Characterization studies of fluorine-induced corrosion crystal defects on microchip Al bondpads using X-ray photoelectron spectroscopy

In wafer fabrication, Fluorine (F) contamination may cause F-induced corrosion and defects on microchip Al bondpad, resulting in bondpad discoloration or non-stick on pad (NSOP). In the previous paper [1], the authors studied the F-induced corrosion and defects, characterized the composition of the “flower-like” defects and determined the binding energy of Al fluoride [AlF₆]^3- using X-ray Photoelectron Spectroscopy (XPS) and Time of Flight Secondary Ion Mass Spectrometry (TOF-SIMS) techniques. In this paper, we further studied F-induced corrosion and defects, and characterized the composition of the “crystal-like” defects using XPS. The experimental results showed that the major component of the “crystal-like” defect was Al fluoride of AlF₃. The percentages of the components of the “crystal-like” defects on the affected bondpad are: Al (22.2%), Al₂O₃ (5.4%), AlF₃(70.0%) and [AlF₆]^3- (2.4%). During high-resolution fitting, the binding energies of Al (72.8eV)Al₂O₃ (74.5eV), AlF₃ (76.3eV) and [AlF₆]^3- (78.7eV) were used.