SI-CMOS-MEMS dual mass resonator for extracting mass and spring variations

This paper presents Si-CMOS-MEMS dual mass resonators (DMRs) which are fabricated using Si-CMOS-MEMS technology for extracting mass and spring variations. The CMOS chip is fabricated in BiCMOS 0.35 μm process from Jazz Semiconductor. 0.2 μm flatness of the backside silicon over 1.5 mm distance is achieved. The Si-CMOS-MEMS DMR includes proof masses, serpentine spring suspensions and comb fingers and serves as the basic structure for a z-axis differential gimbaled gyroscope. The DMR enables the extraction of process variations by comparing measured frequency response with a geometrically parameterized system-level simulation of the DMR. A model-based methodology is proposed to extract mass and spring variations. Three parameters including in-phase displacement, anti-phase displacement and the difference in displacement between two proof masses in anti-phase mode are chosen to extract the geometrical process variation parameters. The variation between the dual masses is approximately 1.2-1.5% and the spring variation is 3.1%.