Microstructure Analysis in As-deposited and Annealed Damascene Cu Interconnects using OIM

Microstructure variation with linewidth was studied for both as‐deposited and annealed damascene Cu interconnect lines. Ten specimens with different linewidth and pitch distances were investigated using Orientation Imaging Microscopy (OIM). The microstructures, examined both before and after annealing, displayed high percentage of Σ3 boundaries. The microstructure was characterized by measuring the mean grain size, grain size distribution, grain boundary misorientation distribution and coincident site lattice (CSL) boundary distribution. The mean grain size increased proportionally until the linewidth was equal to line depth and slowly stabilized thereafter. The role of linewidth to pitch distance ratio was identified on influencing some of the microstructural features. The grain shape was analyzed using the grain aspect ratio parameter. The strain distribution in the line was studied using image quality (IQ) parameter.