Dynamics of electromigration induced void/hillock growth and precipitation/dissolution of addition elements studied by in-situ scanning electron microscopy resistance measurements

Abstract

In the present paper. it has been shown that the in-situ SEM resistance measurement technique is a powerful technique to study the dynamics of void/hillock growth and precipitation/dissolution of addition elements in a metal line submitted to a temperature/current stress. The power of the in-situ SEM resistance measurement technique is shown with the first results on Al1wt.%Si0.5wt.%Cu metal lines. During the electromigration experiment, performed in a SEM equipped with a heating stage, back scattered electron images are taken continuously over the entire length of the metal line monitoring a.o. the growth, shape variation and motion of voids/hillocks, The dissolution and motion of Al2Cu precipitates in the Al1wt.%Si0.5wt.%Cu metal lines can also be monitored since the precipitates appear in the BSE mode as white objects. By comparing the observed electrical resistance drift results with the corresponding SEM micrographs it can be concluded that the resistance changes in the current stressed metal lines are mainly induced by geometrical changes. (C) 1999 Elsevier Science Ltd. All rights reserved.