Mechanical trimming with focused ion beam for permanent tuning of MEMS dual-mass gyroscope

This paper reports mechanical ablation techniques for permanent frequency tuning of the primary wineglass modes in planar gyroscopes with concentric ring suspension. Three different approaches for frequency tuning are discussed: (1) selective mass removal, (2) stiffness reduction via thinning of suspension elements, and (3) stiffness reduction by removal of interconnecting spoke elements between concentric rings. A predictive tuning algorithm is developed for identification of ablation locations to guide the trimming process. A dual-mass Dynamically Amplified Gyroscope (DAG) design is used to demonstrate the tuning approach. It is shown that introduction of "side-spokes" to the concentric ring system of DAG enables coarse (50 Hz) tuning, as well as fine-tuning (<1 Hz) of resonant frequencies, which is performed by means of mechanical ablation with focused ion beam (FIB). Finally, a comparison of the sensor noise characteristics using active electrostatic tuning and mechanical ablation is presented. (C) 2020 Elsevier B.V. All rights reserved.