Ultrathin sputtered W-Si-N films (similar to10 nm) were prepared for copper metallization. While copper was sequentially deposited onto some samples without breaking the vacuum, some samples underwent annealing before copper deposition. The precopper deposition annealing (simplified as preannealing) was carried out by rapid thermal annealing (RTA) in high purity N-2 atmosphere. Sheet resistance measurement, Auger electron spectroscopy (AES) and X-ray diffraction (XRD) results all show that the preannealing procedure significantly increased the failure temperature for copper/diffusion barrier/Si structure by about 100degreesC compared with those without prearmealing. Bias leakage current versus time (I-t) measurement and bias temperature C-V measurement, which are very sensitive for mobile ions in the oxide, also show that the copper gate MOS structure with prearmealing fails at temperatures similar to100degreesC higher than those without prearmealing. By prearmealing, oxygen and nitrogen were stuffed into the grain boundaries of the nanocrystalline films, thus eliminating the rapid diffusion path for copper. (C) 2004 Elsevier B.V. All rights reserved.