Towards an Ultra Sensitive Seismic Accelerometer

A fourth generation MEMS-based silicon accelerometer is designed and fabricated in the process of developing an accelerometer to be used as an ultra sensitive seismometer for noise subtraction arrays. The device uses a novel ratchet system actuated by thermal actuators to compress precurved springs to increase the sensitivity of the system. The fabrication is based on a three-mask process, which is suitable for mass production. A first vertical application of such a device is designed and fabricated as a proof of concept. The flexures are rotated a predetermined angle so that, when placed vertically, the compressed system returns to its original position, effectively handling the offset of 1 g. A two-mask process is used for fabrication. A 2-fold stiffness reduction was obtained by compressing the pre-curved flexures 9 um.