Development and characterization of low temperature Cu-dielectric hybrid bonding

Cu-dielectric hybrid bonding is a technology that enables the assembly of components with very fine interconnection pitch, opening the path to new integrations for advanced applications such as High Performance Computing, Smart Imagers,… Leti has been engaged for more than 10 years in the development of this technology, in partnership with various industries and academies, to master smaller and smaller connection pitches (< 1µm), or to evaluate new techniques such as ‘die-to-wafer’ self-assembly. In this context, low temperature hybrid bonding would allow new integration routes notably for heterogeneous systems (III-V on CMOS,…) or for thermally sensitive components (colored resins, non-volatile memories,…). The objective of this thesis is to develop and characterize Cu-dielectric hybrid assemblies performed at low temperature, from ambient to 250°C. A first part of the thesis will aim at identifying the dielectric materials that are relevant for the hybrid bonding technology (SiN, SiON, SiCN, …). The critical properties of these materials (permittivity, hygroscopy,…) will be measured and compared to the reference high temperature SiO2. In a second part, the selected dielectrics will be integrated in the ‘wafer-to-wafer’ hybrid bonding technology and each process step (damascene level, surface preparation, direct bonding) will be adapted as needed. The third part of the thesis will be dedicated to the electrical characterization and reliability tests of the obtained low temperature hybrid bonding.