Accelerometer by means of a resonant micro actuator

A monolithic resonant micro actuator was developed, fabricated by CMOS-compatible micro machining technology, tested and evaluated. The component is able to measure acceleration in at least two directions. The device made of single-crystal silicon oscillates perpendicularly to the surface plane at a constant frequency in the 8 kHz range. A square-pulse shaped voltage of double the oscillation frequency drives it. It comprises an oscillating plate with a capacitance formed by interdigitating comb fingers. The acceleration in the direction orthogonal to the surface plane is detected by comparing the position of the plate to a reference plane. Without acceleration applied the position is centred in average. Upon acceleration the crossover point of the oscillation is shifted and the magnitude of acceleration can be related to the difference. The acceleration in a second direction can be measured by the common way of comparing e.g. the change of capacitance of two electrodes to each other. The component's stability in frequency and amplitude during testing is shown. Simulation and measurement data is presented and compared.