| Summary: | This report pertains to miniature inductors for integrated switched-mode inductive DC-DC
converters applications. Conventional inductive DC-DC converters generally employ
external discrete inductor components that are bulky and expensive, thereby increasing the
overall form-factor (size) and cost. On the other hand, current-art integrated inductive DC DC converters integrate the inductors as in-package or on-chip components to decrease the
form-factor and cost.
This report investigates state-of-the-art on-chip integrated inductors that are fabricated with
microelectromechanical system (MEMS) technology. Compared to conventional on-chip
inductors realized using CMOS technology, MEMS inductors can achieve higher quality factor
and higher inductance required for integrated DC-DC converters, and they are also relatively
easy to integrate with the on-chip CMOS circuitries.
There are three pertinent aspects pertaining to MEMS integrated inductors that are reviewed
comprehensively in this report: one is the established MEMS fabrication processes; two is the
magnetic cores of the inductors; three is the structures of the inductors. On the fabrication
processes, this report reviews two well-established processes—the bulk and the surface
micromachining. On the magnetic cores, this report reviews the core materials and their
effects on the magnetic losses. On the structures, this report reviews three conventional and
state-of-the-art structures—the 2D planar, the 3D on-sub, and the in-sub TSV.
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