Cross-Bridge Kelvin resistor structures for reliable measurement of low contact resistances and contact interface characterization

The parasitic factors that strongly influence the measurement accuracy of Cross-Bridge Kelvin Resistor (CBKR) structures for low specific contact resistances (ρc) have been extensively discussed during last few decades and the minimum of the ρc value, which could be accurately extracted, was estimated. We fabricated a set of various metal-to-metal CBKR structures with different geometries, i.e., shapes and dimensions, to confirm this limit experimentally and to create a method for contact metal-to-metal interface characterization. As a result, a model was developed to account for the actual current flow and a method for reliable ρc extraction was created. This method allowed to characterize metal-to-metal contact interface. It was found that in the case of ideal metal-to-metal contacts, the measured CBKR contact resistance was determined by the dimensions of the two-metal stack in the area of contact and sheet resistances of the metals used.