Solid-Phase Reactions of Diffusion Barriers of Ti and TiN to Copper Layers on SiO₂

Thin films of Ti and TiN interposed between the Cu layer and SiO 2 are examined as a diffusion barrier as well as an adhesion-promoting layer for Cu metallization technology. Solid-phase reactions and/or interdiffusion taking place in the Cu/Ti/ SiO 2 /Si and Cu/TiN/ SiO 2 /Si systems are examined by X-ray diffraction and the depth profiling method using Auger electron spectroscopy and X-ray photoelectron spectroscopy. The reduction of SiO 2 through the formation of Ti-oxides occurs at the Ti/ SiO 2 interface even in the as-deposited Cu/Ti/ SiO 2 /Si system. In addition to this, the formation of Ti 5 Si 3 and interdiffusion which result in the formation of Cu–Ti intermetallic compounds due to annealing at 450° C are evident, and lead to intermixing of the whole system. The use of TiN instead of Ti drastically suppresses the reaction and interdiffusion, and the Cu/TiN/ SiO 2 /Si system is stable even after annealing at 850° C, though the incorporation of a small amount of Ti into the Cu layer is observed.