Terahertz Absorption Characteristics of NiCr Film and Enhanced Absorption by Reactive Ion Etching in a Microbolometer Focal Plane Array

Nano – scale metallic films have been proven to be an effective terahertz (THz) absorption layer in uncooled infrared (IR) microbolometers operated in THz spectral range. Optimized absorption can be achieved by adjusting the thickness of metallic film. Nickel – chromium (NiCr) thin films are deposited on the diaphragms of 320 × 240 VO_x – based infrared focal plane arrays (IRFPA). Absorption measurements of the diaphragms with different thicknesses of NiCr (5 to 40 nm) agree reasonably well with the predicted absorption. To improve THz absorption further, a reactive ion etching (RIE) process applied to the dielectric support layer is first suggested, which generates nano – scale surface structures and increases the effective surface area of NiCr absorption film. This provides an effective way which is easy to accomplish and compatible with the manufacturing process of microbolometer IRFPAs to improve THz absorption and detection sensitivity.