Fabrication of large dual-polarized multichroic TES bolometer arrays for CMB measurements with the SPT-3G camera

• Published in: Superconductor Science and Technology
• Main Authors: Posada, C. M., Ade, P. A. R., Ahmed, Z., Arnold, K., Austermann, J. E., Bender, A. N., Bleem, L. E., Benson, B. A., Byrum, K., Carlstrom, J. E., Chang, C. L., Cho, H. M., Ciocys, S. T., Cliche, J. F., Crawford, T. M., Cukierman, A., Czaplewski, D., Ding, J., Divan, R., de Haan, T., Dobbs, M. A., Dutcher, D., Everett, W., Gilbert, A., Halverson, N. W., Harrington, N. L., Hattori, K., Henning, J. W., Hilton, G. C., Holzapfel, W. L., Hubmayr, J., Irwin, K. D., Jeong, O., Keisler, R., Kubik, D., Kuo, C. L., Lee, A. T., Leitch, E. M., Lendinez, S., Meyer, S. S., Miller, C. S., Montgomery, J., Myers, M., Nadolski, A., Natoli, T., Nguyen, H., Novosad, V., Padin, S., Pan, Z., Pearson, J., Ruhl, J. E., Saliwanchik, B. R., Smecher, G., Sayre, J. T., Shirokoff, E., Stan, L., Stark, A. A., Sobrin, J., Story, K., Suzuki, A., Thompson, K. L., Tucker, C., Vanderlinde, K., Vieira, J. D., Wang, G., Whitehorn, N., Yefremenko, V., Yoon, K. W., Ziegler, K. E.
• Language: unknown
• Published: 2022
• Subjects: 79 ASTRONOMY AND ASTROPHYSICS; 46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; South Pole; South pole
• Online Access: http://www.osti.gov/servlets/purl/1594616; https://www.osti.gov/biblio/1594616; https://doi.org/10.1088/0953-2048/28/9/094002

This paper presents the procedures used by Argonne National Laboratory to fabricate large arrays of multichroic transition-edge sensor (TES) bolometers for cosmic microwave background (CMB) measurements. These detectors will be assembled into the focal plane for the SPT-3G camera, the third generation CMB camera to be installed in the South Pole Telescope. The complete SPT-3G camera will have approximately 2690 pixels, for a total of 16,140 TES bolometric detectors. Each pixel is comprised of a broad-band sinuous antenna coupled to a Nb microstrip line. In-line filters are used to define the different band-passes before the millimeter-wavelength signal is fed to the respective Ti/Au TES bolometers. There are six TES bolometer detectors per pixel, which allow for measurements of three band-passes (95 GHz, 150 GHz and 220 GHz) and two polarizations. The steps involved in the monolithic fabrication of these detector arrays are presented here in detail. Patterns are defined using a combination of stepper and contact lithography. The misalignment between layers is kept below 200 nm. The overall fabrication involves a total of 16 processes, including reactive and magnetron sputtering, reactive ion etching, inductively coupled plasma etching and chemical etching.