Intermetallic compound formation inhibiting electromigration-based micro/nanowire growth

In this study, we investigated the relationship between intermetallic compounds (IMCs) and electromigration (EM)-based metallic micro-/nanowire growth and concluded that IMC has a negative effect on the wire growth. One of the key features of the sample structure in EM-based wire growth is passivation, which mechanically suppresses the deformation of the metallic interconnect due to the accumulation of atoms diffused by EM. Thicker passivation allows for higher pressure generation for wire growth; thus, the wire can be extruded by the higher pressure. However, as the compressive residual stress of passivation (which causes delamination) increases with the thickness of passivation deposited by sputtering, it is implied that excessively thick passivation causes delamination, which in turn relieves the pressure essential for wire growth, by releasing the interconnect constraints. In EM-based wire growth, generally a sample structure consisting of thin-film multilayers was used, and it often resulted in the delamination due to interlayer separation between the metallic interconnect and the topmost passivation. Mitigation of delamination enables the stable EM-based growth of a wire. To prevent delamination, Ti was introduced between the metallic interconnect and passivation. The relation of IMC formation behavior to the wire growth was investigated. It was experimentally shown that IMC contributed to the prevention of delamination but inhibited the wire growth. Therefore, sandwiching the metallic interconnect with materials that do not form IMC is advantageous for EM-based wire growth.