Dishing-radius model of copper CMP dishing effects

Copper chemical-mechanical polishing (CMP) dishing concerns semiconductor manufacturing yield in contemporary back-end-of-the-line process. In this work, we first propose and validate a dishing model through first-principle analysis and carefully designed experimentation. This model utilizes the novel concept of dishing radius, a metric that assumes cylindrically shaped post-CMP copper surface and directly captures the extent of metal dishing for a CMP process. Additionally, a dishing-model-based method for extracting the parameterized two-dimensional post-CMP metal profile is developed for damascene structures. The case study utilizing this method shows that the extracted parameters are in good agreement with those from cross-sectional scanning electron microscopy and surface profilers, which confirmed that dishing radius is linewidth-independent for typical metal lines. This method is particularly useful in determining dishing artifacts, which are modeled using the dishing radius concept. The approach is nondestructive, precise, and efficient.