Effects of gap error on the capacitive micro accelerometer

Dimension uncertainty inevitably occurs in almost every fabrication of micro structure because of its small size and ununiformity of material, therefore, the dimension error is a significant factor to be considered in MEMS structure design. The unsymmetrical gaps of capacitors induced by processing are selected to analyze the effects of error on the performance of accelerometer including its sensitivity and pull-in voltage. The asymmetry of gaps concerns three type errors, firstly, one gap is smaller than another which equals to the design value, secondly, one gap is bigger than another which equals to the design value, and thirdly, two gaps are not equal, but both have errors. Analytical method is used to construct the force balance equation as the mass located in different position under different types of errors, and corresponding graphs are given to study the relation between parameters interested and structure error directly and vividly. The sensitivity of ideal structure is little larger than that with error, and the pull-in voltages under two conditions varies with the shift of structure parameter, the ratio is opt to 1 when the process error is small, but decreases rapidly with the increase of error.