First demonstration of 25 μm pitch uncooled amorphous silicon microbolometer IRFPA at LETI-LIR

The Laboratoire Infrarouge (LIR) of the Electronics and Information Technology Laboratory (LETI) has been involved since 1993 in the development of subsequent bolometer technological process that aims at reducing the pitch of the amorphous silicon based uncooled microbolometer FPAs. These developments are primarily driven by cost reduction and system miniaturisation concerns. In this outlook, the LIR has recently developed a specific amorphous silicon technology for a 25 mu m pitch IRFPA achievement. This new structure still relies on a single level microbridge arrangement and special cares have been taken in order to ensure noise reduction, thermal insulation increase with a special attention to low thermal time constant achievement. This paper presents a complete characterization of an advanced dedicated 320 x 240 IRCMOS circuit that takes advantage of this new 25 mu m pitch bolometer process. Apart from NEDT (< 70 mK) histogram, the paper also puts emphasis on parameters that appear more and more as key points in IR system, like the thermal time constant and the residual fixed pattern noise.