篇題：Low-Temperature (70°C) Cu-to-Cu Direct Bonding by Capping Metal Layers
文章出處：IEEE Electron Device Letters, vol. 42, no. 10, pp. 1524-1527, Oct. 2021, doi: 10.1109/LED.2021.3105434.
作者：Demin Liu, Po-Chih Chen, Yu-Wei Liu, Han-Wen Hu, Kuan-Neng Chen
任職單位及部門：國立陽明交通大學電子工程學系
Cu-Cu direct bonding at low temperature with Cr wetting layer and Au passivation has been developed, and the bonding mechanism has been investigated. A chip-level Cu-to-Cu direct bonding can be achieved under a very low thermal budget condition at 70 °C for 90 s or 150 °C for 15 s,
while wafer level bonding can be achieved at 100 °C under a low vacuum environment ( 10−2 Torr) by deposition of capping metal layers, which can protect Cu from oxidation, as well as reduce surface roughness and grain
size of Cu. During the bonding process, Cu atoms diffuse through Cr/Au layers into the bonding interface, forming a new inter-layer without voids
to achieve high quality bonding. The phenomenon of recrystallization and effects of grain size have been validated by TEM analyses. This Cu-Cu
bonding with capping metal layers scheme can enable bonding with ultra-low thermal budget, excellent bonding quality, good electrical performance
and high reliability, showing the great feasibility for the 3D integration applications.
文章摘要：
本研究開發了以Cr潤濕層和Au鈍化層達成Cu-Cu低溫直接鍵合，並探討其接合機制。研究結果可在70 °C 90 s 或 150 °C 15 s 的極低熱預算條件下實現晶片級 Cu-Cu 直接鍵合，並能在100 °C下達
成晶圓級接合。其中覆蓋金屬層的沉積可以保護 Cu 不被氧化，並降低 Cu 的表面粗糙度和晶粒尺寸。在接合過程中，Cu 原子可通過 Cr/Au 層擴散到接合界面，形成一個新的沒有空隙的層間，完成高質
量接合，並透過TEM 分析證實了晶粒尺寸對再結晶現象的影響。覆蓋金屬層的 Cu-Cu 接合方案可以實現超低熱預算、高接合質量、良
好電氣性能、和高可靠性，顯示高可行性能應用於3D 集成技術發展。