Fabrication and characterization of low-loss Al/Si/Al parallel plate capacitors for superconducting quantum information applications

Published

January 22, 2025

Author(s)

Raymond Simmonds, Sudhir Sahu, Trevyn Larson, Florent Lecocq, Tongyu Zhao, Anthony McFadden

Abstract

The application of parallel plate capacitors composed of aluminum-contacted, crystalline silicon fins for use in superconducting circuits is explored by evaluating the performance of superconducting lumped element resonators and transmon qubits. High aspect ratio Si-fin capacitors having widths below 300nm with an approximate total height of 3µm are fabricated using anisotropic wet etching of single crystal, float-zone Si(110) substrates followed by aluminum metallization using a self-aligned process. The single-crystal Si capacitors are incorporated in lumped element resonators and transmons by shunting them with lithographically patterned aluminum inductors and conventional Al/AlOx/Al Josephson junctions respectively. RF characterization of these devices at 35mK suggests state-of-the-art performance for superconducting parallel plate capacitors with low power Qi of lumped element resonators greater than 500k and qubit T1 times greater than 25µs. These results suggest that Si-Fins are a promising technology for applications that require low loss, compact, superconducting capacitors with minimal stray capacitance.

Citation

npj Quantum Information

Pub Type

Journals

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Citation

Simmonds, R. , Sahu, S. , Larson, T. , Lecocq, F. , Zhao, T. and McFadden, A. (2025), Fabrication and characterization of low-loss Al/Si/Al parallel plate capacitors for superconducting quantum information applications, npj Quantum Information, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=958235 (Accessed September 20, 2025)