Control of the Micro-Defects on the Surface of Silicon Wafer in Chemical Mechanical Polishing

The final polishing of silicon results in the irresistible formation of micro-defects (i.e., particle residues and scratches) on the surface. In view of this problem, the synergistic effect of surfactants and water-soluble polymers in inhibiting the micro-defects on the silicon surface was studied in this paper to improve the wettability of the slurry and reduce the micro-flocculation of abrasive particles. The results showed that the total number of residual particles (>= 0.06 mu m) on the polished surface was reduced from 24,784 to 277 with the adsorption of cationic polyacrylamide (CPAM) and fatty alcohol polyoxyethylene ether (AEO-9). The water-soluble polyvinylpyrrolidone (PVP) polymer could coat on the SiO2 abrasives, inhibit the flocculation of abrasive particles, avoid scratches on the silicon surface and further reduce the number of residual particles (>= 0.06 mu m) to 67 on the polished surface. Furthermore, a contact angle analyzer was used to characterize the wettability of the components in the slurry, and a large particle counter was used to analyze the changes in the number of large particles in the slurry component. Finally, a mechanism of surfactants and a water-soluble polymer combined system was proposed to suppress the micro-defects on the surface of the silicon wafer.