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

• URL: http://arxiv.org/abs/2408.01369v2
• Date: Fri, 23 Aug 2024 18:13:21 GMT
• Title: Fabrication and characterization of low-loss Al/Si/Al parallel plate capacitors for superconducting quantum information applications
• Authors: Anthony McFadden, Aranya Goswami, Tongyu Zhao, Teun van Schijndel, Trevyn F. Q. Larson, Sudhir Sahu, Stephen Gill, Florent Lecocq, Raymond Simmonds, Chris Palmstrøm,
• Abstract summary: parallel plate capacitors composed of aluminum-contacted, crystalline silicon fins are shown to be a promising technology for use in superconducting circuits. Single-crystal Si capacitors are incorporated in lumped element resonators and transmons by shunting them with lithographically patterned aluminum inductors and conventional $Al/AlO_x/Al$ Josephson junctions.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Increasing the density of superconducting circuits requires compact components, however, superconductor-based capacitors typically perform worse as dimensions are reduced due to loss at surfaces and interfaces. Here, parallel plate capacitors composed of aluminum-contacted, crystalline silicon fins are shown to be a promising technology for use in superconducting circuits by evaluating the performance of lumped element resonators and transmon qubits. High aspect ratio Si-fin capacitors having widths below $300nm$ with an approximate total height of 3$\mu$m are fabricated using anisotropic wet etching of Si(110) substrates followed by aluminum metallization. The single-crystal Si capacitors are incorporated in lumped element resonators and transmons by shunting them with lithographically patterned aluminum inductors and conventional $Al/AlO_x/Al$ Josephson junctions respectively. Microwave characterization of these devices suggests state-of-the-art performance for superconducting parallel plate capacitors with low power internal quality factor of lumped element resonators greater than 500k and qubit $T_1$ times greater than 25$\mu$s. These results suggest that Si-Fins are a promising technology for applications that require low loss, compact, superconductor-based capacitors with minimal stray capacitance.

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