Effect of the Surface Roughness of Chamfer on Edge-bead Effects in Spin-Coating Film Formation

Spin-coating is widely utilized in photolithography for thin-film deposition, but it often generates edge-bead effects that compromise film uniformity and quality. This study investigates the influence of chamfer surface roughness on these edge-bead effects to enhance coating performance. A combination of experimental and simulation approaches was employed to examine the relationship between surface roughness at the substrate's chamfer edge and film formation during spin-coating. The Volume-of-Fluid (VOF) method was used to simulate fluid dynamics, providing insights into how varying levels of surface roughness affect film stability near the substrate edge. The results demonstrate that smoother chamfer surfaces significantly reduce edge-bead effects, resulting in more uniform film thickness and improved coating quality. This reduction is attributed to decreased wettability, as smoother surfaces disrupt the formation of liquid irregularities near the edge. Additionally, experiments reveal that applying hydrophobic treatments to the chamfer surface further mitigates edge-bead effects by amplifying the reduction in wettability. The combination of smooth chamfering and hydrophobic surface treatments minimizes film disruptions, enabling a more uniform coating. These findings underscore the importance of chamfer surface roughness and wettability in controlling edge-bead effects during spin-coating, providing valuable insights for optimizing film deposition processes in photolithography.