Introduction
Mapping materials physical properties,
such as impedance, capacitance,
dielectric constants, dopant density,
etc., at the nanoscale is of great interest
to both materials and semiconductor
industries. Such mapping, however,
usually is not as straightforward as
topography imaging because, in many
cases, these properties are related to
buried structures not directly shown on
the surface. It takes innovative approaches
to “see through” and meanwhile achieve
suf? cient sensitivity and resolution.
With the invention of scanning tunneling
microscopy (STM) and atomic force
microscopy (AFM), a number of STM
and AFM based techniques have been
developed to probe materials properties.
These include scanning near-? eld to
scanning microwave microscopy (SMM),
scanning capacitance microscopy (SCM),
scanning spreading resistance microscopy
(SSRM), electrostatic force microscopy
(EFM), current-sensing (or conductive)
AFM (CSAFM), and Kelvin force
microscopy (KFM).
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?While each method
carries its own pros and cons, SMM
and SCM have shown most promising
potentials in this ? eld for both industrial
applications and scienti? c research.