| As a kind of inertial sensor with high accuracy,long working life and high reliability,hemispherical resonator gyroscopes?HRG?have been widely used in inertial navigation systems which play an important role in aerospace and military applications.Along with the development of new micro position,navigation and timing??PNT?system,micromachined HRG??HRG?based on micro electromechanical system?MEMS?technology becomes research focus.The performance of?HRG is theoretically up to the same level of HRG,however,there are two key problems in the miniaturization of HRG:1.design and fabrication of high Q?quality factor?resonator;2.the actuation and detection of resonator with high precision and efficiency.To solve these two problems,the design and fabrication of micro hemispherical shell resonator and its electrodes for actuation and detection is studied in this paper,based on our previous work of glass hot foaming process.The method of vacuum wafer-level packaging?VWLP?of resonator is also explored.Firstly,the electrodes of resonator are designed on the basis of electrostatic transduction theory.Better consistency of fabrication can be achieved by non-planar electrodes,compared to planar eletrodes.Besides,the assembly process of non-planar electrodes and resonator is easier than planar electrodes,which helps to control the uniformity of the gap size between the resonator and substrate.The number of sub-electrodes is a factor of 4,and the crosstalk can be reduced by the design of isolation electrodes.Furthermore,to enable the resonator to functions as a gyro,different schemes of electrodes configuration under whole-angle mode and force-feedback mode are studied.The configuration of 16 electrodes is better than 8 electordes for the control of amplitude,frequency and orthogonality of resonator mode shape,which helps to reduce the frequency cracking.Secondly,the design and fabrication of micro hemispherical shell resonator and its electrodes for actuation and detection is studied.The micro shell resonator is wafer-level fabricated utilizing hot forming process,and the vibration measurement by laser Doppler technique shows a m=2 wineglass mode at19.26kHz.The non-planar surface electrodes are fabricated by Lift-off method and the non-planar embedded electrodes are achieved by a glass reflow process.In particular,the influence of reflow time and cavity parameters on the filling ratio of glass is examined.Since crystallization maybe observed during the cooling procure after glass reflow,which will lower the structural reliability of substrate,the crystallinity of glass is characterized by X-ray diffraction?XRD?method.Result shows a crystallinity of 78.19%of glass after reflow process of 6 hours.As the resonator and substrate are fabricated separately,a method of micro assembly is raised and realized,during which the gap size between the resonator and substrate is determined by the height of photoresist deposited on substrate.Lastly,a VWLP method by micro glass cavity is explored,based on anodic bonding process,which could be used in the packaging of micro shell resonators.The leak rate of the sealed cavity is measured as3.1×10-10mbar?L/s,suggests a good hermetic packaging.In addition,the air damping in micro shell resonator is investigated.A model of thin film flow between two ring discs is established,and the squeeze film damping is analyzed both by theoretical computation and COMSOL Multiphysics.The pressure distribution shows a maximum damping at the center of the ring disc. |
PDF Full Text Request