PERFORMANCE LIMITATIONS OF SURFACE-MACHINED ACCELEROMETERS FABRICATED IN POLYSILICON GATE MATERIAL

In this paper we seek to determine the limitations imposed on the sensitivity, dynamic range and bandwidth of surface-micromachined accelerometers by their small masses and spring constants. The dynamic behaviour of a simple sprung mass system is considered to obtain a fundamental model for the accelerometer. The model is then extended to include thermal noise. We describe a prototype accelerometer structure fabricated using CMOS-compatible processing, which exploits the polysilicon gate material for the micromachined device. We apply the model to this simple accelerometer structure to determine the potential performance (range, sensitivity and bandwidth) of surface micromachined accelerometers. We conclude that it should be possible to fabricate an accelerometer with a sensitivity of 0.01 m s(-1) using surface-micromachining technology.