Effect of daisy chain structure on electromigration reliability of microbumps: A simulation study

A simulation method was utilized to study the electromigration reliability of two daisy chain structures which were subjected to electric current of 0.05 A at environment temperature of 22°C. The current density and temperature distribution of the two daisy chain structures were compared and the electromigration reliability of two types of daisy chain structures were analyzed. The results show that the current crowding effect of typical bump in parallel daisy chain structure was more prominent than that of typical bump in series daisy chain structure. The current density followed eight-order polynomial distribution. The hot spots of both structures coincided with the current crowding regions and the maximum temperature in typical bump in parallel daisy chain structure was obviously higher than that in typical bump in series daisy chain structure. The electromigration reliability of parallel chain structure was lower than that of series chain structure due to higher temperature and higher current density in hot spots of parallel chain structure. These findings will offer fundamental insights into electromigration and reliability theory.