The diffusion properties of Cu, Cu/titanium nitride (TiN) and Cu/TiN/Ti metallization on GaAs, including as-deposited film and others annealed at 350-550 degreesC, were investigated and compared. Data obtained from X-ray diffractometry, resistivity measurements, scanning electron microscopy, energy dispersive spectrometer and Auger electron spectroscopy indicated that in the as-deposited Cu/GaAs structure, copper diffused into GaAs substrate, and a diffusion barrier was required to block the fast diffusion. For the Cu/TiN/GaAs structure, the columnar grain structure of TiN films provided paths for diffusion at higher temperatures above 450 degreesC. The Cu/TiN/Ti films on GaAs substrate were very stable up to 550 degreesC without any interfacial interaction. These results show that a TiN/Ti composite film forms a good diffusion barrier for copper metallization with GaAs. (C) 2003 Elsevier B.V. All rights reserved.