Digital uncooled IRFPAs based on microbolometers with 17 μm and 12μm pixel pitch

This paper presents the results of high-performance infrared detectors (IRFPA – InfraRed Focal Plane Array) based on uncooled microbolometers with 17 μm and 12 μm pixel pitch and a chip-scale-package as the vacuum package developed and fabricated by Fraunhofer-IMS. Like CMOS image sensor IRFPAs also have been following the trend of reducing the pixel size in order to reduce the costs and increase the optical resolution. For microbolometer based uncooled IRFPA the pixel pitch has been reduced from 35 μm pixel pitch ten years ago via 25 μm and 17 μm down to 12 μm. Fraunhofer IMS has developed digital IRFPAs featuring a direct conversion of the microbolometer’s resistance into a 16 bit value by the use of massively parallel on-chip Sigma-Delta-ADCs achieving a high scene temperature dynamic range of more than 300 K and a very low NETD-value below 50 mK. Due to a broadband antireflection coating the digital IRFPAs achieve a high sensitivity in the LWIR (wavelength 8 μm to 14 μm) and MWIR (wavelength 3 μm to 5 μm) range. In this paper the microbolometer, the vacuum-packaging, the architecture of the readout electronics, and the electro-optical performance characterization will be presented