Scaling Challenges of Nanosheet Field-Effect Transistors Into Sub-2 nm Nodes

Abstract

The scaling of nanosheet (NS) field effect transistors (FETs) from the 12 nm gate length to the ultimate gate length of 10 nm for sub-2 nm nodes brings additional technological challenges. Here, 3D finite element Monte Carlo simulations are employed to explore how to alter the NS architecture to increase the drive current (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{\mathrm {\mathbf { DD}}}$ </tex-math></inline-formula>) because the gate scaling to 10 nm results in a decline of the current (by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {10.7}$ </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">${I}_{\mathrm {\mathbf {DD}}}$ </tex-math></inline-formula> of the 10 nm gate length NS FET will increase by 11% if the maximum n-type source/drain doping reaches <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times 10^{20} \mathrm {cm^{-3}}$ </tex-math></inline-formula>, or increase by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {3.8}$ </tex-math></inline-formula>% if the high-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\kappa $ </tex-math></inline-formula> dielectric layer equivalent oxide thickness (EOT) is less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {1.0}$ </tex-math></inline-formula> nm. The reduction in the channel width below 40 nm or the reduction in the channel thickness below 5 nm will substantially decrease IDD. The sub-threshold figures of merit like the sub-threshold slope (SS) will decrease from 75 to 73 mV/dec, while the drain-induced barrier lowering (DIBL) will increase from 32 to 77 mV/V. Finally, the effect of strain to increase the drive current is strongly limited by quantum confinement. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{\mathrm {\mathbf {DD}}}$ </tex-math></inline-formula> will increase by 3% and by 14% in the 10 nm gate NS FET with the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\langle 110\rangle $ </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">$\langle 100\rangle $ </tex-math></inline-formula> channel orientations, respectively, when a strain of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {0.5}$ </tex-math></inline-formula>% is applied to the channel, with a negligible increase for larger strain values (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathbf {0.7}$ </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">$\mathbf {1.0}$ </tex-math></inline-formula>%).