Advanced packaging development for very low cost uncooled IRFPA

The Laboratoire Infrarouge (LIR) of the Laboratoire d'Electronique, de Technologie et d'Instrumentation (LETI) has been involved in the development of microbolometers for several years. Therefore a first generation of a high performance technology made from amorphous silicon thermometer has been transferred to ULIS in 2000 and a second generation has been transferred in 2003 for being able to manufacture small pixel pitch uncooled IRFPA. LETI is still working to improve uncooled IRFPA and two principal research orientations are currently studied. First LETI improves performances of low cost detectors for both military and civil applications. Secondly LETI develops a very low cost packaging technology for high volume applications like automotive. Since packaging operations represent today the most significant part of detectors price, LETI has studied an original on-chip packaging structure less expensive than wafer level packaging structure. 11 means, that after standard collective technology of bolometers, the process continues with microcaps manufacturing over the microbolometer or over the array of microbolometers. It requires specific technological developments in order to build this micro-caps and the main difficulty consists in closing hermetically micro-events manufactured previously in the caps, while maintaining expected vacuum around the detector. Another difficulty consists in choosing window cap materials and thickness to minimize IR absorption that is crucial for our application. LETI will present status of its developments of this innovating technology and SEM views from the first lab test device.