Correction factors for radial resistivity gradient evaluation of semiconductor slices

Accurate determinations of radial resistivity gradients on semiconductor slices, using the four-point probe, can be made only if correction factors for the finite boundary conditions are applied to the measurements. The off-center correction is different from the center correction. Both are necessary for gradient evaluation. These corrections were derived assuming homogeneous material, but are, nevertheless, useful approximations for nonhomogeneous materials. The corrections are given as generalized formulas and are graphed for the 62 and 25-mil probes for the center and 1/8-inch from the edge positions.