An Improved Methodology for Accurate Extraction of Ultra-Low Specific Contact Resistivity of Alloyed Contacts Using Nanoscale Transmission Line Method
An effective transfer length (ETL) model is developed to accurately extract the specific contact resistivity <inline-formula> <tex-math notation="LaTeX">$\rho _{c}$ </tex-math></inline-formula> for alloyed or recessed contacts by accounting for the modification of sheet resistance of semiconductor under the contact (<inline-formula> <tex-math notation="LaTeX">${R}_{{\textit {shc}}}$ </tex-math></inline-formula>) and uneven contact interface due to the reaction of the contact metal and the semiconductor. This method is applied to an example where the formation of NiGeSn extends into p<sup>+</sup>-Ge<sub>0.95</sub>Sn<sub>0.05</sub> region to form a recessed contact structure. An ultra-low <inline-formula> <tex-math notation="LaTeX">$\rho _{c}$ </tex-math></inline-formula> of <inline-formula> <tex-math notation="LaTeX">$\textsf {2.6}\pm \textsf {0.2}\times \textsf {10}^{-9} \Omega $ </tex-math></inline-formula>-cm<inline-formula> <tex-math notation="LaTeX">$^{\textsf {2}}$ </tex-math></inline-formula> is extracted by the ETL model, which is consistent with <inline-formula> <tex-math notation="LaTeX">$\rho _{c}$ </tex-math></inline-formula> of <inline-formula> <tex-math notation="LaTeX">$\textsf {2.9}\times \textsf {10}^{\textsf {-9}} \Omega $ </tex-math></inline-formula>-cm<inline-formula> <tex-math notation="LaTeX">$^{\textsf {2}}$ </tex-math></inline-formula> extracted by the two-layer resistive-network model. The conventional nano-scale transmission line method extracted a <inline-formula> <tex-math notation="LaTeX">$\rho _{c}$ </tex-math></inline-formula>, that is, ~86% higher, which is due to an underestimated <inline-formula> <tex-math notation="LaTeX">${R}_{{\textit {shc}}}$ </tex-math></inline-formula>. The proposed ETL model can be generally used for <inline-formula> <tex-math notation="LaTeX">$\rho _{c}$ </tex-math></inline-formula> extraction in any alloyed or recessed contacts.