Analysis of Loss Mechanisms and Frequency Mismatch in Microelectromechanical Systems (MEMS)-Based Resonators

A Microelectromechanical System (MEMS) is based on Microelectronic Technique and Micromachining technology. The mechanical systems and electrical components can be built at a micro-scale. The systems can interact with each other by using the combination of those two technologies. MEMS gyroscopes are made up of proof masses, electrodes, springs, anchors, actuators, and detectors. The advantages of MEMS devices are reducing the size, weight, energy usage, and cost while maintaining the functionality of the sensors. Sensitivity is an important parameter to evaluate the performance of a gyroscope. This thesis performed the springs modelling technique to maximize the sensitivity of a vibratory MEMS resonator. This thesis investigates the relationship between the geometric variation of springs and frequency split. The frequency split was determined by using COMSOL simulation. The frequency can be tuned by changing the length and width of the springs. A length of springs tuned to 1834.8 µm resulted in a frequency split of 0 Hz. The results demonstrated that the geometric variation in springs makes a significant difference in frequency split and sensitivity of the gyroscope. Three different geometries were designed, and the one with the best performance was selected. A sensitivity calculation was performed by investigating the quality factor. The overall Q factor can be calculated as 6269.5 and 2705.5 for drive mode and sense modes, respectively. The model simulation showed a sensitivity of 2.22*10-8 m/deg/s for a frequency split of 0 Hz by optimizing the springs’ lengths. The fabrication platform selected was PolyMUMPS, which is cost effective and versatile. The experimental testing was not performed due to the global shortage of material caused by the pandemic

Recent Advances in MEMS-Based 3D Hemispherical Resonator Gyroscope (HRG)—A Sensor of Choice

Macro-scale, hemispherical-shaped resonating gyroscopes are used in high-precision motion and navigation applications. In these gyroscopes, a 3D wine-glass, hemispherical-shaped resonating structure is used as the main sensing element. Motivated by the success of macroscale hemispherical shape gyroscopes, many microscale hemispherical-shaped resonators have been produced due to the rapid advancement in semiconductor-based microfabrication technologies. The dynamic performance of hemispherical resonators depends on the degree of symmetry, uniformity of thickness, and surface smoothness, which, in turn, depend on the type of materials and fabrication methods. The main aim of this review paper is to summarize the materials, characterization and fabrication methods reported in the literature for the fabrication of microscale hemispherical resonator gyroscopes (µHRGs). The theory behind the development of HRGs is described and advancements in the fabrication of microscale HRGs through various semiconductor-based fabrication techniques are outlined. The integration of electrodes with the hemispherical structure for electrical transduction using other materials and fabrication methods is also presented. A comparison of different materials and methods of fabrication from the point of view of device characteristics and dynamic performance is discussed. This review can help researchers in their future research and engineers to select the materials and methods for µHRG development