Preparation And Characterization Of Full Cu₆Sn₅ IMC Micro-Joints

The 3D packaging technology based on silicon through via and micro-joints requires that the micro-joints can be formed at low temperatures and continuously and reliably applied at high temperatures.Full Cu₆Sn₅ IMC micro-joints meet this requirement extremely well.At this time,how to form full Cu₆Sn₅ IMC micro-joints with high performance has become the focus of research.In this thesis,electroplated polycrystalline Cu,（111）single crystal Cu and（111）nt-Cu were used as the substrate,full Cu₆Sn₅ IMC micro-joints were formed by solid-liquid diffusion reaction.The effects of soldering temperature and substrate structure on the grain morphology and orientation of Cu₆Sn₅ were revealed.The growth behavior of interfacial IMCs in solid-liquid interfacial reaction and solid-state aging reaction was elucidated.The reliability of full Cu₆Sn₅ IMC micro-joints in solid-state aging and its electrical properties in digital circuits were evaluated.The results will provide theoretical and practical guidance for the application of full IMCs micro-joints in 3D packaging interconnection technology.The primary findings of this study can be summarized as follows:1.Grain morphology and orientation of Cu₆Sn₅:The special morphology of Cu₆Sn₅grains is related to the structure of Cu substrate,the soldering temperature and the concentration of Cu in the solder.At 300 ^oC and low Cu concentration,the"prism-type"Cu₆Sn₅ grains is easily formed on（111）single crystal Cu and（111）nt-Cu substrate,while the"scallop-type"is formed on the other conditions.At different temperatures（250 ^oC,300 ^oC）,Cu₆Sn₅ grains in electroplating Cu/Sn/electroplating Cu micro-joints are randomly oriented,and Cu₆Sn₅ grains in the interface of（111）single crystal Cu/Sn/（111）single crystal Cu micro-joints are also randomly oriented due to substrate dissolution.The orientation of interfacial Cu₆Sn₅ grain in the（111）nt-Cu/Sn/（111）nt-Cu micro-joint was mainly close to（0001）and（2113）.2.Preparation of full Cu₆Sn₅ IMC micro-joints:The thickness of interfacial IMCs increased with the extension of reaction time.The growth rate of interfacial IMCs was accelerated with the increase of reaction temperature.In solid-liquid interfacial reaction,the influence of substrate structure on interfacial IMCs growth was almost negligible.In the electroplating Cu/IMCs/electroplating Cu micro-joints,a limited amount of Kirkendall voids were observed within the Cu₃Sn layer,but the（111）single crystal Cu/IMCs/（111）single crystal Cu micro-joints and（111）nt-Cu/IMCs/（111）nt-Cu micro-joints were not observed.3.Aging test of full Cu₆Sn₅ IMC micro-joints:In solid state aging reaction,substrate structure was the key factor affecting the growth rate of IMCs.The growth rate of IMCs at the interface of（111）single crystal Cu substrate was the slowest,and that of（111）nt-Cu substrate was the fastest.4.Electrical simulation test of full Cu₆Sn₅ IMC micro-joints:Through the analysis of SI results of Sn micro-joints,full Cu₆Sn₅ IMC micro-joints and full Cu₃Sn IMC micro-joints in3D packaging,the texture of micro-joints had little influence on SI.The PI results showed that the electrical performance of full Cu₃Sn IMC micro-joints was the best,while the electrical performance of full Cu₆Sn₅ IMC micro-joints was similar to that of Sn micro-joints.