New electroless copper plating bath using sodium hypophosphite as reductant

In this paper, a new environment friendly electroless plating bath using sodium hypophosphite as reductant and nitrilotriacetic acid as complexing agent was investigated under the acid condition. The effects of bath temperature, pH, CuSO₄.5H₂O concentration, nitrilotriacetic acid concentration and NaH₂PO₂.H₂O concentration upon the deposition rate and the bath stability were studied. The electrochemical results indicated that the deposition rate of the electroless copper increased with the decrease in the pH, and it reached 2·4 μm h⁻¹ when the bath pH was 6·0. The as deposited Cu films were characterised by energy dispersive X-ray analyser, X-ray diffraction, atomic force microscopy and resistivity measurement. The quality of the Cu films were improved by the addition of a surfactant PEG-600, and a uniform copper film with a low resistivity (2·60 μΩ cm) was obtained, which was able to be used as seed layer for electroplating Cu.