3D IC Bonding via Dielectric Phase Transition for Stress Relief

The patent changes the physical state of dielectric materials by utilizing phase transitions during bonding. Specifically, it employs materials that undergo solid-to-liquid or solid-to-gas transitions at bonding temperatures, enabling stress relief while maintaining bonding strength. This parameter change resolves the contradiction by allowing high integration density through stacking while preventing bonding failure through stress-induced phase changes.

The patent directly applies phase transitions of dielectric materials during the bonding process. Materials such as benzocyclobutene (BCB) polymer undergo thermal decomposition and phase change at bonding temperatures, transforming from a rigid state to a more compliant state that can accommodate stress. This phase transition mechanism enables multiple dies to be stacked with high integration density while maintaining reliable bonding interfaces.

The patent utilizes temperature-dependent parameter changes in dielectric materials to resolve the stress-adhesion contradiction. By selecting materials whose mechanical properties (modulus, viscosity) change dramatically at bonding temperatures, the system achieves strong adhesion at room temperature while experiencing stress relief at elevated temperatures during the bonding process. This temporal separation of properties resolves the contradiction between adhesion and stress.

The patent employs composite dielectric structures combining multiple materials with complementary properties. For example, it uses combinations such as BCB polymer with specific glass transition temperatures, or layered structures of different dielectrics, where each material contributes different characteristics. This composite approach enables simultaneous achievement of strong adhesion and stress management by distributing mechanical loads across materials with different thermal and mechanical properties.

The patent exploits phase transitions that occur at bonding temperatures to convert the harmful effects of high temperature into beneficial stress relief. Materials like BCB polymer undergo thermal decomposition and viscosity changes at bonding temperatures (e.g., 250-350°C), transforming from a brittle state to a more ductile state that can accommodate thermal expansion mismatches and reduce stress concentration. This phase transition mechanism allows high bonding strength to be achieved without proportional increase in stress-induced damage.

The patent converts the potentially harmful thermal stress and material degradation at high bonding temperatures into beneficial effects. By carefully selecting dielectric materials with specific thermal decomposition characteristics, the patent transforms thermal stress that would normally cause damage into a mechanism for stress relief through phase change. The high temperature, which could cause damage, instead triggers material transformation that enhances bonding while reducing stress concentration at interfaces.