Key Technologies Of Optimization And Signal Processing Of A Monolithic Triaxial Micro-accelerometer

The silicon micro-accelerometer has a broad future aspect in both military and civil fields. Triaxial micro-accelerometer can detect acceleration in three directions, in the meanwhile, its volume as well as mass and power consumption is small, and can be fabricated in batches, therefore rapidly becomes a hotspot of research.This paper reports a few design optimization of a kind of capacitive triaxial micro-accelerometer aiming at its problem such as noise, precision and consistency. The work was based on the groundwork of study about the micro-accelerometer in our lab. The main study focused on the optimization of the structure, the fabrication techniques, encapsulation structure, and the decoupling arithmetic was also redesigned. The performance is obviously improved via the test results. Subsequent research contents were included in this dissertation.1. Structure Analysis. Starting from the basics theory of material mechanics, the mathematical model of the accelerometer with double slanted beams was investigated. Then the relationship between sensitivity and structure parameters of the micro-accelerometer was analyzed, and then the theoretical analysis and finite element simulation by ANSYS of the model were put in practice to validate the model. And the optimization direction was put forward.2. Fabrication techniques optimization. Aiming at the problem of over etching of the silicon structure, a new method was used to fabricate the prototype. The test results proved that the new fabrication process can improve the size consistency of the sensitive structure. Aiming at eliminating the parasite capacitance of the former encapsulation design, a new design was investigated, namely attaching the chip to PCB directly, and the attaching area was a small square in the center. Thus the influence of temperature stress was evidently depressed, and the noise and parasite capacitance was also cut down.3. Signal processing. The program of communicating the accelerometer chip and the user was compiled using the software Lab Windows. The 12 location method test was performed on a high precision three axes rotation platform. The software Matlab was used to solve equations by least square method. The test results showed that the performances of the accelerometer are improved as expected.