A Novel Method for Bonding of Dielectric in 3D Integration Packaging Using Area-Selective Self-Assembled Monolayer

Recently, due to the limitation of scaling down technology in semiconductor devices, advanced packaging technology for 3D stacking using hybrid bonding, which enables heterogeneous device packaging, is becoming increasingly important. One of the representative hybrid bonding technologies is surface activation bonding using plasma. This method facilitates bonding by rendering the dielectric surface hydrophilic through plasma treatment. However, surface plasma treatment may cause oxidation of the copper(Cu) metal pad, degrading bonding reliability. Moreover, as the Cu pad becomes increasingly sub-μm fine pitch, the transfer of Cu particles generated by re-sputtering to the dielectric raises concerns about potential short circuits failure issues. Therefore, a method to activate the dielectric surface without plasma was devised, and we found that surface activation bonding between dielectrics without plasma is possible using self-assembled monolayers(SAMs), which can be selectively aligned in a specific region to obtain the desired surface characteristics.<br/>In this study, among the silane-based SAMs that can be deposited on the surface of silicon dioxide(SiO2), which is a representative dielectric material, APTES(3-aminopropyltriethoxysilane) with an amine group(NH2), a hydrophilic functional group that can activate the surface, was deposited through the solution dipping method. The spontaneous alignment of SAMs on the SiO2 surface was confirmed through FT-IR, AFM, and XPS analysis, and an increase in the surface energy of SiO2 was verified through Contact Angle analysis. Interestingly, we observed that the interfacial adhesion strength increased by subsequent heat treatment after bonding. This appears to be due to the formation of an amorphous Si layer at the interface by subsequent heat treatment after bonding at room temperature through hydrogen bonding. Consequently, this SAM bonding technology, which can selectively activate the insulator surface in specific regions, is expected to be applicable to fine-pitch hybrid bonding technology in the near future.