This paper, “Long linear MWIR and LWIR HgCdTe infrared detection arrays for high resolution imaging," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.
This paper reviews ULIS’progress, on 35 μm pitch, in amorphous silicon uncooled microbolometer focal plane (UFPA) technology and product development over the last year. The ULIS FPA products have been described in great detail, including product capabilities and complete EO performances. At 60 Hz frame rate, focal planes with 40 mK (f/1) NETD are now achieved in production with a spatial fixed pattern noise lower than 25 mK after gain and offset compensation. Key improvements, compared to 45 μm pitch technology, have been the achievement of microbolometer resistance uniformity better than 0.5 % (standard deviation) on the IRFPA die for the different formats. Thanks to a new pixel design, high fill factor along with low thermal time constant (7 ms), 35 μm pitch amorphous silicon UFPAs are prime candidates for FLIR applications.
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.
We present the ULIS second generation technology used for producing 320 x 240 (384 x 288) and 160 x 120 IRFPA with a pixel pitch of 35 µm. This enhanced technology was developed by CEA / LETI and has been transferred to ULIS in 2003. The device architecture will be described. This device is well adapted to high volume military applications (i.e. thermal weapons sight, enhanced driver vision) and commercial applications (i.e. predictive maintenance, firefighting, thermography, medical,...) where specifications are the result of a trade-off between pixel pitch, performance and system weight. We have developed for these devices low cost packages. IRFPA electro-optical characterization is presented.
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 manufacture high performance radiometric devices with internal temperature stabilized shield to determine precisely the input infrared flux. We present the characterization of a new radiometric device obtained from 320 x 240 uncooled microbolometer array with f/1.4 aperture. This device is well adapted to radiometric or process control applications and moreover shows a high level of stability due to the internal temperature stabilized shield which prevents the detector from camera internal temperature shift artifacts.
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.
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 manufacture high performance radiometric devices with internal temperature stabilized shield to determine the input infrared flux. We present the characterization of a new radiometric device obtained from 320 x 240 uncooled microbolometer array with f/1.4 aperture. This device is well adapted to radiometric or process control applications and moreover shows a high level of stability due to the internal temperature stabilized shield which prevents the detector from camera internal temperature shift artifacts.
After the development of an amorphous silicon based uncooled microbolometer technology, LETI and ULIS are now working to facilitate the IR focal plane arrays (IRFPA) integration into equipment in order to address a very large market. Achievement of this goal needs the integration of advanced functions on the focal plane and the decrease of manufacturing cost of IRFPA by decreasing the pixel pitch and simplifying the vacuum package. We present in this paper the new designs for readout circuit and packages which will be used for 320×240 and 160×120 arrays with a pitch of 35μm.
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.
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. After a description of the technology and the methodology for reliability enhancement, 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.
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.
During the last 4 years, an infrared technology based on amorphous silicon has been developed by the Infrared Laboratory (Leti-Lir) in France. After having made a first demonstrator of 256 X 64 pixels, Lir and Sofradir have decided to develop a larger format of 320 X 240 on an industrial basis which needed of course a transfer of technology and a real production line installation. All this work has been done and after a 6 month transfer of technology the production line is running at Sofradir. The purpose of this paper is to present our special connection between research and production and to update the results from a production point of view.
New generations of InfraRed (IR) detectors are mature and well within the production stage at Sofradir. The two generations consist of Time Delay and Integration (TDI) long linear arrays (for second generation systems) sensitive in the 8-12 micrometers waveband and large 2D staring arrays (for second or third generation systems) sensitive in the 3-5 micrometers and 8-12 micrometers wavebands. Outstanding progress has been made in product development and production assessment during these last 10 years at Sofradir and the key points for technologies and products are presented as well as lessons learned.
High resolution infrared imaging system calls for very long scanning arrays with several thousands of detectors and high performance. This paper presents the technological developments and the electro-optical performance obtained at LETI/SLIR (Infrared Laboratory) on linear HgCdTe (MCT) arrays working in the 3-5, 8-10 and 11-12.5 micrometers spectral ranges. These large arrays have an indirect hybrid architecture composed of butted HgCdTe PV detection circuits and Si readouts hybridized on a mechanically close-matched fanout substrate. Defect free dicing and butting, respecting the detector pitch, is made by accurate and nondamaging techniques.
