Significance of Work Function Fluctuations in SiGe/Si Hetero-Nanosheet Tunnel-FET at Sub-3 nm Nodes
Narasimhulu Thoti, Yiming Li, Wen-Li Sung
Abstract
This work highlights the work-function-fluctuation (WKF) of the strained Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.6</sub> Ge <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.4</sub> p-n-p-n tunneling field-effect transistor (TFET) using nanosheet geometry at sub-3 nm technology nodes. The reported work exploits 3000 samples to signify the key results of several dc factors such as ON- and OFF-state currents ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{ \mathrm{\scriptscriptstyle ON}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{ \mathrm{\scriptscriptstyle OFF}}$ </tex-math></inline-formula> ), threshold voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {th}}$ </tex-math></inline-formula> ), and the subthreshold swing (SS). Fewer WKFs are identified for higher metal grain number (MGN) due to the shaped low grain size. Collective average energy reduction of 10–15 meV as low with high MGN and 40–60 meV as high with low MGN for a group of metal-grains closer to the tunneling junction is observed. This huge impact of energy reduction proportionally affects electron transport due to reduction in tunneling length. High variability in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {th}}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\geq {15}$ </tex-math></inline-formula> %) is identified at progressively diminished MGN due to parabolic behavior of variation. Furthermore, marginal variation in SS, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{ \mathrm{\scriptscriptstyle ON}}$ </tex-math></inline-formula> , and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{ \mathrm{\scriptscriptstyle OFF}}$ </tex-math></inline-formula> are observed because of the WKF dependability over the subthreshold region of operation.