Electromigration Resistance of Electroplated Gold Thin Films Used for Fine Bumps as a Strong Function of the Crystallinity of Grain Boundaries

2021 ◽  
Vol 2021.56 (0) ◽  
pp. 119_paper
Author(s):  
Genta NAKAUCHI ◽  
Hideo MIURA
Keyword(s):  
Thin Films ◽  
Grain Boundaries ◽  
Strong Function ◽  
Gold Thin Films

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

2020 ◽  
Author(s):  
Genta Nakauchi ◽  
Shota Akasaki ◽  
Hideo Miura
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Electrical Properties ◽  
Grain Boundaries ◽  
Indentation Test ◽  
Electron Back Scatter Diffraction ◽  
Effective Lifetime ◽  
Mechanical And Electrical Properties ◽  
Gold Thin Films ◽  
3D Stacking

Abstract The variation of their crystallinity, in other words, the order of atom arrangement of grain boundaries in electroplated gold thin films was investigated by changing their manufacturing conditions. Then, the effect of the crystallinity on both their mechanical and electrical properties was measured by using nano-indentation test and electromigration test. The crystallinity of the gold thin films was varied by changing the under-layer material used for electroplating. Also, the micro texture of gold thin films was evaluated by EBSD (Electron Back-Scatter Diffraction) and XRD (X-Ray Diffraction). It was clarified that the crystallinity of the electroplated gold thin films changed drastically depending on the crystallinity of the under-layer materials and electroplating conditions such as current density and temperature. This variation of the crystallinity should have caused wide variation of mechanical properties of the films. In addition, their mechanical properties such as Young’s modulus and hardness showed wide variation by about 3 times comparing with those of bulk gold. Similarly, the EM resistance of the electroplated gold bumps varied drastically depending on the ratio of porous grain boundaries and their crystallinity. Both the ratio and crystallinity also varied depending on the crystallinity of the under layer and electroplating conditions. The effective lifetime of the gold bumps was successfully predicted by considering both the crystallinity and residual stress of fine gold bumps. The lifetime 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 under-layer for electroplating in order to control the distribution of the mechanical properties and reliability of the electroplated gold thin films.

The Evolution of Growth, Crystal Orientation, and Grain Boundaries Disorientation Distribution in Gold Thin Films

2018 ◽  
Vol 53 (8) ◽  
pp. 1800038 ◽  
Author(s):  
Prakash Parajuli ◽  
Rubén Mendoza-Cruz ◽  
Ulises Santiago ◽  
Arturo Ponce ◽  
Miguel José Yacamán
Keyword(s):  
Thin Films ◽  
Grain Boundaries ◽  
Crystal Orientation ◽  
Gold Thin Films

Crystallinity-Induced Variation of the Electronic Characteristics of Electroplated Gold Thin Films

2018 ◽  
Author(s):  
Yutaro Nakoshi ◽  
Hideo Miura
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Physical Properties ◽  
Grain Boundaries ◽  
High Current Density ◽  
Indentation Test ◽  
Atomic Diffusion ◽  
Face Centered Cubic ◽  
Anisotropic Mechanical Properties ◽  
Gold Thin Films

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 thin films vary drastically comparing with those of conventional bulk material, depending on their electroplating process. In addition, since one bump is going to consist of a few grains or a single grain due to the miniaturization of the 3D structures, it shows strong anisotropic mechanical properties because a face-centered cubic crystal essentially has strong anisotropy of physical properties. Therefore, there should be the wide distribution of characteristics of the micro bumps depending on their micro structure and the variation of the crystallinity of grains and grain boundaries enlarges the width of the distributions of various properties. Particularly, it was found that the long-term reliability of micro bumps and interconnections is degraded drastically by porous grain boundaries with 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, the effect of crystallinity, in other words, the order of atom arrangement of grain boundaries in electroplated gold thin films on the EM resistance was investigated experimentally. The crystallinity of the gold thin films was varied drastically by changing the under-layer material used for electroplating; such as Cr (30 nm) / Pt (50 nm)/ Au (200 nm) and Ti (50 nm) / Au (100 nm). The mechanical properties of the electroplated gold thin films were measured by using a nano-indentation test. Also, the micro textures such as crystallinity and crystallographic orientation of gold thin films were investigated by EBSD (Electron Back-Scatter Diffraction) and XRD (X-Ray Diffraction). It was clarified that the crystallinity of the electroplated gold thin films changed drastically depending on the crystallinity of the under-layer materials and heat treatment conditions after electroplating. This variation of the crystallinity should have caused the wide variation of mechanical properties of the electroplated gold films. Therefore, it is very important to control the crystallinity of the under layer used for electroplating in order to control the mechanical properties and reliability of the electroplated gold thin films.

Piezoelectric Response and Polarization-Dependent Conductivity of Grain Boundaries in BiFeO3 Thin Films

2019 ◽  
Author(s):  
D.O. Alikin ◽  
Y. Fomichov ◽  
S.P. Reis ◽  
A.S. Abramov ◽  
D.S. Chezganov ◽  
...  
Keyword(s):  
Thin Films ◽  
Grain Boundaries ◽  
Piezoelectric Response ◽  
Bifeo3 Thin Films
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