Achieving an Ultra-Smooth Copper Surface with the Synergistic Effect of 1,2,4-triazole and Sodium Polyphosphate in Chemical Mechanical Polishing

Corrosion inhibitors are crucial for achieving excellent copper surface quality in chemical mechanical polishing (CMP). However, research on composite corrosion inhibitors containing the azole ring and phosphate group remains insufficient. This study chose 1,2,4-triazole (TAZ) and sodium polyphosphate (NaPP) to investigate their effects on copper CMP. The results show that adding NaPP to TAZ induces a first decreasing and then increasing trend in the surface roughness S a of copper. An ultra-smooth copper surface with S a of 0.23 nm (scanning area: 10 μm × 10 μm) is achieved by adding only 0.004 wt% NaPP to 30 mmol l −1 TAZ. Moreover, TAZ and NaPP composite corrosion inhibitors decrease S a by 74.7%, far below the additive effect of TAZ and NaPP acting independently, indicating a synergistic effect. For the synergistic corrosion inhibition mechanism, NaPP likely adsorbs first onto the copper surface, followed by TAZ. They co-adsorb probably in a complementary way to form a protective and relatively uniform passivation film, greatly protecting the copper surface from excessive corrosion and resultant corrosive wear, particularly in the valley areas. Under mechanical abrasion from evenly distributed silica abrasives, copper surface quality improves. This work offers an effective CMP process for achieving outstanding surface quality of copper.