TiW ( N ) as Diffusion Barriers Between Cu and Si

TiW(N) and TiW are employed as diffusion barriers in the Cu/barrier/Si system. The thermal stability of Cu/TiW(N) and Cu/TiW contacted p + n junction diodes was investigated with respect to metallurgical reaction and electrical characteristics. The as-deposited TiW film formed body-centered cubic (bcc) structure, while the TiW(N) film formed face-centered cubic (fcc) structure. The Cu/TiW(600 A)/Si structure remains intact up to 750°C 30 s rapid thermal anneal (RTA) in N 2 ambient ; at 775°C, the Cu diffuses through the TiW layer to form Cu 3 Si with an overlayer of Ti-W-Si on the surface. The Cu/TiW(N)(600 A)/Si system is metallurgically stable up to 1000°C 30 s RTA in N 2 ambient. The Cu/TiW(600 A)/p + n junction diodes were able to withstand the RTA annealing up to 675°C without losing the device integrity ; however, the devices' characteristics are completely destroyed at temperatures above 775°C inconsistent with the occurrence of dramatic metallurgical reaction. The Cu/TiW(N)(600 A)/p + n junction diodes were able to withstand the RTA treatment up to 650°C without electrical characteristic degradation ; and the devices' characteristics degrade gradually with the increase of RTA temperature.