Three-dimensional micromachined diamond birdbath shell resonator on silicon substrate

This paper proposes a novel three-dimensional (3-D) micromachined birdbath shell resonator (mu-BSR) fabricated from polycrystalline diamond on silicon substrate for potential MEMS gyroscope. Design, modal simulation, MEMS fabrication process and vibration test of the micromachined diamond birdbath shell resonator are presented. Key features of the 3-D fabrication process are the etching of the bulk silicon mold and deposition of high-Q polycrystalline diamond films onto the mold. The birdbath shell resonator is fabricated with a good structural symmetry, owing to its supporting anchor and shell are integrated manufactured through the MEMS fabrication process. By using piezoelectric actuation and optical characterization, the M = 2 elliptical vibration mode is determined to be at about 80.61 kHz with a normalized frequency split (Delta fM=2/fM=2) of 0.32%. The frequency separation between the M = 2 elliptical mode and the closest parasitic tilting mode of the mu-BSR is relatively large, which makes the resonator less sensitive to vibration and improves shock resistance. These resonators show great promise for being used as micro birdbath resonator gyroscopes (mu-BRGs) on a chip.