Decoding the suppressing effects of Pluronic triblock copolymers on copper electrodeposition

Triblock Pluronics of polyoxyethylene (PEO) and polyoxypropylene (PPO) are identified as competent suppressors for copper (Cu) electroplating in advanced electronics manufacturing. However, the specific interfacial roles of PEO and PPO blocks in Pluronic suppressors, are not yet fully understood, which is crucial for the rational design of effective suppressors. Herein, the influences of composition and block arrangement of such Pluronics on the inhibition against Cu plating are systematically investigated. The decrease in Cu deposition mass with increasing PPO content suggests that the PPO blocks are the main contributor to the inhibition strength of Pluronics, as demonstrated by the positive correlation between electrodeposited Cu mass and hydrophilic-lipophilic balance (HLB) value. Comparative analysis of normal and reverse Pluronic pairs with similar compositions indicates that an adequately long PEO block is indispensable to maintain the inhibition stability of Pluronics. Moreover, electrochemical attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) offers direct evidence that the PEO block, rather than the PPO block, compactly adsorbs on the chloridion (Cl^-) adlayer covered Cu surface. This work highlights the importance of balancing the PPO-dominated inhibition strength and the PEO-dominated inhibition stability in the design of practical copolymer suppressors, for which the HLB may serve a valuable indicator, together with the PEO block length.