AES depth profile studies of interdiffusion in the AgCu bilayer and multilayer thin films

Interdiffusion in AgCu bilayer and multilayer thin film structures are studied by using Auger depth profiles for anneal temperatures ranging from 150 to 300 °C. The AgCu couple is chosen because it represents a system in which only grain boundary diffusion as opposed to lattice diffusion should occur in the temperature range studied. Bilayers and multilayers are vacuum evaporated onto cleaned quartz and copper substrates. The influence of the substrate surface roughness on the depth resolution is studied. Interdiffusion for AgCu bilayers is detectable at 150 to 300 °C, but differences are found in the extent of the diffusion at different temperatures. Electron beam-enhanced diffusion in bilayers on SiO2, similar to those induced by thermal treatment at much higher temperatures, is found. Analysis of interdiffusion in multilayer AgCu structures allowed to obtain the grain boundary interdiffusion coefficient at 175°C. For higher temperatures saturation of grain boundaries with Ag and Cu is found, for lower temperatures the effect of diffusion is comparable with the experimental error.