Micromachined silicon hemispherical resonators with self-aligned spherical capacitive electrodes

A micromachined silicon hemispherical resonator with self-aligned silicon spherical capacitive electrodes is developed for the first time. Spherical electrodes, owning the same curvature of the resonator shell, surround the shell and extend into the cave deeply (160μm). The gap between the electrodes and shell is made by a sacrificial layer and a uniform and small (1.5μm) gap is obtained, which enables a large drive and sense capacitance of the resonator. Spherical electrodes are integrated as a part of the resonators fabrication process, and no extra assembly process is needed, ensuring the symmetry of the resonator. A resonator with 790μm diameter and thickness of 1.5μm has been demonstrated by the self-aligned fabrication process. The radial deviation of the hemispherical shell is less than 1.22μm for the ~500 radius shell (0.24%).