Highly-Conformal Sputtered Through-Silicon Vias With Sharp Superconducting Transition

Abstract

This paper describes the microfabrication and electrical characterization of aluminum-coated superconducting through-silicon vias (TSVs) with sharp superconducting transition above 1 K. The sharp superconducting transition was achieved by means of fully conformal and void-free DCsputtering of the TSVs with Al, and is here demonstrated in up to 500 µm-deep vias. Full conformality of Al sputtering was made possible by shaping the vias with a tailored hourglass profile, which allowed a metallic layer as thick as 430 nm to be deposited in the center of the vias. Single-via electric resistance as low as 160 mΩ at room temperature and superconductivity at 1.27 K were measured by a three-dimensional (3D) cross-bridge Kelvin resistor structure. This work establishes a CMOS-compatible fabrication process suitable for arrays of superconducting TSVs and 3D integration of superconducting silicon-based devices.

Qubit-Compatible Substrates With Superconducting Through-Silicon Vias

“…Resonator quality factor is often used as a diagnostic predictor of qubit relaxation time for a qubit with electrodes fabricated using the same flow as the resonators. Others have also fabricated superconducting TSVs but the microwave performance of those approaches remains to be measured [29]- [31]. Furthermore, coherence times exceeding 300 µs have recently been demonstrated for transmon qubits on planar sapphire substrates [2], [3].…”

Heat transfer study of 3D packaging structure with superconducting TSV for practical-scale quantum annealing machines

“…[27][28][29] Aluminum(Al)-based superconducting TSVs are successfully fabricated for quantum 3D integration. 30,31) The measured thermal conductivity of Al in the superconducting state is about two orders of magnitude lower than that in the normal state, which worsens the heat transfer issue. 32) In this study, the heat transfer of a 3D packaging QUIP structure with superconducting TSVs is investigated.…”

Qubit-compatible substrates with superconducting through-silicon vias

“…Resonator quality factor is often used as a diagnostic predictor of qubit relaxation time for a qubit with electrodes fabricated using the same flow as the resonators. Others have also fabricated superconducting TSVs but microwave performance of those approaches remains to be measured [28]- [30]. Furthermore, coherence times exceeding 300 µs have recently been demonstrated for transmon qubits on planar sapphire substrates [2], [3].…”