Electrochemical migration of nano-sized Ag interconnects under deionized water and Cl⁻-containing electrolyte

Abstract

With the trend of miniaturization of electronic products, the applications of fine-pitch interconnect have extended in high performance intelligent electronic devices. Thus, electrochemical migration (ECM) would be a concern in fine-pitch scale interconnects under the environment of temperature, humidity and biased voltage. This study investigated ECM behavior of fine-pitch nano-sized Ag interconnects prepared by screen-printing and sputtering methods in deionized water and Cl⁻-containing electrolytes. The ECM induced short-circuit was caused by dendrite formation between the cathode and anode. The ECM time to short circuit decreased with reducing pitch size for both samples but the sputtered samples exhibited better ECM resistance than printed ones due to continuous and consolidated structures of sputtered interconnects. In addition, different microstructure evolution of interconnects were found in different electrolytes and corresponding ion transport mechanism during ECM was discussed. When Cl⁻-containing electrolyte with concentration higher than 554 ppm was introduced, no more dendrite formation between the Ag interconnects was found and the ECM of Ag was suppressed. Instead, AgCl particles were formed at anode of interconnects and continued to grow accompanying with consumption of Ag interconnects, finally leading to open-circuit failure.