3 % Ti-Tungsten Diffusion Barriers I. A Discussion of the Role of the A15 Structure

Sputter-deposited nitrogen-doped titanium-tungsten is useful as a barrier layer in an electroplated gold integrated circuit interconnect structure. However, one persistent problem with the use of this material is the episodic and inexplica-ble appearance of catastrophic barrier failure. Adding a small amount of nitrogen to the sputtering ambient reduces this problem to a negligible level. Various conjectures have been made as to the role of the nitrogen in the improvement of the barrier performance. In the present work, the role of a metastable crystalline form having an A15 structure is discussed. The use of sputter deposited titanium-tungsten, TiW, as a material for diffusion barriers in various metallization schemes has a venerable history. ~-4 Furthermore, ven bet-ter diffusion barriers are obtained by intentionally adding nitrogen to the sputtering ambient. 2'5-7 This produces mate-rial, TiW(N), which is generically described as "titanium-tungsten itride " or "nitrogen-doped titanium-tungsten" (the usage depends omewhat on the amount of nitrogen thought o be incorporated into the film)