodes of the distribution tree show some time difference, the maximum of which is called clock skew. In modern CMOS technologies, copper interconnect is popular for high level interconnects such as clock and power routing. Carbon Nanotube (CNT) exhibits less resistivity than copper making it a better material for interconnect. This paper compares the impact on clock skew of H-tree clock distribution network by replacing the traditional copper interconnects with carbon nanotube interconnects. By applying temperature mismatch, threshold voltage mismatch, and process mismatch, our findings show that using carbon nanotube interconnects reduces the clock skew significantly compared to traditional copper interconnects.