Superconducting High-Aspect Ratio Through-Silicon Vias with DC-Sputtered Al for Quantum 3D integration

Abstract

This paper presents the fabrication and electrical characterization of superconducting high-aspect ratio through-silicon vias DC-sputtered with aluminum. Fully conformal and void-free coating of $300~\mu \text{m}$ -deep and $50~\mu \text{m}$ -wide vias with Al, a CMOS-compatible and widely available superconductor, was made possible by tailoring a funneled sidewall profile for the axisymmetric vias. Single-via electric resistance as low as 80.44 $\text{m}\Omega $ at room temperature and superconductivity below 1.28 K were measured by a cross-bridge Kelvin resistor structure. This work thus demonstrates the fabrication of functional superconducting interposer layers, suitable for high-density 3D integration of silicon-based quantum computing architectures.