The DARPA Wafer-scale Infrared Detectors (WIRED) program requires the development of low cost detector technologies with high quantum efficiency and low dark current based on colloidal quantum dots (CQDs) of compound semiconductors. The program targets the SWIR (900 – 1700 nm) spectral range. This paper focuses on the design of 3 μm pitch, low noise ROICs for interfacing with SWIR CQD detectors. So far, the team has developed and demonstrated PV detector technology based on thin film CQDs IR-absorbing materials. The CQD films are deposited by spin-coating from solution directly on ROIC and fanout wafers at room temperature. The photodiode fabrication is fully compatible with CMOS fabrication at the wafer-level, allowing for large format FPAs limited only by the ROIC size. This paper outlines the preliminary design of a 3 μm pitch 1920 x 1080 modular ROIC, easily scalable to larger formats by mask stitching.<p> </p> DRS has designed a full HD (1920x1080) readout integrated circuit (ROIC) specifically for cost-effective waferscale infrared (WIRED) detectors on 3 μm pitch, for best theoretical image quality optical system performance. The sensor’s pixels use a capacitive trans-impedance amplifier (CTIA) and a metal-insulator-metal (MIM) integration capacitor, to achieve 22 Ke- well capacity, 0.7 V output swing and 37 e- or 18 e- equivalent readout noise, operating at 60 Hz ripple readout mode or 30 Hz correlated double sampling (CDS) mode, respectively. The fully digital ROIC consumes approximately 0.5 W of power, allowing it to be fielded in battery-powered applications.
DRS history in microbolometer and uncooled focal plane array (UFPAA) development mimics that of the entire industry. The history extends over fifteen years as array pitches moved ever-smaller from 51uum to 25um to 17um, and now something smaller than 17uum. The uncooled microbolometer makers have transitioned through smaller pitches about every six years. This has been done while maintaining a noise equivalent temperature difference (NNETD) performance of 20-50mK, and maintaining a thermal time constant (TTTC) of 10-20mmSec. Once a newer pitch is developed to a performance level matching the previous pitch, development on the next smaller pitch is already underway. In this manner, the industry has progressed through smaller pitches without a fundamental performance improvement when measured in NNETD or in TTTC, or more specifically in NNETD*TTC product. Hence, a more-encompassing metric for tracking performance through time would involve the NNETD, the TTCC, and some indicator of bolometer size. Ann NETD*TTC**Area metric, as the appropriate metric for including bolometer size, will be proposed, theoretically justified, and discussed here. A rank-ordering of bolometers which have been published through 22013 is also presented in three charts, one for NETTD, one for NEETD*TTC, and lastly one for NETD*TTC**Area.
The DRS Tamarisk® <sub>320</sub> camera, introduced in 2011, is a low cost commercial camera based on the 17 µm pixel pitch 320×240 VOx microbolometer technology. A higher resolution 17 µm pixel pitch 640×480 Tamarisk®<sub>640 </sub>has also been developed and is now in production serving the commercial markets. Recently, under the DARPA sponsored Low Cost Thermal Imager-Manufacturing (LCTI-M) program and internal project, DRS is leading a team of industrial experts from FiveFocal, RTI International and MEMSCAP to develop a small form factor uncooled infrared camera for the military and commercial markets. The objective of the DARPA LCTI-M program is to develop a low SWaP camera (<3.5 cm<sup>3</sup> in volume and <500 mW in power consumption) that costs less than US $500 based on a 10,000 units per month production rate. To meet this challenge, DRS is developing several innovative technologies including a small pixel pitch 640×512 VOx uncooled detector, an advanced digital ROIC and low power miniature camera electronics. In addition, DRS and its partners are developing innovative manufacturing processes to reduce production cycle time and costs including wafer scale optic and vacuum packaging manufacturing and a 3-dimensional integrated camera assembly. This paper provides an overview of the DRS Tamarisk® project and LCTI-M related uncooled technology development activities. Highlights of recent progress and challenges will also be discussed. It should be noted that BAE Systems and Raytheon Vision Systems are also participants of the DARPA LCTI-M program.
