Design and implementation of high fill factor structures on low-cost uncooled infrared sensors

Ertürk, Ozan
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 resolution with range. However, reducing pixel size reduces the temperature sensitive area, not to mention the need for larger space to design longer thermal isolation legs. Therefore, many uncooled infrared imaging arrays employ additional structures that increase the fill factor. A second level of sacrificial layer is used to form the high fill factor structure (referred as umbrella) to form an optical cavity in order to maximize the absorption. This study demonstrates the design of umbrella layer in mechanical, thermal, and optical domain by providing simulations and examples from the literature. Challenges and optimization steps of realizing the umbrella structure are also conveyed. Successful implementation of umbrella structures onto SOI diode pixels with pixel sizes of 50 μm and 70 μm is demonstrated. The fill factor of the low-cost detector pixels with 50 μm pitch is increased from 46 % to 92 % while the fill factor of the pixels with 70 μm pitch is increased from 36 % to 94 %. The umbrella integrated FPAs are tested under vacuum conditions to obtain responsivity data and evaluate the contribution to the signal generated by addition of umbrella structures. It is concluded that the addition of umbrella structures improve the responsivity of FPAs with 50 μm pitch pixels by 30 % while the responsivity of FPAs with 70 μm pitch pixels is improved by 40 %.


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...
Design and implementation of perforation on high fill factor structures for uncooled infrared sensors
Çetin, Ramazan; Akın, Tayfun; Department of Electrical and Electronics Engineering (2016)
This thesis presents the design and implementation of the perforation on high fill factor structures; e.g., umbrella structures, for uncooled infrared detectors. The study is mostly focused on the effect of the perforation on the absorption performance of the sensor pixels. The introduction of the perforation to the umbrella structure is expected to improve the absorption performance which can be degraded due to a trending issue nowadays, the pixel size reduction. In literature, perforation is also proposed...
Development and characterization of low-cost uncooled infrared sensors for commercial applications
Tankut, Firat; Akın, Tayfun; Eminoğlu, Selim; Department of Electrical and Electronics Engineering (2013)
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...
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 characteristics of high performance mid-wavelength type-2 superlattice sensors
Oğuz, Fikri; Bek, Alpan; Arslan, Yetkin; Department of Micro and Nanotechnology (2018)
Type-II Superlattices (T2SLs) are bandgap engineered structures that have attracted a lot of attention in the last couple of decades and is still some of the hot topics in infrared imaging applications. T2SLs are the most promising member of the quantum structured infrared family. By the end of maturity period of T2SLs, Focal Plane Array (FPA) level products have been released since a decade. Offering performance compatible with high-end infrared systems, yielding respectable results and still being open to...
Citation Formats
O. Ertürk, “Design and implementation of high fill factor structures on low-cost uncooled infrared sensors,” M.S. - Master of Science, Middle East Technical University, 2015.