FEA simulation, design, and fabrication of an uncooled MEMS capacitive thermal detector for infrared FPA imaging

Weidong Wang; Vandana Upadhyay; Christel Munoz; John Bumgarner; Oliver Edwards

doi:10.1117/12.665080

17 May 2006 FEA simulation, design, and fabrication of an uncooled MEMS capacitive thermal detector for infrared FPA imaging

Weidong Wang, Vandana Upadhyay, Christel Munoz, John Bumgarner, Oliver Edwards

Author Affiliations +

Proceedings Volume 6206, Infrared Technology and Applications XXXII; 62061L (2006) https://doi.org/10.1117/12.665080
Event: Defense and Security Symposium, 2006, Orlando (Kissimmee), Florida, United States

Abstract

This paper reports modeling, simulation, design and fabrication results for an uncooled MEMS capacitive thermal detector for IR focal plane array (FPA) imaging. Finite element analysis (FEA) was used to simulate the thermal and thermal-structural behaviors of the device. Sensitivity and thermal response time were simulated, as well as noise equivalent temperature difference (NETD). The detector structure consists of a suspended IR absorption/capacitive plate (100μm×100μm) made of Si₃N₄/Pt. The first section of each supporting arm has a bilayer structure, which consists of a SiO₂ layer and a thick Al layer. The arm and the plate exhibit an out of plane movement due to a bilayer effect caused by temperature rise under IR radiation. This results in a capacitive sensing signal. The second section of each arm has a SiO₂ layer and a very thin Al layer to serve as thermal isolation, as well as an electrical connection for capacitive sensing signal. A FEA parametric model was created and several key dimensions of the structure were simulated for better performance. Especially, the thicknesses of Al thermal isolation layer and bilayer were evaluated regarding sensitivity and thermal time constant. For a 0.8μm bilayer Al thickness and a 30nm isolation layer Al thickness, a simulated displacement sensitivity of 0.83nm/(pW⋅μm^-2) was achieved. Subsequent NETD calculations predicted a temperature fluctuation NETD of 3.4mK, a background fluctuation NETD of 1.0mK, a thermal-mechanical NETD of 9.2mK, a capacitive readout NETD of 7.4mK, and a total NETD of 12.3mK, with a 18.6ms thermal time constant. Following the design for the photomasks, fabrication processes were developed and the detectors were fabricated successfully.

Citation Download Citation

Weidong Wang, Vandana Upadhyay, Christel Munoz, John Bumgarner, and Oliver Edwards "FEA simulation, design, and fabrication of an uncooled MEMS capacitive thermal detector for infrared FPA imaging", Proc. SPIE 6206, Infrared Technology and Applications XXXII, 62061L (17 May 2006); https://doi.org/10.1117/12.665080

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