Fig. 1: Schematic diagram of key processes in the fabrication of superconducting tantalum airbridges, with substrate shown in violet, tantalum in light gray, aluminum in dark gray, and photoresist in orange.
From: Tantalum airbridges for scalable superconducting quantum processors
a Fabrication of the CPW layer with a 200 nm thick α-phase tantalum film on the sapphire substrate. Formation of the photoresist scaffold and base layer for airbridges with b spin coating, c exposure and d reflow of the first layer of photoresist. The red arrows in c denote the ultraviolet light, while the red disk in d represents baking at 140 °C. e Deposition of a barrier layer with 25 nm thick aluminum film. Formation of the bridge layer with f spin coating and g exposure of the second layer of photoresist. h Deposition of the tantalum airbridge with the niobium functioned as the seed layer after the ion milling of the CPW to ensure an electrical connection. i, j SEM images of tantalum airbridges with separate and fully-capped structures connecting the ground planes or two CPW center lines by lift-off method.
