  Resistivity is one of the most important characteristics in the semiconductor
industry. The most common way to measure resistivity is the four-point probe
method, which requires physical contact with the material under test. Terahertz
time domain spectroscopy, a fast and non-destructive measurement method, is
already well established in the characterization of dielectrics. In this work,
we demonstrate the potential of two Drude model-based approaches to extract
resistivity values from terahertz time-domain spectroscopy measurements of
silicon in a wide range from about 10$^{-3}$ $\Omega$cm to 10$^{2}$ $\Omega$cm.
One method is an analytical approach and the other is an optimization approach.
Four-point probe measurements are used as a reference. In addition, the spatial
resistivity distribution is imaged by X-Y scanning of the samples to detect
inhomogeneities in the doping distribution.
