DPP Leveler with Side Chain Modifications: Mechanistic Insights on Charge Sites for Improved Microvia Filling in Copper Electrodeposition

Abstract 2,5‐Bis(6‐(trimethylammonium)hexyl)‐3,6‐diaryl‐1,4‐diketopyrrolo[3,4‐c]pyrrole (DPP) pigments have demonstrated significant potential as levelers in copper electrodeposition. In this study, we synthesized novel diketopyrrolopyrrole‐based quaternary ammonium salts 1a, 1b, 1c, and 1d, each featuring distinct substituents, and assessed their inhibitory properties through electrochemical measurements. Among these, compound 1d exhibited the best inhibitory performance in fundamental electrochemical tests. Additionally, advanced quantum chemical calculations and molecular dynamics simulations were employed to elucidate the reasons behind the superior inhibition performance of compound 1d from molecular and adsorption energy perspectives. Consequently, compound 1d was selected for detailed investigation of its leveling effects in PCB microvia filling. Notably, 1d achieved a filling rate of 97.1% in PCB microvia experiments, highlighting its efficacy as a leveler. Furthermore, elemental analysis confirmed the chemical adsorption of compound 1d on the copper surface. Based on these experimental results, a plausible mechanism explaining the excellent leveling performance of compound 1d is proposed. These findings suggest that 1d is a promising candidate for microvia filling applications and provide valuable insights for the development and synthesis of new levelers. Future research will focus on optimizing the performance of 1d and exploring other novel levelers to further advance the field.