Comprehensive Analysis and Application of Laser Bonding Technology for Glass-Based Integrated Sensors

The laser bonding technology, characterized by low-temperature operation, cost-effectiveness, and high efficiency, progressively found application in glass-based integrated sensors. This study delved into the intricacies of elemental diffusion processes during laser bonding while offering a detailed analysis of the bonding mechanism. Bonding is a diffusion-dependent process. When the laser penetrates the upper glass layer and focuses on the bonding interface, the Si in the glass and the Ti in the metal layer diffuse to the bonding interface to form a Ti-Si covalent structure, thus realizing the bonding process. Crucially, the abundance of formed TiSi2 emerged as a critical determinant of bonding quality. To enhance bonding quality, this study systematically examined the relative content of TiSi2 and tensile strengths across varied laser power (LP), bonding speed (BS), and spot spacing (SS) parameters. Optimal conditions were identified, with peak relative TiSi2 content observed at an LP of 50 W, a BS of 233 mm/ s, and an SS of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5~\mu $ </tex-math></inline-formula>m, yielding a tensile strength of 15.6 MPa. Furthermore, the effects of different contact pressures, metal layer thicknesses, and focal lengths on the bonding quality were investigated, revealing the relationship between bond strength and Ti layer thickness, contact pressure, and focal length. To validate the potential of laser bonding technology in 3-D glass sensors, this study pioneered the establishment of an HFSS simulation model for a CPW-TGVs-CPW-TGVs-CPW double-layer vertical interconnect structure and fabricated experimental samples on double-layer glass interposers using the laser bonding technology. The measured results agreed with the simulation results, and the interconnect loss was below −1.2 dB in the 40 GHz range.