Quality Factor Optimization Techniques for MEMS Gyroscopes of Frame Structures
MEMS gyroscopes of frame structures are capable of isolating the quadrature error between the drive motion and the sense motion, which is often utilized in current gyroscope design. But quality factors of previous reported gyroscopes of frame structure are hardly over 1000, which are far more less than that of gyroscopes manufactured before with only one mass block for sensing and driving. Although the effectiveness of isolating quadrature errors is proved, the sensitivity is decreased as well as the power consumption is increased for higher drive voltage. Reasons why MEMS gyroscopes of frame structure has low quality factors is pointed out here with a method of anchor loss mechanism, and the energy dissipation is modeled with a 2 degree of vibration system, which tells the relationship between the mass ratio of the inner mass and the outer frame and the spring factor ratio for supporting masses, and the quality factor assess techniques is proposed here. Therefore the admissible parameters of the mass ratio and the spring factor ratio are given, which makes MEMS gyroscopes of frame structures have advantages of quadrature error isolation as well as high sensitivity. In the end, gyroscopes with optimized parameters and reported parameters are manufactured on SOI wafer, and variations of the quality factors as expected proves the rationality of the proposed energy dissipation model in this paper. For Process limitations, quality factors of gyroscopes of frame structures are improved lower than expected, but far more improved than previous reported gyroscopes, and better results should be realized in more mature and stabilized process.
C. W. Si et al., "Quality Factor Optimization Techniques for MEMS Gyroscopes of Frame Structures", Advanced Materials Research, Vol. 590, pp. 173-178, 2012