Capabilities of scaled microbolometers for uncooled thermal imaging below 10µm pixel pitch

Abstract

The reduction of the pixel pitch of uncooled thermal imagers is still ongoing and by the end of 2021, reached a size of only 8µm within commercially available products. In case of those small pixel sizes, design and manufacturing requirements become more challenging by facing the main technological objectives of maximizing the temperature rise within the microbolometer membrane and simultaneously, being sensitive towards the latter. Tackling these challenges, Fraunhofer IMS provides a manufacturing process for uncooled thermal imagers optimized for the LWIR regime based on a scalable microbolometer technology incorporating vertical nanotubes. Based on this technological concept, we already demonstrated microbolometers with full electro-optical functionality for pixel sizes ranging from 17µm down to 6µm. A comprehensive study of our measurements regarding the scalable microbolometer technology will be presented here. This includes a discussion about design requirements in correlation to the achieved electro-optical results covering electrical noise, NETD, thermal time constant and spectral absorption characteristics. Those key parameters will be summarized and evaluated with respect to the reduction of the active microbolometer area in case of a shrinked pixel size.