A Comparative Study of Parylene, PSPI and ALD TiO2/TiN/Ru/Cu Multilayer as Adhesion Layers on Glass Surface for Glass-Cu Adhesion Enhancement

Glass substrates exhibit great potential in 2.5D/3D advanced packaging, but poor interfacial adhesion with metal layers remains a critical challenge. This work studies three different adhesion layer strategies, namely Parylene-C, photosensitive polyimide (PSPI), and atomic layer deposition (ALD) TiO2/TiN/Ru/Cu multilayer, to improve glass-Cu adhesion. A 30 µm Cu layer was electroplated over glass-Parylene-Ti/Cu, glass-PSPI-Ti/Cu, and glass-TiO2/TiN/Ru/Cu multilayer stacks. The 90° peel test results show that, at the layer thicknesses investigated here, all three strategies increase the glass-Cu peel resistance (approximately 6.5 to 10 times) compared with the conventional glass-PVD Ti/Cu control group (0.62 ± 0.06 N/cm). Parylene-C achieves the highest adhesion strength of 6.25 ± 0.03 N/cm, which is 31.9% higher than the ALD multilayer (4.74 ± 0.28 N/cm) and 55.5% higher than the PSPI (4.02 ± 0.10 N/cm). The adhesion enhancement mechanisms are analyzed, and the comprehensive performance of the three strategies is compared over multiple aspects. Overall, this work provides three practical solutions to improve the glass-Cu adhesion.