An uncooled microbolometer infrared focal plane array in standard CMOS


Tezcan D., Eminoglu S., Akar O., Akin T.

Conference on Photodetectors - Materials and Devices VI, San-Jose, Costa Rica, 22 - 24 January 2001, vol.4288, pp.112-121 identifier identifier

  • Publication Type: Conference Paper / Full Text
  • Volume: 4288
  • Doi Number: 10.1117/12.429399
  • City: San-Jose
  • Country: Costa Rica
  • Page Numbers: pp.112-121
  • Keywords: uncooled infrared detectors, low cost microbolometers, microbolometers, CMOS sensors
  • Middle East Technical University Affiliated: Yes

Abstract

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 ANSYS were performed to obtain an optimized structure. Various prototype FPAs with 16x16 array sizes have been implemented with 80 mu mx80 mum and 50 mu mx50 mum pixel sizes. The measurements and calculations show that the n-well microbolometers can provide a responsivity of 8.5x10(6) V/W, a detectivity of 5.5x10(9) cmHz(1/2)/W, and an NETD of 260 mK at 30 frames per second using a simple, fully-serial readout approach with an integrator output. The performance of the array can be increased with advanced readout techniques and improved pixel structures. The CMOS n-well microbolometer approach seems very cost-effective to produce large focal plane arrays for uncooled infrared imaging with reasonable performance.