In situ electromigration damage in Al interconnect lines in the SEM and the influence of grain orientation

Abstract

Unpassivated AlSiCu interconnects (thickness 1 μm, width 8 and 1.4 μm, on SiO2) were tested for electromigration in situ in the SEM under accelerated loading conditions. To examine the influence of grain orientation on electromigration damage, orientation mapping of the interconnects was carried out prior to testing using the EBSD technique (Electron BackScatter Diffraction or Backscatter Kikuchi Pattern). Damage micrographs and orientation data were correlated with respect to microstructure (polycrystalline/bamboo), deviation from 〈111〉 fibre texture and grain boundary properties (axis/angle, CSL model). It was found that not the deviation from 〈111〉 fibre texture, but the misorientation class of individual grain boundaries and their course in relation to the current direction are decisive factors for the damage location where the fatal defects occur.