Reliability in Hot Switched Ruthenium on Ruthenium MEMS Contacts

Although metal-to-metal direct contact MEMS switches are a promising alternative to solid state switches in RF communication systems, the reliability of their electrical contacts has proven to be a barrier to entry to the market. Hot switching is known to have the most damaging effect on the contacts although an understanding of all the mechanisms leading to this damage is a work-in-progress. In this investigation, a customized Atomic Force Microscope was used to study the electrical contacts. The contacts were cycled at approach rates of 115 μm/s, 440 μm/s and 4400 μm/s and at different polarities. While material transfer is confirmed to be the primary source of contact damage, the results suggest that two different mechanisms could be at play at the leading and trailing edge of a hot switched cycle. A polarity driven mechanism and a contact separation rate dependent mechanism were observed. Low-level transient currents up to a few μA that may or may not be related to the material transfer, were observed at the leading edge of the switching cycle.