Fabrication and Characterization of Through-Substrate Interconnects

We developed a through-substrate copper-damascene interconnect technology in silicon with minimal impedance. Via impedance was extracted using parameter measurements at 50 GHz that were matched to simple circuit models. The extracted impedance shows resistances ≤ 1 Ω, record-low inductance for aspect ratios > 4, and sidewall capacitance that approaches the theoretical value. For an aspect ratio of 10 (10 in diameter and 100 high), the through-substrate via has an average inductance of 36 pH at 10 GHz, resistance of 0.6 at 1 GHz, and sidewall capacitance of 0.3 pF.