Study on Cu/Ti bonding and its applications in 3D IC

• Main Authors: Hsu, Sheng-Yao, 徐聖堯
• Other Authors: Chen, Kuan-Neng
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/47920105215602384263

碩士 === 國立交通大學 === 電子研究所 === 101 === This thesis focuses on researches of co-sputtering metal bonding in three-dimension integrated circuits (3DIC). Several co-sputtering metal species, such as copper (Cu) and titanium (Ti), are investigated. The corresponding bonding conditions are optimized as well. It is found that metal atoms with higher melting point will diffuse to the silicon substrate side under nitrogen ambient. The diffusion mechanism of co-sputtering metals has been discussed. For co-sputtering Cu/Ti metals, Ti atoms diffuse to the silicon substrate side under nitrogen ambient. However, Ti atoms diffuse to the surface of bond structure to react with oxygen and form Ti oxides if under atmosphere. Therefore, when Cu/Ti interconnects bond at the atmosphere, the Ti adhesion layer is self-formed under Cu and the process step is reduced. Some Ti atoms react with oxygen on the surface to form compact Ti oxides, which prevent Cu oxidation and improve the structure reliability. Finally, the material analysis, bonding strength, contact resistances of Cu/Ti bonding structures are investigated based on the best bonding parameters. According to our researches, the co-sputtering Cu/Ti bonding has the advantages of less fabrication steps and better reliability. The bonded structures meet the requirements of the bond strengths and electrical performance in 3D IC. This novel bonding technology has a high potential for the applications of 3D IC.