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 (¿_c) have been extensively discussed during last few decades and the minimum of the ¿_c 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 ¿_c 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.