Effect of film thickness on the evolution of annealing texture in sputtered copper films

Microstructural evolution during elevated temperature annealing of sputter deposited copper (Cu) films was investigated by electron backscatter diffraction (EBSD). Analysis of films was performed both in situ using a heating stage, and by ex-situ observation of microstructural evolution. It was noted that not only is the Cu film texture and grain size a function of film thickness, but also that the fraction of twin boundaries present in the material is strongly dependent upon film thickness. This is explained by means of a simple model that considers the energy of the system. Surface and interface energies, as well as grain boundary energies for random high angle boundaries and for twin boundaries (both coherent and incoherent planes) are used in the determination. The model was shown to accurately predict the twin boundary size in self-annealed films. This type of analysis also results in a texture map similar to that presented by Thompson,12 but incorporates the development and effect of twin boundaries, so that additional texture components (in addition to 111 and 100 fibers) are included.

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