A Particle Reduction Strategy for Plasma Etching Processes

Random defects caused by “fallen” particles in plasma etch processes have had a chronically detrimental impact on chip product yield. In this study, we conducted a vertical structure analysis of a particle defect and a process partition test methodology to accurately identify the various factors and the points of occurrence of the defects in the complex plasma etch processes. The root cause of particle contamination was identified as being related to the loss of electrostatic force during each processing sub-stage. Based on these findings, a comprehensive particle reduction strategy was devised, customized to each specific case. By exploiting the phenomenon of particle entrapment around the plasma sheath boundary, it was possible to effectively control particle contamination prior to the commencement of the main etch, during the substage etch transition phases, and after the final over-etch step. In addition, the implementation of an O2-based post-plasma treatment (PET) technique was also found to alleviate the byproduct-induced defect that reacted with moisture present in the cleanroom air.