Sputtered Ta-Si-N Diffusion Barriers in Cu Metallizations for Si

摘要

In silicon integrated circuit technology, aluminum is commonly used for contactsand interconnections. Since aluminum reacts easily with silicon and with contacting layers of transition metals or silicides, diffusion barriers are commonly employed in VLSI metallizations. As the dimensions of devices shrink, the problems associated with electromigration in aluminum-based interconnection lines have serious deleterious effects on device reliability. For this reason, metals other than aluminum, like copper and tungsten, are being evaluated for VLSI applications. Copper has a lower electrical resistivity and a higher resistance to electromigration than aluminum, but is very mobile in most metals, as well as in silicon, and causes a failure of contacts by diffusion through metallization layers into silicon. To counter this rapid diffusion of copper, amorphous alloys with high crystallization temperature are appealing candidates for diffusion barriers because they lack grain boundaries that can act as diffusion paths. Ta-Si-N alloy fulfills these conditions and, in addition, is chemically inert with Cu because it consists mainly of elements Ta and N, which do not react with Cu.