Polyacrylic Acid as a Lubricant and a Complement to 1,2,4-Triazole for Copper Chemical Mechanical Polishing

Chemical mechanical polishing (CMP) has been used to achieve local and global planarization for fabricating copper interconnects. Corrosion inhibitors in slurries are critical to realizing planarization. This study used polyacrylic acid (PAA) as a lubricant and a complement to 1,2,4-triazole for copper CMP. It is revealed that in the presence of a primary corrosion inhibitor of 1,2,4-triazole, adding a relatively low content of PAA can lead to an ultra-smooth copper surface with 1 nm surface roughness S a , which is conducive to planarization. A relatively uniform surface film of approximately 1.9 nm is formed. The surface film mainly contains Cu–PAA, Cu-1,2,4-triazole, and copper oxides. Moreover, microscopic atomic force microscopy experiments in liquid were conducted to simulate CMP. After adding PAA, the interfacial friction between the probe and the copper surface significantly decreases to 27%, indicating that the adsorbed PAA can serve as an effective lubricant, presumably due to electrostatic repulsion. In addition, after adding PAA to the 1,2,4-triazole solution, the surface film becomes thicker and denser, suggesting that PAA can complement 1,2,4-triazole to construct a relatively compact passivating film. Therefore, the copper surface quality improves. The findings provide mechanistic insight into the unrecognized role of polymers in copper CMP. Graphical Abstract