Development of high fill factor and high performance uncooled infrared detector pixels

Küçük, Şeniz Esra
This thesis presents the design, fabrication and characterization of high performance and high fill factor surface micromachined uncooled infrared resistive microbolometer detectors which can be used in large format focal plane arrays (FPAs). The detector pixels, which have a pixel pitch of 25 μm, are designed and fabricated as two-level structures using the enhanced sandwich type resistor while the active material is selected as Yttrium Barium Copper Oxide (YBCO). First level of the pixel structure is allocated for the formation of the support arms in order to obtain longer support arms hence lower thermal conductance values to get the desired high performance levels. The pixel body is built in the second level such that the fill factor and absorption of the detector is maximized. Structural and sacrificial layer thicknesses are also optimized in order to increase the absorption coefficient of the pixel in the 8-12 μm wavelength range. The thermal simulations are conducted using finite element method (FEM) by CoventorWare software. The designed pixel has a fill factor of 92 % together with the thermal conductance and thermal time constant values calculated as 16.8 nW/K and 19.3 ms in the simulations, respectively. The pixels are fabricated at METU MEMS facilities after the design of a CMOS compatible process flow. All process steps are optimized individually to obtain the expected high performance. Characterization step of the pixels includes the measurements of temperature coefficient of resistance (TCR), noise and thermal conductance value together with the thermal time constant. Effective TCR of the pixel is measured as -2.81 %/K for a pixel with a support arm resistance of 8 kΩ and total resistance of 55 kΩ. The corner frequency of 1/f noise in the pixel is 9.5 kHz and 1.4 kHz under 20 μA and 10 μA current bias, respectively. The total rms noise is 192 pA within 8.4 kHz bandwidth for a current bias of 20 μA. Thermal conductance, Gth, of the pixel is measured as 17.4 nW/K with a time constant of 17.5 ms. The measurement results indicate that the single pixels designed and fabricated in the scope of this thesis are applicable to large format FPAs in order to obtain a high performance imager. The expected NETD values are 33 mK and 36 mK for 384x288 and 640x480 format FPAs, respectively


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This thesis reports both the optimizations of the vanadium oxide (VOx) thin film as an active infrared detector material by the magnetron sputtering deposition method and its use during fabrication of proper resistors for the microbolometers. Vanadium oxide is a preferred material for microbolometers, as it provides high TCR value, low noise, and reasonable resistance, and a number of high-tech companies have used this material to obtain state-of-the-art microbolometer arrays. This material is first used in...
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Ertürk, Ozan; Akın, Tayfun; Department of Electrical and Electronics Engineering (2015)
This thesis presents the design and implementation steps of high fill factor structures for existing SOI diode low-cost microbolometer FPAs. Advancements in uncooled infrared detectors enable high performance military grade uncooled microbolometers as well as ultra-low-cost infrared imagers for civilian applications. The trend in uncooled microbolometers to reduce the pixel pitch has become increasingly significant to lower the cost of detector and system integration due to optics, and increase spatial reso...
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Keskin, Selcuk; Akın, Tayfun (2012-04-27)
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Understanding thermal stress and warpage behavior of heterogeneous component assemblies is vital in infrared sensor applications of silicon semiconductor material. The silicon semiconductor warpage behavior of the integrated structure composed of silicon material itself, an adhesive layer and a ceramic layer is analyzed by both FEM and experimental studies. The studies are performed between room temperature and 80 K. Thickness of each layer has an effect on the warpage. The silicon warpage of the initial ba...
High performance focal plane array technologies from short to long wavelength infrared bands
Arslan, Yetkin; Beşikci, Cengiz; Department of Electrical and Electronics Engineering (2014)
This thesis work covers the development of three different state of the art infrared sensor technologies: quantum well infrared photodetectors (QWIPs), HgCdTe sensors and extended InGaAs photodetectors. QWIP is the leading member of the quantum structure infrared photodetector family providing excellent uniformity and stability with field proven performance. The utilization of the InP/In0.48Ga0.52As multi-quantum well structure (instead of the standard AlGaAs/GaAs material system) for the implementation of ...
Citation Formats
Ş. E. Küçük, “Development of high fill factor and high performance uncooled infrared detector pixels,” M.S. - Master of Science, Middle East Technical University, 2011.