Optical EngineeringThree-level microbolometer structures: design and absorption optimization
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The design of two new three-level (3-L) microbolometer structures together with their absorption coefficient optimizations are reported. Three-level microbolometers are the detectors where three sacrificial layers are used during their fabrication process. They are needed to increase the performance of the microbolometer detectors when the lithography and etch-process capabilities of the fabrication facility are limited. Two new 3-L microbolometers are proposed and the absorption simulations of these detectors are performed using a cascaded transmission line model of the detectors. The thermal simulations of the proposed detectors are also done using CoventorWare FEM software. The absorption coefficient of the detectors can be as high as 92%, and their thermal conductance values can be as low as 2.4×10 −8 W/K depending on the type of the detector, resulting in an improvement of 50% on the NETD value when compared with a standard 2-L microbolometer structure fabricated using the same technology. The proposed detector structures can be used to decrease the need for high-process capabilities and make it possible to fabricate high-performance microbolometer detectors especially for universities and research centers.