Microstructure and properties of nanocrystalline Cu–Ta thin films prepared by direct current magnetron sputtering

Nanocrystalline (NC) Cu–Ta thin films were successfully fabricated by unbalanced magnetron sputtering on crystal silicon and glass substrates. Thin films doped with different Ta contents were prepared by altering the sputtering current of the Ta target. The micromorphology, microstructure, mechanical properties, electrical properties, and thermal stability of the films were investigated. The results on the microstructure of the as-deposited films demonstrated that Ta forms an FCC Cu (Ta) metastable supersaturated substitutional solid solution in Cu. In addition, with the increase of Ta content, the NC Cu–Ta films tended to be amorphous. Furthermore, the grain size of the post-annealed Cu–Ta films increased slightly due to recrystallization and in the metastable solid solution, Ta was exsolved and precipitated from the Cu matrix. The lowest resistivity (3.165 × 10−7 Ω·m−1) and the highest elastic modulus (125.2 GPa) were obtained with a Ta target current of 0.5 A.