MEMS Process Characterization with an on-Chip Device

We have developed a CMOS-compatible, in-situ micro-device to measure three important fabrication, material, and actuation parameters characterizing planarprocessed microelectromechanical (MEMS) structures: uniform in-plane overor under-cut (cut error), effective Young’s Modulus, and actuation comb-drive forces. Our only measurements are of voltage and capacitance. The device fits in a 1 mm by 1.5 mm area for localized, nondestructive, in-situ testing. A major advantage of our approach results from the use of a complementary combdrive structure for accurately measuring displacement of a cantilevered shuttle. The measurement is insensitive to cut error. Assuming realistic variations in the mask-making process and minimal thermal expansion of the material, this device measures a 6 μm motion with a resolution of less than 1 nm. We report characterization results for a silicon-SOI fabrication run.