Research on Low-Temperature Thermocompression Bonding of Glass Substrates Assisted by Nano Titanium Passivation Layer

Abstract

Low-temperature Cu–Cu bonding is critical for glass-based 3-D advanced packaging, as conventional high-temperature processes induce severe thermal stress via CTE mismatch. This work investigates Ti-passivation-assisted low-temperature Cu–Cu bonding through molecular dynamics (MDs) simulations and experimental characterization. The results reveal that the Ti layer spontaneously undergoes solid-state amorphization (SSAR) under coupled thermodynamic and kinetic effects: negative Cu–Ti mixing enthalpy drives intermixing, while rapid asymmetric interstitial diffusion of small Cu atoms induces lattice distortion and structural collapse. The resulting amorphous layer acts as an ultrafast diffusion channel with reduced activation energy, enabling dense bonding at $200~^{\circ }$ C with >90% wafer-level effective area and 16 MPa tensile strength. Failure occurs at the glass/Ti film–substrate interface rather than the bonded Cu–Cu interface. These findings provide mechanistic insights and a viable pathway for reliable multilayer glass stacking in high-performance 3-D packaging.