Experimental validation of electromigration by low frequency noise measurement for advanced copper interconnects application

Cu based metal trench is essential for the downscaling of interconnects for 20-10nm technologies, where it is important to optimize the materials and processing on the barrier and cap layer for a promising resistivity and electromigration (EM) performance. In order to shorten the period of process evaluation, a fast wafer-level EM characterization method is highly demanded rather than the conventional package-level EM lifetime test. In this paper, the low frequency noise measurement is proposed to investigate the EM reliability on the advanced copper interconnects. The noise expression was studied by an extensive experimental measurement. It was found that the low frequency noise measurement is a more sensitive method for studying EM degradation and can be an early indicator for EM characterization. In particular, the threshold current (I_th) and the power spectral density (PSD) is suggested to be used as a fast and useful tool for evaluating EM performance.