Mechanisms of nodule formation on Ni-Pt targets during sputtering

Ni-Pt alloys are employed in the formation of Ni-Pt silicide to facilitate contact and interconnection functions in semiconductor devices. However, the formation of nodules on the Ni-Pt target during sputtering results in a reduced deposition rate and abnormal discharge, significantly impacting the film quality. This study investigates the nodule formation mechanism on the surface of Ni-Pt targets during sputtering, utilizing field-emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD). The findings reveal that defects and inclusion areas in the target exhibit a slower sputtering rate compared to normal areas, ultimately leading to nodule formation. Notably, platinum-rich layers were observed on the surfaces of nodules, particularly those exceeding a height of 100 μm. The variations in target surface concentration, angular distribution, and sputter yield of Ni and Pt atoms, coupled with the blocking effect of the lateral areas of nodules, contribute to the formation and compositional variation of the Pt-rich layers on the nodule surfaces.