Characterization of Wafer Level Corrosion for Al-Cu Interconnects and Ni-Pd Pads

Corrosion on wafer level aluminium-copper (Al-Cu) interconnects and electroless nickel-palladium (Ni-Pd) pads were characterized using inline metrology and physical failure analysis methods. Chemical methods were then used to study the mechanism of the defects. Al-Cu localized corrosion occurred as Al-oxides growth with the presence of fluorine (F) and chlorine (Cl) due to moisture stain. Using chemical methods, high level of F and mild level Cl were found to adsorb onto the Al-Cu surface when wafer was exposed to moisturized environment. Ni-Pd pads corrosion on the other hand showed Pd layer deformation, Ni-Pd inter-diffusion and Ni voids with no oxides, a typical bimetallic corrosion. During laboratory beaker dip-plate test, air bubble was found to be an inducing factor for the defect.