Design and fabrication of Argonne/KICP detectors for CMB polarization.
We present the design, microfabrication and assembly of dual-polarization absorber-coupled Transition Edge Sensor (TES) bolometer detectors for cosmic microwave background B-mode polarization studies. The device consists of two separate dies incorporating suspended silicon nitride membranes within silicon frames, carefully aligned perpendicularly and fixtured face-to-face. Polarization sensitivity around 95 GHz is provided by a single dipole-like absorber element; we briefly analyze this absorber-in-waveguide configuration in closed form using the EMF method. Proximity effect Mo/Au bilayers provide control of the TES critical temperature between 400 mK and 600 mK, with a normal resistance R{sub n} {approx} 1{Omega}. DC magnetron sputtering, wet etching, and liftoff were employed for TES fabrication. Optimization of the superconducting Mo thin film utilized independent RF bias applied to the substrate during deposition in a confocal geometry. This technique allows outstanding thin film uniformity and stress to be achieved simultaneously over a 4-inch wafer surface, leading to excellent superconducting properties. Device thermal conductance in the range from 25-250pW/K was achieved using suspended silicon nitride membranes 1 micron thick. The value of the thermal conductance depends very strongly upon the surface roughness, and therefore in turn upon the treatment of the silicon nitride material during fabrication.
- Research Organization:
- Argonne National Laboratory (ANL)
- Sponsoring Organization:
- SC; nsf
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 979894
- Report Number(s):
- ANL/MSD/CP-66875
- Journal Information:
- AIP Conf. Proc. Vol. 1185, Journal Name: AIP Conf. Proc. Vol. 1185 Journal Issue: 2009
- Country of Publication:
- United States
- Language:
- ENGLISH
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