Fabrication of arrays of (100) Cu under-bump-metallization for 3D IC packaging

• Published in: 2015 International Conference on Electronics Packaging and iMAPS All Asia Conference (ICEP-IAAC) pp. 518 - 522
• Main Authors: Chiu, Wei-Lan, Lu, Chia-Ling, Lin, Han-Wen, Liu, Chien-Min, Huang, Yi-Sa, Lu, Tien-Lin, Liu, Tao-Chi, Hsiao, Hsiang-Yao, Chen, Chih, Kuo, Jui-Chao, Tu, King-Ning
• Format: Conference Proceeding
• Language: English
• Published: The Japan Institute of Electronics Packaging 01.04.2015
• Subjects: abnormal grain growth; Annealing; Copper; Grain size; nanotwinned copper; oriented Cu; Strain; X-ray diffraction
• DOI: 10.1109/ICEP-IAAC.2015.7111069

Due to the thousands of microbumps on a chip for 3D ICs, the precise control of the microstructure of all the material is required. The nearly -oriented nanotwinned and fine-grained Cu was electroplated on a Si wafer surface and annealed at 400-500 °C for 1 h, many extremely large -oriented Cu crystals with grain sizes ranging from 200 to 400 µm were obtained. The -oriented Cu grains were transformed into super-large -oriented grains after the annealing. In addition, we patterned the -oriented Cu films into pad arrays of 25 to 100 µm in diameter and annealed the nanotwinned Cu pads with same conditions. An array of -oriented single crystals Cu pads can be obtained. Otherwise, single-crystal nano-wire growth displays a process by one-dimensional anisotropic growth, in which the growth along the axial direction is much faster than in the radial direction. This study reported here a bulk-type two-dimensional crystal growth of an array of numerous -oriented single crystals of Cu on Si. The growth process in 3D IC has the potential for microbump applications packaging technology.