Structural and chemical stability of Ta-Si-N thin film between Si and Cu

Abstract

Thermal stability and barrier performance of reactively sputter deposited Ta-Si-N thin films between Si and Cu were investigated. RF powers of Ta and Si targets were fixed and various N-2/Ar flow ratios were adopted to change the amount of nitrogen in Ta-Si-N thin films. The structure of the films are amorphous and the resistivity increases with nitrogen content. After annealing of Si/Ta-Si-N(300 Angstrom)/Cu(1000 Angstrom) structures in Ar-H, (10%) ambient, sheet resistance measurement, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and Auger electron spectroscopy (AES) were employed to characterize barrier performance. Cu3Si and tantalum silicide phase are formed at the same temperature, and the interdiffusion of Si and Cu occurs through the local defect sites. In all characterization techniques, nitrogen in the film appears to play an important role in thermal stability and resistance against Cu diffusion. A 300 Angstrom thick Ta43Si4N53 barrier shows the excellent barrier property to suppress the formation of Cu3Si phase up to 800 degrees C. (C) 1998 Elsevier Science S.A. All rights reserved.