Effect of organic dye on copper metallization of high aspect ratio through hole for interconnect application

Copper metallization of various aspect ratio through hole were performed by bath modification using methylene blue, an organic dye as leveler. Methylene blue (MB) which is a heterocyclic compound was added in different concentration in a three component additive system. Copper deposition inside the through hole was modified with concentration of leveler additive. High concentration of MB in the plating bath leads to greater suppressing effect, whereas at low concentration uniform filling inside the holes and on the board surface was observed. The synergetic effect of different additives during plating was destroyed at high concentration of leveler as revealed from impedance and cyclic voltammetric analysis. The greater interaction of leveler additive to the cathode that disrupt the dynamic nature of adsorption–desorption process, was found to have deleterious effect on super filling as revealed from optical micrograph analysis. There occur void formation inside the through holes at high leveler concentration and has more inhibiting nature as revealed from various analyses. Crystal orientation of the plated films with respect to additive modification was characterized by X-ray diffraction (XRD) analysis.

Schematic representation of additive distribution inside the through – via MB: Methylene Blue (Leveler), MPSA-Mercapto Propane Sulphonic Acid (Accelerator) PEG: Poly ethylene glycol (Suppressor).Figure optionsDownload as PowerPoint slideHighlights
► Methylene blue, an organic dye was used as leveler for copper metallization in electronics packaging.
► Synergistic effect of additives was achieved through bath optimization.
► Low concentration of leveler was superior in forming void free and uniform filling of vias.