This paper reports a non-contact experimental characterization of resonant modes in micromachined glass-blown spherical shells, enabling new architectures of vibratory 3-D MEMS for signal processing, timing, and inertial applications. Wafer-scale glassblowing was previously developed for creation of extremely smooth and symmetric spherical cells for chip-scale atomic devices. The current work investigates an intriguing possibility of using micromachined glass-blown 3-D shells as mechanical vibratory elements. For experimental characterization, 3-D resonant shells were fabricated in-house using wafer-scale glassblowing, eutectically bonded to piezoelectric actuator plates and packaged. For a micro-shell with 0.9mm diameter and 10um average thickness, dynamically balanced 4- and 6-node vibratory modes were experimentally identified at 1.27MHz and 1.44MHz, respectively. The developed analytical model sheds light on the effect of fabrication imperfections on splitting of degenerate modes. Without any trimming or tuning, the relative frequency mismatch df/f for 4- and 6-node vibratory modes was measured as 0.63% and 0.2%, respectively, on par with the state-of-the-art planar silicon MEMS resonators. Even though the presented results are the initial steps toward feasibility of dynamic 3-D MEMS, we believe the approach may lead to high precision devices with increased stability, reduction of energy losses, and truly exploiting the physics of elastic waves on micro-scale.
Journal: TechConnect Briefs
Volume: 2, Nanotechnology 2010: Electronics, Devices, Fabrication, MEMS, Fluidics and Computational
Published: June 21, 2010
Pages: 300 - 303
Industry sector: Sensors, MEMS, Electronics
Topics: MEMS & NEMS Devices, Modeling & Applications