Low--‐cost uncooled infrared imaging sensor using mems and a modified standard cmos process

Download

index.pdf

Date

2013

Author

Gülden, Mehmet Ali

Metadata

Show full item record

Item Usage Stats

217
views

178
downloads

The thesis presents a monolithically integrated low-‐cost uncooled infrared imaging sensor using a MEMS process and a modified standard CMOS process. The designed sensor has an image format of 160×120 with a pixel pitch of 40 μm. The sensor is implemented with microbolometers that sense the infrared radiation in the 8-‐12 μm spectral band, where the sensing elements in each pixel are formed with CMOS diodes to sense the temperature variation in the pixel by monitoring the change in the forward bias voltage of diodes. The pixels have multiple serially connected diodes to increase the temperature sensitivity. The number of serially connected diodes in each pixels can be configured as 4, 5, and 6 with simple modification in the CMOS metal layers, at the expense of using higher supply voltages required to bias the pixel array. The current sensor design has 6 serially connected diodes in the pixel, requiring a 7 V supply voltage in the pixel array. The sensor has been implemented using a 1 μm SOI-‐CMOS process, with a slight process modification, where the pixel area is processed using a higher grade photolithography process allowing a minimum feature size of 0.5 μm. The smaller feature size in the pixel area allows obtaining better thermal isolation of the suspended bridges that hold the diodes through support arms. Suspended bridge like structures are obtained with a simple post-‐ CMOS etching process, which does not require any critical lithography steps. Hence, microbolometer fabrication cost can be decreased drastically, making these microbolometers potentially suitable for newly emerging various cost-‐effective infrared imaging applications, such as automotive, advanced presence detection, security, and consumer electronics. The designed infrared imaging sensor has a system-‐on-‐chip (SoC) architecture, and it runs on a single 7 V supply voltage. The designed sensor has both analog and digital integrated circuit modules, typically running at 5 V supply voltage except the pixel array. The designed imaging sensor is highly programmable, where timing of the critical digital signals and level of analog voltage and current biases can be programmed using programmable on-‐chip digital controllers and digital-‐to-‐analog converter (DAC) based voltage and current biasing circuits. The chip has also an integrated output buffer to drive high capacitance external loads. The infrared imaging sensor developed in this thesis has been fabricated in a 1 μm SOI-‐CMOS process using a wafer-‐level test run with a slight modification to allow fabrication of pixels with 0.5 μm minimum features size in the pixel area. Fabricating the imaging sensor at wafer-‐level allows also using conventional wafer-‐level microfabrication and MEMS processing steps, avoiding any difficulties that may arise due to use of die-‐level processing. The fabricated imaging sensor measures 10.5 mm×11.0 mm, where the readout circuitry is integrated in two parts at the top and the bottom of the chip. In this way, the pixel array is placed in the middle of the chip, hence it is possible to add a rectangular ring structure around the pixel array, which can later be used as a bonding surface required by several wafer-‐level vacuum packaging processes. The fabricated infrared imaging sensor is tested in detail to verify its functionality and to perform its characterization. The sensitivity and DC responsivity of single pixel test structures having 6 serially connected diodes are measured to be -‐7.05 mV/K and 18,194 V/W, respectively. The overall output noise of the readout circuit is measured as 124 μVrms. The integrated detector noise of the single pixel is measured as 5.19 μVrms in a 4 kHz bandwidth, resulting in an expected NETD value of 840 mK for the imager with an f/1 optics.

Subject Keywords

Infrared imaging., Infrared technology., Microelectromechanical systems.

URI

http://etd.lib.metu.edu.tr/upload/12615986/index.pdf
https://hdl.handle.net/11511/22683

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Low-cost microbolometer infrared detectors utilizing CMOS resistive layers Öztürk, Hande; Akın, Tayfun; Department of Electrical and Electronics Engineering (2017) This thesis presents the efforts to develop low-cost microbolometer type uncooled infrared detector architectures that utilize standard CMOS layers and components. Various resistance structures of different CMOS technologies are investigated and possible resistors are determined as the active material. In order to figure out potential microbolometer structure, all possible layers in the CMOS technologies are analyzed in terms of mechanical and thermal parameters. Mathematical modeling and computer simulatio...
Moving hot object detection in airborne thermal videos Kaba, Utku; Akar, Gözde; Department of Electrical and Electronics Engineering (2012) In this thesis, we present an algorithm for vision based detection of moving objects observed by IR sensors on a moving platform. In addition we analyze the performance of different approaches in each step of the algorithm. The proposed algorithm is composed of preprocessing, feature detection, feature matching, homography estimation and difference image analysis steps. First, a global motion estimation based on planar homography model is performed in order to compensate the motion of the sensor and moving ...
Low-cost uncooled infrared detector arrays in standard CMOS Eminoglu, S; Tanrikulu, MY; Akın, Tayfun (2003-04-25) This paper reports the development of a low-cost 128 x 128 uncooled infrared focal plane array (FPA) based on suspended and thermally isolated CMOS p(+)-active/n-well diodes. The FPA is fabricated using a standard 0.35 mum CMOS process followed by simple post-CMOS bulk micromachining that does not require any critical lithography or complicated deposition steps; and therefore, the cost of the uncooled FPA is almost equal to the cost of the CMOS chip. The post-CMOS fabrication steps include an RIE etching to...
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...
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

M. A. Gülden, “Low--‐cost uncooled infrared imaging sensor using mems and a modified standard cmos process,” M.S. - Master of Science, Middle East Technical University, 2013.