Electrochemical behaviors of additives in high Cu(II) concentration solution for high-aspect-ratio through ceramic holes filling

The electrochemical behavior of additives determinates the filling process of through ceramic holes (TCHs), which is severely affected by Cu(II) concentration in the virgin make-up solution (VMS). High concentrations of Cu(II) are rarely reported in through-holes (THs) filling owing to its insufficient throwing power. High concentration CuSO 4 (0.7 M) and low concentration H 2 SO 4 (0.61 M) were confirmed as VMS, and thiazolinyl polydipropyl sulfonate (SH110), polyethylene glycol (PEG), and nitrotetrazolium blue chloride (NBT) were chosen as the accelerator, suppressor, and leveler, respectively. The electroplating performances were investigated under different plating solutions. The electrochemical behavior of additives and their combinations were evaluated by galvanostatic and cyclic voltammetric measurements. The filling performance of PEG-SH110-NBT in high Cu(II) solution is affected by convection. Plating efficiency is effectively improved by SH110 in the designed high Cu(II) plating solution. PEG and NBT have a synergistic effect on inhibition, while NBT shows a leveling effect only in the presence of SH110. The plating solution with a low air agitation flow rate effectively promotes the high-quality filling of TCHs with a high aspect ratio (AR) of 5, 4.75, and 3.8. The filled TCHs display mirror-bright surface and grain refinement without the void defects.