Effect Of Ni Orientation On Microstructure Of IMC Interface And Preparation Of Full IMC Joint

Under the continuous drive of miniaturization,multifunction and high integration of microelectronic devices,the micro-joint density of IC integrated package needs to be greatly improved,which requires the rapid reduction of the scale of micro-joints,especially the three-dimensional IC integrated package that represents the highest integration.The sharp reduction of the micro-joint scale will lead to its reliability problem:the remelt and collapse of the micro solder joint of the lower chip in the 3D IC integrated bonding process will lead to the performance failure of the solder;the volume ratio of interfacial intermetallic compounds（IMC）in micro-joints increases,resulting in early brittle fracture and thermal fatigue failure.Only one or more grains can be formed in the micro-joints,and the orientation is random,resulting in different performance of each micro-joint in the package,which can easily lead to early failure and signal transmission problems of some micro-joints.In this study,the effect of Ni orientation on the microstructure of interfacial IMC was studied,and a new interconnection structure of single crystal orientation Ni/Sn/polycrystalline Ni and the corresponding temperature gradient assisted bonding method were proposed.The microstructure of IMC is regulated by Ni orientation and the growth of IMC is driven by temperature gradients,and IMC micro-joint with controllable microstructures are rapidly fabricated.The main findings are as follows:（1）The microstructures of（（100）,（110）,（111））single crystal Ni/Sn and polycrystalline Ni/Sn interface Ni₃Sn₄ were studied.The research results show that the Ni orientation has a very significant control effect on the microstructure of the interface Ni₃Sn₄.The interface Ni₃Sn₄ presents a regular morphology,and its grain size is uniform and has a certain growth direction,while the polycrystalline Ni interface Ni₃Sn₄ shows as Irregular morphology,and its grain size is not uniform.This is related to the preferential nucleation of Ni₃Sn₄ grains on the crystal planes with low misfit with single-crystal Ni.Compared with the Ni interface Ni₃Sn₄of the other two orientations,the single crystal（110）Ni interface Ni₃Sn₄ has a more regular morphology.（2）The microstructure evolution of single crystal（110）Ni/Sn interface Ni₃Sn₄ during interfacial solid-liquid reaction was studied.With the increase of reaction time,the morphology of Ni₃Sn₄ at the interface of single crystal（110）Ni/Sn changed from the primary tip prism to the large plane prism gradually.During the reaction process,the interface Ni₃Sn₄always maintains a regular prismatic main body morphology,the interface Ni₃Sn₄ morphology is regular,the grain size is uniform and has a regular arrangement direction.The morphology of Ni₃Sn₄ at the polycrystalline Ni/Sn interface gradually evolves from rod shape to back dart shape and block shape and still shows the irregularity of morphology,and its grain size is uneven,and the grain growth direction is random.This is mainly related to the microstructure of primary Ni₃Sn₄ and the diffusion ability of interface atoms through Ni₃Sn₄.（3）The bonding structure of single crystal（110）Ni/（10μm）Sn/polycrystalline Ni was prepared.The microstructure of Ni₃Sn₄ interface was controlled by Ni orientation and the growth of Ni₃Sn₄ interface was driven by temperature gradient.The Ni₃Sn₄ micro-joints with controllable microstructure were rapidly prepared.The formation mechanism of rapid and controllable microstructure was studied.Under the influence of temperature gradient,the non-uniform growth of Ni₃Sn₄ appears at the interface of cold and hot ends.The cold end interface is regular prism-like Ni₃Sn₄ grains,and the hot end interface is fine rod-like Ni₃Sn₄ grains.With the increase of reaction time,the size of the fine rod-like Ni₃Sn₄ at the hot end interface remains almost unchanged,and the regular prismatic Ni₃Sn₄ at the cold end interface continues to increase until it passes through the entire interconnection layer,forming a fully Ni₃Sn₄interconnection with controllable microstructure.Its rapid growth is related to the directional diffusion of Ni atoms at the hot-end interface driven by temperature gradient,and its regular morphology and orientation are mainly affected by the initial Ni₃Sn₄ microstructure controlled by Ni orientation.The research results provide a new bonding structure and corresponding bonding method for 3D IC integration of high-performance microelectronic devices,and the formed Ni₃Sn₄ micro-joint is expected to solve the reliability problem of 3D IC integration joint.