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.
The performance of an InfraRed (IR) system is based on a high spatial resolution and on a high thermal resolution. An increase in spatial resolution means an increase in number of pixels, a decrease in detector pitch and an increase in the detector pixel MTF. Regarding thermal resolution increase, it will be achieved mainly by an increase in the maximum quantity of charges which can be stored in the silicon read-out circuits for 2D staring arrays. At present, only cooled detectors answer this need of high performance detectors, such as 2D arrays with TV format resolution and high NETD. In this paper these trends regarding high performance are discussed and recent IRFPA results at Sofradir are presented. Finally, a comparison with uncooled detectors, also processed at Sofradir, is presented, to outline the remaining gap between both types of detectors.
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.
Today, Sofradir has delivered more than 2000 LW new generation IR detectors which gives a very important data base for yield and performance analysis. The target of this paper is on one hand to show a performance statistical analysis both globally and over the year which demonstrates the validity of MCT choice and on the other hand to present the impact of the improvement of the process and the adaptation of tooling on the cost.
Sofradir, the European company totally dedicated to second and third generation of IR detectors has focused its activities on development and production based on MCT material. As a matter of fact, Sofradir is one of the sole companies in the world able to master the MCT technology for SW, MW, and LW and then to produce this type of arrays in good conditions allowing affordable prices. This activity covers TDI long linear arrays and staring arrays. Performances of TDI arrays like the 480 X 6 or staring arrays like the 320 X 240/ 256 X 256 will be presented. Then the most advanced activities in France in the field of IR detectors will be presented. This will cover the new MCT 640 X 480 but also the approach of QWIPs and microbolometers.
High resolution infrared imaging system calls for very long scanning arrays with several thousands of detectors and high performance. This paper presents the recent technological developments an the electrooptical performances obtained at LETA/LIR on 1500 detector linear HgCdTe arrays working in the 3-5 and 8-10 micrometers spectral ranges. These very large arrays have an indirect hybrid architecture composed of butted HgCdTe PV detection circuits and Si CMOS readouts hybridized on a fanout substrate. Defect free dicing and butting, respecting the detector pitch, is made by accurate and non damaging techniques.
Sofradir, the European company totally dedicated to second and third generation of IR detectors has focused its activities on development and production based on MCT material. As a matter of fact, Sofradir is one of the sole companies in the world able to master the MCT technology for SW, MW and LW and then to produce this type of arrays in good conditions allowing affordable prices. This activity covers TDI long linear arrays and staring arrays. Performances of TDI arrays like the 480 X 4 staring arrays like the 320 X 240 will be presented. Then the most advanced activities in France in the field of IR detectors will be presented.
High resolution infrared imaging system calls for very long scanning arrays with several thousands of detectors and high performance. This paper presents the recent technological developments and the electro-optical performances obtained at LETI/LIR (infrared laboratory) on 1500 detector linear HgCdTe arrays working in the 3 - 5 and 8 - 10 micrometer spectral ranges. These very large arrays (length approximately equals 50 mm) have an indirect hybrid architecture composed of butted HgCdTe PV detection circuits and Si CMOS readouts hybridized on a mechanically close-matched fanout substrate. Defect free dicing and butting, respecting the detector pitch, is made by accurate and non damaging techniques.
High resolution infrared imaging system calls for very long scanning arrays with several thousands of detectors and high performance. This paper presents the recent technological developments and the electrooptical performances obtained at LETI I LIR (Infrared Laboratory) on 1500 detector linear HgCdTe arrays working in the 3-5 and 8-10 pm spectral ranges. These very large arrays (length 50 mm) have an indirect hybrid architecture composed of butted HgCdTe PV detection circuits and Si CMOS readouts hybridized on a mechanically close-matched fanout substrate. Defect free dicing and butting, respecting the detector pitch, is made by accurate and non damaging techniques. Keywords: Infrared, HgCdTe, linear array, butting, focal plane array
High resolution infrared imaging system calls for very long scanning arrays with several thousands of detectors and high performance. This paper presents the recent technological developments carried out at LETI/LIR on long butted arrays and gives the results obtained on a 1500 detector linear HgCdTe array with a 30 micrometer pitch and a 5.5 micrometer cut-off wavelength. This very large array (length approximately equals 50 mm) has an indirect hybrid architecture composed of 5 butted HgCdTe PV detection circuits and 5 Si CMOS readouts hybridized on a mechanically close-matched fanout substrate. Defect free dicing and butting, respecting the detector pitch, is made by accurate and non damaging techniques. A detailed description of the array and the main electro-optical performances are presented.