Uncooled infrared sensor markets have grown dramatically over the past decade due to significant
improvements in sensor performance, producibility and cost reductions. Current uncooled sensors
are dominated by VOx and amorphous silicon based microbolometers with spectral responses in the
7-14 μm wavelength region (LWIR). The majority of uncooled microbolometer focal plane array
(UFPA) formats currently in production are 160x120, 320x240, 640x480 with 20 to 38 um pixel
pitch. Most suppliers have reported good UFPA performance with less than 50 mK NETD(f/1
optics, 30 -60 Hz frame rates). Recently, 17 μm pixel pitch UFPAs have been introduced to the
market. The smaller detector pixel pitch allows manufacturing of larger format such as 1024x768
UFPAs without photolithographic stitching. In the past, uncooled IR sensor developments were
primarily driven by military needs; however, as low cost uncooled sensors began to proliferate in the
commercial market, uncooled sensors with FPA formats of 320x240 and smaller are rapidly
becoming commodity items. Reduction of sensor system size, weight, and power (SWaP) as well as
cost is the key driver for the next generation of uncooled sensors. This paper presents a brief
overview of the uncooled sensors status, developmental trends and challenges facing the industry.
While InGaAs-based SWIR imaging technology has been improved dramatically over the past 10 years, the motivation
remains to reduce Size Weight and Power (SWaP) for applications in Intelligence Surveillance and Reconnaissance
(ISR). Goodrich ISR Systems, Princeton (Sensors Unlimited, Inc.) has continued to improve detector sensitivity.
Additionally, SUI is working jointly with DRS-RSTA to develop innovative techniques for manufacturing dual-band
focal planes to provide next generation technology for not only reducing SWaP for SWIR imagers, but also to combine
imaging solutions for providing a single imager for Visible Near-SWIR (VNS) + LW imaging solutions. Such
developments are targeted at reducing system SWaP, cost and complexity for imaging payloads on board UASs as well
as soldier deployed systems like weapon sights. Our motivation is to demonstrate capability in providing superior image
quality in fused LWIR and SWIR imaging systems, while reducing the total system SWaP and cost by enabling Short
Wave and Thermal imaging in a single uncooled imager.
Under DARPA MTO awarded programs, a LW bolometer (DRS-RSTA) is fabricated on a Short Wave (SW) InGaAs
Vis-SWIR (SUI-Goodrich) Imager. The combined imager is a dual-band Sensor-Chip Assembly which is capable of
imaging in VIS-SWIR + LW. Both DRS and Goodrich have developed materials and process enhancements to support
these dual-band platform investigations. The two imagers are confocal and coaxial with respect to the incident image
plane. Initial work has completed a single Read Out Integrated Circuit (ROIC) capable of running both imagers. The
team has hybridized InGaAs Focal planes to 6" full ROIC wafers to support bolometer fabrication onto the SW array.
Significant progress has been made over the past decade on uncooled focal plane array technologies and production capabilities. The detector pixel dimensions have continually decreased with an increase in pixel performance making large format, high-density array products affordable. In turn, this has resulted in the proliferation of uncooled IR detectors in commercial and military markets. Presently, uncooled detectors are widely used in firefighting, surveillance, industrial process monitoring, machine vision, and medical applications. Within the military arena, uncooled detectors are ubiquitous in Army soldier systems such as weapon sights, driver's viewers, and helmet-mounted sights. Uncooled detectors are also employed in airborne and ground surveillance sensors including unmanned aerial vehicles and robot vehicles.
This paper provides an overview of the recent DRS RSTA, Inc. (DRS) Vanadium Oxide (VOx)
uncooled focal plane arrays (UFPA), sensor electronics, and camera development activities. Presently,
DRS UFPAs consist of 25 μm and 17 μm pixel pitch detectors in 320x240 and 640x480 formats.
