Design and fabrication of a vibration sensor using a conductive ball

We have fabricated a MEMS-based vibration sensor with a conductive ball. The vibration sensor consisted of a conductive ball placed in a 600 μm deep anisotropically micromachined silicon cavity, two electrodes on the non-planar surface, and a cover glass for encapsulation. Before Au film deposition, the sharp convex corner at the upper edge of the cavity was rounded to deposit the metal film without disconnecting on the non-planar surface. The shadow-mask technique allowed for the simultaneous metal deposition and patterning on three-dimensional structures without the conventional photolithography. The frequency responses of the proposed MEMS-based vibration sensor using a conductive ball ranging from 0 to 30 Hz were stable.