Mechanical resonator for hermeticity evaluation of RF MEMS wafer–level packages
Master's Thesis from the year 2002 in the subject Electrotechnology, grade: 1.0 (A), University of Applied Sciences Berlin (FB1), 49 entries in the bibliography, language: English, abstract: Common test standards for evaluating the hermeticity of microsystem packages are unsuitable for small MEMS-devices. It is the task of this Master thesis to create a universal test device to measure and to compare the hermeticities of different wafer-level packaging concepts, especially for RF MEMS devices. Resonator structures were found to be most suitable to measure low pressures and low pressure changes over time, due to the high sensitivity of their Q-value to the pressure in the cavity. The resonators are electrostatically actuated by using a novel coupling concept of the excitation voltage. The detection of the resonator movement is done by laser-interferometry. Sensors fulfilling the specific demands were designed, simulated and fabricated in the cleanroom. The fabrication process is based on SOI (Silicon On Insulator) wafers. Finally, the sensors were evaluated and characterized. A suitable resonator with a length of 500 μm reaches a Q-factor of 8070, at an ambient pressure of 0,02 mbar, and a resonance frequency of 36329 Hz. The sensitivity of the Q-value to pressure change is 4000 %/mbar at 0,02 mbar. This work was carried out within the Summit RF MEMS project, a collaborative project involving Ericsson, the Royal Institute of Technology-S3, Acreo and Saab Ericsson Space.
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amplitude Anodic bonding applied approximately back side beam structure bottom silicon calculated cantilever beam capacitance cavity coefficient damping factor devices double-clamped beam electrode Electrostatic excitation encapsulated Evaluation of RF excitation and detection excitation voltage fabrication process flexural mode force Frequency kHz)|constant front side gap distance glass wafer Hermeticity Evaluation hermeticity sensor Ium Wp Ium kHz]|constant leak rate Mask Master Thesis mbar measured Mechanical Resonator MEMS Wafer–level Packages monocrystalline silicon natural frequency Natural Frequency kHz natural spring natural optical detection paddle structure parameter photoresist plate pressure dependent Q-factor ratio reflected refractive index resonance frequency Resonator for Hermeticity resonator structure RF MEMS Wafer–level sealing technologies Sebastian Fischer shown in fig silicon dioxide silicon wafer SIMULATION RESULTS single-clamped beam SOI-wafer spring constant stiction surface technique temperature thickness torsional Vacuum vibrating structure vibration mode Wafer–level Packages FIG wavelength width Wp Ium Wp Young’s modulus