A novel processing concept for reduction of substrate artifacts in ultrasound transducer arrays

Free-standing tungsten membranes supported by polyimide pillars were fabricated, demonstrating the general feasibility of the process. To reduce the warping due to the stress in the deposited tungsten layer four different membrane shapes were tested. The type B membrane shape gave the best result with the average peak to thorough distance of 162 nm. While the result is encouraging, the warping is still posing risk to the reliable operation of the CMUT since the gap of the transducer that is to be fabricated on the membrane is on the same order of magnitude.