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26 July 1999 Design and fabrication of a high-fill-factor microbolometer using double sacrificial layers
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In the present paper we report a high-fill factor uncooled IR micro-bolometer array; and, more particularly, a three- level IR bolometer including an almost 92 percent fill factor absorber and a separately-designed bridge structure for the electro-thermal isolation of thermal sensor; and a method for the silicon-based fabrication. The present 256 X 256 bolometer array comprises a CMOS readout circuitry, a bridge level, a pari of posts, and an absorption level. The fabrication of the presented bolometer feature that it uses double sacrificial layers so as to separate the absorber level from the bridge structure, electrical and thermal path between the absorber and substrate. Also, we chose a titanium thin-film as a bolometer material which is patterned to make a connection between the substrate contact and the post. The absorber level is compared of titanium metal film sandwiched between PECVD deposited silicon dioxide layers to preserve thermal isolation of a bolometer absorber and release the inertial stresses. Additional contact is formed to connect the metal thin-film to the serpentine resistive pattern on the absorbing membrane defined on the top of the second sacrificial layer. From the structural design, we can obtain a good thermal isolation without reducing IR absorbing area.
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Sang-Baek Ju, Yoon-Joong Yong, and Sang-Gook Kim "Design and fabrication of a high-fill-factor microbolometer using double sacrificial layers", Proc. SPIE 3698, Infrared Technology and Applications XXV, (26 July 1999);

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