Flow Field Simulation Assisted Investigation of Aspect Ratio on Transformation Mechanism of Micro Through Holes Cu Electroplating Performance

In this paper, flow field simulation, electrochemical measurements, and electroplating experiments were combined to investigate the effect of aspect ratio (AR) variation on the Cu electroplating processes’ formation and transformation mechanism. The flow field simulation model was based on the actual electroplating parameters with the micro THs ARs 4.75:1~1.27:1 (thickness 380 μm) as research targets. The flow field distribution of micro THs and the additives’ adsorption characteristics with different convection were systematically examined. The simulation results indicated that the high flow rate zone extended from both ends to the center, and the flow rate in the micro THs center increased with the decreasing ARs. The electrochemical measurement results revealed the convection-enhanced inhibition effect of the additives. More miniature accelerators and more inhibition regents tended to adsorb on the cathodic surface with the descending ARs, resulting in the Cu deposition amount raise in the THs center with ARs while seldom changed around micro THs mouth. Therefore, three categories of Cu electroplating processes were provided: defect-free electroplating with high TP and low TP, and insufficient electroplating, which corresponded with high ARs of 4.75:1~3.17:1 (weak convection), moderate AR of 2.53:1 (medium convection), and low ARs of 1.9:1~1.27:1 (strong convection), respectively.