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 µm reaches a Q-factor of 8070at an ambient pressure of 002 mbar and a resonance frequency of36329 Hz. The sensitivity of the Q-value to pressure change is4000 %/mbar at 002 mbar.This work was carried out within the Summit RF MEMS projecta collaborative project involving Ericsson the Royal Institute ofTechnology-S3 Acreo and Saab Ericsson Space.