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采用倒装芯片互连凸点串联回路研究了高温、高电流密度条件下倒装芯片上金属布线/凸点互连结构中原子的定向扩散现象,分析了互连结构中受电应力和化学势梯度作用的各相金属原子的扩散行为.在电迁移主导作用下,Ni(V)镀层中的Ni原子的快速扩散导致原本较为稳定的Ni(V)扩散阻挡层发生快速的界面反应,造成Al互连金属与焊料的直接接触.Al原子在电子风力作用下沿电子流方向向下迁移造成窗口附近焊料中Al原子含量逐步上升,同时,空位的反向迁移、聚集形成过饱和,导致Al互连中形成大面积空洞.焊料中的Sn,Pb原子在化学势梯度和压应力作用下形成向上的原子通量,原子扩散方向与浓度梯度方向一致,使Al互连中形成空洞的同时,出现凸点焊料对Al互连的侵蚀现象.整个电迁移过程中,Al原子和Sn,Pb原子在各自的主导作用力的驱动下,发生着持续的互扩散,直至互连结构最终因质量通量的差异而发生开路失效.
The directional diffusion of atoms in flip-chip metal wiring / bump interconnect structure under high temperature and high current densities was investigated by using flip-chip interconnection bump series circuits. The effects of electrical stress and chemical potential (V) diffusion in the Ni (V) coating resulted in the rapid interfacial reaction of the originally stable Ni (V) diffusion barrier, resulting in the formation of Al The direct contact between the interconnected metal and the solder.Al atoms move downward along the electron flow under the action of the electron wind, causing the content of Al atoms in the solder near the window to gradually increase. At the same time, the vacancy moves backward and aggregates to form supersaturation, Even in the formation of a large area of hollow solder Sn, Pb atoms in the chemical potential gradient and compressive stress formed upward atomic flux, atomic diffusion direction and the concentration gradient in the same direction, so that the formation of interconnections in the Al hole at the same time, there Bump solder erosion of Al interconnection phenomenon.In the entire electromigration process, Al atoms and Sn, Pb atoms in the respective dominant force of driving, there is a continuous mutual diffusion until the interconnection The final configuration is due to differences in mass flux open circuit failure occurs.