Interconnect opportunities for gigascale integration

Throughout the past four decades, semiconductor technology has advanced at exponential rates in both productivity and performance. In recent years, multilevel interconnect networks have become the primary limit on the productivity, performance, energy dissipation, and signal integrity of gigascale integration. Consequently, a broad spectrum of novel solutions to the multifaceted interconnect problem must be explored. Here we review recent salient results of this exploration. Based upon prediction of the complete stochastic signal interconnect length distribution of a megacell, optimal reverse scaling of each pair of wiring levels provides a prime opportunity to minimize cell area, clock period, power dissipation, or number of wiring levels. Using a heterogeneous version of Rent's rule, a design methodology for the global signal, clock, and power/ground distribution networks for a system-on-a-chip has been derived. Wiring area, bandwidth, and signal integrity are the prime constraints on the design of the networks. Three-dimensional integration offers the opportunity to reduce the length of the longest global interconnects in a distribution by as much as 75%. Wafer-level batch fabrication of chip input/output interconnects and chip scale packages provides new benefits such as I/O bandwidth enhancement, simultaneous switching-noise reduction, and lower cost of packaging and testing. Microphotonic interconnects have long-term potential to reduce latency, power dissipation, and crosstalk while increasing bandwidth.