Silicon take-up by aluminum conductors layered with refractory metals

The mechanism of Si take-up by aluminum conductor films layered with one of four refractory metals (Ti, Ta, Mo, or W) was studied. It was found that silicidation of refractory metal layers proceeded with the existence of Al, and this reaction was the cause of Si take-up, especially in the cases of Ta and Ti. The effect of a W barrier was examined in an attempt to reduce this take-up reaction. A W layer as thick as 400 nm is needed to prevent junction degradation in a device.