Effects of fabrication error on thermal drift of capacitive micro accelerometer

Dimension uncertainty inevitably occurs in almost every fabrication of micro structure due to its small size and uniformity of material. The dimension error, however, will result in the asymmetry of the sensitive structure. The unsymmetrical structure will change the distribution of the thermal stress when the micro sensors are subjected to changed temperature and further impact the thermal stability of devices which is characterized by the quantity of thermal drift. This study investigates the effects of fabrication error on the thermal drift of a comb capacitive micro accelerometer fabricated by deep reactive ion etching(DRIE) process. The accelerometers with supporting folded beams width error ranging from the ideal layout design to the actual fabricated dimension are modeled to simulate the deformation of sensitive component induced by temperature change. The thermal drifts are acquired by the calculation of the differential capacitance of the deformed structure. In order to reduce the thermal drift induced by the fabrication error, the design dimension of the beam width is enlarged under the premise of constant sensitivity of the accelerometer. The calculated results indicate that the supporting beam fabrication error will significantly affect the thermal drift of the capacitive micro accelerometers and an increased design dimension of the beam width can improve the symmetry of the sensor, and then reduce the thermal drift.