Fabrication of niobium-carbonitride Josephson junctions onmagnesium-oxide substrates using chemical-mechanical polishing

摘要

We have developed a fabrication technique for narrow NbCx N1-x/MgO/NbCxN1-x junctions on MgO substrates using chemical-mechanical polishing (CMP) for the removal of SiO2 insulation layer from the top of junctions. Parameters of CMP have been optimized so that the run-to-run deviation of removal rate for SiO2 is less than ±20% and uniformity across a 10 mm×10 mm area is better than ±20%. Using the optimized CMP, NbCxN1-x/MgO/NbCx N1-x junctions with width of 1-4 μm have been successfully fabricated. Fabricated junctions showed no superconducting leakage current and critical current densities of interconnections between the counter electrode and the wiring were larger than 1×10 8 A/m2. This CMP-based fabrication technique is applicable to SIS mixers and Josephson local oscillators operated near 1 THz