Improvement of Ta-based thin film barriers on copper by ion implantation of nitrogen and oxygen

Magnetron sputtered polycrystalline Ta and Ta(Si) barriers for copper metallization schemes were modified by nitrogen or oxygen high dose ion implantation to improve their thermo-mechanical stability. The ion bombardment changes the initially polycrystalline microstructure to amorphous-like. In contrast to pure Ta, Ta(Si) layers are already X-ray amorphous after deposition. Here the implantation enhances the recrystallization temperature by about 100 K. In order to demonstrate the improvement in the barrier properties of the implanted Ta films the intermixing of Ta and Cu at the interface of corresponding layer structures was measured by AES depth profiling as a function of the annealing temperature. The thermal stability of Ta and Ta(Si) barriers increases from 6000C/ 1h for the non-implanted layers up to 750° C/1h after implantation of nitrogen or oxygen.