Effect of various slurry injection system configurations on removal rates of silicon dioxide using a ceria-based chemical mechanical planarization slurry

In this work, the position of the novel slurry injection system (SIS) was optimized to achieve a more cost-effective and environmentally benign chemical mechanical planarization process using a widely-adopted ceria-based "reverse slurry". SIS was configured with different angles in order to investigate slurry dilution characteristics caused by residual pad rinsing with ultrapure water (UPW) that affected silicon dioxide removal rates. UPW dilution effect on removal rate, coefficient of friction and pad surface temperature was explained by maintaining a constant dilution ratio for each of the SIS configuration tests. Results indicated that the negative rotation angle of the SIS increased the actual slurry dilution ratio on top of the polishing pad. This generated more Ce³⁺ which boosted the removal rate. Application of negatively rotated SIS allowed significantly lower slurry flow rate and/or shorter polishing time leading to achieve a more environmental friendly semiconductor manufacturing process. Finally, it was confirmed that variations in SIS configuration had no impact on silicon dioxide to silicon nitride removal rate selectivity.