(Dielectric Science and Technology Division Poster Award, 1st Place) The Influence of Pad Micro-Features on Chemical Mechanical Polishing (CMP) Performance: Insights from Computational Fluid Dynamics (CFD)

With semiconductor chip dimensions shrinking below 7 nanometers, Chemical Mechanical Planarization (CMP) becomes more critical 1, 2. To meet the increasing demand for precision and uniformity in the fabrication of wafers and chips, enhancements in CMP consumables and operating conditions are necessary. To address these requirements, novel pad designs have been developed, particularly those that do not require conditioning 3. It is known that the CMP polishing rate depends on pressure, pad wafer relative velocity, and the distribution of pad asperities 4. As conventional pads provide small and random contact areas, the external pressure applied by the head determines the material removal rate (MRR) 5 Advanced pads with micro-features provide more contact areas and help deliver consistent pressure and slurry distribution during Chemical Mechanical Polishing (CMP) 6, 7. This study uses computational fluid dynamics (CFD) to simulate the flow between pad and wafer surfaces to determine how pad surface micro-features affect the CMP process. The abrasive residence time, total fluid pressure, and slurry flow velocity are evaluated for four distinct pad micro-feature geometries: square, square-circle, circle, and ellipse. Increasing the number of edges in the pad micro-feature patterns increases pressure drop, leading to more interaction between pad and slurry and enhancement of MRR. The findings of this study confirm the effectiveness of micro-featured pads in optimizing CMP processes and provide valuable insights into the influence of microfeature geometries on critical parameters for improving the semiconductor fabrication process. 1 J. Seo, Journal of Materials Research , 36 , 235–257, Jan, 2021. 2 B. Suryadevara, Advances in Chemical Mechanical Planarization (CMP) . Woodhead Publishing, 2021. 3 S. Lee and E. Hwang, “Smart pad fabrication for CMP,” LMA Res Rep , vol. 10, pp. 100–104, 2002. 4 G. Ahmadi and X. Xia, J Electrochem Soc , 148 , G99, 2001. 5 X. Xia and G. Ahmadi, Particulate Science and Technology , 20 , 187–196, 2002. 6 S. Lee, G. Kim, M. Mcgahay, H. Kim, and H. Cho, “Pad Designs-To navigate the fundamentals of CMP.” 7 M. Mcgahay, G. Kim, S. Lee, H. Cho, and H. Kim, “Critical Feature Size of Polishing Pad and Its Performance.”