Automated Crystal Orientation Mapping (ACOM) of Thin Metallization Layers and Interconnects

Abstract

ABSTRACTA system for acquisition and interpretation of Kikuchi patterns with computer-controlled electron microscopes is presented. It enables interactive as well as fully automated determination of individual grain orientations. Special features for automated crystal orientation mapping (ACOM) with the scanning electron microscope (SEM) are digital beam scan, autocalibration and dynamic focus controlled by the computer. With the present setup about three orientations per second can be measured unattendedly. In the transmission electron microscope (TEM) the on-line determination of Burgers vectors and identification of deformation systems are based on crystal orientation measurement. The characterization of dislocations is facilitated by the simulation of diffraction patterns on the computer as a function of specimen tilt.Crystal orientation maps are obtained by assigning to the raster points in the image a color specific for the grain orientation, the misorientation or character of the grain boundary. The dala set of grain orientations is used to calculate the Schmid factors grain by grain, the orientation distribution function (ODF) and the correlated as well as the uncorrelated misorientation distribution functions (MODF) which characterize crystallographic texture in a statistical sense.Applications of individual grain orientation measurement are:. Thermomechanical hillocks in aluminum metallization layers on silicon substrates. Stress-induced grain growth in aluminum metallization layers on silicon substrates. Electromigration voids and hillocks in aluminum interconnectsA working hypothesis for electromigration failure, based on experimental findings, is discussed