Stencil Mask Enabled Fabrication for Superconducting Qubits (Part 2)

Two-level systems (TLS) originating from amorphous dielectrics and organic residues are a major source of decoherence in superconducting quantum circuits. Although the microscopic origins of TLS remain unclear, they are believed to reside at metal and substrate interfaces, as well as within junction barriers. Surface treatments aimed at eliminating these interface dielectrics have improved both resonator quality factors and qubit coherence times. While ground metal can be thoroughly cleaned, the resist-based liftoff process for Josephson junctions is not robust enough to endure such harsh cleaning. As a result, organic resists can leave behind residues that contribute to TLS formation. Employing a resist-free process for fabricating Josephson junctions may therefore enhance qubit coherence.



In this second part of this two-part talk, we first demonstrate the precise alignment of the stencil mask on a silicon wafer, followed by the fabrication of Josephson junctions through deposition using the stencil mask. Next, we perform DC characterization of these junctions at room temperature and compare their characteristics with those fabricated using a resist-based liftoff process. Finally, we demonstrate the fabrication of standard transmons incorporating stencil mask-deposited junctions.