Geometrical correction factors for finite-size probe tips in microscopic four-point-probe resistivity measurements

The sheet resistance of thin film structures is commonly measured using a four-point-probe setup and involves the application of geometrical correction factors depending on the sample geometry and electrode pitch. The characterization of small thin film structures in the micrometer range requires probe tip diameters and spacings that are of similar size. An experimental realization with micro-manipulators is possible as tip distances in a range of a few micrometers can be achieved. However, such a setup requires an additional correction factor accounting for the finite probe tip contact area. Neglecting such a correction leads to an underestimation of the sheet resistance when the electrode pitch is comparable to the probe contact area diameter. Based on numerical simulation results, we develop a simplified method applying a new phenomenological correction scheme which takes into account the finite contact area size for small probe distances. This method can be applied directly without any additional numerical simulations and corrects the underestimation due to the probe tip size significantly.