The Effects Of The Oxide Layer Of Silicon And Fringe Effect Of Capacitor On The Performance Of Microaccelerometers

Microaccelerometer has been widely used for navigation, earthquake monitor, video games, etc. Comb microaccelerometer is the representative of the accelerometer for simple process, stability and small temperature coefficient. Although MEMS processing technology is more and more mature, it is undeniable that there are still many shortcomings and disadvantages. The typical errors, which are caused by comb microaccelerometer process, is gap error and tilt of plates. And the temperature cycle from house temperature to rather high temperature can affect the thickness of the plates’ oxide layer. These factors will impact on the performance of microaccelerometer.Currently, many researches is based on gap error of microaccelerometer. With the improvement of the precision, the effects of the tilt plate and the thickness of the plates’ oxide layer on performance of microaccelerometer can not be ignored. Thus, research of the influence of fringe effect and the thickness of the plates’ oxide layer to the performance of the accelerometer is essential to the improvement of the microaccelerometers’ performance. The main contents are:1. The tilt plates and the parallel plates are covered by oxide layer, the formulas of capacitance are derived. And describe change of capacitance with different the thickness of oxide layer.2. Establish a multi-conductor model of microaccelerometer structure. Calculate the value of the capacitance of edge effect by finite element software COMSOL Multiphysics. The results show that when the proof mass don’t moves, the capacitance of fringe effect accounts for 12.95% of overall capacitance for parallel plates and the capacitance of fringe effect accounts for 13.12% of overall capacitance for tilt plates. Analyze the relationship between displacement of the proof mass and capacitance of fringe effect for parallel plates and tilt plates.3. Describe the effect of the oxide layer thickness to the electrostatic stiffness, sensitivity, linearity and zero position of the accelerometer. Accelerometer sensitivity and linearity are calculated under the influence of fringe effect by numerical method. Compare the results of simulation and theory computation, and illuminate the effect of the fringe effect to the sensitivity and linearity.