A low-cost 128x128 uncooled infrared detector array in CMOS process

Eminoglu S., Tanrikulu M. Y. , AKIN T.

JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, vol.17, no.1, pp.20-30, 2008 (Peer-Reviewed Journal) identifier identifier

  • Publication Type: Article / Article
  • Volume: 17 Issue: 1
  • Publication Date: 2008
  • Doi Number: 10.1109/jmems.2007.910235
  • Journal Indexes: Science Citation Index Expanded, Scopus
  • Page Numbers: pp.20-30
  • Keywords: CMOS infrared detector, CMOS micromachined sensor, low-cost infrared detector, microbolometer, microbolometer readout circuit, uncooled infrared detector, FOCAL-PLANE ARRAY, MICROBOLOMETER


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 40 mu m x 40 mu m and a fill factor of 44%. The p(+)-active/n-well diode detector has a measured dc responsivity (R) of 4970 V/W and a thermal time constant of 36 ms at 50 mtorr vacuum level. The total measured rms noise of the diode type detector is 0.69 mu V for an 8 kHz bandwidth, resulting in a detectivity (D*) of 9.7 x 10(8) cm . Hz(1/2)/W. The array is scanned by an integrated 32-channel parallel ROC including low-noise differential preamplifiers with an electrical bandwidth of 8 kHz. The 128 x 128 focal plane array (FPA) has one row of infrared-blind reference detectors that reduces the effect of FPA fixed pattern noise and variations in the operating temperature relaxing the requirements for the temperature stabilization. Including the noise of the reference and array detectors together with the ROC noise, the fabricated 128 x 128 FPA has an expected noise equivalent temperature difference (NETD) value of 1 K for f/1 optics at 30 frames/s (fps) scanning rate. This NETD value can be decreased to 350 mK by improving the post-CMOS fabrication steps and increasing the number of readout channels.