Effectiveness of oxygen plasma versus UHV bakeout in cleaning MEMS switch surfaces

MEMS switch reliability studies have identified contamination of the electrical contact surfaces as an important source of failure. It has been previously reported that the formation of electrically insulating organic deposits degrades switch performance by increasing contact resistance. Previously, we performed a high temperature bakeout under ultra-high vacuum (UHV) to desorb possible contaminant sources from Pt electrodes prior to cycling tests in a MEMS switch. In this work, an in-situ plasma-cleaning method of Pt is assessed for its ability to actively remove adsorbed contaminants. Microswitch contact resistance is measured before and after UHV bakeout or plasma cleaning of the switches. While plasma cleaning is seen to reduce water contact angle, it raises contact resistance. The likely reason is the formation of a metal oxide on the switch surface associated with sputtering of the plasma electrode material.