2011CYC

江鎮宇 (Cheng-Yu Chiang)

Testing and improvement of a single-chip dual-axial capacitive micro accelerometer

單晶片雙軸電容式微加速規的改進與測試

Based on the previous design of our group, with symmetric coil-type suspension in the micro accelerometer, here the fabrication process is further improved, sensing circuit and MEMS structure are integrated, and the electrical output signal are measured for the development of a single-chip capacitive micro accelerometer.

For the structural design of micro accelerometer, differential sensing pair we used to achieve the capacitive measurement. In order to reduce side stiction, the sensing fingers are fixed at both ends in current design. At the same time, fabrication process is modified to reduce residual stress of polysilicon structure and the flaws during the whole process.

For the result of the fabrication process, scanning electron microscope (SEM, NCTU) and 3D profiler (ET-4000, NCTU) are used to measured geometric sizes of fabricated accelerometers. The optical profiler (white-light interferometer, CIC) and MEMS motion analyzer (MMA, CIC) are used to characterize the deflection of proof mass and the dynamic response of accelerometer, respectively.

For the electrical signal output, sensitivity of dual-axial accelerometers is shown to reach above 300 mv/G with the dynamic range of ±5G, however cross sensitivity is about 15%. The all signal self-test actuator is shown to successfully provide electrostatic force to move the proof mass. Currently, capping process of the micro accelerometer has been developed, and further package process in under way.