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

Abstract

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 (111)-oriented nanotwinned silver (NT-Ag) films and thoroughly investigated the influence of (111) texture on the interfacial microstructure and bonding strength of the joints. The results demonstrated that high-quality bonding of highly (111)-oriented NT-Ag films was achieved even at 200 °C in air. The defect-free, coherent Ag(111)Ag(111) bonding interface was formed via face-to-face bonding of the highly (111)-oriented columnar grains. The shear strength of the joints significantly increased with the rise in (111) texture intensity. Moreover, we developed the void closure model to quantitatively elucidate the contribution of (111) texture to void closure and bonding ratio. Modeling results revealed that the (111) 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.