Superconducting Pathways Through Kilopixel Backshort–Under–Grid Arrays

• Published in: Journal of low temperature physics Vol. 184; no. 3-4; pp. 615 - 620
• Main Authors: Jhabvala, C. A., Benford, D. J., Brekosky, R. P., Costen, N. P., Datesman, A. M., Hilton, G. C., Irwin, K. D., Maher, S. F., Manos, G., Miller, T. M., Moseley, S. H., Sharp, E. H., Staguhn, J. G., Wang, F., Wollack, E. J.
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.08.2016
• Subjects: Characterization and Evaluation of Materials; Condensed Matter Physics; Magnetic Materials; Magnetism; Physics; Physics and Astronomy; Through wafer via; Transition edge sensor; Backshort–Under–Grid; HAWC; Indium bump bonding; Atomic layer deposition; Bolometer
• ISSN: 0022-2291; 1573-7357
• DOI: 10.1007/s10909-016-1487-y

We have demonstrated in the laboratory multiple, fully functional, kilopixel, bolometer arrays for the upgraded instrument, the High-resolution airborne wideband camera plus (HAWC+), for the stratospheric observatory for infrared astronomy (SOFIA). Each kilopixel array consists of three individual components assembled into a single working unit: (1) a filled, Transition Edge Sensor (TES) bolometer array, (2) an infrared, back-termination, and (3) an integrated, two-dimensional superconducting quantum interference device (SQUID) multiplexer readout. Kilopixel TES arrays are directly indium-bump-bonded to a 32   ×   40 SQUID multiplexer (MUX) circuit. In order to provide a fully superconducting pathway from the TES to the SQUID readout, numerous superconductor-to-superconductor interfaces must be made. This paper focuses on the fabrication techniques needed to create the superconducting path from the TES, out of the detector membrane, through the wafer, and to the SQUID readout.