Influence of (1 1 1) texture on bonding strength in low-temperature bonding of nanotwinned Ag films: Experimental insights and void closure modeling

Low-temperature bonding of nanotwinned (NT-) metals holds great potential for enhancing the performance and reliability of electronic interconnections. In this study, we performed low-temperature bonding of (1 1 1)-oriented nanotwinned silver (NT-Ag) films and thoroughly investigated the influence of (1 1 1) texture on the interfacial microstructure and bonding strength of the joints. The results demonstrated that high-quality bonding of highly (1 1 1)-oriented NT-Ag films was achieved even at 200 °C in air. The defect-free, coherent Ag(1 1 1)Ag(1 1 1) bonding interface was formed via face-to-face bonding of the highly (1 1 1)-oriented columnar grains. The shear strength of the joints significantly increased with the rise in (1 1 1) texture intensity. Moreover, we developed the void closure model to quantitatively elucidate the contribution of (1 1 1) texture to void closure and bonding ratio. Modeling results revealed that the (1 1 1) texture, with the highest surface diffusion coefficient, greatly increased the interfacial bonding ratio by accelerating surface source diffusion, thereby enabling high-strength bonding at low temperatures. The experimental validation and modeling results presented here contribute a novel perspective for optimizing interfacial microstructure and bonding strength by regulating the surface texture in the solid-state bonding of metals.