Title :
Micron and submicron Nb/Al-AlOx/Nb tunnel junctions with high critical current densities
Author :
Meng, Xiaofan ; Zheng, Lizhen ; Wong, Andre ; Van Duzer, Theodorc
Author_Institution :
Dept. of Electr. Eng. & Comput. Sci., California Univ., Berkeley, CA, USA
fDate :
3/1/2001 12:00:00 AM
Abstract :
To increase superconducting IC speed and density, it is necessary to reduce junction size and increase critical current density. We describe the fabrication and properties of high critical current density micron and submicron Nb/Al-AlOx/Nb tunnel junctions. Using a 10:1 reduction wafer stepper with I-line photoresist, we obtained a minimum linewidth of 0.6 μm and junctions as small as 0.3 μm2 . The critical current densities can be as high as 20 kA/cm2 still with low subgap currents. The measured critical current spreads are small. This is due to the use of low-temperature, low-stress ECR (Electron Cyclotron Resonance)-based PECVD (Plasma Enhanced Chemical Vapor Deposition) SiO2 insulation layers and light anodization around junction areas. The junctions have potential applications in very high-speed superconducting digital circuits and submillimeter microwave devices
Keywords :
aluminium; aluminium compounds; critical current density (superconductivity); niobium; superconductive tunnelling; 0.6 micron; ECR PECVD SiO2 insulation layer; Nb-Al-AlO-Nb; Nb/Al-AlOx/Nb tunnel junction; anodization; critical current density; high-speed superconducting digital integrated circuit; i-line photoresist; subgap current; submillimeter microwave device; wafer stepper; Critical current; Critical current density; Current measurement; Fabrication; Josephson junctions; Niobium; Plasma measurements; Resists; Superconducting integrated circuits; Superconducting microwave devices;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
