EFFECT OF PROCESS INDUCED VARIATIONS ON PERFORMANCE CHARACTERISTICS OF A DUAL MASS VIBRATORY MEMS GYROSCOPE

摘要

Resonant frequencies of a MEMS vibratory gyroscope are one of the key design parameters, since these frequencies dictate the performance characteristics such as resolution, range, bandwidth and sensitivity of the device. These performance characteristics are affected by several factors, one of them being the fabrication process followed to realize the structure. In this paper, we discuss the influence of process induced variations on key design parameters. The key parameters considered are structural thickness, sense capacitance gap and residual stress. We have carried out detailed sensitivity analysis with respect to these parameters for a tuning fork gyroscope. The variations in the afore mentioned parameters change the dynamic behavior of the designed structure, thus affecting the performance characteristics of the device. We consider two processes - surface micromachining (i.e. PolyMUMPs @ MEMSCAP) process and Silicon-on-Insulator on Glass (SOIG) process - that can be adopted to fabricate the same device. We carry out a comparative analysis of PolyMUMPs process with SOIG process to study the effect of variations in the above mentioned parameters on the device performance and show the superiority of the SOIG process on all parameters.