Microfabrication and Device Parameter Testing of the Focal Plane Arrays for the Spider and BICEP2/Keck CMB Polarimeters
Abstract
Spider and BICEP2/Keck are projects to study the polarization of the cosmic microwave background (CMB). The focal planes for both require large format arrays of superconducting transition edge sensors (TES's). A major challenge for these projects is fabricating arrays with high uniformity in device parameters. A microfabrication process is described that meets this challenge. The results from device testing are discussed. Each focal plane is composed of 4 square wafers (tiles), and each wafer contains 128 membrane-isolated, polarization-sensitive, antenna-coupled TES's. After processing, selected wafers are pre-screened in a quick-turn-around, cryogen-free, 3He fridge. The pre-screening is performed with a commercial resistance bridge and measures transition temperatures (Tc) and normal state resistances (Rn). After pre-screening, 4 tiles at a time are fully characterized in a testbed employing a SQUID readout and SQUID mulitplexing. The tests demonstrate the values of Tc, Rn, thermal conductance, g, and the standard deviations of each, across a wafer and from wafer to wafer, are within design specifications.
- Publication:
-
The Thirteenth International Workshop on Low Temperature Detectors - LTD13
- Pub Date:
- December 2009
- DOI:
- 10.1063/1.3292354
- Bibcode:
- 2009AIPC.1185..367B
- Keywords:
-
- bolometers;
- solar system;
- cryogenics;
- 95.55.Rg;
- 98.80.-k;
- 07.20.Mc;
- Photoconductors and bolometers;
- Cosmology;
- Cryogenics;
- refrigerators low-temperature detectors and other low-temperature equipment