The micromachined silicon accelerometer, which has a stiffness-tuning capability to improve the sensor resolution, is developed. The accelerometer consists of: a planar proof mass which has combs; 28 pairs of the differential capacitor type sensing electrodes which sense the proof mass motion; and the folded type springs. The stiffness of the sensor structure is reduced by providing the negative stiffness, which is due to the electrostatic force generated between the mass and the sense electrodes, when a dc voltage is supplied to the sense electrodes. The accelerometer has the active size of 400×620μ㎡, the thickness of the polysilicon structure of 6.5㎛, and the proof mass of 1.1㎍. Experimental results show that the silicon accelerometer has the sensitivity of 10.5mV/g, the resolution of 150mg and the linearity of 2%FS. It is shown that the resolution is improved two times by using the stiffness-tuning.
