Investigation of slurry composition and triboelectrochemical effects on copper electrochemical–mechanical polishing

Copper electrochemical mechanical polishing (ECMP) is a critical planarization technique for advanced integrated circuit manufacturing, particularly as feature sizes shrink below 65 nm and low‑k dielectrics—vulnerable to mechanical damage—are increasingly adopted. To address the limitations of conventional chemical mechanical polishing, this study aims to develop high-performance ECMP slurries by optimizing hydroxyethylidene diphosphonic acid (HEDP)-based electrolytes with enhanced corrosion inhibition and surface quality. We systematically investigate the corrosion inhibition performance of 5-Methyl-1H-benzotriazole (TTA), both alone and in synergy with chloride ions, under acidic (pH 6) and alkaline (pH 8) conditions. Electrolyte formulations were evaluated based on material removal rate (MRR ≥ 600 nm/min), planarization efficiency (PE ≥ 0.7), and post-polish surface integrity, using electrochemical analysis, scanning electron microscopy (SEM), and profilometry. Triboelectrochemical behavior was further analyzed through the correlation between frictional power and electrochemical impedance. The results show that while TTA combined with Cl⁻ significantly improves PE and widens the usable potential window in acidic media, alkaline electrolytes deliver superior surface quality. Specifically, an optimized alkaline slurry containing 6 wt.% HEDP, 0.3 wt.% TTA, and 3 wt.% triammonium citrate (TAC) achieves a stable PE ≥ 0.7 over a broad potential range and yields a surface roughness of only 9.0 nm—outperforming acidic counterparts. Moreover, the inverse relationship between frictional power and impedance reveals the dynamic competition between anodic oxidation and mechanical removal during ECMP. This work demonstrates that alkaline ECMP with TTA and TAC provides an effective strategy for achieving high planarization efficiency and excellent surface integrity, offering practical guidance for next-generation copper interconnect fabrication.