Metal Nanoparticles Assisted Ultrafast Laser Plasmonic Microwelding of Oxide-Semiconductor Interconnects.

Integration of wafer-scale oxide and semiconductor materials meets the difficulties of residual stress and materials incompatibility. In this work, Ag NPs thin film is contributed as an energy confinement layer between oxide (Sapphire) and semiconductor (Si) wafers to localize the materials interaction during ultrafast laser irradiation. Due to the plasmonic effects generated within constructed dielectric-metal-dielectric structures (i.e., Sapphire-Ag-Si), thermal diffusion and chemical reaction between Ag and its neighboring materials facilitate the microwelding of Sapphire and Si wafers. Ag NPs can be totally sintered within the junction area to bridge oxide and semiconductor, while Al─O─Ag bond and Ag─Si bond are formed at Ag-Sapphire and Ag─Si interfaces, respectively. As-received heterogeneous joint exhibits a high shear strength up to 5.4 MPa, with the fracture occurring inside Si wafer. Meanwhile, insertion of metal nanolayer can greatly relieve the residual stress-induced microcracking inside the brittle materials. Such wafer-scale Sapphire and Si interconnects thus show robust strength and excellent impermeability even after thermal shocking (-40 °C to 120 °C) for 200 cycles. This metal NPs layer-assisted plasmonic microwelding technology can extend to broad materials integration, which is promising for high-performance microdevices development in MEMS, MOEMS, or microfluidics.