Scanning Auger microprobe study of gold–nickel–copper diffusion in thin films

The gold–nickel–copper system, with nickel the intended diffusion barrier, has been used extensively in the electronics industry for wire spring connectors, thin films on ceramic, and connectors on printed circuit boards. Although no visible contamination can be seen on the surface of the gold, poor bonding or high contact resistance frequently occurs. It has been assumed that some grain boundary diffusion of nickel has been occurring through the 2 μm gold film. A scanning Auger microanalysis was conducted on the surface and in depth on the thin film structure before and after heating at 300 °C for 4 h. Two‐dimensional Auger analysis, after heating, showed the nickel to be distributed along the grain boundaries on the surface of the gold film. Subsequent Auger depth profiling showed the nickel layer to be oxidized and approximately 50 A in depth. This characterization has led to improved understanding of the bonding problems and variation of contact resistance with this metallization system.