Fabrication and thermal stability of highly (111)-oriented nanotwinned Cu films and their applications in 3D IC packaging

• Main Authors: Huang, Yi-Sa, 黃以撒
• Other Authors: Chen, Chih
• Format: Others
• Language: zh-TW
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/49958553110955192994

博士 === 國立交通大學 === 材料科學與工程學系所 === 102 === This study investigates the fabrication, thermal stability, and applications in microelectronics packaging. This dissertation contains five parts. In the first part, we discussed the fabrication of highly (111)-orientated nano-twinned copper by pulse plating. After annealing at 300oC for an hour, the nano-twinned copper showed good thermal stability. Moreover, the columnar nano-twinned grain grew to the bottom side and transformed the fine grain region into columnar nano-twinned structure with (111)-preferred orientation. The (111)-orientated nano-twinned copper with good thermal stability was applied to the Cu lines and under bump metallization (UBM) in the second to sixth parts. In the second part, we observed the thermomigration of Cu atom in Cu/SnAg/Cu microbumps. Micro bumps were reflowed under a temperature gradient. After reflow, there was asymmetrical intermetallic compounds (IMCs) growth due to the thermomigration of Cu atoms. In the third part, we discussed the effect of solder thickness to the IMC growth in Ni/SnAg/Cu microbumps. The thicknesses of solder were from 10 to 60 μm. IMC growth rates were changed with the concentrations of Ni and Cu. In the fourth part, the thermomigration of Cu atom in Ni/SnAg/Cu micro bump was observed. There are two factors, which are thermomigration of Cu atoms and concentration gradient of Cu and Ni, to affect the IMC growth in Ni/SnAg/Cu microbumps. The main factor which dominated the IMC growth is thermomigration of Cu atoms. In the fifth part, we discuss the effect of solder thicknesses to IMCs growth in Cu/SnAg/Cu micro bump after high temperature storage. After 1000-hr-150oC aging, the growth rate of Cu3Sn increased when all the solder was consumed. Moreover, the microbumps were also polished by focus ion beam to observe the microstructure. We found that there were few Kirkendall voids on the interface of nano-twinned Cu UBM and Cu3Sn. These results indicated the use of nano-twinned Cu can improve the reliability of microbumps.