Molecular dynamics simulation study of Zr interposer promoting Cu-Cu low-temperature hybrid bonding

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With the development of the microelectronics industry, microelectronics packaging technology continues to develop towards higher integration and smaller size. To overcome the problem that the micro-bump size of solder cannot meet the fine pitch bonding, Cu-Cu direct bonding has become one of the most promising methods in advanced packaging technology. However, since the temperature required for Cu-Cu direct bonding is approximately 400 °C, currently Cu-Cu direct bonding is mostly achieved through a hot-pressing process. Such high temperatures will lead to reduced alignment accuracy, damage to device performance, and increased equipment requirements. In order to overcome these problems, this study proposed to use active metal Zr as the interposer material to improve the Cu-Cu atomic diffusion ability and reduce the Cu-Cu direct bonding temperature. The research results indicated that the interposer structure of Zr with (111), (11-2), and (1-10) surfaces contribute to promote Cu-Cu diffusion and bonding at low temperatures. Among them, the Zr (11-2) structure had the strongest promoting effect. Due to the tight arrangement of atoms in the densely packed crystal plane, the diffusion ability of atoms is significantly weakened during the bonding process of the densely packed crystal plane. Therefore, the Zr (001) structure can only promote bonding process under specific crystalline surface of Cu, and the bonding ability was very weak. The application of this research result will have a beneficial effect on the reliability and manufacturability of three-dimensional integrated packaging.