Copper electrodeposition from an acidic plating bath containing accelerating and inhibiting organic additives

Abstract

Copper electrodeposition on copper from still plating solutions of different compositions was investigated utilising electrochemical impedance spectroscopy (EIS), cyclic voltammetry, and scanning electron microscopy (SEM). An acid copper sulphate plating base solution was employed either with or without sodium chloride in the presence of a single additive, either polyethylene glycol (PEG) or 3-mercapto-2propanesulphonic acid (MPSA), and their mixture. Thallium underpotential deposition/anodic stripping was employed to determine the adsorption capability of additives on copper. In the absence of chloride ions, MPSA shows a moderate adsorption on copper, whereas PEG is slightly adsorbed. At low cathodic overpotentials, the simultaneous presence of MPSA and chloride ions accelerates copper electrodeposition through the formation of an MPSA-chloride ion complex in the solution, particularly for about 220 mM sodium chloride. The reverse effect occurs in PEG-sodium chloride plating solutions. In this case, from EIS data the formation of a film that interferes with copper electrodeposition can be inferred. At higher cathodic overpotentials, when copper electrodeposition is under mass transport control, the cathode coverage by a PEG-copper chloride-mediated film becomes either partially or completely detached as the concentration of chloride ions at the negatively charged copper surface diminishes. The copper cathode grain topography at the mm scale depends on the cathodic overpotential, plating solution composition and average current density. Available data about the solution constituents and their adsorption on copper make it possible to propose a likely complex mechanism to understand copper electrodeposition from these media, including the accelerating effect of MPSA and the dynamics of PEG-copper chloride complex adsorbate interfering with the surface mobility of depositing copper ad-ions/ad-atoms.

Polyquaternium-2: A New Levelling Agent for Copper Electroplating from Acidic Sulphate Bath

“…5,7,8 Organic additives are widely used in copper electrodeposition as an effective way to control the current distribution in TH during electroplating or other certain properties of the copper deposit. [9][10][11] The additive system, used for PCB electroplating, generally includes accelerator (i.e., bis(3-sulfopropyl) disulfide), inhibitor (i.e., poly (ethyleneglycol)) and leveler (i.e., Janus Green B). [12][13][14][15] The synergy of these additives gives rise to a uniform plating or superfilling in the TH.…”

Interpretation of Negative Resistance Observed in Electrochemical Impedance during Copper Electrodeposition Containing Thiourea

“…13,[31][32][33][34][35][36][37][38][39][40][41] The impedance spectra of Cu fabricated by electrodeposition were often analyzed by equivalent circuit. 5,11,15,31,34,40,41 Pasquale et al 40 measured the impedance spectra of Cu fabricated by electrodeposition in acid solution containing additives such as NaCl, Polyethyleneglycol, and 3-mercapto-2-propanesulphonic acid. They proposed two equivalent circuits to analyze the impedance spectra measured at the high and the low overvoltage during the Cu electrodeposition in the presence of each additive.…”

Gold electrodeposition in organic media

“…[1][2][3][4][5][6] Capping agents are used in electrodeposition to guide the growth of metal or semiconductor crystals. [7][8][9][10][11][12][13][14][15][16][17][18][19] These organic species adsorb onto electrodes and electrodeposits as a result of the high surface energy of these materials, which ultimately influence the shape of the growing grains. Therefore, the chemical nature of the organic ions present in ionic liquids and organic electrolytes may have a strong impact on the morphology of the deposits produced.…”