POST-CMOS INTEGRATED PLANAR INDUCTORS FOR MONOLITHIC POWER MANAGEMENT CHIPS

摘要

The large demand for fabrication of magnetic-based microsystems such as on-chip DC/DC power converters can be satisfied using microinductors as basic magnetic components. In this paper, a scheme of encapsulated spiral microinductors (3.5mm X 4mm) is described using a fully-integratable post-CMOS fabrication process. The microinductor is composed of a copper spiral conductor sandwiched between two layers of a magnetic alloy. This structure is placed on the surface of a silicon wafer that already features power electronics. Via openings in the top magnetic layer allow connection between the CMOS power circuit and the micromagnetic components. The thick electroplated Cu spiral windings have low resistance (～0.18Ω), and the inductors with inductance up to 360 nH, are suitable for high power applications. The electroplated magnetic core is made of a Fe-Co-based alloy, which shows high resistivity (125 μΩ* cm), high saturation magnetization (1.7 T), and a low coercivity (0.2 Oe).