Effect of temperature on energy loss and internal friction in nanocrystalline copper thin films

This study employed a temperature controlled capacitance-based system to measure the mechanical behaviors associated with temperature dependent energy loss in ultra-thin copper (Cu) films. Thin Cu films are widely used in electronic interconnections and micro-electromechanical systems (MEMSs); however, most studies have focused on temperature-dependent dynamic properties at larger scales. This study designed a paddle-like test specimen with a Cu film deposited on the upper surface in order to investigate the in-situ temperature-dependent mechanical properties of thin metal films at elevated temperatures of up to 160 °C under high vacuum conditions at very small scales. In-situ energy loss was measured according to the decay in oscillation amplitude of a vibrating structure following resonant excitation. Film thickness and grain size were closely controlled with respect to the dynamic properties of the films. It was also determined that the internal friction of ultra-thin metal films is strongly dependent on film thickness and temperature.