Chemical–Mechanically Planarized Cross-Type Josephson Junctions in Nb-Al-AlOx-Nb Technology

Fabrication of devices composed of Josephson junctions in trilayer technology is usually compromised by the topography of the subjacent layers. If the structures of subsequent layers traverse steps, several adverse effects arise. Lithography may be impaired because of issues with resist thickness uniformity and focus depth, and the superconducting ampacity of the Nb wiring is reduced. Various methods have been tried to planarize perturbing structures. In this contribution, we address a few of the challenges of chemical mechanical polishing. The proposed improvements are based on the well-established IPHT cross-type junction technology.