Advanced packaging development for very low cost uncooled IRFPA

Abstract

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. Il 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 exhausts holes 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.

Uncooled infrared focal plane arrays

“…The most popular vacuum packaging technology for uncooled IRFPAs is one‐by‐one pumping through a fine‐bore tube, and this packaging process has been a bottleneck in lowering the cost of uncooled IRFPAs. Efforts have been made to improve the productivity and reduce cost in the vacuum packaging process, and various vacuum packaging technologies have been reported up to now, including wafer‐level packaging , collective packaging , chip‐scale packaging , batch packaging , and pixel‐level packaging technologies.…”

Status of Uncooled Infrared Detector Technology at ULIS, France

“…The cost objectives for small sensors (alarm sensors or abandoned sensors) however require a technological breakthrough, particularly in regard to the vacuum packaging of these components, which remains an adverse cost driver for any microbolometer technologies. In this context, CEA-LETI has proposed the PLP technology development for some years [3][4][5] . According to this unique technology, each bolometer pixel is sealed under vacuum directly at the wafer level, using an IR transparent thin film deposition.…”

High-performance uncooled amorphous silicon video graphics array and extended graphics array infrared focal plane arrays with 17-<italic>μ</italic>m pixel pitch

“…Another concern is the development of simplified techniques for vacuum packaging, which is a cost driver of thermal IR sensors. 7,8 Nevertheless, more and larger basic efforts must be completed in the near future to attain the ultimate goal of very low cost that the large market of infrared sensors is still expecting. From its first product in 2002 up to its large 0091-3286/2011/$25.00 C 2011 SPIE range of detectors presently available, ULIS has endeavored to address its customer needs by developing ever higher performance detectors.…”