The specific contact resistivity of a metal-semiconductor ohmic contact can be determined in various ways and several of these use the transmission line model approach. Concentric circular contacts have circular equipotential and using this and the transmission line model equations for such contacts, a new technique for determining specific contact resistivity is presented. An analytical technique is used to determine the error of this structure and the developed analytical equations are presented. Finite-element modeling results for Al-SiC ohmic contacts are presented to validate the analytical equations. The scaling behavior of this structure is also discussed.
Low resistance contracts to highly doped silicon carbide (SiC) are investigated. Using a novel test structure that is easy to fabricate and easy to use, this paper demonstrates how it is used to reliably determine relatively low specific contact resistivities which vary with heat treatment. The test structure requires no error correction and is not affected by parasitic resistances. Using the test structure, small changes in specific contact resistivity are determined for small temperature changes. Results will be presented and discussed on the application of this novel test structure for nickel to highly doped SiC.
This paper proposes a method to determine the design of the Circular Transmission Line Model (CTLM) in order to ensure accurate results are obtained. The CTLM is used to measure the specific contact resistance of a metalsemiconductor barrier. Through analytical modelling it has been shown that the accuracy of the measurements obtained using a particular CTLM pattern, depends on the geometry chosen. By determining which geometries will yield the most sensitive measurement will ensure an accurate result when compared to the sheet resistance and specific contact resistance of an ohmic contact sample. Analysis of the equations reveals that for any given sample a smaller geometry is preferable. This is determined by comparing the differential of specific contact resistance of the sample with the contact end resistance of the test structure. It has been found that for confident results to be obtained then the annular (centre) ring of the structure should be as narrow as is possible within testing constraints.
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