Three-Dimensional Metrology for CMP process evaluation with In-line Wide-Area Atomic Force Microscope

We have developed a new in-line CMP (Chemical Mechanical Polishing) metrology tool which enables us to measure surface-topography from local dishing-erosion to global planarity with AFM (Atomic Force Microscope). To achieve a balance between the high-through- put operation and the high-accuracy measurement, and to get a large amount of statistically viable data efficiently, we have employed a new scanning-stage system with three mechanical guides built into an in-line AFM system designed for 300 mm wafer. With this set up we verified a through-put of 30 wafer / Hr with 5-site profile measurements with a measurement stability of 0.1 nm. The work was carried out in a clean room environment where the guide conditions could be changed automatically as needed. We then measured CMP and CMP-related samples. For the local area measurement we employed CNT (Carbon Nano Tube) probe to measure the dishing of Cu / Low-k patterns, the high aspect-ratios, and the narrow trench structures of STI. We also showed the possibility of perpendicular sidewall roughness measurement of Cu-seed sample by obtaining 3D images of the wall. Moreover, we measured the global flatness from 20 mm x 20 mm to 40 mm x 40 mm area to meet the larger chip size requirement. Finally, we discussed the effectiveness of the process evaluation and of the feedback to device design with the high-throughput and high-accuracy AFM system.