4.2 - Uncooled thermocouple air-bridge structure for a THz imaging system

Event
AMA Conferences 2013
2013-05-14 - 2013-05-16
Nürnberg
Band
Proceedings IRS² 2013
Chapter
I4 - Imaging
Author(s)
U. Schinkel, E. Kessler, A. Ihring, U. Dillner, F. Haenschke, A. Brown, T. May, H. Meyer - Institute for Photonic Technology e.V.(IPHT), Jena (Germany)
Pages
76 - 79
DOI
10.5162/irs2013/i4.2
ISBN
978-3-9813484-3-9
Price
free

Abstract

We have developed an air-bridge structure supporting a thermocouple-based conducting strip, which acts as both a terminating resistance of an antenna and temperature sensor [1]. The fabrication of the 30 μm long and 3.5 μm wide air-bridge was accomplished by surface micromachining with a polyimide sacrificial layer. As the supporting layer, a 200 nm PE-CVD SixNy layer was patterned on the sacrificial
layer. For passivation a 25 nm thin ALD-SiO2 with a low thermal conductance and a high conformal coverage was used. The influences of the geometry, the substrate thickness and the thermal properties of the freestanding air-bridges were investigated by computer simulations. Based on these results a compatible technology was developed to obtain high performance thermoelectric terahertz (THz) sensing structures. The responsivity of the thermocouple air-bridge structure was evaluated by electrical characterization. For these measurements the sensing structures were loaded by a welldefined AC bias, which simulated an absorbed incoming terahertz radiation and its conversion into heat resulting in a corresponding measurable DC signal. The NEP of the structure was measured to be 18 pW/Hz1/2 under vacuum conditions and 67 pW/Hz1/2 under atmospheric conditions, respectively.

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