Enhancement of Bonding Strength between Cured Polymer Dielectrics and SiO₂ by Plasma Activation Treatment

Cu-Cu hybrid bonding will be applied to multi die-stacking devices. In these devices, the most important challenge is to lower Cu-Cu hybrid bonding process temperature from the standard process temperature (350–400 °C). The polymer adhesive can be pre-bonded to inorganic materials such as SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and SiCN at room temperature. By additional annealing process at 150°C or higher temperature, the permanent bonding can be obtained. In this paper, we investigate the effect of plasma activation treatment on polymer surfaces with respect to the bonding strength. The plasma treatment resulted in the polymer adhesive achieving bonding strengths at room temperature that surpassed those of SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>-SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> bonding. Additionally, the bonding strength was further enhanced by an annealing process at 150°C. To ensure precise measurement of bonding strength at room temperature, several methods were employed and reported in this study.