Infrared Sensing With Self-Supporting YBCO Uncooled IR Microbolometer Array Integrated With On-Chip CCBDI Readout Circuit

This paper presents the integration and characterization of self-supporting yttrium barium copper oxide (YBCO) microbolometer arrays (pixel size of 31 times 31 mum²) with on-chip constant current buffered direct injection (CCBDI) readout circuit in AMI Semiconductor 1.5 mum double-poly-double-metal n-well 2.5 V complementary metal-oxide-semiconductor (CMOS) technology. The uncooled semiconducting YBCO microbolometer array was fabricated using two different electrode arm geometries to achieve either a traditional 30 Hz frame rate and a higher frame rate of 200 Hz. The CCBDI readout circuit was designed to work both with the traditional frame rate of 30 Hz, as well as a higher frame rate of 200 Hz when extrapolated to a 640 times 480 array for faster thermal imaging in commercial, military and biomedical applications. The CCBDI readout circuit offers advantages of high linearity and uniformity, low offset error and provides maximum sensitivity at a bias current. The CCBDI readout has a great potential due to higher injection efficiency of the CCBDI amplifier and the stable microbolometer bias control. The measured value of thermal conductance is 1.01 times 10^-7 W/K for the 30 Hz frame rate electrode arm geometry. The maximum responsivity of 1.62 times 10⁵ V/W and maximum detectivity of 3.51 times 10⁷ cm Hz^1/2 /W were measured for a single YBCO microbolometer pixel from the 4 times 4 array with CCBDI readout circuit and a 200 Hz frame rate electrode arm geometry. The maximum responsivity of 1.24 times 10⁵ V/W and maximum detectivity of 1.98 times 10 ⁷cm Hz ^1/2 /W were measured of a single YBCO microbolometer pixel from the 4 times 4 array with CCBDI readout circuit and a 30 Hz frame rate electrode arm geometry.