Ultrafast laser microwelding and joint performance of silicon-sapphire heterogeneous structure for microfluidic device packaging

In micro/nano sensor devices, integrated heterogeneous structures can determine the quality of devices packaging, and further affect their performance. For Silicon and sapphire, the heterogeneous joining technology that is flexible, environmentally friendly and suitable for large-scale materials integration is still lacking. In this paper, the welding feasibility of silicon-sapphire is explored by ultrafast laser transmission welding technology. When the gap between silicon and sapphire is less than 1 μm and the incident laser power is 7.5 W, sapphire and silicon at the heterogeneous junction can be fused with each other to form an interlocking area within width ~ 3 μm. Meanwhile, defects such as pores and cracks that could normally be introduced at the junction area during brittle materials welding have also been effectively suppressed. The joint strength measured by shear test is up to 2.9 MPa. The welding of silicon and sapphire by ultrafast laser provides an alternative for the heterogeneous interconnection of hard and brittle materials with large difference. This microwelding technology has thus shown great potential in microfluidic device packaging.