| dc.description.abstract | In recent years, electroplating nano-twinned Cu has gradually attracted a very attention in the field of the package because it can improve the mechanical properties without greatly affecting the electrical properties. Some studies also have pointed out that nano-twinned Cu has good thermal stability and certain electromigration resistance, which makes nano-twinned Cu materials having a place in the field of high-frequency and high-speed product packaging. The first part of this study is to use different concentrations of gelatin additives to produce electroplated nano-twinned Cu films with different twin boundary densities, then, conduct tensile properties research. This experiment proposes a Cu film with a columnar twin crystal structure. When the tensile stress is parallel to the substrate, processes such as coalescence, grain-size reduction, and grain refinement will occur successively. When this type of Cu film with twin structure is subjected to tensile stress parallel to the substrate, the de-twinning process that occurs can be divided into two steps: (1) the ledge formation by the engagement of the dislocations with the twin boundaries and (2) the collapse of the ledges with the opposite twin-boundaries which make the twin structure disappear. It is also confirmed that the strength of the film is highly correlated with the twin boundary density. The electroplated nano-twinned Cu film with a larger twin boundary density has greater fracture strength than the electroplated nano-twinned Cu film with a smaller twin boundary density. The second part explains the deformation mechanism of Cu with twin structure parallel to the substrate under ultra-high normal stress and how the stacking faults parallel to the twin boundary at the twin boundary occurs after the plastic deformation. The dislocation takes the protrusions on the top of the pillar as the place where the dislocation is generated. Under the initial ultra-high stress, ultra-rapid plastic deformation occurs at the top of the Cu pillar at an unobservable speed. The protrusions are subjected to ultra-high stress. After that, it becomes a fulcrum without moving, and under the condition of continuous application of stress, the plane between the fulcrums undergoes elastic deformation after being stressed, forming a bend contour. When the bending plane reaches the curvature limit, the elastic deformation turns into plastic deformation. Using Schmid′s law and double Thompson tetrahedron, we can infer that under ultra-high normal stress, the stacking faults parallel to the twin boundary come from the cross-slip of the 30° Shockley partial dislocation on the twin boundary with the subsequent stair-rod dislocation dissociation, 60° perfect dislocation, 90° Shockley partial dislocation cross-slip onto the twin boundary and its transmission across the twin boundary. | en_US |