Characterization of the glass–silicon interface produced by ultrafast laser welding

We report a direct fabrication approach for welding crystalline silicon wafers and quartz glass via ultrafast picosecond laser welding. By optimizing the laser parameters, robust joints with a shear strength of 26.6 ± 1.2 MPa were achieved. SEM and EDS examination of the silicon-side fracture surface revealed an 85 nm-thick modified layer containing Si and O, with 50.48 at.% Si and 49.52 at.% O in the selected analysis area. The observed elemental redistribution may be associated with plasma generation, electric-field-assisted oxygen migration, and enhanced silicon reactivity. Ultrafast laser welding thus offers a scalable, clean, and precise route for the fabrication of glass–silicon heterostructures for glass–silicon integration and microdevice fabrication.