Characterization of gold/gold, gold/ruthenium, and ruthenium/ruthenium ohmic contacts in MEMS switches improved by a novel methodology

摘要

Comparisons between several pairs of contact materials are done with a new methodology using a commercial nanoindenter coupled with electrical measurements on test vehicles specially designed to investigate microscale contact physics. Experimental measurements are obtained to characterize the response of a 5-μm~2-square contact bump under electromechanical stress with increased applied current. The data provide a better understanding of microcontact behavior related to the impact of current at low- to medium-power levels. Contact temperature rise is observed, leading to shifts of the mechanical properties of contact materials and modifications of the contact surface. The stability of the contact resistance, when the contact force increases, is studied for contact pairs of soft (Au/Au contact), harder (Ru/Ru contact), and mixed material configuration (Au/Ru contact). An enhanced stability of the bimetallic contact Au/Ru is demonstrated, considering sensitivity to power increase related to creep effects and topological modifications of the contact surfaces. These results are compared to previous ones and discussed in a theoretical way by considering the temperature distribution around the hottest area at the contact interface.