30 August 2004 Wafer-level self-packaged infrared microsensors
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One common requirement of microbolometers fabricated on both rigid and flexible substrates is the need for vacuum packaging to eliminate the thermal conductivity of air and achieve high performance. However, vacuum packaging of microbolometers is expensive and is a limiting factor in achieving truly low-cost uncooled infrared detection. Vacuum packing of microbolometers on flexible substrates requires a novel approach unless flexibility is to be sacrificed. This paper explores the vacuum packaging of microbolometers through self-packaging. In this case, the micromachined encapsulation in a vacuum cavity is investigated through computer simulation of microbolometers in flexible polyimide films and through the encapsulation of microbolometers on rigid Si substrates with a Si3N4 shell. In this manner, self packaged uncooled microbolometers were fabricated on a Si wafer with semiconducting yttrium barium copper oxide (YBCO) as the infrared sensing material. The self-packaged structure is designed such that it can be covered with a superstrate, yielding low stress in the flexible skin sensors and better detection figures of merit. The devices have demonstrated voltage responsivities over 103 V/W, detectivities above 106 cm Hz1/2/W and temperature coefficient of resistance around -3.3% K-1. Computer simulations using CoventorWare and MEMulator have been used to determine suitable materials for the process, the optimum design of a vacuum element and a streamlined process flow.
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Aamer Mahmoud, Aamer Mahmoud, Aasutosh Dave, Aasutosh Dave, Zeynep Celik-Butler, Zeynep Celik-Butler, Donald P. Butler, Donald P. Butler, } "Wafer-level self-packaged infrared microsensors", Proc. SPIE 5406, Infrared Technology and Applications XXX, (30 August 2004); doi: 10.1117/12.542680; https://doi.org/10.1117/12.542680

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