Revealing the acceleration effect of SPS and Cl - on copper Surface: Instantaneous nucleation and Multi-Step energy change

• According to the theoretical and experimental analysis results, the Cl - can accelerate after complexation with SPS and become the “engine” of copper electroplating. • In this paper, charge density difference, charge transfer and dynamic analysis are used to describe the effect of the SCS and SCCS on the copper surface changes. The acceleration effect of Cl - and bis-(sodium sulfopropyl)-disulfide (SPS) in electroplating solution was analyzed by various electrochemical methods and dynamic simulation with DFT. The cathodic polarization, solution resistance, and nuclear transfer coefficient of the two electroplating systems were analyzed by electrochemical methods; OLYMPUS confocal laser microscope was used to explore the throwing power (TP) and average thickness of the coating (ATCH) in PCB. The multi-step energy change of two systems are used to analyze the reduction process of Cu 2+/1+ based on the first principles. The TP and ACTH of SCS (SPS-Cu 2+/1+ ) and SCCS (SPS-Cu 2+/1+ -Cl - ) are 85%, 95%, 56.57 μm and 65.77 μm, respectively. Scanning electron microscope analysis shows that the nucleation rate of the SCCS system is higher than that of the SCS system in 0.2 s. In the dynamic analysis of the system, the reduction of Cu 2+/1+ in the SCCS system only needs three steps, while that in the SCS system needs five steps. The experimental and theoretical results show that the reduction rate of Cu 2+/1+ in the bath containing Cl - is faster than that in the bath without Cl - .