A Novel Fast-Turn-Around Ladder TLM Methodology with Parasitic Metal Resistance Elimination, and 2×10−10 Ω-cm2Resolution: Theoretical Design and Experimental Demonstration

A novel ladder transmission line method (LTLM) that features eliminated parasitic resistance from contact metal and access electrodes, simple fabrication process, and $2\times 10^{-10}\Omega-\text{cm}^{2}$ resolution for highly-accurate extraction of specific contact resistivity $(\rho_{c})$ in the $\sim 10^{-10}$ to 10⁻⁹$\Omega-\text{cm}^{2}$ regime is demonstrated. The current distribution and extraction of $\rho_{c}\text{ln}$ LTLM are verified by TCAD and numerical distributive-resistor-network method, respectively. The extraction error caused by the current spreading and crowding in LTLM are modeled, and design guidelines to achieve 10⁻¹⁰$\Omega-\text{cm}^{2}$ resolution for $\rho_{c}$ extraction are provided. By applying LTLM to the Ni/p⁺-Ge0.95Sn0.05 contact, a record-low $\rho_{c}$ down to $4.0\pm 2.0\times 10^{-10}\Omega-\text{cm}^{2}$ was obtained. LTLM is insensitive to variation of metal resistance, unlike the refined TLM (RTLM) which could overestimate $\rho_{c}$ by at least tens of times.