Bimaterial Cantilever Focal Plane Array for Uncooled Infrared Imaging Using Sandwich-Framed Structure

This paper reports a novel infrared focal plane array (FPA) using SiNx/SiO2/SiNx sandwiched structure as the supporting frames for bimaterial cantilever pixels. The device was fabricated by a bulk silicon process, where a trench backfill technique was employed to form the SiNx/SiO2/SiNx sandwiched frames. By replacing the silicon frame with SiNx/SiO2/SiNx sandwiched frame, the fill factor of the FPA is increased to 42%. Compared with other substrate-free FPAs with frames making of a thin layer of SiNx, the sandwiched frame provides more supporting strength for the cantilever pixels. Meanwhile, the reliability and the uniformity of the FPA were improved with a design of staggered arrangement of cantilever pixels. Thermal images of human bodies were captured successfully at room temperature. A complete analysis of device performance was also carried out both theoretically and experimentally, including thermomechanical sensitivity, noise equivalent temperature difference, and response time.