电流驱动择优取向IMC微焊点的形成与调控机理

Rapid formation of an intermetallic compound (IMC) micro interconnect of stacked chips at a low temperature has been became the new research focus in 3D package technology. In this project, to overcome the low formation rate and difficulty of control crystal orientation of the whole IMC interconnect, according to the early study of the liquid-solid electromigration behavior of the micro interconnect, a current driven bonding (CDB) method was proposed. Single crystal and preferred orientation Cu film were used as UBM. Synchrotron radiation real-time imaging technology was used to observe the growth and fusion process of preferred orientation interfacial IMC under CDB. The project will study the bonding mechanism of rapid and preferred growth of IMC based on the atomic diffusion flux. The crystal orientation characterization technology was used to identify the orientational relationship between IMC and Cu UBM, and then establish the orientation relationship model between them. The effects of current density, Cu orientation, temperature and other factors on the preferred growth of IMC were revealed, and currents influence the diffusion of metal atoms to control the growth behavior of IMC, and finally the formation and growth regulation of whole IMC micro interconnect was achieved. The result will provide theoretical and technical foundation for the industrial application of the preferred orientation whole IMC micro interconnect.

低温下制备全金属间化合物(IMC)微焊点实现叠层芯片互连已成为3D封装研究的新热点。本项目针对全IMC微焊点形成速度慢、晶体取向难以控制等问题，结合前期微焊点液-固电迁移行为研究发现，提出电流驱动键合(CDB)制备全IMC微焊点的新方法。拟采用单晶和择优取向Cu薄膜作为凸点下金属层(UBM)，利用同步辐射实时成像技术观测CDB条件下界面IMC生长和融合过程，基于原子扩散通量揭示CDB诱导界面IMC快速、择优生长并形成全IMC微焊点的键合机理；采用晶体取向表征技术明确择优取向IMC与Cu UBM的位向关系，并建立它们之间的位向关系模型；揭示电流密度、Cu取向、温度等因素对IMC择优生长的影响规律及机制，利用电流影响金属原子扩散进而调控IMC的生长行为，最终实现特定取向全IMC微焊点的形成与生长调控。研究成果将为择优取向全IMC微焊点在3D封装互连技术中的应用提供理论和实践指导。

该项目研究了单晶Cu界面反应，揭示了焊接温度、焊接时间及钎料成分对棱晶状Cu6Sn5形成的影响规律。基于无铅钎料中Cu6Sn5中程有序原子团簇（MRO）尺寸和界面Cu原子低错配度关系对界面Cu6Sn5的形核及晶粒取向进行了解析。针对全Cu6Sn5 IMC微焊点形成速度慢、晶体取向难以控制等问题，结合前期微焊点液-固电迁移行为研究发现，提出电流驱动键合(CDB)制备全IMC微焊点的新方法。采用单晶和择优取向Cu薄膜作为凸点下金属层(UBM)，利用同步辐射实时成像技术观测CDB条件下界面IMC生长、融合过程，基于原子扩散通量揭示CDB诱导界面IMC快速、择优生长并形成全IMC微焊点的键合机理；采用晶体取向表征技术明确择优取向IMC与Cu UBM的位向关系，并建立它们之间的位向关系模型；揭示电流密度、Cu取向、温度等因素对IMC择优生长的影响规律及机制，利用电流影响金属原子扩散进而调控IMC的生长行为，最终实现特定取向全IMC微焊点的形成与生长调控。表征了择优取向全IMC微焊点可靠性，制备的全IMC焊点具有单一晶体取向、IMC/基体界面无空洞与裂纹、高拉伸强度、高服役温度、高温抗电迁移可靠性等优点。研究成果将为择优取向全IMC微焊点在3D封装互连技术中的应用提供理论和实践指导。