Additives for Bottom-up Copper Plating from an Alkaline Complexed Electrolyte

Choe

et al. 2015

J. Electrochem. Soc.

The electrolyte for Cu superfilling generally consists of copper sulfate, sulfuric acid, a chloride ion, an accelerator, and a suppressor. In this study, the characteristics of citric acid-based electrolytes and the interaction between citrate species and accelerators are investigated, with the ultimate goal being the replacement of both sulfuric acid and the suppressor with citric acid. Electrochemical impedance measurements were adopted to measure the changes in solution and charge transfer resistances with respect to citric acid and accelerator concentrations. In addition to a decrease in solution resistance resulting from the addition of citric acid, charge transfer inhibition was observed during Cu electrodeposition, which is likely the result of adsorption of citrate species onto Cu surface. A competitive adsorption between the citrate species and the accelerator was also observed and the new additive system was applied to the feature filling in the absence of the conventional polyethylene glycol suppressor. Using this new copper sulfate, citric acid, chloride ion, and accelerator system, trenches were successfully bottom-up filled, resulting in no internal defects.

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confidence: 99%

Electrochemical Behavior of Citric Acid and Its Influence on Cu Electrodeposition for Damascene Metallization

Choe

et al. 2015

J. Electrochem. Soc.

“…Lizama [22] also deduced that the fully deprotonated copper citrate dimer ([Cu 2 Cit 2 H -2 ] 4À ) inhibited the electro-reduction of copper ion by the electrochemical study combined with the chemical equilibrium diagram. Joi and Im et al [23][24][25] reported the application of citrate-coordinated copper electroplating bath on the dual-damascene copper metallization. After improving the alkaline citrate copper plating process by decreasing the solution viscosity and increasing the deposition current density, we [26,27] successfully applied the process in the through-hole metallization of PCB and MEMS (Micro-electromechanical Systems) manufacture.…”

Section: Introductionmentioning

confidence: 99%

Toward Preeminent Throwing Power from a Novel Alkaline Copper Electronic Electroplating Bath with Composite Coordination Agents

Jin

Yang

et al. 2022

ChemElectroChem

In this work, an electronic copper electroplating bath with low copper ion concentration and preeminent throwing power in through hole (TH) thickening of the printed circuit board (PCB) was successfully developed. Based upon the weak alkaline bath containing the composite complexants of citrate (Cit) and ethylenediamine (En), their synergistic effects on the preeminent bath throwing power were carefully investigated and theoretically proved. The UV‐vis spectroscopy results illustrated that En exhibited a stronger coordination ability with Cu (II) ion than citrate, and the stoichiometric coordination ratio between En and Cu (II) ion was 2 : 1. The linear sweep voltammetry (LSV) results showed that the electro‐reduction peak potential of Cit−Cu coordination ion was −0.55 V (vs. Hg/HgO), whereas that of En−Cu ion was at a more negative potential of −0.82 V. The in situ Fourier transform infrared (FTIR) spectroscopy revealed that the adsorptions of the Cit−Cu and En−Cu coordination ions were potential dependent on the copper electrode. The Cit−Cu coordination ion was easily adsorbed at the interior sites of through holes with lower over‐potential to promote the growth of copper coating. Moreover, the En−Cu coordination ion adsorbed preferably on the surface and the edge of through hole for its higher electro‐reduction overpotential, to hinder the germinating of copper nuclear. The cross‐section observation of optical microscope proved that the throwing power of novel copper electroplating bath behaved surpassingly, up to 105.8 %.

“…Electrochemical measurements and trench filling results are presented for the tartrate complexed cupric sulfate electrolyte, containing 0.1 mol/L CuSO 4 · 2H 2 O + 0.5 mol/L Na 2 C 4 H 4 O 6 · 2H 2 O. The electrolyte differs from that in the earlier study 54 in the cation of the tartrate (KNaC 4 H 4 O 6 · 2H 2 O) and 1800 MW branched PEI (Alfa-Aesar a ) rather than 600 MW. As in the earlier study, the pH was adjusted to 12.5 through the addition of sodium hydroxide.…”

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confidence: 96%

“…53 A more recent publication details superconformal deposition in micrometer size trenches in a tartrate complexed Cu electrolyte of pH > 12. 54 Superconformal filling was obtained in the presence of two additives, polyethyleneimine (PEI) and bis-(3-sulfopropyl) disulfide (SPS), with conformal filling obtained in the presence of just one additive. The superconformal filling was suggested to be consistent with the Curvature Enhanced Accelerator Coverage (CEAC) mechanism, the SPS referred to as a "suppressor" and the PEI referred to as an "antisuppressor".…”

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confidence: 99%

Superconformal Copper Electrodeposition in Complexed Alkaline Electrolyte

Josell¹,

Moffat²

2014

J. Electrochem. Soc.

This paper examines superconformal filling of trenches during copper electrodeposition from alkaline cupric tartrate electrolyte. Localized bottom-up filling of submicrometer damascene trenches with minimal deposition on the sidewalls and the field around them is observed in electrolyte containing the deposition rate suppressing additive bis-(3-sulfopropyl) disulfide (SPS) for applied potential near that where suppression breakdown is observed. Deposits have rough surfaces and the deposited copper contains large voids. In contrast, conformal filling of trenches is observed in electrolyte containing polyethyleneimine (PEI), the deposits exhibiting macroscopically smoother surfaces with finer scale embedded porosity revealed by scanning electron microscopy. Electrolytes containing both additives yield bottom-up filling, in some cases with dense deposits at the bottoms of the features that transition to the porous structures observed for the PEI containing electrolyte. The feature filling and electrochemical measurements are discussed in the context of existing models for bottom-up deposition. Evolution of suppressor breakdown coupled with the electrical response of the electrochemical cell is of central importance.