THz Interconnect

Background

Continuous scaling of semiconductor devices allows more processor cores 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 inter-/intra-chip communication bandwidth, which has been a big challenge over decades. This challenge has motivated active research to improve interconnect capacities, characterized by two key specs: bandwidth density, defined as gigabits per second per square millimeter, determining the aggregate throughput; and energy efficiency, defined as Joules per bit, indicating the overall power consumption. The required off-chip I/O bandwidth doubles about every two years, significantly exceeding the growth rate of the I/O pin number due to packaging/assembly limitations. The gap between the interconnect requirement and the supporting capability forms the “interconnect gap.” With the projecting trend, the power consumption and chip size to support interconnect only will be intolerable for most high performance computers and data centers in the near future . In addition, cost, defined as dollars per gigabit per second, also needs to scale down inversely proportional to the interconnect bandwidth to be sustainable. To support the continuous demands for inter-/intra- chip interconnect, the “interconnect gap” must be filled.

Our Approach: THz Interconnect

To ultimately solve the problem and close the gap, bandwidth density, energy efficiency and cost should be all be significantly improved. 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, as shown in Figure 1. Continuous scaling of mainstream silicon technologies enables terahertz electronics in silicon, which favors low cost and high reliability. On the other hand, terahertz waveguides, similar to their optical counterparts, have small dimensions and present low loss, which alleviates the TI link budget to allow low transmission output power and improves the energy efficiency. In addition, TI favors technology scaling because the increasing frequency supports higher communication data rates and reduces channel dimensions, thus resulting in a larger bandwidth density. These unique features equip TI with high energy efficiency, high bandwidth density, low cost, and high resilience with the potential to ultimately fill the
interconnect gap.

Publications

  1. Y. Wang, B. Yu, Y. Ye, C.-N. Chen, Q. J. Gu, and Huei Wang, “A G-Band On-Off-Keying Low Power Transmitter and Receiver for Interconnect Systems in 65-nm CMOS,” Accept IEEE Transactions on Terahertz Science and Technology, Nov. 2019
  2. 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
  3. S. Ma, H. Yu, Q. J. Gu, and J. Ren, “A 5-10 Gbps 12.5 mW Source Synchronous I/O Interface with 3D Flip Chip Package,” IEEE TCAS-I, vol. 66, Feb. 2019
  4. 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
  5. 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
  6. 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
  7. Y. Ye, B. Yu, X. Ding, X. Liu, and Q. J. Gu, “High Energy-Efficiency High Bandwidth-Density Sub-THz Interconnect for the Last-Centimeter Chip-to-Chip Communications,” IEEE International Microwave Symposium IMS2017
  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, X. Liu, and Q. J. Gu, “Low-loss and Broadband G-Band Dielectric Interconnect for Chip-to-Chip Communication,” IEEE Microwave and Wireless Components Letter, June 2016
  10. 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
  11. Q. J. Gu, “THz Interconnect, the Last Centimeter Communication,” IEEE Communication Magazine, vol. 53, no. 4, pp.206-215, April 2015
  12. B. Yu, Y. Ye, X. Liu, Q. J. Gu, “Microstrip Line based Sub-THz Interconnect for High Energy-Efficiency Chip-to-Chip Communications,” IEEE International Symposium on Radio-Frequency Integration Technology(RFIT), 2016
  13. S. Ma, J. Ren, N. Li, F. Ye, and Q. J. Gu, “A Wideband and Low Power Dual-Band ASK Transceiver for Intra/Inter-Chip Communication,” 2015 IEEE International Microwave Symposium
  14. Q. J. Gu, “Integrated Circuits and Systems for THz Interconnect,” 2015 IEEE Wireless and Microwave Conference, Invited Paper
  15. B. Yu, Y. Liu, X. Hu, X. Ren, X. Liu, and Q. J. Gu, “Micromachined Sub-THz Interconnect Channels for Planar Silicon Processes,” 2014 IEEE International Microwave Symposium
  16. 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
  17. Q. J. Gu, Z. Xu, and M.-C. F. Chang, “Millimeter Wave and Sub-millimeter Wave Circuits for Integrated System-On-a-Chip,” 2011 IEEE International Symposium on Radio-Frequency Integration Technology(RFIT), Best Paper Award

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