Geometric Imperfection Characterization and Precise Assembly of Micro Shell Resonators

Micro glassblowing can be utilized in the fabrication of high-precision micro shell resonator due to its acceptable cost and promising performance. Geometric imperfection characterization and electrode assembly are important but challenging tasks for manufacturing high-quality resonators. This paper characterizes the geometric imperfection of the micro shell resonator and proposes a novel precise assembly process for micro shell resonators with out-of-plane electrodes. The crucial geometric imperfections including thickness imperfection, circularity error and anchor non-planarity of the glassblowing structures are experimentally characterized. The sample resonator exhibits a circularity error below 0.2 % and an anchor non-planarity of 300 nm. The relationship between frequency asymmetry and circularity error is discussed, which can be used to predict the resonator performance. A simplified model is built to analyze the effect of gap deviation on the capacitance variation of the resonator. Finally, a sacrificial layer-free electrode assembly method is proposed, which achieves small (<; 20 μm) capacitance gaps with relatively low tolerance.