Choice of Intermetallic Compounds for Structural Applications in Near Submicron Joints

For 3D IC application, The thickness of micro joint is basically smaller than that in the conventional joint. IMCs can easily occupy micro joints during assembling or operation and then dominate the properties of micro joint. It is predicted that IMCs are going to be utilized as structural materials in near submicron-scale micro joint in these few years. The micromechanical behavior of IMCs is the important criterion to evaluate the suitability of IMCs as structural material in micro joints. In this study, the micromechanical behaviors of single crystalline IMCs generally formed in micro joints was conducted by micropillar compression. The failure mode of single-crystalline Cu6Sn5 and Ni3Sn4 are cleavage, however, the in-situ images and cross-section view showed that both Cu6Sn5 and Ni3Sn4 still preformed plastic deformation before failure, however, both Cu6Sn5 and Ni3Sn4 somehow plastically deformed through slip along the certain crystallographic direction on certain crystallographic planes. Most importantly, Ni3Sn4 can withstand a large amount of plastic deformation strain by compression which is more than 4 % in certain orientation. In comparison of these two IMCs, Ni3Sn4 showed the better mechanical performance including yield strength, strain to yield, failure strength, strain to failure and Young's modulus than Cu6Sn5. Thus, Ni3Sn4 has higher toughness and should be more promising to use as structure materials of 3D IC micro joints.