A Micro-Oven-Controlled Wafer-Level Vacuum Packaging Process Platform for MEMS Resonant Devices

This paper presents a novel wafer-level vacuum packaging platform with monolithically integrated micro-oven-controlled system, which can be used for resonant MEMS devices to reduce frequency error over wide temperature range. The platform, consisting of thermistor, isolation beam and heater, not only has the ability to adjust and maintain uniform heated-temperature by using micro-oven, but also can effectively suppress the packaging stress and achieve thermal isolation. Thanks to the three layers wafer-level vacuum packaging process and grinding release technique, the MEMS resonator is designed and successfully integrated into the platform. The test results show that a vacuum level of approximately 6 mTorr is achieved. The temperature coefficient of the resonant frequency (TCF) of the micro-oven-controlled MEMS resonator are as low as <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.6 \text{ppm}/^\circ \mathrm{C}$</tex> within the temperature range from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-40^{\circ}\mathrm{C}$</tex> to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$80^{\circ}\mathrm{C}$</tex>.