Nb-AlO_x-Nb SNAP Technology for 125 mm Wafers Developed in Partnership with Silicon Technology

Abstract

We have demonstrated a 4-mask-level selective niobium anodization process (SNAP) technology for 125 mm wafers. With the exception of the initial Nb-AlO_x-Nb trilayer preparation, this process is carried out almost exclusively within a VLSI fabrication area and utilizes existing 1x lithography, Cl-based reactive ion etching, and materials deposition capability developed for Si technology. Our design consists of a personalized wafer layout with a number of 6 × 6 mm diagnostic chips and a wide variety of SQUIDs, magnetometers (as large as 12 × 12 mm), gradiometers (as large as 12 × 24 mm), soliton oscillators, and other Josephson devices at minimum design rules of 2 μm. We have used this process to produce high quality Josephson junctions with the figure of merit Vm > 60 mV for a Josephson critical current density J_c of 500–1000 A/cm2. Resistors were fabricated with 35-nm-thick e-beam evaporated Pt having a sheet resistance of about 4Ω/□. This approach to Josephson fabrication provides a low overhead, fast turn-around process particularly well suited for trilayer development and for production of many physically large, application specific integrated Josephson devices.