Electrolyte additive chemistry and feature size-dependent impurity incorporation for Cu interconnects

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The role of electrolyte additive chemistry in the incorporation of non-metallic impurities (such as C, S, and Cl) in electrodeposited Cu and its subsequent recrystallization behavior was characterized for both blanket electrodeposited Cu films and Cu plated into Damascene features. Chemistries yielding both pure and "doped" Cu were considered. For wide features (~ >1 μm), impurity levels correspond well with blanket Cu film observations, while for narrow features (~50 nm), impurity levels were elevated within the features, regardless of chemistry type. Recrystallization within Damascene features was observed to be relatively insensitive to the electrodeposited Cu purity and instead more dependent on feature size and the post-plate anneal temperature employed. The correlation of the electrodeposited Cu purity to electromigration and stress migration behavior is discussed. © 2012 The Electrochemical Society.