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 μm 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 μm 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.
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 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.
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 are being developed for a wide range of thermal imaging applications. Developments are focused on the improvement of their sensitivity enabling the possibility of reducing the pixel pitch in order to decrease the total system (size and weight) by using smaller optics. The amorphous silicon technology is the latest one developed by CEA / LETI and transferred to ULIS to manufacture 160 x 120 2D arrays. We developed for this device a low cost package based on existing technologies. This device is well adapted to high volume process control applications where spatial resolution (in terms of pixel number) is less important than device costs.
Uncooled infrared focal plane arrays are being developed for a wide range of thermal imaging applications. Developments are focused on the improvement of their sensitivity enabling the possibility to reduce the pixel pitch in order to decrease the total system by using smaller optics. We present the characterization of a 160 x 120 infrared focal plane array with apixel pitch of 35 μm. The amorphous silicon technology is the latest one developed by CEA/LETI and transferred to ULIS to manufacture 160 x 120 2D arrays. We developed for this device a low cost package based on existing technologies. The readout integrated circuit structure is using an advanced skimming function to enhance the pixel signal exploitation. This device is well adapted to high volume process control applications where spatial resolution is less important than device costs. The electro-optical characterization is presented.
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