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

The mechanism for detecting defects by the nonbias-optical beam induced cur rent technique is clarified by examining images and conducting simulations. This technique, using an electromotive current as a result of optical lase r irradiation with no application of voltage, is very useful for analysis o f metal interconnect failure in ultra large scale integrated devices. The c haracteristic images obtained by this technique, consisting of pairs of bri ght and dark regions, reveal point defects, such as voids in metal stripes and vias. It is found, by examining the characteristic images of defects, t hat the electromotive current generated near the defects originates as a re sult of the thermoelectromotive effect. Furthermore, it is confirmed by the rmal simulations and transient current simulations, that the asymmetric tem perature profiles near the defects generate the electromotive current and s how the characteristic images. (C) 1999 American Institute of Physics. [S00 21-8979(99)00923-8].