Development of double-cantilever infrared detectors: Fabrication, curvature control and demonstration of thermal detection

This paper reports the recent progress on the development of double-cantilever infrared (IR) detectors, including the fabrication, the post-process curvature control, and also the first-time demonstration of thermal detection using capacitive-based IR focal plane arrays (FPAs). In this work, simplified double-cantilever IR FPAs based on bimaterial SiNx/Al and Al/SiNx cantilevers are fabricated using a surface micromachining module with polyimide as the sacrificial material. Thermal-cycling experiments of both 200 nm-thick Ebeam Al and 200 nm-thick PECVD SiNx films reveal that the residual stresses in IR materials can be significantly modified by thermal annealing. Therefore, an engineering approach to flattening IR FPAs is developed by using rapid thermal annealing (RTA). This article also demonstrates the thermal detection of cantilever IR FPAs using commercialized weak capacitance readout IC.