Experimental and computational investigation of complexing agents on copper dissolution for chemical mechanical polishing process

Complexing agents are important additives in chemical mechanical polishing (CMP) slurries, and they play key roles in the removal rate (RR) and surface quality of copper (Cu). However, it is a great challenge to clarify the complexing mechanism of Cu at the microscopic level. In this study, the effects of glycine (GLY), potassium tartrate (PT), and potassium citrate (CAK) on the RR and dissolution behavior of Cu are investigated. The results show that the complexing capability is in the order of GLY > PT > CAK. The complexing mechanism is elucidated by single-frequency electrochemical impedance spectroscopy, X-ray photoelectron spectroscopy, ultraviolet -visible spectrometer, density functional theory, and molecular dynamics simulation. Copper hydroxide (Cu (OH)2) on the Cu surface ionizes, giving rise to Cu2+ ions, which are attracted by negatively charged oxygen atoms of carboxylate groups in complexing agents, resulting in the formation of water-soluble complexes. This process destroys the integrity of the oxide layer on the Cu surface. Therefore, the oxide layer can be easily removed by a polishing pad. These findings provide significant theoretical guidance for the development of Cu CMP slurries in the microelectronics industry.