Fabrication of complementary metal-oxide-semiconductor compatible semiconducting yttrium barium copper oxide uncooled infrared microbolometer arrays

Abstract

This article presents the fabrication of complementary metal-oxide-semiconductor (CMOS) compatible micromachined semiconducting yttrium barium copper oxide (YBCO) microbolometer arrays. YBCO in the semiconducting phase at room temperature is used as an uncooled IR microbolometer. It possesses a relatively high temperature coefficient of resistance, a relatively low 1∕f noise, and the ease of fabrication by rf magnetron sputtering at ambient temperature. In this work, YBCO microbolometers are integrated with CMOS readout circuits using capacitive transimpedance amplifier and constant current buffered direct injection design techniques in AMI 1.5μm double-poly-double-metal n-well 2.5V CMOS technology. The self-supporting micromachined YBCO exhibits low thermal mass and hence provides low thermal time constant for the same degree of thermal isolation. The thermal isolation of the microbolometers is varied by designing two different electrode arm geometries. The first geometry is designed to obtain a relatively fast 200Hz frame rate while maintaining a moderate detectivity that provides the potential for a faster frame rate imaging that is advantageous in a variety of applications where the camera or objects in the scene are in motion, and the second arm geometry is designed to achieve a traditional 30Hz frame rate with high detectivity microbolometers.