Continuous epitaxial growth of extremely strong Cu_6Sn_5 textures at Iiquid-Sn/(111)Cu interface under temperature gradient

摘要

As the diameter of solder interconnects in three-dimensional integrated circuits (3D ICs) downsizes to several microns, how to achieve a uniform microstructure with thousands of interconnects on stacking chips becomes a critical issue in 3D IC manufacturing. We report a promising way for fabricating fully intermetallic interconnects with a regular grain morphology and a strong texture feature by soldering single crystal (111) Cu/Sn/polycrystalline Cu interconnects under the temperature gradient. Continuous epitaxial growth of η-Cu_6Sn_5 at cold end liquid-Sn/(111)Cu interfaces has been demonstrated. The resultant η-Cu_6Sn_5 grains show faceted prism textures with an intersecting angle of 60° and highly preferred orientation with their <1120> directions nearly paralleling to the direction of the temperature gradient. These desirable textures are maintained even after soldering for 120 min. The results pave the way for controlling the morphology and orientation of interfacial intermetallics in 3D packaging technologies.