Defectivity Study during Oxide CMP with Composite Polymer Core - Silica Shell Abrasives: the Effect of the Silica Particle Shape.

摘要

The effect of particle shape on the chemical mechanical planarization (CMP) process is the focus of this paper. Fumed silica particles are compared with colloidal silica abrasives in terms of material removal rate (MRR) and defectivity after oxide CMP. In particular, the effect of a polymer core on the behavior of a composite abrasive, whose shell consisting of fumed versus colloidal silica particles, is also explored. The interaction between the particle and the wafer surface for different contact geometry has a different influence on the removal mechanism, on the shape of the scratches formed and on the possibility that the particle remains on the wafer surface after CMP. We use oxide CMP as a convenient test vehicle for defectivity characterization and comparison between different abrasives. Due to the higher complexity of the composite abrasive with respect to the simple silica particle-wafer system, we combine different surface analysis techniques with methods of defect quantification and enhancement. Overall fewer and shallower scratches are detected for the composites with colloidal silica shell with respect to colloidal silica. Higher defectivity is observed for the composites with fumed silica shell compared with simple fumed silica. Nevertheless, in the same pH conditions, fumed silica and fumed silica-coated abrasives lead to a comparable scratch depth.