A Vertical Combo Spacer to Optimize Electrothermal Characteristics of 7-nm Nanosheet Gate-All-Around Transistor
Renhua Liu, Xiaojin Li, Yabin Sun, Yanling Shi
Abstract
In this article, the impact of self-heating effect (SHE) on nanosheet gate-all-around (GAA) transistor with a vertical combo spacer and different underlap/overlap channels is studied by the 3-D TCAD simulation. To achieve high authoritative evidences, the I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sub> -V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">g</sub> characteristic with SHE is calibrated with the experimental data. First, the change of electrical characteristic introduced by different dielectrics of a single-k spacer is investigated, and the results show that the current of ON-state (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> ) is a power function of relative permittivity, whereas the OFF-state (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OFF</sub> ) exhibits a linear dependence. Second, a novel vertically wrapped combo spacer is proposed to achieve a compromise between thermal characteristic and electrical performance for the first time. The electrothermal characteristics of the combo spacer under different underlap/overlap channels are also studied, and the results showed that the combo spacer composed of inner Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> and outer HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> has the highest ION/IOFF but smaller thermal resistance and lower lattice temperature compared with other different combinations. At last, a CMOS inverter with Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> /HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> combo spacer is demonstrated for its improvement in propagation delay.