Hydrogen-Induced Grain Growth in Electrodeposited Cu Films

We proposed that the grain growth observed in electrodeposited Cu films at room temperature is caused by hydrogen-induced superabundant vacancy-hydrogen clusters. In this study, the relation between grain growth and hydrogen behavior in the electrodeposited Cu films was investigated using different types of plating baths. The Cu films were electrodeposited from an acid sulfate bath, an acid sulfate bath containing chloride ion, polyethylene glycol, and bis(3-sulfopropyl)disulfide (additive-containing bath), a pyrophosphate bath, and a chloride bath containing citric acid. Thermal desorption spectroscopy revealed that extremely high concentration of hydrogen is contained in the Cu films deposited from the additive-containing bath and the chloride bath. The room-temperature grain growth was observed in these Cu films with passage of time after deposition, concurrently with hydrogen desorption. Such grain growths were not observed in the Cu films with low hydrogen content deposited from the acid sulfate bath and the pyrophosphate bath. The changes in crystal orientation and internal stress during the grain growth of the Cu films differed between the additive-containing bath and the chloride bath. These results suggest that the room-temperature grain growth was induced by the co-deposited hydrogen in films.