Polymer composite based microbolometers

Abstract. This work focuses on the basic suitability assessment of polymeric materials and the corresponding technological methods for the production of infrared (micro-) bolometer arrays. The sensitive layer of the microbolometer arrays in question is composed of an electrically conductive polymer composite. Semi-conducting tellurium and vanadium dioxide, as well as metallic silver, are evaluated concerning their suitability as conductive filling agents. The composites with the semi-conducting filling agents display the higher temperature dependence of electrical resistance, while the silver composites exhibit better noise performance. The particle alignment – homogeneous and chain-shaped alike – within the polymer matrix is characterized regarding the composites' electrical properties. For the production of microbolometer arrays, a technology chain is introduced based on established coat-forming and structuring standard technologies from the field of polymer processing, which are suitable for the manufacture of a number of parallel structures. To realize the necessary thermal isolation of the sensitive area, all pixels are realized as self-supporting structures by means of the sacrificial layer method. Exemplarily, 2 × 2 arrays with the three filling agents were manufactured. The resulting sensor responsivities lie in the range of conventional microbolometers. Currently, the comparatively poor thermal isolation of the pixels and the high noise levels are limiting sensor quality. For the microbolometers produced, the thermal resolution limit referring to the temperature of the object to be detected (NETD) has been measured at 6.7 K in the superior sensitive composite layer filled with silver particles.