THz Interconnect

Background

The continuous evolution of semiconductor technologies allows more transistors in the processor and integrated functionalities into a single chip to support the growing computation demands of scientific and commercial workloads in both increasing speed and volume. This trend mandates an ever-increasing data rates cross communication links ranging from inter-chip to inter-data center with the distance from millimeters to kilometers. Among these, the most challenging scenario lies in the medium-range communication span of 10s centimeters to 10 meters, which both conventional electrical interconnect and optical interconnect face great challenges. The gap between the interconnect demands and the supporting capability forms the “interconnect gap,” which has been further exacerbated by the emerging applications, such as autonomous driving and AI. To support continuous evolving of advanced technologies and applications, interconnect solutions must drastically advance two most critical performance metrics: bandwidth density, defined as Gbps/mm2, determining the aggregate throughput; and energy efficiency, defined as pJ/b, indicating the overall power consumption. In addition, cost, defined as $/Gbps, must be scaled down inversely proportional to the interconnected bandwidth for long-term sustainability.

Our Approach

To ultimately address interconnect challenge, bandwidth density, energy efficiency, and cost should be significantly improved coherently. THz Interconnect (TI), utilizing the frequency spectrum sandwiched between microwave and optical frequencies, holds high potential to complement Electrical Interconnect (EI) and Optical Interconnect (OI) by leveraging the advantages of both electronics and optics. Continuous scaling of mainstream silicon technologies enables terahertz (THz) electronics in silicon, which favors low cost and high reliability. On the other hand, THz dielectric waveguides (DWG), similar to their optical counterparts, have wide bandwidth and present low loss to support high speed data with high energy efficiency. Furthermore, TI is well-suited for technology scaling because the increasing device speed supports higher communication data rates and higher carried frequency reduces channel dimensions, leading to larger bandwidth density. These unique features equip TI with high energy efficiency, high bandwidth density, and low cost with the potential to fill the interconnect gap and meet the escalating demand for massive data communication.

Publications

  1. X. Ding, H. Yu, S. Sabbaghi and Q. J. Gu, “Design and Analysis of a Mode-Coupler-Based Multimode Multidrop Si Dielectric Waveguide Channel for Sub-THz/THz Interconnect,” in IEEE Transactions on Microwave Theory and Techniques, vol. 72, no. 1, pp. 111-123, Jan. 2024
  2. X. Ding, B. Yu, H. Yu, S. S. Saber and Q. J. Gu, “Multiplexing Schemes for sub-THz/THz Interconnects (Invited),” 2022 IEEE International Symposium on Radio-Frequency Integration Technology (RFIT), Busan, Korea, Republic of, 2022, pp. 18-20, Invited Paper
  3. Q. Jane Gu, “Sub-THz/THz Interconnect, Complement to Electrical and Optical Interconnects,” Fall 2020 IEEE Solid-State Circuits Magazine
  4. Q. J. Gu, Bo Yu, Xuan Ding, Yu Ye, Xiaoguang Liu, and Zhiwei Xu “THz interconnect: the last centimeter communication,” SPIE, May 2019, Invited Paper
  5. B. Yu, Y. Ye, X. Ding, C. Neher, X. Liu, Z. Xu, Q. J. Gu, “Sub-THz Interconnect for Planar Chip-to-Chip Communications,” IEEE SiRF 2018, Invited Paper
  6. B. Yu, Y. Ye, X. Ding, Y. Liu, Z. Xu, X. Liu, and Q. J. Gu, “Ortho-Mode Sub-THz Interconnect Channel for Planar Chip-to-chip Communications”, IEEE Transactions on Microwave Theory and Techniques, December 2017
  7. B. Yu, Y. Ye, X. Ding, Y. Liu, X. Liu, and Q. J. Gu, “Dielectric Waveguide Based Multi-Mode sub-THz Interconnect Channel for High Data-Rate High Bandwidth-Density Planar Chip-to-Chip Communication,” IEEE International Microwave Symposium IMS2017, Best Student Paper Award, 3rd Place Winner
  8. Y. Ye, B. Yu, and Q. J. Gu, “A 165 GHz Transmitter with 10.6% Peak DC-to-RF Efficiency and 0.68 pJ/bit Energy Efficiency on 65 nm Bulk CMOS,” IEEE Transactions on Microwave Theory and Techniques, pp. 4573-4584, vol.64, no. 12, Dec. 2016
  9. B. Yu, Y. Liu, Y. Ye, Junyan Ren, X. Liu, and Q. J. Gu, “High Efficiency Micromachined Sub-THz Channels for Low Cost Interconnect for Planar Integrated Circuits,” IEEE Transactions on Microwave Theory and Techniques, vol. 64, no. 1, pp. 96-104, January 2016
  10. Q. J. Gu, “THz Interconnect, the Last Centimeter Communication,” IEEE Communication Magazine, vol. 53, no. 4, pp.206-215, April 2015
  11. B. Yu, Y. Liu, X. Hu, X. Ren, X. Liu, and Q. J. Gu, “Micromachined Silicon Channels for THz Interconnect,” 2014 IEEE Wireless and Microwave Conference, Best Conference Paper Award