Electrical characterization of ALD-coated silicon dioxide micro-hemispherical shell resonators

This paper reports on electrical characterization of ALD-coated thermally-grown silicon dioxide micro-hemispherical shell resonators (μHSRs) with capacitive electrodes. A high aspect ratio silicon dioxide μHSR with a thickness of 2.6 μm and diameter of 910 μm, uniformly coated with 30 nm of platinum using ALD process, demonstrated Q of 19,100 at 19.17 kHz and 14,300 at 55.2 kHz for m=2 and m=3 wineglass modes, respectively. An optimized isotropic dry etching recipe was developed to create highly symmetric hemispherical molds in (111) silicon substrates, from which the oxide shells were thermally grown. This resulted in a significant improvement of frequency mismatch between m=2 degenerate modes, achieving 21 Hz split as fabricated for m=2 modes of an 8kHz SiO₂ μHSR that is 1240 μm in diameter and 2 μm in thickness. This creates a path for fabricating high Q and highly symmetric hemispherical shell resonators for microscale hemispherical resonator gyroscopes.