1. Performance of SAFARI Short-Wavelength-Band Transition Edge Sensors (TES) Fabricated by Deep Reactive Ion Etching
- Author
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Khosropanah, P., Hijmering, R. A., Ridder, M., Schoemans, M., Hoevers, H., Gao, J. R., and Suzuki, Toyoaki
- Subjects
Physics ,Radiation ,Fabrication ,business.industry ,Bolometer ,law.invention ,chemistry.chemical_compound ,Optics ,Silicon nitride ,chemistry ,law ,Etching (microfabrication) ,Deep reactive-ion etching ,Optoelectronics ,Electrical and Electronic Engineering ,Transition edge sensor ,Reactive-ion etching ,business ,Dark current - Abstract
We are developing the SAFARI/S-band transition edge sensor (TES) based on a superconducting Ti/Au bilayer on a suspended silicon nitride (SixNy) membrane with narrow, thin, and long SixNy legs. To develop a suitable fabrication process for a large TES array, we have recently replaced a wet KOH etching step for Si by a deep reactive ion etch (RIE) fabrication step. We measured the current-voltage characteristics, noise performance, and impedance of a few Ti/Au TESs fabricated by deep RIE at different bath temperatures. The measured critical temperatures (\mbi Tc) are found to be around 105 mK and are in good agreement with the values obtained from an unprocessed Ti/Au bilayer. This shows that the new fabrication process does not affect the Tc. This is a positive result for the fabrication of large TES arrays. In addition, we find that a measured dark noise equivalent power (NEPmeas) approaches the phonon noise-limited NEP (NEPph) with a ratio NEPmeas NEPph=1.2, which is supported by observing clear bath temperature dependence of the NEPmeas. This result is extremely encouraging because we can realize a lower NEP with a larger possible dynamic range. A very low-G TES with low heat capacities of the SixNy legs and SixNy membrane compared with that of the TES is a promising route to realize such performance.
- Published
- 2014