Microstructures and strength and reliability of electroplated gold thin film for micro bump

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  • NAKOSHI Yutaro
    Department of Finemechanics, Graduate School of Engineering, Tohoku University
  • SUZUKI Ken
    Fracture and Reliability Research Institute, Graduate School of Engineering, Tohoku University
  • MIURA Hideo
    Fracture and Reliability Research Institute, Graduate School of Engineering, Tohoku University

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Other Title
  • マイクロバンプ用めっき金薄膜の微細組織と強度・信頼性

Abstract

<p>Electroplated gold thin films have been used for micro bumps in flip chip packing structures. However, it has been reported that physical properties and micro texture of the electroplated gold thin films fluctuate drastically depending on their manufacturing process. In particular, it was found that the long-time reliability of micro bumps and interconnections is degraded drastically by porous grain boundaries due to a lot of defects because of the acceleration of atomic diffusion along the porous grain boundaries under the application of high current density (electromigration) and high mechanical stress (stress-induced migration). In this study, in order to evaluate the effect of atomic arrangement of under layer on the crystallinity of electroplated gold thin films, under layer material used for electroplating was changed; such as Cr (30 nm) /Pt (50 nm) /Au (200 nm) and Ti (30 nm) /Au (100 nm). The micro texture of the films such as crystallinity and crystallographic orientation was analyzed by EBSD (Electron Back-Scatter Diffraction) and XRD (X-Ray Diffraction). It was found that the crystallinity of both grain and grain boundaries of the electroplated gold varied depending on the quality of atomic arrangement of under layer and heat treatment. Therefore, it is significantly important to control of the crystallinity of under layer in order to control of physical properties and reliability of the electroplated gold thin films.</p>

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