Wafer-Level Fabrication of On-Chip Single/Double Layer Rectangular Spiral Inductors for Implantable Biosensors

This study presents the wafer-level fabrication of on-chip single/double layer rectangular spiral inductors using MEMS processes and micro-casting technology, achieving enhanced performance through high-thickness metal layers. The double layer inductor demonstrates a 1.46 μH inductance with a compact 42 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> footprint and high integration density of 34.8 nH/mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>, representing 20% inductance density improvement and 39.3% quality factor enhancement compared to single layer designs. With a self-resonant frequency exceeding 20MHz, these inductors effectively support low-frequency operations (sub-20MHz) required for implantable biosensor inductive links. The wafer-level micro-casting technique enables on-chip inductor coil integration, highlighting the potential for miniaturized biomedical microsystem applications demanding high-efficiency wireless power transfer and data transmission.