Investigation of Plasma Treatment and Bonding Parameters in Cu/SiO₂ Hybrid Bonding

Moore's Law has been slowing down as conventional transistor scaling to improve chip speed becomes ever more challenging. Semiconductor industries are seeking the solution in advanced packaging technologies, for example, heterogeneous integration and hybrid bonding. Hybrid bonding enables simultaneous bonding of metal and insulating layers, providing a fine-pitch interconnection to improve integration density and system performance. This study focuses on plasma treatment and bonding parameters in terms of the bond strength of the Cu/SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> hybrid bonding interface. The oxygen, nitrogen, and forming gas plasma treatments were used to induce oxide bonding. SEM, AFM, and contact angle measurements were used to assess the surface features and bonding quality. Additionally, bonding quality and strength were evaluated using SEM, SAM, and pull tests. The bonding strength evaluation showed that applying pressure during either initial bonding or subsequent annealing stage significantly enhanced the bond area and bond strength. Regarding copper bonding, XPS analysis verified that the Cu surface underwent oxidation during the O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> plasma treatment. However, the NH<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf>OH treatment successfully reduced CuO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> levels.