Under the Army NVESD sponsored 17 μm Large Format Uncooled FPA Development program and
internal projects, DRS has developed a 17 μm pitch 1024x768 UFPA product (U8000). The 17 μm
pixel pitch UFPAs provide sensor systems with significant size, weight, and power (SWaP) savings as
well as cost reductions over the 25 μm pixel pitch counterparts. There is a growing demand to
transition current products to the 17 μm pixel technologies. For example, next generation military
systems such as thermal weapon sights (TWS), enhanced night vision goggles (ENVG), driver viewer
enhancers (DVE) and unmanned aerial vehicle (UAV) infrared (IR) surveillance sensors all called for
the 17 μm pixel technologies. To meet market demand, DRS has improved its production facilities to
accommodate 17 μm pixel detector manufacturing. In conjunction with these efforts, DRS has also
developed a family of signal processing electronics based on a new FPGA architecture for various
sensor modules and cameras that can be incorporated into commercial OEM products as well as DoD
weapon systems. Under the DARPA funded AWARE Multiband (formerly DUDE) program, DRS and
Goodrich Sensors Unlimited, Inc are collaborating on the development of a single, integrated, twocolor
detector by combining the VOx microbolometer (8-14 μm) and InGaAs (0.4 -1.6 μm) detectors
into a single focal plane array. The first AWARE Multiband dual mode focal plane array fabrication is
Significant progress has been made over the past decade on uncooled focal plane array
(UFPA) technology development and production capacity at DRS as well as other
domestic and overseas suppliers. This resulted in the proliferation of uncooled IR
detectors in commercial and military markets. The uncooled detectors are widely used in
firefighting, surveillance, industrial process monitoring, machine vision, and medical
applications. In the military arena, uncooled detectors are fielded among diverse systems
such as weapon sights, driver enhancement viewers, helmet-mounted sights, airborne and
ground surveillance sensors including UAVs and robot vehicles. Pixel dimensions have
continually decreased with an increase in pixel performance.
This paper presents an overview of the DRS 25- and 17-micron pixel pitch uncooled VOx
detector technology development and production status. The DRS uncooled FPA
products include 320x240 and 640x480 arrays while the larger 1024x768 17-micron pitch
array is at engineering prototype quantities. Current production of the 25-micron pitch
320x240 and 640x480 arrays exceeds 5,000 units per month, supporting U.S. military
systems such as Army thermal weapon sights (TWS) and driver vision enhancers (DVE).
Next generation systems are moving towards the 17-micron pixel pitch detectors.
Advancement in small pixel technology has enabled the 17-micron pitch detectors performance to surpass their 25-micron pitch counterparts. To meet future production demand of the 17-micron pitch UFPAs, DRS has made significant investment in production infrastructure to upgrade its tools. These investments include a new DUV stepper, coater, and plasma etcher plus improvements in its manufacturing techniques to enhance yield. These advanced tools reduce the minimum line width in production below 0.35μm and are now being used to manufacture the 17-micron 320x240 and 640x480 arrays.
To further technology development, DRS continues to engage in R&D activities focusing on VOx microbolometer detector design, packaging, test capability, materials and fabrication processes to further improve the detector performance, reliability, producibility and yield. Some of the results are summarized in this paper.
This paper provides an update of 17 micron pixel pitch uncooled microbolometer
development at DRS. Since the introduction of 17 micron pitch 640x480 focal plane
arrays (FPAs) in 2006, significant progress has been made in sensor performance and
manufacturing processes. The FPAs are now in initial production with an FPA noise
equivalent temperature difference (NETD), detector thermal time constant, and pixel
operability equivalent or better than that of the current 25 micron pixel pitch production
FPAs. NETD improvement was achieved without compromising detector thermal
response or thermal time constant by simultaneous reduction in bolometer heat capacity
and thermal conductance. In addition, the DRS unique "umbrella" microbolometer
cavities were optically tuned to optimize detector radiation absorption for specific
spectral band applications. The 17 micron pixel pitch FPAs are currently being
considered for the next generation soldier systems such as thermal weapon sights (TWS),
vehicle driver vision enhancers (DVE), digitally fused enhanced night vision goggles
(DENVG) and unmanned air vehicle (UAV) surveillance sensors, because of overall
thermal imaging system size, weight and power advantages.
DRS is a major supplier of the 25μm pixel pitch 640x480 and 320x240 infrared uncooled focal plane arrays (UFPAs) and camera products for commercial and military markets. The state-of-the-art 25μm pixel focal plane arrays currently in production provide excellent performance for soldier thermal weapon sights (TWS), vehicle driver vision enhancers (DVE), and aerial surveillance and industrial thermograph applications. To further improve sensor resolution and reduce the sensor system size, weight and cost, it is highly desired to reduce the UFPA pixel size. However, the 17μm pixel FPA presents significant design and fabrication challenges as compared with 25μm pixel FPAs. The design objectives, engineering trade-offs, and performance goals will be discussed. This paper presents an overview of the 17μm microblometer uncooled focal plane arrays and sensor electronics production and development activities at DRS. The 17 μm pixel performance data from several initial fabrication lots will be summarized. Relevant 25μm pixel performance data are provided for comparison. Thermal images and video from the 17μm pixel 640x480 UFPA will also be presented.