Low cost equipment is the universal motto with the decrease in military budgets. A large panoply exists to solve partially this problem, such as simplification of the process, industrialization and the use of a collective manufacturing concept; but this is not enough. In the field of IRFPA using Mercury Cadmium Telluride (MCT), Sofradir has spent a lot of time in order to develop a very simple process to ensure producibility which has been totally demonstrated today. The production of more than 25 complex IRFPA per month has also allowed us to industrialize the process. A key factor is quantities. Today the only solution to increase quantities is to standardize detectors but in the field of IRFPA it is not so easy because each imaging system is specific. One solution to decrease the cost is to obtain the best trade-off between the application and the technology. As an example, people focus on indium antimonide staring array detectors today as they consider them as less expensive than other cooled infrared detector technologies. This is just because people focus on the FPA only, not on the global cost of the equipment. It will be demonstrated in this paper that MCT is a material so flexible that it is possible to obtain InSb detector performance at a higher temperature which allows decreased cost, volume and weight of the infrared equipment.
Thanks to the continuing effort in the field of infrared detectors in France, Sofradir has now a large number of different IRFPAs operating in both wavelengths MW and LW. During the last two years, as the maturity of the technology was demonstrated and the producibility of complex components was achieved, Sofradir has focused recent activity on new products. The target of this paper is to focus on new products such as 128 by 128 LW IRFPA and 480 by 4/576 by 4 monolithic MCT IRFPA. Typical results are presented.
High resolution second generation infrared focal plane arrays (FPAs) are not yet fully mature. However, 480 X 4 infrared FPAs have been designed, developed, and demonstrated for the U.S. Army Line-of-Sight Antitank (LOSAT) Weapon System. The infrared FPAs were developed on schedule and in budget by Sofradir (Grenoble, France) by taking a low risk approach based upon the technology incorporated into their 288 X 4 production infrared FPAs. First pass processor success was achieved on the silicon readout integrated circuit, and concurrent engineering was used to optimize the infrared FPA for the particular requirements of the LOSAT program. The success of the 480 X 4 development has resulted in the availability of a high resolution infrared FPA that can now be produced for incorporation into forward looking infrared systems.
For a wide variety of applications, imaging infrared seeker allows new generation weapon systems to reach high performance in terms of accuracy, standoff capability, target/false target discrimination, target recognition, etc. In the design of the seeker, the detector is a key component because the global performance is strongly related to the detector's and also because it has a large impact on the opto-mechanical concept. Thanks to the use of state-of- the-art CMT 2D IRFPA, new generation imaging infrared seeker (IIS) has very high performance (sensitivity, resolution, number of pixels) as well as a simple opto-mechanical architecture. Thomson-CSF Missile Electronics Division (DEM) has designed, manufactured, and tested breadboards of IIS with the support of French MoD. These IIS are based on 2D IRFPA provided by Sofradir under DEM requirements. The IRFPA selected for this development is a 128 X 128 CMT IRCCD sensitive in the 3-5 micrometers waveband integrated in an operational dewar cooled by a Joule-Thomson cooler. In this paper, first a technical description of the IR detector is given, then the electronic set developed is described, and finally the measured main figures are given.
Sofradir has developed a series of products by using the second generation IRFPA technology developed by the French research laboratory Lir with the support of the French MoD. This technology is based on the use of MCT photovoltaic diodes coupled to silicon readout circuit thanks to indium bump technique. The maturity is so good that producibility of such high performance, high complexity components was demonstrated several years ago. As a consequence, Sofradir produces now in quantities large IRFPAs sensitive in the 8 - 12 micrometers waveband. Beyond this success, Lir and Sofradir continue to update the technology and to build new products. Developments are on progress for long monolithic TDI arrays 3 to 5 and 8 to 12 micrometers , 480 X 4, 576 X 4 or staring arrays using CMOS or CCD readout circuits. All the work is performed within the frame of producibility and reliability.
