Current stressing effect on interfacial reaction characteristics of Cu pillar/Sn-3.5Ag microbumps for 3D integration

Cu pillar bumps are known to be one of the most promising candidates for the fine pitch interconnection materials because they do not cause bump bridging between adjacent bumps.[1] Also, Cu pillar bump is widely adopted as chip-to-substrate or chip-to-chip interconnect in 3D integration as well as flip chip package [2]. However, Cu pillar bump makes excessive intermetallic compound (IMC) and Kirkendall void at Cu pillar/solder interface, which can degrade the electrical and mechanical reliability of solder joints [3–5]. Therefore, it is essential to understand the fundamental growth mechanisms of IMC and Kirkendall void in the Cu pillar bump. In this work, current stressing effect on interfacial reaction characteristics of Cu pillar/Sn-3.5Ag microbumps for 3D Integration was quantitatively evaluated by using in-situ SEM.