Microwave Characterization of a Wafer-Level Packaging Approach for RF MEMS Devices Using Glass Frit Bonding

This paper presents the microwave characterization of a wafer level packaging approach for RF MEMS devices, using glass frit as the bonding material. Coplanar waveguide transmission lines are packaged by silicon caps to carry out the RF characterization of the package structure. Prior to bonding of the cap on the transmission lines, cap wafers are bulk micromachined to form the cavities for housing the device to be packaged and pad windows to access the RF ports of the devices. Lateral feedthroughs are designed under the glass frit ring transitions in order to decrease the impedance loading effect of the silicon cap and the glass frit ring. The package is implemented using both high and low resistive silicon wafers in order to assess the microwave effects of cap wafer. A circuit model is used to extract the parameters of the feedthrough from the RF measurements. The loss of the feedthrough is measured to be 0.1 dB/transition at 10 GHz for high resistive silicon caps demonstrating the viability of glass frit in the packaging of RF MEMS devices.