Chemical mechanical polishing of silicon wafers using developed uniformly dispersed colloidal silica in slurry

It is a challenge to enhance the material removal rate (MRR) during the chemical mechanical polishing (CMP) of silicon wafers, with increasing the size of a wafer and reducing the feature size of integrated circuit. In this study, potassium ions were employed to improve the MRR of silicon wafers effectively in CMP, which was performed by developed slurry, consisting of monodisperse alkaline colloidal silica, organic/inorganic acids and inorganic salts. Experimental results show that the developed slurry has a good stability and dispersity for colloidal silica. The MRR of silicon wafers in CMP was increased by 53.42 % to 1778.71 angstrom/min, when the concentration of potassium ions was 125 mmol/L. In addition, the surface roughness Sa was also improved slightly to 0.887 nm. The CMP mechanism was investigated using X-ray photoelectron spectroscopy, friction coefficient meter and electrochemical analysis. It reveals that potassium ions could change the electrical characteristics of the formed soft layer on the silicon wafer surface, dissolving the soft layer and oxidizing the surface of silicon.

Automated summary

In this study, potassium ions were used to effectively improve the material removal rate (MRR) of silicon wafers during chemical mechanical polishing (CMP). Experimental results showed that the MRR increased by 53.42% to 1778.71 angstrom/min when the concentration of potassium ions was 125 mmol/L. The surface roughness Sa was slightly improved to 0.887 nm. X-ray photoelectron spectroscopy, friction coefficient meter, and electrochemical analysis were used to investigate the CMP mechanism, revealing that potassium ions could alter the electrical characteristics of the formed soft layer on the silicon wafer surface, leading to the dissolution of the soft layer and oxidation of the silicon surface.