Interfacial engineering with a low-k organic buffer layer for Cu metallization of through-glass vias in glass core substrates

Reliable Cu metallization remains a major challenge in through-glass via (TGV) technology because of the poor adhesion between glass and Cu and the coefficient of thermal expansion (CTE) mismatch between the two materials. Here, we report a low-k organic buffer layer integrated into TGV glass core substrates through O₂ plasma treatment, film lamination, and post-curing while preserving via openness without additional re-drilling. The low-k buffer film exhibited multi-stage curing behavior, enabling conformal buffer layer formation along the TGV sidewall while preventing via plugging. The film showed a dielectric constant of 2.384 and a dielectric loss of 2.57 × 10⁻³ at 28 GHz. O₂ plasma treatment increased the average peel strength from 0.327 ± 0.008 N/mm to 0.675 ± 0.011 N/mm (mean ± SD, n = 3), and continuous electroless Cu seed deposition followed by complete Cu electroplating was achieved throughout the TGV structure. The metallized TGV structure demonstrated stable adhesion retention after 500 thermal shock cycles between − 40 °C and 125 °C under the conditions investigated in this study. HFSS electromagnetic simulations predicted reduced insertion loss, improved impedance matching, enhanced electric-field confinement, and reduced near-end and far-end crosstalk. These results suggest that the proposed low-k buffer layer provides a practical interfacial engineering strategy for Cu metallization in TGV glass core substrates while maintaining stable adhesion under thermal shock conditions and has the potential to enhance high-frequency electrical performance.