Time Dependence Investigation of the Electrical Resistance of Au / Au Thin Film Micro Contacts

As MEMS microswitches realization time is too long for experiments aimed at the evaluation of new contact materials, an innovative test method is designed for studying electrical resistance of metallic micro contacts by reproducing microswitches geometry. The test structures, constituted by micro bars that are flat on one side and provided with tens of aligned spherical micro bumps on the other one, are put in contact at low loads in the 100 - 1000 μN range using a nanoindenter, thus enabling direct electrical contact resistance (ECR) measurements. This configuration is used for the study of gold/gold thin film contacts and allows the comparison of first contact closure resistance for different parameters sets including statistical results with the same sample. Results present resistance variations in the 0.2 - 2 Ω range primarily governed by time. Adhesion is also considered through pull-off forces. It is increased by load and values of the order of several hundreds of μN are needed to separate the contact surfaces. Finally, effects of successive contact openings and closings are investigated for both ECR and pull-off forces.