The Influence of Strain Energy Minimization on Abnormal Grain Growth in Copper Thin Films

Abstract

AbstractSputtered Cu films on Si, Al and Cu substrates were thermally cycled to 300 °C at a rate of 6 °/min, which induced an applied thermal strain that was compressive, tensile and zero, respectively. Microstructural characterization of the annealed films revealed abnormal (100) grain growth in the films on Al and Si, but not Cu substrates. In addition, symmetric x-ray diffraction scans demonstrated that the films in which abnormal grain growth was observed were primarily (100) in orientation. In contrast, the Cu film on a Cu substrate was largely randomly oriented after cycling, with a small degree of (111) preferred orientation. These results are consistent with a strain energy driving force for abnormal grain growth, which predicts that the growth should occur in compression, as on the Si substrate, or in tension, as on the Al substrate, but not when there is no applied thermal strain, as on the Cu substrate.