Crystallographic characterization of interconnects by orientation mapping in the SEM

Abstract

We show in this paper how electron backscatter diffraction and orientation mapping within a scanning electron microscope can be used to measure local variations in crystallographic texture and grain boundary structure in interconnects. The reliability-limiting phenomena of stress voiding and electromigration are two examples of interconnect failure modes that depend strongly on local crystallographic structure. Several analysis examples are presented to show the utility of this technique for characterization of local microstructures in both copper- and aluminum-based lines. The advantages of a local measurement technique over a global texture method for orientation determination became immediately apparent in these investigations. This local approach to characterizing crystallography is expected to play an even larger role in technologies such as damascene or lift-off processing, where lines are deposited directly into precisely-defined geometries. Particularly in these more advanced processing technologies, one cannot extrapolate measurements of blanket film structure and properties to the case of narrow lines.