Ultrafast laser welding of silicon

TL;DR

This paper presents a novel ultrafast laser welding method for silicon that uses metallic nanolayers to enhance absorption, enabling strong, efficient bonds suitable for microelectronics and optics.

Contribution

It introduces a technique combining nanolayer-enhanced absorption and filament relocation to overcome nonlinear effects in silicon welding.

Findings

Shear strengths >4 MPa achieved with 21-nm gold nanolayers

No laser-induced transmittance alteration in silicon

Effective bonding demonstrated for microelectronics applications

Abstract

While ultrafast laser welding is an appealing technique for bonding transparent workpieces, it is not applicable for joining silicon samples due to nonlinear propagation effects which dramatically diminishes the possible energy deposition at the interface. We demonstrate that these limitations can be circumvented by local absorption enhancement at the interface thanks to metallic nanolayer deposition. By combining the resulting exalted absorption with filament relocation during ultrafast laser irradiation, silicon samples can be efficiently joined. Shear joining strengths >4 MPa are obtained for 21-nm gold nanolayers without laser-induced alteration of the transmittance. Such remarkable strength values hold promises for applications in microelectronics, optics, and astronomy.