Scalable nanotube-microbolometer technology with pixel pitches from 12 down to 6 µm

Abstract

Uncooled FIR-imagers decreased in pixel pitch from latest state-of-the-art value of 17 µm to 10 µm. Following this trend of a reduction of pixel size, Fraunhofer IMS provides a manufacturing process for FIR-imagers (IRFPAs) based on a scalable microbolometer technology. Beside conventional approaches of a thermal isolation of microbolometer membranes realized by lateral legs, Fraunhofer IMS developed a manufacturing process for a thermal isolation realized by nanotubes. To demonstrate the scalability of the nanotube-microbolometers the nanotube contact is applied to microbolometer membranes with 12, 10, 8 and 6 µm pixel size on top of a 17 µm digital readout integrated circuit (ROIC). The arrays are sealed by a chip-scale vacuum package to evaluate the microbolometers’ performance by means of a complete IRFPA. Quantitative measurement results for the responsivity as well as qualitative test pictures of the 12, 10 and 8 µm nanotube-microbolometers will be presented. A direct visual comparison in a test scene demonstrates no obvious decrease in sensitivity between 12 and 8 µm. Only at 6 µm pixel size a reduced sensitivity is observed. In summary, a fully working uncooled IRFPA with QQVGA resolution based on a 6 µm nanotube-microbolometer technology is presented here. The scalability of the nanotube-microbolometer technology from state-of-the-art pixel sizes down to 6 µm is demonstrated.