On the design of high performance spiral inductors for communication system in a package (CSIP)

This paper presents the fabrication and characterization of high performance spiral inductors with a magnetic core on glass substrates. The porous anodic aluminum oxide (AAO) membranes with average pore diameter of 70 nm and thickness of 18 μm were fabricated and electroplated with Ni to serve as a magnetic core for spiral inductors. The 3.5 turns spiral inductors were fabricated on Ni-AAO membranes by using standard photolithography and Cu electroplating processes. The fabricated spiral inductors has a dimension of 1370 μm × 1010 μm with 5μm thickness, 15 μm trace width, 15 μm spacing, 400 μm outer diameter, and 220 μm inner diameter. The RF characterization of spiral inductors was performed over a frequency range of 1 - 20 GHz. The inductance of spiral inductors with a magnetic core was measured to be 10.12 nH and enhanced 21% at 5 GHz compared to an air core of the same coil size. The quality factor of 14.48 was obtained at 5 GHz. The AAO template with ferromagnetic nanowires promises a great potential in serving as a magnetic core for fabrication of high performance spiral inductors for CSIP.