| Popis: |
The colloidal silica is usually used as the abrasive for the copper CMP polishing slurry in integrated circuit multilayer copper wiring. The aggregation of colloidal silica in the slurries tend to aggregate spontaneously, resulting in the continuous changes of the polishing effect, such as scratch defects, removal rate, etc. This situation can lead to the potential instability of the polishing slurry, which should be avoided in industrial production. In this paper, the aggregation and dispersion properties of polishing slurries were systematically studied, and an improved scheme was proposed to improve the dispersion of slurries to prevent agglomeration. These affecting factors including slurries’ pH, electrolyte additive (KNO3) and polyelectrolyte (PAA-Na) were assessed with LPC, Zeta potential and particle size. A better pH range for slurries was determined from the point of view of isoelectric point and dissolution of colloidal silica. And the dissolution of colloidal silica was verified by UV-vis experiment. Anionic surfactant (SDS), Cationic surfactant (DTAC) and Nonionic surfactant (AEO-15) was analyzed for their dispersion in slurries from the point of view of static electricity force and steric hindrance space force, and the synergistic mechanism of mixed SDS and AEO-15 on slurries dispersion was put forward. In addition, the effect of the improvement of slurry dispersion on reducing scratching defects on the surface of polished copper blanket was also tested in this paper. |
