HTS edge junction dependence on base electrode edge smoothness

A series of experiments were performed in a Taguchi experimental matrix to examine and compare critical fabrication process factors in junction electrical performance. Factors such as angle of HTS deposition by pulsed laser deposition (PLD), pre-cleaning and annealing dwell time prior to epitaxial depositions, and angle of film edges created by ion milling were examined. The most critical factor influencing junction performance was the inherent morphology and smoothness of the base electrode. Based on this we focused on improving base electrode film smoothness. Using this approach we reduced junction excess current by a factor of 5 to 10 as confirmed by subsequent wafer fabrications, improved technique was then integrated into our two-inch wafer process which incorporates automated stepping equipment providing deep sub-micron layer-to-layer alignment capability.