Nb/AlO<i>x</i>/Nb trilayer process for the fabrication of submicron Josephson junctions and low-noise dc SQUIDs

Abstract

A trilayer deposition process for making high quality all-refractory Nb/AlOx/Nb Josephson junctions is described. The sputtering parameters were optimized to deposit very uniform Al films, less than 5 nm in thickness. We found that it was essential to keep the substrate temperature below 40 °C during Al deposition but not during Nb depositions. Rapid anodization of the Nb counterelectrode allowed us to use positive photoresist as an anodization mask even for submicron geometries. The dc superconducting quantum interference devices made with this process have the lowest intrinsic energy sensitivity reported to date for an all-refractory technology.