Guidelines for symmetric threshold voltage in tunnel FinFETs with single and dual metal gate electrodes

Abstract

We report guidelines for symmetric threshold voltage (V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> ) in double gate (DG) tunnel FinFETs (tFinFETs) with single and dual metal gate electrodes. To realize the symmetric V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> =±0.2V, the work function difference (ΔΦ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> ) of each gate electrode in n- and p-type tFinFETs with a nondoped Si channel must be 1.34 eV, indicating that tuning the effective work functions in the dual metal gates is difficult. By adding Ge in the channel, the work function required in Ge-channel p-tFinFETs can be reduced to 4.46 eV, furthermore, ΔΦ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</sub> required to realize a symmetric V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> in n- and p-type tFinFETs can be as small as the minimum value of 0.28 e V. This result means that a symmetric V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> is realized in realistic dual metal gate materials by adding Ge. By using our independent DG tFinFETs with a novel source profile, a symmetric V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> can be realized in a single metal gate in a Ge channel.