Optimization of O₂ Plasma Treatment on Cu Surface for Hybrid Cu Bonding

Pre-surface treatment in hybrid Cu bonding is plays a crucial role in improving bonding quality. Among the various pre-surface treatment methods, O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> plasma treatment is known to significantly enhance a mechanical bonding property of dielectric-to-dielectric bonding. In this study, we focused on optimizing the condition of O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> plasma treatment for enhancing the quality of Cu bonding and studing the bonding mechanism. The condition for O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> plasma treatment were optimized using the Response Surface Methodology (RSM) based on Design of Experiments (DOE), utilizing the results obtained from X-ray Photoelectron Spectroscopy (XPS). Subsequently, bonding was conducted at 260°C and 1.4 MPa for 1 hour. Following this, annealing was performed at 200°C for an additional hour. The bonding mechanism was analyzed through Transmission Electron Microscopy (TEM) analysis. Through this study, it is possible to understand the effect of O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> plasma on the Cu surface and its role in hybrid Cu bonding.