Journal of the Microelectronics and Packaging Society

The possibility of improving plating thickness distribution was investigated through quantitative consideration of bipolar electrodes without external power applied. By having the cathode tilted with respect to the anode, the potential distribution in the electrolyte solution adjacent to the cathode is different due to the difference in iR drop due to the path difference to the anode in each region of the cathode. The purpose of this study is to observe the bipolar characteristics in the case of an auxiliary anode for the non-uniform potential distribution of such a Hull cell. In particular, in order to evaluate the possibility of improving the non-uniform thickness distribution of the cathode by utilizing these bipolar characteristics, it was verified through experiments and simulations, and the electric potential and current density distribution around the bipolar electrode were analyzed. The electroplating in a Hull cell was performed for 75 min at a current density of 10 mA/cm2, and the average thickness is about 16 μm. The standard deviation of the thickness was 10 μm in the normal Hull cell without using the auxiliary anode, whereas it was 3.5 μm in the case of using the auxiliary cathode. Simulation calculations also showed 8.9 μm and 3.3 μm for each condition, and it was found that the consistency between the experimental and simulation results was relatively high, and the thickness distribution could be improved through using the auxiliary anode by the bipolar phenomenon.

Keywords Hull cell, electroplating, copper, numerical calculation