THz Interconnect: The Last Centimeter Communication

Terahertz, sandwiched between conventional microwave and optical frequencies, has inspired increasing interest due to its uniqueness and high potential applications, such as imaging, sensing, and communications. This article, on the other hand, focuses on one emerging application of the terahertz spectrum: THz interconnect. Intra-/inter-chip communication has doubled every two years over recent decades, and the trend is projected to continue in the future. However, the bandwidth supportable by chip I/O pins cannot keep up with the requirement, which forms the increasing gap between the bandwidth requirement and support capability, or the interconnect gap. To ultimately solve the problem and close the gap, both bandwidth density and energy efficiency should be boosted. THz interconnect holds high potential to boost key performance by leveraging the advantages of both high-speed electronics devices and low-loss quasi-optical channels. This article discusses THz interconnect from different aspects: system architecture, circuit specifications, design challenges, and non-ideality effects. Particularly, this article exemplifies both active and passive circuit design techniques for THz interconnect, a 140 GHz transceiver and a terahertz generator in 65 nm CMOS technology, and a low-loss and process-compatible silicon waveguide channel. THz interconnect opens high potential new revenue to solve the long-standing interconnect issue.