Microstructure Optimization of Magnetron-Sputtered Silver Films for Low-Temperature Interconnection

The capacity for low-temperature interconnection of metal films correlates closely with their microstructure. Optimizing the microstructure of deposited metal films is crucial for achieving the desired low-temperature interconnection characteristic. In this paper, the effects of sputtering power on the microstructure of silver (Ag) films prepared using magnetron sputtering technology were investigated. The results demonstrated that variations in sputtering powers led to significantly distinct microstructures, including surface morphology, texture, and grain size. Specifically, with the increase of sputtering power, the microstructure of as-deposited Ag films evolved from randomly oriented nanocrystalline grains to (111)-preferred-oriented columnar grains with high-density twins, and eventually to equiaxed micron-sized grains displaying strong (111) out-of-plane texture. Furthermore, property testing results showed that nanotwinned Ag films displayed an exceptional combination of hardness and electrical conductivity, presenting great potential as promising low-temperature bonding materials. Lower sputtering powers effectively prevent grain coarsening during film thickening, making them preferable for depositing Ag films used in low-temperature interconnections.