Omer HaLevy

We report on a new architecture and theoretical and experimental feasibility study of a resonant accelerometer, combining a robust single proof mass design with a compliant parallel motion linkage -type force amplifier. The device, incorporating four effectively oblique force-transmitting links and a resonant sensing beam attached at its ends to two shutters, is distinguished by a simple, manufacturable geometry, purely axial, free from any bending, loading of the vibrating sensing beam and low parasitic compliance. The device was fabricated from the 25 $\mu$ m thick layer of a silicon-on-insulator (SOI) wafer. The acceleration-dependent frequency of the electrostatically driven 300 $\mu$ m long and 3.8 $\mu$ m wide resonator was measured using capacitive sensing, combined with open or closed-loop excitation scenarios. Consistently with the lumped and the full scale FE models prediction, 760Hz/g sensitivity of the device, with the $\approx$ 2600 $\mu$ m × 2600 $\mu$ m proof mass, was demonstrated during the $\pm g$ experiment.

We report on the theoretical and experimental feasibility study of a resonant sensing device implementing a compliant, parallel linkage-type, force amplification architecture. The work is motivated by the development of resonant sensors and, particularly, of vibrating beam accelerometers. A beam-type resonator is clamped at its two ends to two proof masses, each attached to the substrate using two links with pseudo-hinges. Due to the offset between the hinges, the links effectively operate as oblique linkages, allowing in-plane, parallel to the substrate, motion of the masses and resulting in significant amplification of the forces transferred by the masses to the resonator. This single-layer device of a simple, manufacturable, Manhattan geometry, is distinguished by low parasitic compliance and allows an axial, lacking any bending, loading of the resonators. The design parameters and performance estimates of the devices are obtained using simple lumped reduced order (RO) models, combined with a detailed finite element (FE) analysis. The devices, fabricated from silicon on insulator (SOI) wafers were open-loop, operated in ambient air; the acceleration was emulated by applying an appropriately scaled electrostatic force acting on the masses and provided by gap-closing electrodes. A sensitivity of ≈ 2.1 Hz/V ² or ≈ 300 Hz/g, in the case of a non-differential measurement and ≈ 4.39 Hz/V ² in case of a differential measurement, was registered in the experiments, consistently with the models predictions. Our results indicate that the suggested architecture can be implemented for high-end robust inertial sensors.

We report on the fabrication and characterization of a generic, manufacturable, cantilever-type resonant sensing element, actuated by fringing electrostatic fields and fabricated from a silicon on insulator (SOI) wafer. The architecture of the electrode, designed to be thicker than the cantilever, was tailored to allow efficient electrostatic up-tuning of the beam's frequency and enhancement of the device frequency to voltage/displacement sensitivity in the initial “as fabricated” configuration. The device is not prone to undesired pull-in instability and can be operated at large deflections, which increases the dynamic range. The multilevel structure was fabricated using a two-stage critically timed deep reactive ion etching (DRIE). The device was operated statically and dynamically by a combination of dc and ac voltages, and an increase of the resonant frequency with the increasing voltage/deflection was registered. Consistently with the model predictions, the experimental results suggest that this type of sensing element can be promising for implementation in a large variety of resonant, inertial, force or pressure sensors.