Effects of inhomogeneous strain on room-temperature recrystallization in copper thin films

Cu thin films were prepared either by sputtering or by electroplating. The two types of films were investigated for the evolution of microstructure and texture in relation to the progress of room temperature recrystallization using an X-ray diffractometer and an EBSP apparatus. It was found that room-temperature recrystallization was observed in both types of films. The texture in the as-deposited films strongly affected the occurrence of room-temperature recrystallization. XRD and EBSP results indicated that room-temperature recrystallization was not observed in highly (111)-orientated films, while it was observed in randomly orientated films. Measurement of full width at half maximum of X-ray diffraction peaks indicated that the degree of inhomogeneity in strain distribution was larger in the randomly orientated films than in the highly (111)-orientated films. The inhomogeneous strain distribution in the randomly orientated films decreased with the progress of room temperature recrystallization. These results suggest that room-temperature recrystallization was induced by the presence of large inhomogeneous strain and random texture.