  This study investigates a high Q-factor spiral inductor fabricated by the
CMOS (complementary metal oxide semiconductor) process and a post-process. The
spiral inductor is manufactured on silicon substrate using the 0.35 micrometers
CMOS process. In order to reduce the substrate loss and enhance the Q-factor of
the inductor, silicon substrate under the inductor is removed using a
post-process. The post-process uses RIE (reactive ion etching) to etch the
sacrificial layer of silicon dioxide, and then TMAH (tetra methyl ammonium
hydroxide) is employed to remove the underlying silicon substrate and obtain
the suspended spiral inductor. The advantage of the post process is compatible
with the CMOS process. The Agilent 8510C network analyzer and a Cascade probe
station are used to measure the performances of the spiral inductor.
Experiments indicate that the spiral inductor has a Q-factor of 15 at 11 GHz,
an inductance of 4 nH at 25.5 GHz and a self-resonance frequency of about 27
GHz.