DRS Technologies has designed and delivered Thermal Weapon Site (TWS) and Driver's Viewer Enhancer (DVE) system using its U3500 (320x240) and U6000 (640x480) 1-mil detector arrays. The detectors are modified to enhance its manufacturability, thermal time constant, package life time, and its reliability under shock and vibration to meet TWS and DVE requirements. The U6000 array operates at 30 Hz frame rate with NETD less than 50 mK normalized to F/1.0 optics. At a saving to the system weight and power, these arrays operate from -40°C to +65°C without the aid of a TE cooler. This is accomplished through a combination of sensor calibration and smart ROIC architecture.
DRS has developed and demonstrated a family of miniaturized, low-power uncooled infrared focal plane camera products integrated with our 1-mil pixel size 640 x 480 and 320 x 240 uncooled infrared focal plane arrays (UIRFPA). The UIRFPA cameras operate from -40°C to +55°C without UIRFPA temperature regulation using our patented TCOMP sensor concept. Furthermore, they are software based, with significant memory and signal processing overcapacity, which supports significant camera setup reconfigurations without having to undergo camera firmware and hardware modifications. The elimination of the UIRFPA temperature regulation requirement results in reduced sensor power and prompt sensor turn-on. The new 320 x 240 camera weighs less than a quarter pound (including batteries and a 23 mm aperture F/1.2 optic), and dissipates approximately one watt when operated at a full 60 Hz frame rate. The 640 x 480 camera dissipates about two watts when operated at a TV compatible 30 Hz frame rate. This paper describes the UIRFPA camera products, their features and capabilities, and their key performance characteristics. Illustrative examples of thermal image quality are also included.
To improve its capacity to meet customer needs, DRS Infrared Technologies began technology transfer of the VOx uncooled FPA process from its Anaheim facility to its Dallas facility in the Fall of 2002. The new facility delivered its first U3000 arrays (320x240, 51μm pitch) three months after the VOx deposition system was installed, and produced over 300 units of U3000 per month just twelve months after beginning the transfer. Process enhancements and tool upgrades have enabled excellent control of the microbolometer process. Today, this line selectively fabricates arrays with NETD varying from 30mK to 80mK in 15mK bins with less than 30 ms time constant. The same arrays also have low defect density of less than 2% dead pixels and no more than one row and one column out. The arrays are packaged in imager or radiometer (F/1.4) packages. DRS also transferred small and large format arrays with 25μm pitch under the PEO-Soldier Sensor Producibility to the Dallas facility. Production of the 25μm pitch devices is currently more that 100 units per month and is ramping up to meet customer demand. This paper reports on production progress on the U3000s and the status of U3500 and U6000 25μm pitch array.
DRS has previously demonstrated and reported a concept for operating uncooled infrared focal plane arrays (UIRFPA) without the need for UIRFPA temperature regulation. DRS has patented this proprietary technology, which DRS calls TCOMP. TCOMP is a concept that combines an operating algorithm, a sensor architecture and a sensor calibration method, which allow pixel response and offset correction to be performed as a function of the UFPA sensor's operating temperature, thereby eliminating the need for the UIRFPA temperature regulation that would be required otherwise. As a result of the elimination of the temperature regulation requirement, the sensor turn-on time for high performance imaging can be significantly reduced, sensor power is significantly reduced, and the need for stray thermal radiation shields is effectively eliminated. The original TCOMP technique was demonstrated in 1998. Since then DRS has made significant improvements in both the TCOMP algorithm and the calibration process. This paper describes the patented TCOMP concept, presents the results of analysis of the improved TCOMP concept, and provides sensor level data of UIRFPA/sensor performance with the improved TCOMP algorithm.
