Metal-voiding phenomenon in aluminum and its alloys

It is shown that metal void generation is not a single-dimensional problem. The extent of voiding was found to be related to metal deposition conditions, the presence and extent of solutes (Si, Cu), the etch process, the postetch cleaning process, the passivation material and postpassivation temperature cycling. A simple, rapid (5-min), nondestructive technique, thermal wave imaging (TW1) is presented. It allows for the accurate determination of the extent of cracking in metal lines that are underneath passivation films. This technique is compared with backscatter electron (BSE) imaging, which is also capable of looking at cracks through passivation films. Thermal wave data on the impact of accelerated aging of devices (at 400°C) on metal voiding are presented