Acceleration insensitive hemispherical shell resonators using pop-up rings

This work introduces DICE (Deep Isotropic Chemical Etching) process for fabrication of highly symmetric 3D Hemispherical Shell Resonators (HSR) based on HNA etching of <111> silicon using a pop-up ring mask. The proposed method is used to fabricate 650 nm thick SiO2 hemispherical shell with a diameter of 180 μm, demonstrating a 3D symmetry of 99%. The quality factor (Q) of the wine glass n=2 mode is measured as 31542 at 100 kHz with a frequency mismatch of 512 Hz (Δf/fr=0.5%) between the two n=2 degenerate modes. COMSOL simulations show that a symmetric shell resonator has simultaneous shock insensitivity to in-plane and out-of-plane acceleration.