Parametric Investigation of Surface Morphology in Through Glass Vias(TGVs) Fabricated via Femtosecond Laser Processing

2.5D packaging integrates chips with diverse functionalities using an interposer substrate, enabling high-density interconnection and shorter interconnection length, making it ideal for electronic devices, high performance computing (HPC), and internet of things (IoT). Glass has emerged as a promising material for interposers due to its low dielectric constant, high dimensional stability, and adjustable coefficient of thermal expansion (CTE). Femtosecond pulse laser is highly suitable for micromachining brittle materials like glass, as its ultrashort pulse duration minimizes thermal effects during through glass vias (TGVs) processing. However, laser-induced periodic surface structures (LIPSS) formed on sidewall of the via during processing can adversely affect reliability after plating. Therefore, in this study, we investigate the surface morphology that changes with the number of pulses of laser and propose a burst mode approach to suppress LIPSS formation and improve TGVs quality.