Ruthenium/Gold Hard-Surface/Low-Resistivity Contact Metallization for Polymer-Encapsulated Microswitch with Stress-Reduced Corrugated SiN/SiO2 Diaphragm

This paper presents a RF MEMS switch with a new ruthenium/gold multi-layer contact metallization scheme, which combines the advantages of a hard ruthenium contact surface for high contact reliability and of a low, total contact resistance as typical for gold alloys. The performance of the new concept has been analyzed theoretically and was experimentally verified by contact resistance and life-time characterization of fabricated MEMS switches with conventional Au-Au and with the novel Au/Ru-Ru/Au contact metallization scheme. The switches are based on a low-stress SiN/SiO2 diaphragm which is polymer transfer-bonded and equipped with corrugations for reducing the stiffness and for lowering the stress. The reduced stiffness allows for early encapsulation by clamping the membrane all around its circumference, by maintaining medium actuation voltages.