Analysis of asperity dominated contacts in nanoelectromechanical relays using thin films

Development of nano-electromechanical relays (NEMRs) has led to a new focus on the thermal behavior at nano-scale contacts. The asperity-asperity contacts in NEMRs are susceptible to deformation and melting due to high pressures and temperatures at the contacting surfaces. Furthermore, because of their small size, these contacts are very difficult to analyze either experimentally or theoretically. Thin films are often deposited on the contact in order to improve the material and electrical properties of the relay. This work presents new methods for analyzing the thermal behavior at the contacts formed by these thin films, thus providing design tools to help avoid or facilitate welding, depending on the purpose of the device. First, theoretical analysis of nano-scale contacts is presented in order to provide a framework for predicting the thermal behavior of devices with thin films. Second, this paper presents experimental results using NEMRs that are electrostatically actuated, then welded and released repeatedly. A welding voltage bias is applied across the contacts which melts the film (TiN), and welds or releases the device. The welding event is observed visually and electrically.