Development and assessment of next-generation nanoelectromechanical switch contact materials

The deficiency of existing electrical contact materials is currently a significant impediment to the commercialization of nanoelectromechanical (NEM) contact switches - a low power “beyond CMOS technology”. NEM switches utilizing traditional metallic electrical contact materials, even those composed of inert, noble metals such as Au and Pt, demonstrate premature failure due either to their adhesiveness, or to catalytic activity leading to buildup of insulating interfacial contaminants. Commercially viable NEM switches demand novel contact materials along with efficient methods to evaluate the performance of these materials. This study highlights the development of one promising switch contact material: platinum silicide (Pt_xSi) thin films formed from a-Si and Pt precursors. Using CMOS-compatible fabrication methods, the stoichiometry of these silicide films was varied between PtSi and a Pt₂Si/Pt₃Si mixture by controlling the thickness of the precursor a-Si and Pt films. The stoichiometry had a significant impact on the mechanical and electrical characteristics of the films. Pt-rich silicides demonstrated metallic surface conductivity while electrical contact conductance was reduced with higher Si film content. We then present a novel, high-throughput electrical contact screening method using atomic force microscopy (AFM) to cycle nanoscale electrical contacts for up to two billion contact cycles under NEM switch-like conditions. The ability of this technique to resolve degradation of nanoscale Pt-Pt interfaces is demonstrated and, along with its ease of adoption, motivates future interrogation of Pt_xSi and other promising switch contact materials using this method.