A CMOS n-well microbolometer FPA with temperature coefficient enhancement circuitry

Eminoglu, S
Tezcan, DS
Akın, Tayfun
This paper reports the development of a low-cost CMOS microbolometer focal plane array with a new temperature coefficient enhancement readout circuit. We have recently reported an uncooled microbolometer detector that uses the CMOS n-well layer as the active material, where the suspended and thermally isolated n-well structure is obtained by silicon bulk micromachining of fabricated CMOS dies. In addition, we have successfully fabricated a 16x16 n-well microbolometer FPA. Although n-well is single crystal silicon and has very low 1/f noise, the fabricated array performance was limited due to low TCR of the n-well. The n-well. has a TCR of 0.50-0.70%/K, which is the highest among the CMOS layers, but lower compared to the state-of-the-art microbolometer materials whose TCR values are about 2-3%/K. This paper reports a new n-well microbolometer FPA with a readout circuit that enhances the temperature coefficient (TC) of the microbolometer current, compensating for the low TCR value of the detector. The TC enhancement is achieved by passing the pixel current through a 4(th) power taking circuit prior to integration, increasing the pixel current TC four times and resulting in an effective TC of 2.0-2.8%/K. A 16xl6 test array has been designed and fabricated using a 0.8mum standard CMOS process. The chip measures 2.4x3.8 mm(2) and contains 80mumx80mum microbolometer pixels with 13% fill factor. The measurements and calculations show that the 16xl6 prototype FPA can provide a responsivity (R) of 2x10(7)V/W, a detectivity (D*) of 1.68x10(9)cmrootHz/W, and NETD of 290mK at a scanning rate of 260fps. The same NETD value can be obtained for a 128x128 pixel array operating at 30fps. NETD can further be decreased by improving the noise performance of the readout circuit, since the performance is not limited by the n-well microbolometer noise.


An uncooled microbolometer infrared focal plane array in standard CMOS
Tezcan, Ds; Eminoglu, S; Akar, Os; Akın, Tayfun (2001-01-24)
This paper reports implementation of a low-cost microbolometer focal plane array using n-well layer in a CMOS process as the microbolometer material. N-well microbolometer structures are suspended for thermal isolation by postetching of fabricated CMOS dies using silicon bulk-micromachining techniques. Although n-well has a moderate TCR of 0.5-0.65 %/K at 300 K, it still provides a reasonable performance due to its single crystal structure which contributes low 1/f noise. Detailed thermal simulations in ANS...
A low-cost 128x128 uncooled infrared detector array in CMOS process
Eminoglu, Selim; Tanrikulu, Mahmud Yusuf; Akın, Tayfun (2008-02-01)
This paper discusses the implementation of a low-cost 128 x 128 uncooled infrared microbolometer detector array together with its integrated readout circuit (ROC) using a standard 0.35 mu m n-well CMOS and post-CMOS MEMS processes. The detector array can be created with simple bulk-micromachining processes after the CMOS fabrication, without the need for any complicated lithography or deposition steps. The array detectors are based on suspended p(+)-active/n-well diode microbolometers with a pixel size of 4...
A CMOS visible image sensor array using current mirroring integration readout circuitry
Akbay, Selim Sermet; Bircan, A.; Akın, Tayfun (null; 2000-08-30)
This paper reports the development of a CMOS visible sensor array using a high performance readout circuit called Current Mirroring Integration (CMI). The sensor element is a photodiode implemented using n-well and p+ -active layers available in any CMOS process. The current generated by optical excitation is mirrored and integrated in an off-pixel capacitor using the CMI readout circuit, which provides high injection efficiency, low input impedance, almost-zero and stable detector bias, and a high dynamic ...
A Two-Stage Digital-to-Analog Converter for Bias Correction in Uncooled Microbolometer Arrays
Toprak, Alperen; Tepegoz, Murat; Akın, Tayfun (2011-04-29)
This paper introduces a detector biasing scheme proper for resistive microbolometer type uncooled thermal detector focal plane arrays (FPAs). The proposed scheme utilizes a 2-stage digital-to-analog converter (DAC) architecture where the first DAC stage generates the voltage interval that covers the bias voltage range of the overall FPA, while the second stage generates the high resolution analog voltages that are used to apply pixel-specific bias voltages. The second DAC stage output includes a resistive l...
A current mirroring integration based readout circuit for high performance infrared FPA applications
Külah, Haluk; Akın, Tayfun (2003-04-01)
This paper reports a current mirroring integration (CMI) CMOS readout circuit for high-resolution infrared focal plane array (FPA) applications. The circuit uses a feedback structure with current mirrors to provide stable bias voltage across the photodetector diode, while mirroring the diode current to an integration capacitor. The integration capacitor can be placed outside of the unit pixel, reducing the pixel area and allowing to integrate the current on larger capacitance for larger charge storage capac...
Citation Formats
S. Eminoglu, D. Tezcan, and T. Akın, “A CMOS n-well microbolometer FPA with temperature coefficient enhancement circuitry,” 2001, vol. 4369, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/38344.