Copper Deposition in the Presence of Polyethylene Glycol: I. Quartz Crystal Microbalance Study

Abstract

The addition of polyethylene glycol (PEG) and Cl-to an acid copper electrolyte inhibits the deposition reaction for cathodic overpotentials of up to about 150 mV. Adding Cl-only promotes the deposition reaction, while adding PEG alone has a relatively small effect on electrode kinetics. Frequency shifts of an electrochemical quartz crystal microbalance suggest the adsorption of a monolayer of PEG molecules that are collapsed into spheres provided chloride ions are present, with little adsorption occurring when Cl-is absent. This behavior is the same for gold and copper surfaces. Transient current measurements suggest that chloride ions affect the PEG adsorption equilibrium rather than adsorption kinetics alone.

Quantitation of Chloride in Cupric Oxide Recovered from Copper-Containing Etchant Waste

“…The addition of Cl increases conductivity and accelerates the etching rate in comparison to processes with relatively lower concentrations of Cl. On the other hand, high concentrations of Cl inhibit Cu deposition, as has been reported in other studies [6][7][8][9] . Thus, a robust, sensitive and simple method is required for quantitation of Cl in recycled CuO.…”

Additive influence on Cu nanotube electrodeposition in anodised aluminium oxide templates

“…It is well known that PEG or Cl -alone do not influence the Cu deposition process significantly on planar or structured substrates [14][15][16][17][18][19]. When they are both added however, an inhibition of the Cu deposition process is observed.…”

“…[14,20] The cyclic voltammograms of Fig. 3 show the first cycle deposition and dissolution of Cu [15][16][17][18][19][20] leads to an increase in the overpotential for the reaction taking the deposition into the hydrogen region resulting in gas evolution which 8 promotes tube growth by forcing the reaction to occur at the sides of the porous templates by shielding the central portion of the structure and preventing deposition in that region.…”

“…The second effect of the adsorbed Cl -: PEG complex is on the seed layer where the deposition is inhibited in the central portion of the base or seed layer thereby promoting the deposition around the edge of the seed layer resulting in the formation of nanotubes. The PEG complex which is assumed to be spherical [16,17] may be sterically impeded at the template wall or the alumina may present energetically favourable sites [10] for metal atom adsorption leading to preferential Cu nucleation and lower overpotential tube growth.…”

“…It has also been extensively investigated for nanoscale deposition of interconnect in the electronics industry. Polyethylene glycol (PEG) and chloride ion (Cl -) are additives that have been typically used in copper sulphate baths for many years whether for printed circuit board applications [14] or the most advanced sub-100 nm interconnect of Si chips [15][16][17][18][19]. The synergistic effect of these additives and others such as Bis-(sodium sulphopropyl)-disulphide (SPS) required for specific purposes such as enhanced bottom-up fill of blanket seed layer deposited 3 interconnect vias or trenches have been investigated to enhance the minimum feature size achievable with electrochemical deposition.…”