Enhanced Inductors and Balun Transformers Performance for 5G-6G Applications with Patterned Magnetic Materials Using Special Rinse Solution

In the realm of 5G-6G communication device applications with high-frequency requirements, planar inductors and balun transformers were crucial passive components in low-height wafer-level packaging. Previous studies by the authors had demonstrated that the patterning magnetic material around balun transformers and inductors significantly enhanced electromagnetic shielding and increased inductance while reducing coil size by 45%, as calculated via COMSOL® simulation. To create these patterned magnetic materials, the authors investigated i-line photosensitive magnetic materials that could be developed using a conventional aqueous alkaline developer suitable for wafer processing. These i-line sensitive negative tone magnetic materials were formulated with an aqueous alkaline-soluble polymer, crosslinker, photo-initiator, and magnetic particles dispersed in an organic solvent. Lithographic performance was demonstrated using the USHIO UV exposure system with contact mask printing, successfully forming 200 µm lines and spaces and 300 µm contact holes. However, defect issues were found due to the high specific gravity of the magnetic particles, which led to particle residue at the bottom of contact holes and substrates during the aqueous development process. To address this patterning defect, the authors were investigating new rinse solutions that could solve the residue problem without compromising lithographic performance.