Combined low-frequency noise and resistance measurements for void extraction in deep-submicrometer interconnects

Abstract

Electromigration stress can give rise to voids that increase the resistance and localized thermal stress in interconnects. Estimation of the extent of voiding can provide information on the material quality and the amount of degradation that has resulted from the electrical stress. In this paper, a model is proposed that can be used to estimate the effective void volume in deep-submi-crometer interconnects. The model uses a combination of low-frequency noise and resistance measurements, and also considers the thermal coefficient of resistance in calculating the change in resistance of the interconnect line. A de-convolution scheme was employed to extract the iff noise component from the noise measurements to improve the accuracy of the extraction algorithm. To verify the accuracy of the model, the focused ion beam (FIB) technique was used to mill holes (to simulate voids) of known dimensions. The model was further applied to an electromigration stress study of aluminum (Al) interconnects as a method of testing its validity for stress-induced voids. The proposed technique is a useful reliability tool for void detection in deep-submicrometer interconnects.