Design, Fabrication, and Characterization of a Polymer-Based MEMS Uncooled Infrared Focal Plane Array

This paper presents the design, fabrication, and characterization of a polymer-based uncooled infrared (IR) focal-plane-array (FPA). In order to achieve high-temperature resolution, a thin-film IR absorber made of multiwalled carbon nanotubes (MWNTs) was adopted to absorb more than 90% of incident IR radiation. Furthermore, novel bimaterial microbeams composed of polyvinyl chloride and gold (Au), whose thermal expansion coefficient mismatch is up to 140 ppm/K, were utilized to convert the IR absorption-induced temperature rise to a thermal deflection with an ultrahigh sensitivity. The FPA was successfully fabricated with a low residual stress based on polymer surface micromachining techniques, and the MWNTs were integrated onto suspended microstructures in the FPA using a method combining screen printing with liftoff. To obtain a thermal image, an optical readout system utilizing an interferometric displacement detection based on integrated gratings was designed and implemented, which simultaneously measured the displacements of all pixels. Thermomechanical sensitivity of the fabricated FPA was measured to be 230 nm/K. Experimental results reveal that the current FPA is capable of detecting IR radiation power and temperature change in a target object with 27-nW and 14-K resolutions, respectively.