Project title: Si Through-Substrate Interconnects for Millimeter-Wave, Mixed-Signal Systems
Staff: Joyce H. Wu
Sponsor: MARCO Interconnect Focus Center, Applied Materials Graduate Fellowship
Advances in Si technology may eventually displace III-V semiconductor devices in many systems operating in the millimeter-wave regime. This would make bandwidth available for affordable and pervasive applications. The challenges for Si are low-loss interconnects and packaging, substrate isolation, and thermal management. We have developed a Si through-substrate via technology that allows for low-impedance ground distribution and substrate crosstalk isolation and has potential for addressing other substrate issues in the mm-wave regime.
Substrate crosstalk between sensitive RF circuits and analog and digital blocks is one of the most critical problems facing mixed-signal circuit designers. By means of deep-reactive ion etching, we have developed a Faraday cage isolation structure using through-wafer vias to surround noisy or sensitive circuits. We have demonstrated an isolation of 30 dB at 10 GHz and 16 dB at 50 GHz. New measurements show that a Faraday cage with only a few vias dramatically improves substrate noise isolation. This isolation technique offers potential for mixed-signal systems in the mm-wave regime.
J. H. Wu, J. Scholvin, and J. A. del Alamo, "A through-wafer interconnect in silicon for RFICs," IEEE Trans. Electron Devices, vol. 51, pp. 1765-1771, Nov. 2004.
J. H. Wu and J. A. del Alamo, "An equivalent circuit model for a Faraday cage substrate crosstalk isolation structure," IEEE Radio Frequency Integrated Circuits Symp., June 2004, pp. 635-638.