Integration of Cu-CMP process with combination of abrasive-free copper polishing and low selective barrier polishing for 90nm Cu/low-k interconnect

Process integration study of a copper CMP process combining a high selective abrasive-free slurry copper polishing followed by a low selective abrasive slurry barrier metal polishing for 90nm Cu/low-k interconnect metallization is reported. We demonstrated well-controlled dishing and erosion, tight control of dielectric loss and copper thinning with this process. Desired electrical results such as low comb leakage, good meander continuity and low VDP (Van Der Pauw) sheet resistance were also realized. V-ramp tests further confirmed the robustness of this integration scheme. The CMP process characterization and challenges of incorporating this combined copper CMP process into the 90nm BEOL integration are also discussed.