Fabrication of Deep-Sub-Micrometer NbN/AlN/NbN Epitaxial Junctions on a Si Substrate
arXiv:2004.00922 · doi:10.35848/1882-0786/abbfde
Abstract
We have developed a novel fabrication process for ultra-small, full-epitaxial NbN Josephson junctions on a silicon (Si) substrate. A full-epitaxial NbN/AlN/NbN tri-layer was grown on a Si (100) wafer with a (200)-oriented TiN buffer layer. It was patterned into Josephson junctions by an electron beam lithography (EBL) for junction definition followed by a reactive ion etch (RIE). A chemical mechanical polishing (CMP) process and an additional RIE by using CHF gas formed reliable electrical contacts between the junction counter electrodes and the wiring layer. All fabricated junctions, with a junction size down to 0.27 m in diameter, showed excellent current-voltage characteristics with a clear gap structure and a small sub-gap leakage current. The dielectric layer of SiO that served as an insulator between base and counter electrodes was removed in a wet etching process using a buffered HF solution. We have confirmed that the quality of the junctions was maintained after the removal of the SiO dielectric layer.
arXiv comment15 pages, 6 figures
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