Influence of electric current on the grain orientation of Cu-Sn intermetallic compounds in Cu/molten Sn/Cu interconnection system

Abstract

In this paper, the interfacial reaction and the grain orientation of Cu₆Sn₅ intermetallic compound was investigated in Cu/molten Sn/Cu interconnection system under the current density of 1.0 × 10²A/cm² at 260 °C. The imposed electric current significantly accelerated the Cu₆Sn₅ growth rate at anode side under the effect of solid-liquid electromigration, while it has no obvious effect on the Cu₃Sn growth rate. The growth kinetics calculation results showed that with the passage of electric current, the growth of Cu₆Sn₅ compound at the cathode was determined by reaction process, while the Cu₃Sn growth was diffusion-controlled. In addition, the current can strongly influence the orientation of Cu₆Sn₅ phase in Cu-molten Sn-Cu system. There was a strong texture of [0001] direction in Cu₆Sn₅ phase, which was paralleled with the direction of electron flow. This result indicated that the electrons traveled along some particular directions and were scattered least by the lattices. The newly formed Cu-Sn compounds orientated themselves in those particular growth directions to facilitate electron flow.