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Proceedings Paper

Uncooled IR-sensor array based on MEMS technology
Author(s): Vinoy K. Jain; C. R. Jalwania
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Paper Abstract

Uncooled thermal IR arrays have attracted a great deal of interest due to its large number of applications in military as well as in civilian sector. These systems contain microbolometers, which can be made using silicon micromachining technology. An integrated approach is also needed to design the complete system by developing the large number of IR sensing elements, electronics, optics and housing. This paper discusses the design approach and technology used her to develop the IR-sensing microbolometers. The most significant achievement is the perfection of the sacrificial layer to obtain 1.0 micrometers air gap between the oxide diaphragm and the silicon substrate. This provides a very good thermal isolation required to obtain the high sensitivity for the IR sensing. Silicon dioxide diaphragms of 0.3 micrometers thickness and of 375 micrometers X 275 micrometers sizes have been made with 1.0 micrometers air gap from the silicon substrate. This is supported by four hinges. Technology has also been perfected here to make 30 mm X 30 mm diaphragms of 1.0 micrometers thickness with the same air gap. Four layer structures have been grown on this diaphragm by evaporation and structured to form titanium microbolometers using many steps of photolithography. These microbolometers are made of 1000 A thick Ti with gold contacts. The surface has been passivated by SiO2 layer to maintain the characteristics of the Ti-bolometer stable and reproducible. The temperature coefficient of resistance (TCR) of Ti - bolometers has been measured and found 0.23 percent per degree centigrade. The value of TCR decreases with the reduction in the thickness of Ti of the bolometer. A 20 element array has been made using this technology.

Paper Details

Date Published: 9 November 1999
PDF: 10 pages
Proc. SPIE 3903, Indo-Russian Workshop on Micromechanical Systems, (9 November 1999); doi: 10.1117/12.369462
Show Author Affiliations
Vinoy K. Jain, Solid State Physics Lab. (India)
C. R. Jalwania, Solid State Physics Lab. (India)

Published in SPIE Proceedings Vol. 3903:
Indo-Russian Workshop on Micromechanical Systems
Vladimir I. Pustovoy; Vinoy K. Jain, Editor(s)

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