Third generation FPA development status at Raytheon Vision Systems (Invited Paper)

Abstract

Raytheon Vision Systems (RVS) is developing two-color, large-format infrared FPAs to support the US Army's Third Generation FLIR systems**. RVS has produced 640 x 480 two-color FPAs with a 20 µm pixel pitch. Work is also underway to demonstrate a 1280 x 720 two-color FPA in 2005. The FPA architecture has been designed to achieve nearly simultaneous temporal detection of the spectral bands while being producible for pixel dimensions as small as 20 microns. Raytheon's approach employs a readout integrated circuit (ROIC) with Time Division Multiplexed Integration (TDMI). This ROIC is coupled to bias-selectable two-color detector array with a single contact per pixel. The twocolor detector arrays are fabricated from MBE-grown HgCdTe triple layer heterojunction (TLHJ) wafers. The single indium bump design is producible for 20 µm unit cells and exploits mature fabrication processes that are in production at RVS for Second Generation FPAs. This combination allows for the high temporal and spatial color registration while providing a low-cost, highly producible and robust manufacturing process.High-quality MWIR/LWIR (M/L) 640 x 480 TDMI FPAs with have been produced and imaged from multiple fabrication lots. These FPAs have LWIR cutoffs ranging to 11 µm at 78K. These 20 µm pixel FPAs have demonstrated excellent sensitivity and pixel operabilities exceeding 99%. NETDs less than 25 mK at f/5 have been demonstrated for both bands operating simultaneously.

Fabrication and Characterization of Small Unit-Cell Molecular Beam Epitaxy Grown HgCdTe-on-Si Mid-Wavelength Infrared Detectors

“…The current status at RVS for state-of-the-art large format FPAs with small pixel pitch detectors includes single color HgCdTe/Si short wavelength infrared (SWIR) 2048 · 2048 pixel 20 lm unit-cell and mid-wavelength infrared (MWIR) 2560 · 512 pixel 25 lm unit-cell, and two-color HgCdTe/CdZnTe midwavelength infrared (MWIR)/long wavelength infrared (LWIR) 640 · 480 and 1280 · 720 pixel 20 lm unit-cell. 1,6,9,10 High quality 6-in. MWIR HgCdTe/Si growth has been demonstrated, and single color HgCdTe/Si LWIR 256 · 256 pixel 30 lm unit-cell FPAs show the potential for extending HgCdTe/Si technology to LWIR wavelengths.…”

“…[1][2][3][4][5] Significant benefits can be realized for both infrared system performance and FPA manufacturing yield and cost by increasing the FPA format while also reducing the unit-cell size. Large format FPAs are required to meet ground and space-based imaging applications over wide fields of view, while a reduction in unit-cell size provides higher resolution imaging that is compatible with high density television displays and the ability to print an increased number of FPA die per processed wafer.…”

“…Large format FPAs are required to meet ground and space-based imaging applications over wide fields of view, while a reduction in unit-cell size provides higher resolution imaging that is compatible with high density television displays and the ability to print an increased number of FPA die per processed wafer. [1][2][3][4][5] HgCdTe heteroepitaxy growth on 4-in. and 6-in.…”

Third-generation sensors for night vision

“…Raytheon has already demonstrated [7] working two-colour MWIR/ LWIR arrays with 20-ìm pixels in a 480´640 format with high response operability ³ 99%. NEDT values less than 25 mK at f/5 have been demonstrated for both bands.…”

New material systems for third generation infrared photodetectors

“…A variation on the original back to back concept was implemented using HgCdTe at Rockwell [112] and Santa Barbara Research Center [113]. Following the successful demonstration of multispectral detectors in LPE-grown HgCdTe devices [113], the MBE and MOCVD techniques have been used for the grown of a variety of multispectral detectors at Raytheon [27,[114][115][116][117], BAE Systems [118], Leti [28,30,[119][120][121], Selex and QinetiQ [29,122,123], DRS, [26,124,125] Teledyne and NVESD [126,127]. For more than a decade a steady progression have been made in a wide variety of pixel size (to as small as 20 µm.…”