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.
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.
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.
A mosaic array of resistively heated microbridges offers flexibility for infra red scene simulations. The array may operate without flicker and display high-intensity dynamic scenes over a wide bandwidth. Honeywell completed fabrication of a 512 X 512 resistor array with 3.5 mils pitch for AEDC's 7V and 10V test chambers. The emitter has a broad bandwidth covering from 2 micrometers to 26 micrometers . The array operates at 20 K to simulate low radiation backgrounds in space. Up to 16,000 pixels may be turned on to simulate targets and target clusters. Each emitter element may heat up to 550 K with 1 kelvin resolution. The maximum power dissipation per pixel is 830 (mu) W for a pixel heated up to 550 K. The maximum power required is 13.2 watts for 16,000 pixels. This low power capability is derived from Honeywell's silicon nitride microbridge structure. Each emitter has approximately 85% fill factor and an average emissivity of 70% over the 2 - 26 micrometers bandwidth. Defect count in the array is less than 1% with one column out. The array may be addressed at 30 frames per second.
Honeywell and MRC have been developing a range of thermal scene projector arrays through the Wright Laboratory Armament Directorate's cryovacuum resistive infrared scene projector (CRISP) program and the Defense Nuclear Agency's nuclear optical dynamic display system (NODDS) program. The resistive emitters are fabricated on silicon nitride structures on pitches as small as 2 mils. These structures have low thermal mass, low thermal conductance, and high fill factor. Monolithic address and pixel storage electronics provide flicker-free operation of large arrays at high frame rates. The emitters have demonstrated > 600 K blackbody temperatures, high radiance, and > 10<SUP>3</SUP> dynamic range at very low power when operated at 40 K temperatures to achieve low background. This paper describes the performance of a CRISP 512 X 512 array consisting of 3.5 mil pixels and a high-speed 128 X 128 NODDS array consisting of ultra-low-power emitters.
Honeywell Inc. and Mission Research Corporation (MRC) are jointly developing micro resistive heater array displays for projecting dynamic background scenes and targets in the short-wavelength infrared (SWIR) to long-wavelength infrared (LWIR) wavebands. There are two joint government contracts supporting this work: the Nuclear Optical Dynamic Display (NODDS) program under DNA contract DNA001-92-C-0041, which is developing a 512 X 512 array of 50- by 50-micrometers display pixels, and the Cryovacuum Resistor Infrared Scene Projector (CRISP) program for the USAF Wright Laboratory at Eglin AFB, which is developing a 512 X 512 array of 87.5- by 87.5-micrometers pixels. The requirements on the two programs are somewhat different due to their different missions. While the NODDS program is developing an array that can be used to create dynamic nuclear clutter scenes, the CRISP arrays are being designed for simulating multiple independently moving targets; and while the frame rate on the NODDS arrays requires an array capable of 1-kHz frame rates, the CRISP arrays will be operated at 30 Hz.