三維積體電路之銅/銦/錫低溫接合及可靠度研究

Abstract

銅對銅接合技術具有低電阻和良好的熱導率等優點，是目前應用在三維積體電路內連線(interconnection)的主流接合技術。然而，銅對銅接合技術需要高於300°C的接合溫度，以致於熱膨脹的問題導致了對準位移(alignment shift)，並且高溫製程也限制了堆疊元件的種類。儘管低溫接合技術已經有許多的文獻討論，但是對於低於150°C的低溫結合研究則相對缺乏。本文提出不同的銅/銦/錫接合結構並且探討其材料特性、接觸電阻特性、以及可靠度的研究。研究的結果指出，本文提出的銅/銦/錫接合結構可以形成耐高溫(>500 °C)的介金屬化合物(Intermetallic Compounds)，而此介金屬化合物在後續製程中不會因為溫度的影響而產生相變化。另外，銅/銦/錫接合結構具有良好的電性以及可靠度的性質，可以在濕度測試環境下非常穩定，更可以抵抗熱應力的測試。這些發現對於將銅/銦/錫接合結構應用在三維內連線(3D interconnection)或是異質整合(heterogeneous integration)都有很大的應用性。

Direct Cu-Cu bonding can perform superior heat conductance and low resistance. However, there are still some issues of Cu-Cu bonding, such as high bonding temperature requirement and alignment shifts caused by thermal expansion. While low temperature bonding has been extensively investigated, the low temperature bonding below 150 °C is relatively unexplored. In this work, a low temperature bonding technology of Cu-In-Sn based interconnect was proposed and investigated. This research focuses on Cu-In-Sn interconnect material analysis, electrical measurements, and reliability tests. The findings suggest that the intermetallic compounds formed in the bonded interconnects can survive well in the following process. The Cu-In-Sn interconnects bonded at low temperature all exhibit excellent electrical performance and high reliability after multiple current stressing. The high electrical stability against humidity and thermal stress shows a great potential in 3D integration. These findings also have implications for heterogeneous applications.