A universal process development methodology for complete removal of residues from 300mm wafer edge bevel

摘要

Many yield limiting, etch blocking defects are attributed to "flake" type contamination from the lithography process. The wafer edge bevel is a prime location for generation of this type of defect. Wafer bevel quality is not readily observed with top down or even most off axis inspection equipment. Not all chemistries are removed with one "universal" cleaning process. IC manufacturers must maximize usable silicon area as well. These requirements have made traditional chemical treatments to clean the wafer edge inadequate for many chemistry types used in 193nm processing. IBM has evaluated a method to create a robust wafer bevel and backside cleaning process. An August Technology AXiTM Series advanced macro inspection tool with E20TM edge inspection module has been used to check wafer bevel cleanliness. Process impact on the removal of post apply residues has been investigated. The new process used backside solvent rinse nozzles only and cleaned the wafer bevel completely. The use of the topside edge solvent clean nozzles was eliminated. Thickness, wet film defect measurements (wet FM), and pattern wafer defect monitors showed no difference between the new backside rinse edge bead removal process and the process of record. Solvent topside edge bead removal of both bottom anti-reflective coatings and resist materials showed better cut width control and uniformity. We conclude that the topside solvent edge bead removal nozzle can be removed from the process. Backside solvent rinse nozzles can clean the backside of the wafer, the wafer bevel, and can wrap to the front edge of the wafer to provide a uniform edge bead removal cut width that is not sensitive to coater module tolerances. Recommendations are made for changes to the typical preventive maintenance procedures.