Philip E. Howard

Design and performance of the ULTRA 320x240 uncooled focal plane array and sensor

The ULTRA (Uncooled, Low cost, Technology Reinvestment Alliance) Consortium, consisting of the Honeywell Technology Center of Honeywell Incorporated, the Autonetics Missile Systems Division of Rockwell International Corporation, Inframetrics Incorporated, and the New Jersey Institute of Technology, has been formally working together over the past year in an effort to develop, manufacture and sell industrial and military sensors and components incorporating silicon microbolometer uncooled focal plane array (UFPA) technology. Towards that end, Rockwell has been actively engaged in developing the UFPA component, with assistance from Honeywell, with the intention of being a merchant supplier of the UFPA. Inframetrics has been developing subsystems required to construct and characterize a prototype sensor, and NJIT is designing a Multi-Wavelength Imaging Pyrometry system around the performance of the uncooled prototype sensor. TRP Office funding administered by ARPA has been key to the significant advances made over the course of the year in this program. This paper will describe both the UFPA component specification and the prototype sensor. It will give a architectural overview of the detector array, with the anticipated performance characteristics. Multiplexer design and simulation, and array processing, will be addressed. A description of the array packaging, interface requirements, and unique design considerations will be provided. Anticipated and actual component performance will be explained and contrasted. The background of the sensor development will be presented. An overview of the camera architecture will be given, with some discussion of trade-offs in subsystem design of the sensor. Specific emphasis is placed on the radiometric evaluation of the sensor.

High-performance 5-um 640 x 480 HgCdTe-on-sapphire focal plane arrays

A high-performance 5-μm 640 X 480 HgCdTe/CdTe/Al2O3 infrared focal plane array (FPA) that offers full TV-compatible resolution with excellent sensitivity at temperatures below 120 K has been developed. Mean FPA D* at 95 K and background of 1014 photons/cm2 s is background-limited at ~1 x 1012 cm Hz1/2/W for the typical mean quantum efficiency of 60 to 70%. The key technology making this large, high-sensitivity device producible is the epitaxial growth of HgCdTe on a rugged CdTe-buffered sapphire substrate. Mean camera noise-equivalent temperature difference NEΔT of 13 mK has been achieved at ≤ 120 K operating temperature and 3.4- to 4.2-μm passband; this is about an order of magnitude better than similar currently available cameras, which use PtSi FPAs and require cooling to ≤ 77 K to maintain performance at low scene temperatures.

Advances in microbolometer focal plane technology at Boeing

This paper reviews Boeings progress, over the last three years, in Vanadium Oxide (VOx) uncooled microbolometer focal plane (UFPA) technology and product development. Boeings UFPA product technology is described, including product capabilities and performance. Focal plane NETD equals 31 mK (F/1), at a 30 Hz sensor frame rate, has been demonstrated on the U3000 320 X 240 UFPA product. At a 60 Hz frame rate, the NETD (F/1) achieved on production U3000 UFPAs is typically less than 60 mK, and spatial pattern noise levels are consistently less than 33 mK after sensor level gain and offset compensation. Key improvements in VOx tin- film technology have been the achievement of a Temperature Coefficient of Resistance (TCR) approximately 3%, and the achievement of microbolometer resistance uniformity of approximately 1/3% ((sigma) /(mu) ) on the UFPA die. Looking into the future, this year Boeing expects to achieve NETD approximately 20 mK (F/1) with very low pattern noise, and within the next three years higher density 640 X 480 focal planes will be demonstrated with essentially equivalent NETD performance. Large high density uncooled LWIR focal planes, combined with low NETD, will make UFPA technology a prime candidate for higher performance FLIR applications.

DRS U6000 640x480 VOx uncooled IR focal plane

DRS (formerly Boeing) has completed the development and demonstration of a 25-micron pixel size 640x480 VOx 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 U6000s functional capabilities, and provides U6000 functional validation and performance data.

Progress in DRS production line for uncooled focal plane arrays

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.

Recent advances in TEC-less uncooled FPA sensor operation

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 sensors 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.

Technical overview of the UL3 ALPHA and OMEGA uncooled cameras

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 worlds 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.

Uncooled infrared focal plane producibility improvements at DRS

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.