Alkyl-terminated PEG suppressors for copper electroplating and their hydrophilic and hydrophobic properties

Abstract

This study explores the structure-activity relationship of copper electroplating suppressors, with a focus on alkyl-terminated polyethylene glycols (PEGs), to better understand their efficacy in electronic interconnect fabrication. Electrochemical analysis demonstrated that an increase in the molecular weight of PEG suppressors significantly raises the electrochemical polarization overpotential during copper electrodeposition. Additionally, alkyl terminal capping was observed to amplify this polarization effect, with the extent of overpotential increase directly correlating with the alkyl chain length. However, the advantageous impact of molecular weight on overpotential diminishes at higher molecular weights. In contrast to the electrochemical results, through-hole electroplating experiments revealed that a suppressor with a molecular weight of 1 k and butyl termination exhibits superior through-hole throwing power. Further analysis indicated that a greater proportion of alkyl functional groups within the suppressor's molecular chain enhances uniform electroplating capabilities. The study also suggests that measuring contact angles, as an expression of hydrophobicity, could provide a more efficient and precise method for evaluating suppressor performance.