25.01.2023Open Position MEP/BEP

Open position for master thesis project: resist-free fabrication of Josephson junctions

Image
Share this article

Josephson junctions are the heart of superconducting qubits, controlling the Josephson energy of the qubit and hence it’s frequency, anharmonicity, tunability. Being the only point of current flow in the qubit, the Josephson junctions quality heavily impacts the coherence time of the qubit, both the energy relaxation time T1 and phase decoherence time T2.

In a conventional fabrication process the Josephson junctions are patterned in the resist stack, which is much thicker than the smallest dimension of the Josephson junction leads, which makes the residue-free development difficult and unverifiable. Resist residues can have a severe impact on qubit coherence if there is even 1 Ohm contact resistance, as it adds another loss channel and might make a parasitic junction in series [1]. Additionally, resist processing at the nanoscale is susceptible to even tiny variations in the environment during spinning, baking, development, which leads to extra variations in Josephson junctions dimensions and targeting the qubits frequencies.

In this project we aim to develop a resist-free technique for Josephson junction fabrication by use of SiN membrane based nano-stencil directly in contact with the qubit base plane [2]. We will investigate extensively the limits of RIE patterning of SiN membrane, SEM inspection, KOH anisotropic etching of Si. It will also require development of the alignment tool suitable for Plassys e-beam evaporator. The bulk of the work will be done in the Kavli Nanolab Cleanroom.

Join the project

If you are interested to join this project, please contact Matvey Finkel.

References

  1. Ran Gao et al., ‘An inorganic shadow-mask platform for Josephson junction fabrication,’ APS March Meeting 2021, Vol. 66, N 1, V30.00001.
  2. Tsioutsios, K. Serniak, S. Diamond, V.V. Sivak, Z. Wang, S. Shankar, L. Frunzio, R.J. Schoelkopf, and M.H. Devoret, AIP Advances 10, 065120 (2020).

Requirements:

  • Applied Physics Master’s Program
  • Preferably followed NB2081 Nanotechnology
  • Ideally have completed all coursework
Back to overview
Image

QuTech Scholarships 2023 open for registration

QuTech is offering full scholarships for excellent, international applicants interested in a Master’s track in quantum. We are always ...
Read more
Back to QuTech