Analytical and Finite-Element Modeling of a Cross Kelvin Resistor Test Structure for Low Specific Contact Resistivity

Various test structures have been employed to determine the specific contact resistivity (rhoc) of ohmic contacts, and cross Kelvin resistor (CKR) test structures are most suitable for estimating low rhoc values. The value determined by CKRs includes error due to parasitic resistances that have been difficult to account for when rhoc is low (< 10^-7 Omega ldr cm²). In this paper, an analytical technique for determining the error in measurements from CKR test structures is presented. The analytical model described for circular contacts is based on Bessel function expressions. Using several contacts of different diameter (d) with d/w les 0.4 (w is the width of the CKR arms), the parasitic resistance can be accurately accounted for by extrapolation of experimental data to d/w rarr 0. Finite-element modeling and experimental results for metal-to-silicide contacts are used to validate the analytical expressions presented.