WCVD Seam Hole Improvement to Prevent BEOL Copper Diffusion

With the feature size shrinking in IC manufacturing, copper is to be used in BEOL metallization to decrease RC delay and improve electro-migration for 0.13um technology node and below. Moreover, tungsten still remains as the material of choice for the contact. As reported in most papers, copper is easily to diffuse through the seam of tungsten plug. Many researches focus on the dielectrics or Ta/TaN barrier layer enhancement to prevent Cu diffusion. In our study, another copper diffusion mechanism, which tunnels through the contact Tungsten seam hole and induces product device failure, is proposed. WCVD process optimization for seam hole improvement is also studied to prevent copper diffusion.