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The adhesion of Pt/Ti thin films on SiN x /Si substrates with respect to the substrate pretreatment and annealing ambient was investigated using the adhesive tape test, the peel test, and the scratch test. Pt/Ti thin films were deposited a DC magnetron sputtering system. The in situ Ar+ RF plasma treatment was more effective in enhancing adhesion between the Pt/Ti thin films and the SiN x /Si substrate than chemical cleaning. After annealing in an oxygen ambient, the adhesion of the Pt/Ti/SiN x /Si specimen was degraded. This adhesion degradation was attributed to the depletion of the Ti adhesion layer due to the formation of the rutile TiO2 phase.

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The microstructure of the ultrasmall eutectic Bi-Sn solder bumps on Au/Cu/Ti and Au/Ni/Ti under-bump metallizations (UBMs) was investigated as a function of cooling rate. The ultrasmall eutectic Bi-Sn solder bump, about 50 µm in diameter, was fabricated by using the lift-off method and reflowed at various cooling rates using the rapid thermal annealing system. The microstructure of the solder bump was observed using a backscattered electron (BSE) image and the intermetallic compound was identified using energy dispersive spectroscopy (EDS) and an x-ray diffractometer (XRD). The Bi facet was found at the surface of the ultrasmall Bi-Sn solder bumps on the Au/Cu/Ti UBM in almost all specimens, and the interior microstructure of the bumps was changed with the solidification rate. The faceted and polygonal intermetallic compound was found in the case of the Bi-Sn solder bump on the Au (0.1 µm)/Ni/Ti UBM, and it was confirmed to be the (Au 1-x-y Bi x Ni y )Sn 2 phase by XRD. The intermetallic compounds grown form the Au (0.1 µm)/Ni/Ti UBM interface, and they interrupted the growth of Bi and Sn phases throughout the solder bump. The ultrasmall eutectic Bi-Sn solder bumps on the Au (0.025 µm)/Ni/Ti UBM showed similar microstructures to those on the Au/Cu/Ti UBM.