Effects of Cu Self-Capping and Ta Capping on Nanometer-Sized Cu Films Sputter-Deposited on β-Ta

Abstract

The Cu(111) texture evolution in Cu films sputter-deposited on 35-nm β-Ta barrier layers on Si(100) (Ta/Cu) and in those capped by 5-nm Ta (Ta/Cu/Ta) were studied by X-ray diffraction (XRD). The Cu thicknesses (t_Cu) ranged from 5 to 500 nm. For Ta/Cu, the intensity of the Cu 111 reflection exhibited a step-like increase for t_Cu between 22 and 33 nm, indicating that subsequent deposition of Cu caused the Cu(111) texture evolution in the already-deposited Cu film (Cu self-capping effect). For Ta/Cu/Ta, the 5-nm Ta capping caused the Cu(111) texture evolution in the already-deposited Cu films for t_Cu between 10 and 30 nm (Ta capping effect). These capping effects indicate that the texture evolution took place at room temperature in nanocrystalline Cu films. The capping effects and the initial growth stage of Cu on β-Ta are discussed as they relate to Ta and Cu interfacial and grain boundary energies in the nanocrystalline structures.