RESONANT-BRIDGE 2-AXIS MICROACCELEROMETER

This paper describes a two-axis silicon microaccelerometer consisting of two pairs of polysilicon resonant bridges orthogonally attached to a silicon proof mass. Acceleration in the plane of the substrate causes differential axial loads on opposing microbridges in each pair, thereby shifting their resonant frequencies. The acceleration component aligned with a pair is measured by the difference in resonant frequencies. The device has a 1.45 mg proof mass and 250 μm long, 100 μm wide, 1.6 μm thick polysilicon bridges. To suppress rotation and vertical displacement of the proof mass, it is also supported on the backside of the wafer by eight, 8 μm thick silicon bridges. Initial measurements indicate a sensitivity to inline acceleration of 160 Hz/g. © 1990.