A surface analysis on oxygen plasma-cleaned gold pattern-plated substrates for wire bondability

The surface properties of the bond pads of gold pattern-plated (GPP) substrates cleaned by oxygen plasmas dependent on the wire bondability with gold wires are investigated. Optical microscope and scanning electron microscopy are used to interpret the surface morphology of the bond pads. Auger electron spectroscopy and X-ray photoelectron spectroscopy are applied to analyze the surface compositions dependent on the depths and the surface chemical bonds of the bond pads. Oxygen plasmas are found that can reduce the surface impurities such as C, O and Cu for GPP pad and enhance the bonding strength with gold wires. The surface impurities such as Cu, Ni and O are found to cause no gold residue on GPP pad after the wire peel test due to Cu2O/CuO and NiO are formed at GPP pad. As the high contents of C and O are observed at the top surface of GPP pad with the contaminants of Cu2O/CuO and NiO, the bond pad will be non-bondable with gold wires.