Validation of bending test by nanoindentation for micro- contact analysis of MEMS switches

Research on contact characterization for microelectromechanical system (MEMS) switches has been driven by the necessity to reach a high-reliability level for micro-switch applications. One of the main failures observed during cycling of the devices is the increase of the electrical contact resistance. The key issue is the electromechanical behaviour of the materials used at the contact interface when the current is flowing through the contact asperities. Indeed metal contacting switches have a large and complex set of failure mechanisms driven by the current level. This paper demonstrates the validity of a new methodology using a commercial nanoindenter coupled with electrical measurements on test vehicles specially designed to investigate the micro-scale contact physics. Dedicated validation tests and modeling are performed to assess the introduced methodology by analysing the response of gold contact with 5 μm2 square bumps under various levels of current flowing through contact asperities. Contact temperature rise is measured leading to shifts of the mechanical properties of contact material and modifications of the contact topology. In addition, the data provide a better understanding of micro-contact behaviour related to the impact of current at lowto medium-power levels.