Scalable Manufacturing of Multi-Stacked Copper Spiral Inductors Using a Novel Fully Additive Method

This study reports, for the first time, the fully additive fabrication of miniaturized, embedded triple-stacked copper spiral inductors—an unprecedented achievement in multilayer inductor manufacturing. Using our novel Sequential Build-Up–Covalent Bonded Metallization (SBU–CBM) method, we demonstrate a etch-free, room-temperature process capable of producing complex 3D inductor architectures with sub-10 μm features and high vertical integration. Unlike conventional additive, subtractive or hybrid subtractive–additive techniques, the SBU–CBM method enables high-resolution laser-defined patterning, selective electroless copper deposition, and accurate optical alignment— eliminating the need for vacuum systems, chemical etching, or thermal sintering. The successful fabrication of three vertically interconnected spiral inductors through 10 μm copper microvias confirms the method’s unmatched capability in fabricating intricate multilayer geometries through a fully additive process. Optical microscopy and X-ray Computed Tomography (XCT) imaging validates the structural integrity, precise interlayer alignment, and continuous electrical connectivity across all layers. Critically, the method achieves uniform miniaturized copper strip widths of 10 μm, underscoring its strength in high-density packaging and next-generation integrated systems. This breakthrough establishes SBU–CBM as a transformative approach for realizing compact, high-performance, and scalable 3D embedded components in future electronic applications.