This paper describes effective thin-film structure barrier metals for use as eutectic solder bumps. Shear strength and bump interconnection resistance were evaluated. The mutual diffusion in metals was investigated. Barrier metal structures -Cu/Ti, Ni/Ti and Cu/Cr - were evaluated after ageing. The Ni/Ti structure has good reliability according to ageing test results. Pd is used for improvement of solder wettability and as an oxidisation barrier. Consequently, it was concluded that a thin-film Pd/Ni/ Ti barrier metal is suitable for use as eutectic solder bumps. The broken interfaces of the solder bumps were analysed by scanning auger electron spectrometry. In the thin-film Cu/Ti structure, decrease in the shear strength is caused by three mechanisms, as determined from the broken interface analysis. The three mechanisms are mixed metal formation, Ti oxidisation and diffusion between barrier metals and Al. Furthermore, TCT and PCT were carried out on these eutectic solder bumps to confirm the interconnection reliability. The TCT and PCT results prove that electrical connection is stable.
ASJC Scopus subject areas