Stacked Channel Transistors with 2D Materials: An Integration Perspective
Yun-Yan Chung, Bo-Jhih Chou, Wei‐Sheng Yun, Chen-Feng Hsu, Shao-Ming Yu, Yu-I Chang, Chen‐Yi Lee, Sui-An Chou, Po‐Hsun Ho, Aslan Wei, D. Mahaveer Sathaiya, Bo-Heng Liu, Chien-Wei Chen, Chien-Ying Su, Chi‐Chung Kei, Fu-Kuo Hsueh, Tuo‐Hung Hou, Wen‐Hao Chang, Jin Cai, Chung-Cheng Wu, Jeff Wu, Wei‐Yen Woon, Tung-Ying Lee, Chao-Hsin Chien, Chao-Ching Cheng, Iuliana Radu
Abstract
This report presents the first electrical demonstration of a stacked nanosheet (NS) FET with a monolayer MoS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> channel, utilizing a typical nanosheet release process prior to high- <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\kappa$</tex> metal gate deposition. We demonstrate the fabrication of flat, two-stacked nanosheets with a monolayer MoS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> channel and a conformal <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{HfO}_{\mathrm{X}}/\text{TiN}$</tex> gate stack. The stacked nanosheets exhibit good release behavior, allowing for an integration scheme that supports gate lengths of up to 250 nm. <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{I}_{\text{MAX}}/\mathbf{I}_{\text{MIN}}$</tex> ratios of ~1E5 and a subthreshold swing of ~220 mV/dec are reported. Additionally, for the first time, the integration of stacked two NS WSe2 and two NS MoS<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> in the same structural FET is demonstrated using the NS release and high <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$-\kappa$</tex> metal gate conformal deposition process. The two channel materials represent typical PMOS and NMOS 2D materials, respectively.