An uncooled optically readable infrared imaging detector

This paper presents a design and fabrication of bi-material micro-cantilever array (focal plane array, FPA) made of silicon nitride (SiN_x) and gold (Au) for uncooled optical readout infrared (IR) imaging system, in which silicon (Si) substrate is removed. Compared with the conventional thermal imaging detectors where the FPA must be put in high vacuum, IR thermal images can be obtained even though the cantilever array is placed in the atmosphere. The reason is the elimination of air gap (～2 μm) between the cantilever beam and substrate, which introduces the air conduction of high temperature gradient. The preliminary experimental results with the micro-cantilever array of 140 × 98 elements and a 12-bit charge-coupled device (CCD) indicate that objects at temperature of higher than 120 °C can be detected and the noise-equivalent temperature difference (NETD) is ～7 K. Also, the experimental results are well accordant with the thermomechanical analysis of designed micro-cantilever array.