Title :
SIS Mixer Fabrication for ALMA Band10
Author :
Kroug, Matthias ; Endo, A. ; Tamura, T. ; Noguchi, T. ; Kojima, T. ; Uzawa, Y. ; Takeda, M. ; Wang, Z. ; Shan, W.
Author_Institution :
Nat. Astron. Obs. of Japan, Tokyo, Japan
fDate :
6/1/2009 12:00:00 AM
Abstract :
Band10 of the Atacama Large Millimeter Array (ALMA) is a planned heterodyne receiver covering the frequency range 790 GHz-950 GHz. The waveguide mixers are superconductor insulator superconductor (SIS) Nb/Al-AlOx/Nb junctions integrated with NbTiN/SiO2/Al tuning circuits. Our junction definition process has been greatly simplified by introducing an inductively-coupled-plasma (ICP) etcher to the fabrication. The etching process, which employs a low-pressure CF4/O2 plasma, allows to remove the entire Nb/Al-AlOx/Nb tri-layer in a single step. SIS mixers with current densities up to 10 kA/cm2 and quality factor above 15 have been fabricated with good reproducibility. Minimum receiver noise temperature, corrected for optical losses, is 210 K at 860 GHz. With the goal to further improve the performance, optimization of circuit design and fabrication technology are discussed.
Keywords :
aluminium; aluminium compounds; current density; niobium; niobium compounds; plasma materials processing; silicon compounds; sputter etching; submillimetre wave mixers; superconducting microwave devices; superconductor-insulator-superconductor mixers; titanium compounds; ALMA Band10; Atacama large millimeter array Band10; CF4/O2 plasma; Nb-Al-AlOx-NbTiN-SiO2-Al; SIS mixer; are ductor insulator superconductor junctions; current densities; etching process; frequency 790 GHz to 950 GHz; heterodyne receiver; inductively-coupled-plasma etcher; optical losses; quality factor; temperature 210 K; waveguide mixers; ICP etching; SIS mixer; submillimeter wave receiver;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
DOI :
10.1109/TASC.2009.2017856
