Insight into leveler Basic Blue 7 towards copper superfilling within microvias

Achieving metal interconnect for printed circuit boards (PCBs) is pivotal for electronics industry. Through electrochemical analysis for Basic Blue 7 (BB7), excellent suppressing effect was analyzed. Chronopotentiometry was used to study the possible concentration range for microvias filling and 50-150 mg·L-1 was selected to achieve superfilling electrodeposition. Difunctional mechanism of coordination and adsorption of BB7 during electrodeposition is proposed by density functional theory (DFT) calculation and in situ Raman spectroscopy analysis. The interaction among BB7, copper substrate and Cu2+ leads to the suppression for copper growth. Superfilling electroplating process is optimized and high filling performance can be achieved at 100 mg·L-1 with filling percentage (FP) values of 80.19%, 84.70% and 87.90% for microvias with diameters of 100 μm, 125 μm and 150 μm, respectively. Besides, Differential Diffusion Filling Mechanism was proposed to illustrate the blind microvias filling process of newly proposed electroplating system based on interaction analysis among additives and diffusion kinetics. What’s more, the performance of copper interconnect layer, including surface morphology, phase structure and signal transmittance, was evaluated.