Method for contact resistivity measurements on highly phosphorus-doped silicon using a multiline transmission line model

As the size of a transistor decreases, the parasitic resistances of the transistor become dominant for contact resistance. In-situ phosphorus-doped epitaxial silicon with high doping concentrations has been used to reduce contact resistivity. In this study, we measured the contact resistivity of in-situ phosphorus-doped silicon using a circular transmission line model (CTLM). The distribution of the contact resistivity for films with high phosphorus concentrations was found to be about 400 times larger than that for films with low phosphorus concentrations. To explain the large distribution of the measured contact resistivity, the potential distribution and current flow in phosphorus-doped silicon films with various phosphorus concentrations were simulated using the CTLM and a transmission line model (TLM). In silicon films with high phosphorus doping concentrations, the greater effects of metal resistance and the vertical current reduced the accuracy of the extracted contact resistivity. A multiline transmission line model (ML–TLM) was proposed to improve the accuracy of the extracted contact resistivity at a given phosphorous concentration. The use of the ML–TLM increased the ratio of the contact resistance to the total resistance; thus, the effect of metal resistance was significantly reduced, and the accuracy of contact resistivity was improved.