Grain growth and twinning in copper thin films for ULSI circuits

For an analysis of microstructure influence on electromigration behavior of different deposited copper films, a thorough study of microstructure is necessary. Therefore the temperature dependence of grain growth and twinning of PVD-Cu and the grain growth at room temperature (self-annealing) of electroplating-Cu has been studied. The grain boundaries and the grain size have been measured by backscatter Kikuchi technique (EBSD) and X-Ray Diffraction (XRD). PVD Copper shows a strong 〈111〉 fibre texture and electroplating Copper more randomly oriented grains. During the self-annealing of EP-Copper the 〈111〉 texture remains but the fraction of randomly oriented crystallites increases. The EBSD data exhibit an accumulation of Σ3 grain boundaries for both depositions (PVD: 35%; EP: 60%). A considerable amount of small angle grain boundaries (PVD: 23% EP: 7%) was found. The results are represented and their improtance for electromigration research is discussed.

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