Statistical modeling of transmission line model test structures. II. TLM test structure with four or more terminals: a novel method to characterize nonideal planar contacts in presence of inhomogeneities

For pt.I see ibid., vol.37, pp.2350-2360, Nov. 1990. A modified transmission line model (redundant TLM or RTLM) test structure (with four or more terminals) and a novel data extraction method are suggested to improve the accuracy of the TLM method. Statistical modeling by both statistical simulation and the method of error propagation shows that with four terminals and independently known sheet resistances between the contacts, the errors of the extracted parameters can be reduced considerably. With the use of five or more terminals, the accuracy of the parameter extraction can also be determined by a single structure, allowing the separation of inhomogeneities within a test structure from the inhomogeneities over the wafer. Experimental data gathered by Kelvin cross-bridge resistors and by traditional and modified transmission line model structures on Al-Si-Cu/TiW/p-n Si contacts clearly show the advantage of the RTLM method over the traditional TLM method. On a wafer with small inhomogeneities, both methods gave consistent results