Accurate microfour-point probe sheet resistance measurements on small samples

We show that accurate sheet resistance measurements on small samples may be performed using microfour-point probes without applying correction factors. Using dual configuration measurements, the sheet resistance may be extracted with high accuracy when the microfour-point probes are in proximity of a mirror plane on small samples with dimensions of a few times the probe pitch. We calculate theoretically the size of the “sweet spot,” where sufficiently accurate sheet resistances result and show that even for very small samples it is feasible to do correction free extraction of the sheet resistance with sufficient accuracy. As an example, the sheet resistance of a 40 μm (50 μm) square sample may be characterized with an accuracy of 0.3% (0.1%) using a 10 μm pitch microfour-point probe and assuming a probe alignment accuracy of ±2.5 μm.