Atmospheric pressure plasma reduction of copper oxide to copper metal

Copper oxide films were reduced to copper with an atmospheric pressure argon and hydrogen plasma at temperatures between 25 and 300 °C. A 50-nm-thick CuO layer on a Cu-coated Si wafer, 200 mm in diameter, was fully reduced by the plasma in 200 s at 200 °C. The activation energy for the reaction was found to be 3.7 kcal/mol. X-ray photoelectron spectroscopy confirmed that the copper oxide was reduced to metallic copper. Cross-sectional scanning electron microscopy revealed that voids appeared between the oxide and the base metal layer when the CuO was thicker than 20 nm. These voids remained at the interface after reduction of the copper oxide back to copper metal.