Numerical simulation of the vertical Kelvin test structure for specific contact resistivity

Abstract

The vertical Kelvin test structure for the measurement of the specific contact resistivity, ρ C, is numercially investigated by employing a 2-D model. The study is concentrated on three effects, i.e. the current spreading effect, the misalignment effect, and the lateral diffusion and depletion width effect, which affect the accuracy to derive ρ C for this test structure. It is found that the current spreading effect is small as compared to the lateral current crowding effect in the conventional horizontal type of Kelvin test structure. It can be reduced to minimum if the junction depth of the implanted conducting bar is chosen to, for an example, less than 0.15 μm. The misalignment effect is more significant in producing errors in measuring ρ C. However, the study shows that this effect can be cancelled in first order by taking average readings sensed at the left arm and the right arm of the implanted conducting bar for the misalignment δ < 0.2 μm. The lateral diffusion and depletion width effect, although is larger than the current spreading effect and smaller than the misalignment effect, can cancel the error caused by the current spreading effect to some extent. Overall, the study shows that the vertical Kelvin test structure can give the most accurate specific contact resistivity measurement.