DRS has been conducting several significant ongoing efforts to improve the producibility of its uncooled IR focal plane products. Those efforts are described in this paper. First, pixel dimensions are being reduced by a factor of two or mroe, while maintaining NETD performance levels fully comparable to that of the previous standard approximately 50-micron pixel size. The results for a given array size is smaller die size and mroe die per wafer. Second, DRS is transitioning UIRFPA production from its 5-inch wafer diameter process facility in Anaheim, CA to its 6-inch wafer diameter process facility in Dallas, TX, which results in more die per wafer and in enhanced wafer throughput capacity. Furthermore, the Dallas UFPA production facility is being tooled for a smooth future transition to 8-inch wafer processing. Third, a new ceramic UIRFPA vacuum package has been developed, which has lower material cost, fewer parts and assembly operations, and is lighter significantly weight than the current standard metal package. Since packaging is inherently the most expensive part of UIRFPA manufacture, packaging producibility improvements can provide significant cost leverage. Fourth, DRS is developing a batch-mode UIRFPA vacuum bake and sealign system, which will achieve significant throughput capacity gains, reduce touch labor requirements, and reduce production cycle times.
DRS (formerly Boeing) has completed the development and demonstration of a 25-micron pixel size 640x480 VO<SUB>x</SUB> microbolometer uncooled IR focal plane product, the U6000. The U6000 incorporates several advanced features to enhance its performance and functional capabilities. A parallel six- bit Smart-Sensor data bus provides external command and data interface capability between the sensor and the focal plane. This includes on chip 6-bit pixel offset correction, detector bias selection and regulation, programmable signal gain, interlaced and non-interlaced output video format selection, signal integration time selection and input referred global offset selection capabilities. The U6000 also includes a high resolution on-chip temperature measurement that is incorporated into the single channel output video during horizontal blanking. This paper describes the U6000's functional capabilities, and provides U6000 functional validation and performance data.
This paper provides a review of the significant progress achieved in uncooled VO microbolometer LWIR focal plane and sensor technology at The Boeing Company during the last four years. When Boeing (formerly Rockwell) first introduced its first 320x240 uncooled FPAproduct in 1996, the U3000, it had a specified product NETD <0.1 K (F/i). Today, as a result of on-going improvements in VOx microbolometer design, processes and materials, the U3000 product is an established workhorse that is achieving an F/i NETD in the range of 0.033 to 0.040 K. The new U4000 320x240 product, that is being introduced by Boeing this year, has already demonstrated an F/i NETD <0.023 K at a 60 Hz frame rate, while having a thermal time constant <0.025 sec. In addition, significant progress has been made with innovative uncooled sensor operating concepts. Boeing has demonstrated its "TCOMP" response and offset compensation concept, which allows the uncooled IRFPA to operate without the need for temperature regulation. The elimination of the need for temperature regulation also means that uncooled LWIR imaging sensors can now have essentially instant-on operating capability, while requiring significantly less power. Spatial F/i NETD as low as 0.027 K, which is a measure of the level of spatial pattern noise in the displayed sensor image, has been demonstrated with a U4000/TCOMP sensor, and TCOMP has already been demonstrated over an at least 30 K calibration range.
This paper describes two camera systems based on the advanced 160 X 128 uncooled micro-bolometer FPAs. The UL3 ALPHA camera is in production and takes advantage of the patented bias equalization FPA performance to produce the world's smallest IR production camera. UL3 ALPHA weighs less than 195 grams, uses 1.5 W of power (nominal) and has a overall dimensions of 4.3 cm X 4.3 cm X 7.5 cm. ULS ALPHA production cameras have demonstrated 62 mK NEdT operation with over 99% operability.
This paper describes the UL3 camera system based on the advanced 160 X 128 uncooled micro-bolometer FPA. The UL3 camera takes advantage of the patented bias equalization FPA performance techniques to produce the world's smallest IR camera. The UL3 camera weights less than 2.3 ounces, uses less than 600 mW of power, and has overall dimensions of 3 cm X 3 cm X 6 cm. The architectures feature an approach that integrates the required system functions on ASICs and FPGAs rather than including discrete components and microprocessors.
This paper presents background and measured performance data on a novel, low cost, high performance readout integrated circuit (ROIC) for microbolometer uncooled detector applications. The array is designed to offer better than 80mK NEdT performance using f/1.8 optics. The design incorporates advanced on-ROIC signal processing electronics that allow bolometer element non-uniformity control over a wide range of ROIC substrate temperatures. The small format array is ideally suited for high volume low-cost production applications.