Contact resistance, stiction force, and field-assisted growth and migration in MEMS and NEMS metals

Contact resistance and its evolution are important parameters that determine the useful lifetime of MEMS switches. This work investigates the stiction force and evolution of contact resistance for five different metals (iridium, tungsten, nickel, ruthenium, and platinum). A Pt AFM probe was used as the counter electrode and the contact resistance over 100,000 cycles in nitrogen were recorded. Although this is small number of cycles compared to the desired 1 quadrillion cycles, it reveals a great deal about the contact quality provided that very small changes in the contact resistance are monitored and analyzed. Tungsten showed the largest increase in the contact resistance of 4% that was attributed to its surface anodic oxidation as imaged with AFM. We also used an infrared camera to monitor the contact temperature and noted a small flash of light when the probe touched the surface. Heating and the nano-plasma deposits carbonous materials on the metal contact area increasing contact resistance.