Interfacial mechanism studies of electroless plated Cu films on a-Ta : N layers catalyzed by PIII

Abstract

This study evaluated the interface reaction and crystallography of the electroless plated copper film (similar to0.2 mum thick) catalyzed by plasma immersion ion implanted (PIII) Pd on the 150-Angstrom-thick amorphous tantalum nitride (a-Ta:N) barrier layer. The copper plated specimens were annealed at various temperatures in an ambient atmosphere of 90% nitrogen + 10% hydrogen mixed gases. Sheet resistivity, Auger electron spectroscopy (AES) analyses showed that the PIII Pd atoms were diffused into the copper layer from the interface of a-Ta:N and copper layers after 500 degreesC annealing for 1 h. Results based on x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) showed a phase transformation from a-Ta:N into crystallized Ta2N phase at annealing. The Cu(111) texture was strengthened at 300degreesC annealing for I h because of the relaxation of the residual stress and recovery of the copper film. The texture was reduced at the 500 degreesC annealing for I h because of the copper grain growth. The adhesion strength of copper films on a-Ta:N barrier layer was enhanced by the annealing because of the interdiffusion of copper layer, Pd clusters and a-Ta:N barrier layer. The annealing temperatures lower than 300 degreesC help to reduce the electric resistivity of copper film, to strengthen the Cu(111) preferred orientation. and to enhance the adhesion strength of copper films on a-Ta:N layer. However, the specimen annealed at 500 'C manifested the diffusion of Pd atoms into the copper film and resulted in a significant increase of the electric resistivity of copper film. (C) 2002 American Vacuum Society.