Jean-Luc Martin

Uncooled amorphous silicon technology enhancement for 25-μm pixel pitch achievement

The emergence of uncooled infrared detectors has opened new opportunities for IR imaging both for military and civil applications. Infrared imaging sensors that operate without cryogenic cooling have the potential to provide the military or civilian users with infrared vision capabilities packaged in a camera of extremely small size, weight and power. Uncooled infrared sensor technology has advanced rapidly in the past few years. Higher performance sensors, electronics integration at the sensor, and new concepts for signal processing are generating advanced infrared focal plane arrays. This would significantly reduce the cost and accelerate the implementation of sensors for applications such as surveillance or predictive maintenance. We present the uncooled infrared detector operation principle and the development at CEA/LETI from the 256×64 with a pitch of 50 μm to the 320×240 with a pitch of 35 μm. LETI has been involved in Amorphous Silicon uncooled microbolometer development since 1992. This silicon IR detection is now well mastered and matured so that industrial transfer of LETI technology was performed in 2000 towards Sofradir. Industrial production of 320 μ240 microbolometer array with 45μm pitch is then started., we present the readout circuit architectures designs and its evolution from the 256×64 array to the different version of 320×240 arrays. Electro-optical results obtained from these IRCMOS are presented. NEDT close to 30 mK is now obtained with our standard microbolometer amorphous silicon technology.

Amorphous silicon based uncooled microbolometer IRFPA

LETI LIR has been involved in Amorphous Silicon uncooled microbolometer development for a few years. This paper reports recent progress that have been carried out both in technological and product field. Due to the very particular features of LETI LIR technology, large fill factor, high thermal insulation, associated with small thermal time constant, can be achieved, resulting in a large detector responsivity. In addition, pulsed bias has been introduced showing performance improvement in terms of power consumption, reliability, faster thermal response. A model has been developed which accounts for these improvements. Electro-thermal results obtained from an IRCMOS 256 X 64, 47 micrometers detector sizes, laboratory prototype show that NETD less than 50 mK at f/1 can be obtained even at a high video scanning rate, that is compatible with micro scanning techniques.

Enhanced amorphous silicon technology for 320 x 240 microbolometer arrays with a pitch of 35 um

LETI LIR has been involved in Amorphous Silicon uncooled microbolometer development for years. This technology is now in production at Sofradir and first delivery have already been done to customers. From our background in modeling and material mastering LETI/LIR concentrate now on performance enhancement. This is a key point for cost reduction due to the fact that signal to noise ratio enhancement will allow us to decrease the pitch. A new approach of packaging is also described in this paper and first results are displayed. A new technological stack of amorphous silicon fully compatible with industrial process is presented. Electro-optical results obtained from an IRCMOS 320 X 240 with 35 μm pitch are presented. NETD close to 35 mK has been obtained with our new embodiment of amorphous silicon microbolometer technology.

320 x 240 microbolometer uncooled IRFPA development

LETI LIR has been involved in amorphous silicon uncooled microbolometer development for a few years. This silicon IR detection is now well mastered and matured so that industrial transfer LETI/LIR technology is performed towards Sofradir. Industrial production of 320x240 microbolometer array with 45 micrometers pitch is now started. After a short description of the technology and the readout circuit architecture we focus on device reliability which is the key point for microbolometer application. Methodology for reliability enhancement is described. First results obtained on amorphous silicon reliability are presented. Electro-optical results obtained from an IRCMOS 320x240 with 45 micrometers pitch are presented. NEDT close to 70 mK can be obtained with our standard microbolometer amorphous silicon technology.

320x240 microblometer uncooled IRFPA

LETI LIR has been involved in Amorphous Silicon uncooled microbolometer development for a few years. This silicon IR detection is now well mastered and matured so that industrial transfer LETI/LIR technology is performed towards Sofradir. Industrial production of 320 X 240 mirobolometer array with 45 micrometer pitch started. After a short description of the technology and the readout circuit architecture we focus on device reliability which is the key point for microbolometer application. Methodology for reliability enhancement is described. First results obtained on amorphous silicon reliability are presented. Electro-optical results obtained from an IRCMOS 320 X 240 with 45 micrometer pitch are presented. NEDT close to 70 mK can be obtained with our standard microbolometer amorphous silicon technology.

Uncooled amorphous-silicon technology: high-performance achievement and future trends

The emergence of uncooled infrared detectors has opened new opportunities for IR imaging both for military and civil applications. Infrared imaging sensors that operate without cryogenic cooling have the potential to provide the military or civilian users with infrared vision capabilities packaged in a camera of extremely small size, weight and power. Uncooled infrared sensor technology has advanced rapidly in the past few years. Higher performance sensors, electronics integration at the sensor, and new concepts for signal processing are generating advanced infrared focal plane arrays. This would significantly reduce the cost and accelerate the implementation of sensors for applications such as surveillance or predictive maintenance. We present the uncooled infrared detector operation principle and the development at CEA/LETI from the 256 x 64 with a pitch of 50 micrometers to the 320 x 240 with a pitch of 35 micrometers . LETI has been involved in Amorphous Silicon uncooled microbolometer development since 1992. This silicon IR detection is now well mastered and matured so that industrial transfer of LETI technology was performed in 2000 towards Sofradir. Industrial production of 320 x 240 microbolometer array with 45micrometers pitch is then started., we present the readout circuit architectures designs and its evolution from the 256 x 64 array to the different version of 320 x 240 arrays. Electro-optical results obtained from these IRCMOS are presented. NEDT close to 30 mK is now obtained with our standard microbolometer amorphous silicon technology.

Pixel-level ADC by small charge quantum counting

A pixel-level ADC technique for CMOS image sensors is presented. As the charge represents accurately the amount of illumination, the principle consists in counting small charge packets which come from the detector. Based on a 0.13 mum CMOS technology, simulation results and first measurements are presented showing that the LSB value can be reduced to 1900 electrons with a static power of 250 nW per pixel. For the moment, due to the available technology, this technique, is restricted to medium size pixels, i.e. 50x50 mum2.

Advanced uncooled infrared focal plane development at CEA/LETI

LETI/LIR has been involved for a few year in the field of uncooled detectors and has chosen amorphous silicon for its microbolometer technology development. Uncooled IR detectors pave the way to reduced weight systems aboard satellites. The silicon compatibility of our thermometer is a key parameter which has enabled a very fast technology development and transfer to industry. This competitive technology is now able to provide a new approach for IR detectors for space applications. This paper presents the main characteristics of the CEA / LETI technology which is based on a monolithically integrated structure over a fully completed readout circuit from a commercially available 0.5 μm design rules CMOS line. The technology maturity will be illustrated by the results obtained at LETI/LIR and SOFRADIR on a 320 x 240 with a pitch of 45 μm. First improvement on device reliability and characterization results will be presented.