Chemical stability of Ta diffusion barrier between Cu and Si

The reactions in the Si/Ta/Cu metallization system produced by the sputteri ng process were investigated by means of sheet resistance measurements, X-r ay diffraction (XRD), Rutherford backscattering spectroscopy (RBS), scannin g electron microscopy (SEM) and optical microscopy. In particular, the reac tion sequence was emphasized. The reaction mechanisms and their relation to the microstructure and defect density of the thin films are discussed on t he basis of the experimental results and the assessed ternary Si-Ta-Cu phas e diagram at 700 degreesC. It was found out that the effectiveness of the T a barrier is mainly governed by the defect density and their distribution i n the Ta film. The failure was induced by the Cu diffusion through the Ta f ilm and almost simultaneous formation of Cu3Si and TaSi2. (C) 2000 Elsevier Science S.A. All rights reserved.