Simulation of bulk micromachined vibration sensors with low noise

In this paper a novel capacitive micro-vibration sensor with multi-folding beams, fabricated by bulk micromachining, is presented. The microstructures of the vibration sensor are simulated by the finite element method (FEM). The relations between the structural parameters and the sensitivity and frequency response of the sensor were considered in the simulation. The static and modal analyzing results of the sensors show that the higher sensitivity and mechanical strength with multi-folding beam structure were achieved. The microstructure with beam thickness under 400um can be fabricated with DRIE technology. When the area of silicon proof mass is 2.5 × 10⁵ μ m², and the thickness of the proof mass vary from 40 μ m to 80 μ m, the mechanical noise is about 9 × 10^-6g/√Hz. The sensor with resonant frequency up to 5kHz can be used to measure the vibration signal in a wider frequency range.