Low Cost Microbolometer Development Using Commercially Available CMOS Foundry Processes

Abstract

We have demonstrated the monolithic fabrication of uncooled microbolometer Focal Plane Arrays (FPAs) for infrared imaging applications using available CMOS, BiCMOS foundry processing and micromachining techniques which trade higher performance with potentially much higher yield and lower production costs. Past and current efforts have exclusively focused on using the commercial silicon foundries for the Readout Integrated Circuits (ROICs) fabrication, and then the microbolometer detector bridges are fabricated on top of the ROICs using processes that involve many complex growth layers and etching steps. These current approaches require specialized microbolometer fabrication facilities and foundries to be built and maintained. We have demonstrated methods to fabricate inexpensive, reasonable performance uncooled microbolometer FPAs using commercially available silicon foundries. To be truly cost effective, we are using the commercial foundries to fabricate the microbolometer FPAs. To release or suspend the bolometer structures, we have used a simple post-foundry maskless anisostropic or isotropic wet/dry etch. We have fabricated a prototype 13×14 uncooled microbolometer FPA using the commercial AMI 1.5um CMOS process as well as a 38×38 microbolometer array using the AMI 0.5um CMOS process. Discussions of the microbolometer circuit designs, MEMS micromachining techniques, and test results will be presented.