Fast phase transformation due to electromigration of 18 μm microbumps in three-dimensional integrated-circuit integration

摘要

The electromigration behavior was investigated in 18-μm SnAg microbumps at 150 ℃. The monitored resistance increase abruptly soon after the current stressing of 4.6 × 10~4 A/cm~2 was applied but the resistance rose much slower after a certain period of time. The formation of the high-resistivity Ni_3Sn_4 intermetallic compounds (IMCs) was responsible for the abrupt resistance increase in the beginning of the current stressing. The whole solder joint was transformed into an IMC joint. Because IMC has a higher electromigration resistance than the solder, a much slower increase in resistance was resulted after the solder joint was transformed into IMCs.