Investigation of microstructure and properties of ultrathin graded ZrN _x self-assembled diffusion barrier in deep nano-vias prepared by plasma ion immersion implantation

Ultrathin graded ZrN _x self-assembled diffusion barriers with controllable stoichiometry was prepared in Cu/p-SiOC:H interfaces by plasma immersion ion implantation (PIII) with dynamic regulation of implantation fluence. The fundamental relationship between the implantation fluence of N ⁺ and the stoichiometry and thereby the electrical properties of the ZrN _x barrier was established. The optimized fluence of a graded ZrN thin film with gradually decreased Zr valence was obtained with the best electrical performance as well. The Cu/p-SiOC:H integration is thermally stable up to 500 °C due to the synergistic effect of Cu ₃ Ge and ZrN _x layers. Accordingly, the PIII process was verified in a 100-nm-thick Cu dual-damascene interconnect, in which the ZrN _x diffusion barrier of 1 nm thick was successfully self-assembled on the sidewall without barrier layer on the via bottom. In this case, the via resistance was reduced by approximately 50% in comparison with Ta/TaN barrier. Considering the results in this study, ultrathin ZrN _x conformal diffusion barrier can be adopted in the sub–14 nm technology node.