Uncooled IRFPAs based on scalable nanotube microbolometers with 6 μm pixel pitch for thermal imaging

Abstract:
Fraunhofer IMS developed a manufacturing process for uncooled IRFPAs based on scalable nanotube microbolometers for thermal imaging. This manufacturing process allows for a variable scaling of the pixel pitch with a lower limit at a pixel pitch of only 6 µm. However, this lower limit of the pixel pitch is not owed to restrictions in the manufacturing process itself but to the fundamental optical limit in the LWIR, occurring at a wavelength of approximately 5 µm. In this regard, the variable scalability of Fraunhofer IMS’s nanotube microbolometer technology is enabled by means of vertically oriented nanotubes arranged underneath the actual sensor membrane, resulting in a decoupling of the thermal insulation from the latter. In this publication, the electro-optical performance of a fully integrated IRFPA realized by a nanotube microbolometer array with a pixel pitch of 6 µm at QVGA resolution is evaluated. Key parameters as electro-optical responsivity, noise, NETD and thermal time constant are extracted by means of a digital ROIC. Despite the downscaling of the pixel pitch close to the fundamental optical limit in the LWIR, full electro-optical functionality of the IRFPA is maintained.