ON THE ROLE OF POLY(ETHYLENE GLYCOL) IN DEPOSITION OF GALVANIC COPPERCOATINGS

A literature review is provided of the influence and the behaviour of polyethers of the type of polyethylene glycol (PEG) and polypropylene glycol (PPG) on electrodeposition of copper coatings in acidic electro lytes. Emphasis is given to the scientific understanding of various ph enomena associated with the processes being discussed. The topics incl ude the influence of PEG (PPG) (alone or in the presence of Cl-) on th e kinetics of the electrocrystallization process as a function of: deg ree of cathode polarization; molecular weight and concentration of PEG (PPG) and of chloride ions. The probability of complex formation of C u+ and Cu2+ with PEG (PPG) and Cl- is also discussed. Based on an anal ysis of published literature data it is shown that: (i) PEG (PPG) stro ngly inhibits the cathodic process; (ii) there exists a critical poten tial (on cathode polarization) which is responsible far the great diff erence in the degree of suppression of the deposition current in the p resence of PEG (PPG); (iii) in the presence of CI-in the electrolyte, the potential region within which PEG (PPG) is adsorbed most readily i ncreases dramatically. The possibilities of complex formation between Cu+(Cu2+) ions and PEG (PPG) in the absence and in the presence of Cl- are also discussed. It is pointed out that the presence of PEG (PPG) in the acidic electrolytes for copper electrodeposition leads to the f ormation of complexes of the type (Cu+(-CH2-)(3) . H2O) and {Cu2+(-CH2 -)(3) . 2H(2)O} as well as to a significant increase in concentration of the so called ''ate'' -complexes (CuCl2-, CuCl32-, CuCl+, CuCl42-). The formation of such complexes and their possible adsorption on the cathode surface are proposed as an explanation for the effect of suppr essing copper deposition current.