Interaction mechanism of Al 2 O 3 abrasive in tantalum chemical mechanical polishing.

Al 2 O 3 abrasive is expected to enhance chemical mechanical polishing (CMP) efficiency compared to the SiO 2 abrasive. However, Al 2 O 3 powder has dispersion issues and the material removal mechanism by Al 2 O 3 remains unclear. This study investigated the role of Al 2 O 3 abrasive in the tantalum CMP. It is revealed that (NaPO 3 ) 6 can effectively disperse Al 2 O 3 powder in water. PO 3 - improves the stability while Na + deteriorates it. The total Na + concentration should be lower than the turning point to attain high stability. With stable Al 2 O 3 -containing slurries, a relatively high material removal rate of tantalum can be obtained at an alkaline pH. The characterization results indicate that the Ta element can be adsorbed on Al 2 O 3 probably due to the chemical interaction between Al 2 O 3 and the tantalum surface. Moreover, the Al 2 O 3 microsphere tip starts to remove tantalum at 0.48 GPa, which is much lower than the yield strength of the tantalum surface film. For the mechanism, tantalum can be oxidized by H 2 O 2 at alkaline pH. When Al 2 O 3 presses and slides on the tantalum surface, tribochemical reactions occur, forming a chemical bond of Al-O-Ta at the interface. As Al 2 O 3 moves, the bond is stretched and tantalum is detached. The findings provide mechanistic insight into Al 2 O 3 abrasive in CMP.