https://doi.org/10.1140/epjqt/s40507-023-00213-x
Research
Improved parameter targeting in 3D-integrated superconducting circuits through a polymer spacer process
1
Department of Physics, ETH Zürich, Zurich, Switzerland
2
Quantum Center, ETH Zürich, Zurich, Switzerland
3
ETH Zürich—PSI Quantum Computing Hub, Paul Scherrer Institut, Villigen, Switzerland
a
graham.norris@phys.ethz.ch
g
andreas.wallraff@phys.ethz.ch
Received:
31
July
2023
Accepted:
14
December
2023
Published online:
11
January
2024
Three-dimensional device integration facilitates the construction of superconducting quantum information processors with more than several tens of qubits by distributing elements such as control wires, qubits, and resonators between multiple layers. The frequencies of resonators and qubits in flip-chip-bonded multi-chip modules depend on the details of their electromagnetic environment defined by the conductors and dielectrics in their vicinity. Accurate frequency targeting therefore requires precise control of the separation between chips and minimization of their relative tilt. Here, we describe a method to control the inter-chip separation by using polymer spacers. With the spacers, we measure a mean tilt of (76 ± 36) μrad, and a mean deviation of (0.4 ± 0.8) μm from the target inter-chip separation of 10 μm. We apply this process to coplanar waveguide resonator samples and observe chip-to-chip resonator frequency variations below 50 MHz (
). We measure internal quality factors of 
at the single-photon level, suggesting that the added spacers are compatible with low-loss device fabrication.
Key words: Three-dimensional integration / Flip-chip bonding / Superconducting microwave resonators / Coplanar Waveguide or CPW / Frequency targeting / Quality factor
© The Author(s) 2024
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