Micromachined Arch-type cantilever as high sensitivity uncooled infrared detector

In this article, we discuss an uncooled infrared (IR) detector based on an "arch-type" design realized with advanced microelectromechanical systems technology. Bimaterial microcantilevers undergo bending as their temperature changes due to the absorption of infrared photons. The bending is proportional to dissimilar thermal expansion of the two different materials composing the cantilever. We select the most optimal combination of materials used commonly in the micromachining technology resulting in highest bimaterial effect. Well known SU8 negative resist is one promising candidate having high thermal expansion coefficient (alpha = 52 x 10(-6)/K), and relatively low thermal conductivity (0.2 W/m K). Creating a micromechanical "arch" shaped cantilever a differential stress is induced due to different thermal expansion of middle beam formed from the SU8-film. Moreover, we fabricate a design microcantilever IR detector that consists two unique skills: (i) a Si/SU8 bimaterial system as material combination with beneficial bimaterial effect and (ii) tiny silicon "arch" shaped loop which includes two beams for piezoresistive detection of the bending. (c) 2005 American Vacuum Society.