Morphology, structure and mechanical properties of copper coatings electrodeposited by pulsating current (PC) regime on Si(111)

Abstract

Copper electrodeposition on (111)-oriented Si substrate was performed by the pulsating current (PC) regime at various average current densities in the range of 15-70 mA cm-2, obtained by varying either the frequency (30, 50, 80 and 100 Hz for the current density amplitude of 100 mA cm-2) or the current density amplitude (120 and 140 mA cm-2 at 100 Hz). The produced Cu coatings were examined by SEM, AFM and XRD techniques. The morphology of the coatings changed from those with large grains to fine-grained and globular, while the crystal structure changed from the strong (220) to the strong (111) preferred orientation by increasing the average current density. The mechanical characteristics of coatings were examined using Vickers micro-indentation tests, applying the Chicot-Lesage (C-L) composite hardness model for the analysis of microhardness. The maximum microhardness was obtained for the Cu coating produced at an average current density of 50 mA cm-2, with a current density amplitude of 100 mA cm-2 and a frequency of 100 Hz. This copper coating was fine-grained and showed the smallest roughness in relation to the other coatings, and it was obtained in the mixed activation-diffiusion control between the end of the effect of the activation control and the beginning of the dominant effect of diffiusion control.