Low Temperature Direct Bonding of Nanotwinned Ag Thin Films

The vertically integrated systems, three-dimensional integrated circuit (3D-IC), are regarded as a solution to the demand of both the trend of miniaturization for electronic devices and the better performance. Metal-to-metal direct bonding technology has been considered as a promising method to connect different chips in 3D-IC packaging. In this study, nano-twinned Ag was used as direct bonding material. The Ag nanotwinned thin film with highly (111) preferred orientation was fabricated using unbalanced magnetron sputtering system. The low temperature Ag-Ag direct bonding was developed by thermal compression process under air atmosphere and bonding temperature of 200°C. The corresponding bonding mechanism and mechanical strength would be discussed.