TIW(N) AS DIFFUSION-BARRIERS BETWEEN CU AND SI

Abstract

TiW(N) and aw 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 Angstrom)/Si structure remains intact up to 750 degrees C 30 s rapid thermal anneal (RTA) in N-2 ambient; at 775 degrees C the Cu diffuses through the TiW layer to form Cu,Si with an overlayer of Ti-W-Si on the surface. The Cu/TiW(N)(600 Angstrom)/Si system is metallurgically stable up to 1000 degrees C 30 s RTA in N-2 ambient. The Cu/TiW(600 Angstrom)/p(+)n junction diodes were able to withstand the RTA annealing up to 675 degrees C without losing the device integrity; however, the devices' characteristics are completely destroy at temperatures above 775 degrees C inconsistent with the occurrence of dramatic metallurgical reaction. The Cu/TiW(N)(600 Angstrom)/p(+)n junction diodes were able to withstand the RTA treatment up to 650 degrees C without electrical characteristic degradation; and the devices' characteristics degrade gradually with the increase of RTA temperature.