Implementation of thin film metallic-glass/Cu (TFMG/Cu) Bi-layer as diffusion barrier in Cu/Sn/Cu bonding structures for IC interconnection

Abstract

The development of three-dimensional integrated circuits and advancements in electronic packaging technology have increased the volume fraction of intermetallic compounds during the miniaturization of solder joints, thereby dominating the material properties of the solder joints. Thin film of metallic glass (TFMG) is an excellent diffusion barrier material. When maintained below its crystallization temperature, it retains its amorphous state, meaning that its barrier performance is completely independent of film thickness, and they exhibit good thermal stability. This characteristic provides significant advantages for the miniaturization of next-generation electronic devices. To ensure that a moderate amount of IMC remain in the solder joints without excessive growth, this study proposes the use of a bilayer thin film composed of metallic glass (Zr₆₉Cu₂₄Ti₇) and Cu as a diffusion barrier to regulate the interfacial reaction at the Cu/Sn/Cu interface. We investigated the influence of thermal compression bonding temperature on the development of IMC regulated by the use of a bilayer thin film diffusion barrier and showed that thermal compression bonding had optimal results at temperatures between 250 °C and 300 °C. Within this temperature range, the bilayer thin film effectively suppressed the excessive diffusion and reaction between Cu and Sn, reducing IMC overgrowth and preventing the formation of Kirkendall voids. The rounded Cu₆Sn₅ were the main IMC that formed in random distribution within the solder joints. This controlled diffusion promoted uniform and predictable IMC growth, effectively managing IMC morphology during bonding. It can be observed that this enhances resistance to thermal and mechanical stresses commonly encountered in 3D interconnect applications, contributing to the advancement and application of 3D IC packaging technologies.