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Microtexture Dependence of Mechanical and Electrical Properties of Electroplated Gold Thin Films Used for Micro Bumps of 3D Modulus

2020; Japan Society Mechanical Engineers; Volume: 2020; Linguagem: Inglês

10.1299/jsmemecj.2020.j03202

2424-2667

Genta Nakauchi, Ken Suzuki, Hideo Miura,

Surface Roughness and Optical Measurements

In this study, the possibility of the application of gold thin films made by electroplating for bumps was investigated to improve the reliability of the TSV interconnection system. The variation of their crystallinity, in other words, the order of atom arrangement of grains and grain boundaries in electroplated gold thin films was investigated by changing their manufacturing conditions. It caused wide variation of mechanical and electrical properties of the films. By uniaxial tensile test of electroplated gold thin films, it was clarified that Young’s modulus and yield stress decreased with decreasing the volume ratio of low-crystallinity grain boundaries by increasing annealing temperature. In addition, fracture strain of the films annealed at temperatures higher than 300oC increased by about 2 times. Similarly, the EM (Electro Migration) resistance of the electroplated gold interconnections varied drastically depending on the volume ratio of porous grain boundaries and their crystallinity. The effective lifetime of the gold bumps was successfully predicted by considering both the crystallinity, and varied more than 10 times as a strong function of the crystallinity of grain boundaries in the fine bumps. Therefore, it is very important to control the crystallinity of the films in order to control the distribution of the mechanical properties and reliability of the electroplated gold thin films.