Lower-temperature fabrication of airbridges by grayscale lithography to increase yield of nanowire transmons in circuit QED quantum processors

• URL: http://arxiv.org/abs/2301.04065v1
• Date: Tue, 10 Jan 2023 16:33:20 GMT
• Title: Lower-temperature fabrication of airbridges by grayscale lithography to increase yield of nanowire transmons in circuit QED quantum processors
• Authors: T. Stavenga and L. DiCarlo
• Abstract summary: Quantum hardware uses airbridges to suppress unwanted modes of wave propagation in coplanar-waveguide transmission lines. Traditional airbridge fabrication produces a curved profile by reflowing resist at elevated temperature prior to metallization. We employ grayscale lithography in place of reflow to reduce the peak airbridge processing temperature from $200$ to $150circmathrmC$.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Quantum hardware based on circuit quantum electrodynamics makes extensive use of airbridges to suppress unwanted modes of wave propagation in coplanar-waveguide transmission lines. Airbridges also provide an interconnect enabling transmission lines to cross. Traditional airbridge fabrication produces a curved profile by reflowing resist at elevated temperature prior to metallization. The elevated temperature can affect the coupling energy and even yield of pre-fabricated Josephson elements of superconducting qubits, tuneable couplers and resonators. We employ grayscale lithography in place of reflow to reduce the peak airbridge processing temperature from $200$ to $150^\circ\mathrm{C}$, showing a substantial yield increase of transmon qubits with Josephson elements realized using Al-contacted InAs nanowires.

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