Sofradir IRFPAs using MCT material are generally cooled down with classical coolers such as regulated or non regulated Joule Thomson coolers, rotary or linear closed cycle Stirling machines. By using these coolers, it is possible to satisfy a large range of application requirements. Nevertheless, the requirements for new military equipment increased during the last two years putting more pressure on cooling system requirements. On the other hand, the continuous increase of the size of available IRFPA also puts more pressure on cooling system requirements. Finally, the reduction of military budgets and the potential commercial market forces one to propose new configurations. Therefore, Sofradir has worked in the following different fields: (1) development of a very small flat detector dewar using a flat Joule Thomson cooler for severe environmental conditions such as seeker applications; (2) development of a detector dewar using the IDCA (integrated dewar/cooler) concept for high performance, and low cost application; and (3) development of detector dewar using thermoelectric coolers for low cost application. Sofradir presents the results of these activities.
IR systems require more and more performance (high sensitivity, resolution,...) to be adapted to specific system applications (such as surveillance and tracking systems...). To achieve such requirements, IRFPA manufacturers have to perform tradeoffs involving many parameters such as FPA operating temperature, number of TDI elements, cutoff wavelength, and diode area. IRFPA technologies and system limitations must be taken into account for these analyses. Thus, the authors present the general analysis of effects of these parameters on Sofradir IRFPA performance mainly utilizing 8 to 12 micron spectral band mercury cadmium telluride detector arrays. Impacts on electro-optical performance parameters and on thermal characteristics are presented. For example TDI linear scanning arrays are analyzed with emphasis on high IRFPA performance based on existing IRFPA technologies. Advantages of choices of different IRFPA configurations are presented.
The SOFRADIR IRFPA technology is now used in production and there is no question mark about the producibility of such IRFPA. Nevertheless the competition is still worldwide open at the level of the performances as the existing technologies are different. Indeed, SOFRADIR technology is based on an homojunction approach together with a fully planar technique which allows very good yields in production. The competing technologies are mainly based on an heterojunction principle using a mesa technology. The goal of this paper is to present, after a brief overview of the SOFRADIR IRFPA technology the last results in comparison with the standard application needs and to give an idea of the SOFRADIR existing products line.
The SOFRADIR technology is in fact the result of years of studies in the field of CMT photovoltaic detectors and CCD readout circuits on silicon. The resulting components are so good that it has been possible to put them in production. Very good yield have been obtained and now it is necessary to go deeper into the production analysis as the question is no longer basic productibility. Therefore the target of this paper is toshow the very detailed approach we have taken in order to obtain the best cost in production.
The present status of SOFRADIR IRFPA technology is briefly reviewed. Sensitive arrays, readout circuits, interconnections, and dewar technologies are examined. Typical SOFRADIR products are listed, and production of these products is discussed, including the production center, production equipment, test equipment, and production yield. A manufacturing flow chart is shown.
KEYWORDS: Sensors, Staring arrays, Telescopes, Infrared cameras, Multiplexing, Imaging systems, Video, Charge-coupled devices, Simulation of CCA and DLA aggregates, Cryogenics
This paper describes the successful completion of a long wavelength second generation infrared camera which was
designed, fabricated and tested at Kolisman Co. The design focused on a low cost approach based on state-of-the art
components which were sufficiently mature in their development cycle to be readily available if no design
modifications were necessary (i.e. 'off the shelf'). The system design approach for the sensor package allows for
retrofit to existing sensor platforms thereby reducing integration costs while offering second generation performance.
The design is based on a 7.5-10.7 micron long wavelength focal plane array (FPA) consisting of 240 x 4 elements.
Cryogenic cooling is supplied for the array using a state-of-the-art linear drive Stirling cycle refrigerator. The
system is a parallel scanned type utilizing on-focal plane time delay and integration to achieve improved signal to
noise ratio. Digital scan conversion is used to obtain RS-170 TV compatible output.
A series of currently available IR detectors for astronomical observations are reviewed and various applications of the devices to instrumental astronomy are examined, emphasizing the parameters relevant to each of them. Emphasis is given to the 1-5 micron window critical to near-IR astronomy. Some recent results in this field are reviewed.
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