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), language: English, abstract: Common test standards for evaluating the hermeticity of microsystempackages are unsuitable for small MEMS-devices. It is the task of this Master thesis to create a universal test device tomeasure and to compare the hermeticities of different wafer-levelpackaging concepts, especially for RF MEMS devices. Resonator structureswere found to be most suitable to measure low pressures and lowpressure changes over time, due to the high sensitivity of their Q-value tothe pressure in the cavity. The resonators are electrostatically actuated byusing a novel coupling concept of the excitation voltage. The detection ofthe resonator movement is done by laser-interferometry. Sensors fulfillingthe specific demands were designed, simulated and fabricated in thecleanroom. 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 m reaches a Q-factor of 8070,at an ambient pressure of 0,02 mbar, and a resonance frequency of36329 Hz. The sensitivity of the Q-value to pressure change is4000 %/mbar at 0,02 mbar. This work was carried out within the Summit RF MEMS project,a collaborative project involving Ericsson, the Royal Institute ofTechnology-S3, Acreo and Saab Ericsson Space.