Design And Fabricate Process Of A Three-frame MEMS Gyroscope

A novel de-coupled MEMS (Micro Electro Mechanical system) three-frame gyroscope is presented in this thesis. This structure resolves the shortcomings that large coupling errors and highly dependence on the fabrication processes in the fabricated double-frame MEMS gyroscopes.In traditional double-frame MEMS gyroscopes, the bilateral capacitance resulted from the movement of the mass with detecting combs in the driving mode can not be counteracted because of fabrication error, therefore, the performance of these gyroscopes are reduced. The structure of this three-frame gyroscope is composed of a driving frame, a mid-frame and a sensing frame. The mid-frame without combs functions as a transitional frame of the Coriolis effect. Because of its special structure, this three-frame gyroscope can effectively bring down this kind of coupling error.This thesis introduces the principle of the MEMS gyroscopes, analyzes the impact of static-electronics force driving, differential capacitive sensing as well as spring structures upon the performance of gyroscopes, and finally proposed the three-frame gyroscope model. On the base of the kinetic analysis and finite element simulation, the detailed structure and its parameters of the three-frame gyroscope are presented.Considering the fabrication cost and the fabrication conditions in China, this gyroscope is fabricated with the bulk silicon process technology. The fabrication processes are simple and batch productable. According to the design regulation of layout and the requirements of bulk silicon processes, the layouts and the feasible processes are presented. Then, the fabrication and simple encapsulation of this gyroscope are completed. Finally, the interface circuits of the gyroscope are designed and some of its primary tests are carried out.