31 May 2005 Enhancement of YBCO microbolometer performances with regionally thinned microbridges
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Abstract
Silicon nitride microbridges (50x50 mm2, 0.6 mm thick), suspended over a silicon substrate, were patterned and thinned. These patterns consist of 2 to 12 windows that were thinned to approximately 0.3 mm. Microbolometers were fabricated by sputtering a YBaCuO thin film over the bridges. The experimental results showed that the regionally thinned microbridges have a lower thermal time constants t (about 1.6 ms) than that of the standard pixel configuration (2.6 ms). On the other hand, the fact that the regionally thinned microbolometers having detectivity D* values comparable to or even six times superior than that of the standard pixel showed that the decrease in response time is not penalized by loss of detection performance. The simulation results also show that as the amount of material removed is increased, the thermal time constant drops significantly while the (τ/G)1/2 ratio (where G is the thermal conductance of the pixel) only decreases slightly, suggesting that the reduced response time will not cause a significant drop in detectivity D*. The simulation results of mechanical integrity show that a specific regionally thinned microbridge design has 22 % higher stiffness than that of a standard pixel design with similar thermal properties. The fact that thick regions remained on the regionally thinned pixels (like the edges of the pixels) provide significant mechanical support to the microstructures. This confirms the validity of the regionally thinned microbridges approach.
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Philippe Merel, Philips Laou, Franklin Wong, "Enhancement of YBCO microbolometer performances with regionally thinned microbridges", Proc. SPIE 5783, Infrared Technology and Applications XXXI, (31 May 2005); doi: 10.1117/12.603810; https://doi.org/10.1117/12.603810
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