Contact resistance measurements of a MOSFET

The paper examines in detail a recent technique for measuring contact resistance of a MOSFET. It is observed that the equations used for determining the contact resistance based on the ‘diode’ mode and the ‘MOSFET’ mode differ by a constant factor depending on the device geometry in the limit when the sheet resistance dominates. Ideally, the ratio of the probe voltage/drain current (Vm/I) is independent of the drain current and always higher for the MOSFET mode. In the measurement of a conventional MOSFET we observe a current-dependent Vm/I. This could be explained by the presence of a depletion region near the voltage probe. A word of caution is given with regard to the effects of leakage in the oxide side-wall for a smallgeometry MOSFET.