A Refined Ladder Transmission Line Model for the Extraction of Significantly Low Specific Contact Resistivity

Abstract

In this article, a refined ladder transmission line model (R-LTLM) test structure capable of extracting significantly low specific contact resistivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rho _{c}$ </tex-math></inline-formula> ) eliminating parasitic metal resistance is proposed. Theoretical derivations, technology computer-aided design (TCAD) simulations, and experiments are performed to verify the validity and superiority of R-LTLM. Compared with refined transmission line model (RTLM) and ladder transmission line model (LTLM), R-LTLM not only achieves higher extraction accuracy than RTLM but also relieves the impact of process variation during the formation of contact area patterns and contact spacings. Moreover, the impacts of process variation on the extraction of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rho _{c}$ </tex-math></inline-formula> using LTLM and R-LTLM are analyzed. As for experimental verification, RTLM, LTLM, and R-LTLM test structures are fabricated to extract <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rho _{c}$ </tex-math></inline-formula> of TiSix/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{n}^{+}$ </tex-math></inline-formula> -Si Ohmic contacts. Results show that R-LTLM can eliminate parasitic metal resistance, leading to higher extraction accuracy than RTLM.