Development of Rapid Evaluation Method on Chemical Additives for Cu Superfilling in Sub-Micron Trenches
A rapid evaluation method on chemical additives for Cu filling performance in 120 nm is developed in this study. Two new levelers; 4-amino-2,1,3-benzothiadiazol and 6-aminobenzo-thiazole were employed to validate the usefulness of this method. A faster and a lower rotating speed were used to simulate the convection rates at the trench open and trench bottom, respectively. The potential difference between these two rotating speeds under galvanostatic measurements were used to predict the superfilling abilities. Levelers in various concentrations were explored. The prediction from the RDE analysis was consistent with the results of SEM observations. In addition, it was found that the chemical structure and concentration of leveler exerted considerable influences over the filling performances. To further explain the influence of leveler concentration to the filling behavior, galvanostatic measurements using wafer fragments as working electrode were conducted to investigate the responsible mechanism of leveler. The results of AFM analysis and X-ray diffraction did not reveal any notable influence of leveler concentration on the surface roughness and preferential phase.
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