Development and characterization of low-cost uncooled infrared sensors for commercial applications

Tankut, Firat
This thesis reports the study on the development and characterization of low-cost uncooled microbolometer type infrared detectors, which are fabricated using standard CMOS and MEMS processes. Characterization of the detectors is the first step of developing infrared sensors with better performance. The characterized pixel has a 70 μm pitch and includes 4 serially connected diodes as the detector circuit. Thermal conductance (Gth), temperature sensitivity (TC) and, optical absorption are measured in scope of the characterization tests. The optical absorption of the detectors is measured by Fourier Transform Infrared Spectroscopy (FTIR) method and average absorption is found as 78 % for 7-14 μm wavelength range. The noise of the detector is characterized in detail. Test results show that, the predominant noise mechanism in the characterized low-cost infrared sensors is the Random Telegraph Signal (RTS) noise. After characterizing the pixel, the readout electronics of the 70 μm pixel pitch QCIF (160x120) resolution Focal Plane Array (FPA) are improved for better performance. Three main revisions on the current design are made, and the revised readout circuits are verified with detailed tests in the scope of this thesis. In the first revision, power dissipation of the chip is decreased by changing the architecture of various blocks of the readout circuit. After this revision, the Noise Equivalent Temperature Difference (NETD) value is improved to 280 mK. The second design revision decreased the impact of the column noise that was caused by the RTS mechanism. Lastly, a third revision is made in order to improve the temperature stability and noise rejection. These revised sensors are used in developing miniature thermal camera systems in the scope of another work, and the resulting miniature cameras are among the smallest thermal camera cores in the world. As the final step, second generation low-cost uncooled microbolometer pixels are developed, where the pixel pitch is reduced to 50 μm while preserving the same performance level as the 70 μm pixels. In order to alleviate the performance degradation caused by the reduction of the area that absorbs radiation, more serially connected detector diodes and thinner support arms are used. Thermal parameters are simulated using Finite Element Method (FEM). The expected thermal conductance and the thermal time constant are calculated as 222 nW/K and 48.8 ms respectively from the simulations. Optical absorption is also simulated and the average optical absorption is calculated to be 77 % for 7-14 μm wavelength region from the simulations. The FPA chip utilizing second generation pixels is tested, and average pixel noise is measured as 9.8 μVRMS including the readout circuit noise.


Development of high performance uncooled infrared detector materials
Kebapçı, Başak; Akın, Tayfun; Turan, Raşit; Department of Micro and Nanotechnology (2011)
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...
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 ...
Development of high fill factor and high performance uncooled infrared detector pixels
Küçük, Şeniz Esra; Akın, Tayfun; Department of Electrical and Electronics Engineering (2011)
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 allo...
Investigation of warpage behavior of single crystal silicon on a silicon Adhesive ceramic integrated structure at cryogenic temperatures
Baloğlu, Can; Okutucu Özyurt, Hanife Tuba; Dursunkaya, Zafer (2016-03-17)
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...
Design and implementation of high fill factor structures on low-cost uncooled infrared sensors
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...
Citation Formats
F. Tankut, “Development and characterization of low-cost uncooled infrared sensors for commercial applications,” M.S. - Master of Science, Middle East Technical University, 2013.