1995 Volume 59 Issue 11 Pages 1095-1102
Diffusion across the Al2O3 film in the Au/Al2O3/Al film system (the Al film with 1 μm thickness was vapor-deposited on a SiO2/Si substrate and exposed to the atmosphere to form a natural oxide layer, then the Au film was deposited on it.) at temperatures between 25° and 500° has been studied by using Auger Electron Spectroscopy, X-ray Photoelectron Spectroscopy and electrical resistivity measurement. The temperature where Al is detected on the surface of the Au/Al2O3/Al system is 100°C higher than that on the surface of the regular Au/Al system without the Al2O3 film. The activation energies for the intermetallic layer growth of the Au/Al2O3/Al system and the Au/Al system are 110 and 72 kJ/mol, respectively. The Al2O3 film formed by the exposure in air (ca. 3.2 nm in thickness) acts as a barrier for diffusion in Au/Al. In addition, we observed the SEM image of cross section of the Au/Al2O3/Al system. The Au-Al intermetallic layer is formed in the Al layer in the initial stage of Au/Al2O3/Al diffusion by Au diffusion through the Al2O3 film into the Al layer.
On the other hand, we studied the effect of annealing environment on the diffusion for the Au/Al2O3/Al system by using 18O as tracer for SIMS analysis. The Au-Al intermetallic layer grows in an island formation for the Au/Al2O3/Al system and when annealed in air, the number of islands decreases. Because, during heat treatment in air, the Al2O3 film is formed continuously by supply of O2 to the Al2O3 film through Au film.
