US Patent 9425376 Plasma cleaning of superconducting layers

In a “window-junction” formation process for Josephson junction fabrication, a spacer dielectric is formed over the first superconducting electrode layer, then an opening (the “window” is formed to expose the part of the electrode layer to be used for the junction. In an atomic layer deposition (ALD) chamber (or multi-chamber sealed system) equipped with direct or remote plasma capability, the exposed part of the electrode is sputter-etched with Ar, H2, or a combination to remove native oxides, etch residues, and other contaminants. Optionally, an O2 or O3 pre-clean may precede the sputter etch. When the electrode is clean, the tunnel barrier layer is deposited by ALD in-situ without further oxidant exposure.