Sensitivity Deviation Probability Model of Close Loop Micro- Accelerometer Based on Comb Finger Gaps MEMS Process Error

Abstract

A sensitivity deviation probability model is proposed, for the first time, to describe the sensitivity deviation probability of micro-accelerometer brought by the MEMS process error in comb finger gaps. The sensitivity model is set up following the capacitance probability model on the premise that the error is in an interval with equal probability. Its indicated that, by the model, the probabilities for two kinds of deviation, decreasing and increasing, are different with the same process error degree. When the process error is about 25%, the sensitivity will decrease 5-10% with 40-50% probability, and increase 5-10% with 25-30% probability. Meanwhile, when the comb fingers number n is small, the deviation probability is big. When n is less than 20, the sensitivity decreases 10% with about 30% probability, but when n is close to 50∼60, the probability deceases to about 10%. Furthermore, the model is helpful in research and development field of MEMS accelerometers.