Detection of defects in metal interconnects by the nonbias-optical beam induced current technique

Abstract

The mechanism for detecting defects by the nonbias-optical beam induced current technique is clarified by examining images and conducting simulations. This technique, using an electromotive current as a result of optical laser irradiation with no application of voltage, is very useful for analysis of metal interconnect failure in ultra large scale integrated devices. The characteristic images obtained by this technique, consisting of pairs of bright and dark regions, reveal point defects, such as voids in metal stripes and vias. It is found, by examining the characteristic images of defects, that the electromotive current generated near the defects originates as a result of the thermoelectromotive effect. Furthermore, it is confirmed by thermal simulations and transient current simulations, that the asymmetric temperature profiles near the defects generate the electromotive current and show the characteristic images.