Exploring W-Cu hybrid dual damascene metallization for future nodes

In this exploratory study, selective tungsten (W) deposition is used before the copper (Cu) metallization steps with the aim to solely fill the via with W. The W deposition is tested on the bottom metal cobalt (Co) or ruthenium (Ru) and shows an excellent selectivity towards the dielectric SiO2 and dense low-k material 3.0. The via resistance shows up to a 40% reduction for the W-Cu hybrid system compared to a Cu dual damascene (DD) filled via. The material compatibility is tested in a thermal storage study and shows no performance degradation of the bottom barrierless W vias. This feasibility study using a middle of line (MOL) metal shows that a W-Cu hybrid system can be an option for further extension of Cu interconnects while suppressing the via resistance.