Whole-wafer fabrication process for three-terminal double stacked tunnel junctions

A new fabrication process for three-terminal superconducting devices consis ting of two Josephson junctions in a stacked configuration is reported. The process is based on the deposition of the whole Nb/AlxOy/Nb-Al/AlxOy/Nb mu ltilayer on a Si crystalline wafer without any vacuum breaking. Lift-off te chniques, anodization processes and a SiO film deposition have been adopted for patterning and insulating the two tunnel stacked junctions. Devices ha ve been characterized in terms of current-voltage (I-V) curves and Josephso n critical current vs. the externally applied magnetic field. They show hig h quality factors (V-m values up to 65 mV at 4.2 K), and good current unifo rmity.