Pentaerythritol-Based Compound as a Novel Leveler for Super-Conformal Copper Electroplating

Leveler is one of the most important organic additives in copper electroplating for microvia filling. To enhance the microvia filling efficiency and reduce the bath control difficulty, novel levelers with high filling performance and wide application concentration range has long been pursued. Herein, a novel leveler named L1 with four pyrrolidine rings linked by a pentaerythritol backbone is designed and synthesized. Compared with the previously reported leveler TPM-1, L1 shares the same nitrogen-containing group but has an additional pyrrolidine ring. The structure-property relationship of L1 is thoroughly characterized by electrochemical measurements, theoretical calculations, and electroplating experiments. Results show that with one more positively charged ammonium groups, L1 exhibits stronger interactions with Cl − and the accelerator SPS compared to TPM-1. However, due to the variation of the connecting group, its interaction with the suppressor PEG is much weaker. With L1 as the leveler, both good microvia filling performance and high-quality copper deposition was obtained within a wide concentration range. The findings indicate that L1 is a very promising leveler for microvia filling copper electroplating, and both nitrogen-containing groups and linking groups in a leveler significantly influence its properties and performances.