負電容超薄絕緣場效電晶體的模擬與探討

Abstract

這篇論文藉由TCAD搭配一維Landau方程式模擬探討負電容超薄絕緣場效電晶體的閘極長度對於次臨界擺幅和元件開關性能的影響。我們的研究指出，雖然傳統的場效電晶體的次臨界擺幅會因短通道效應而惡化，但負電容場效電晶體的次臨界擺幅反而進步。原因在於負電容場效電晶體，隨著閘極長度縮短，汲極對於通道的電壓耦合增強，因此得到較佳的閘極電壓放大效果。除此之外，我們也探討了鐵電材料對於整體閘極電容的影響。我們的研究指出，雖然負電容場效電晶體的閘極電容被放大了，但是元件的性能依然可以獲得改善。另外，負電容場效電晶體的元件開關性能，將隨著閘極長度的縮減而增進。

This thesis investigates the gate-length (Lg) dependence of subthreshold swing (SS) and switching performance for Ultra-Thin-Body Negative-Capacitance FET (UTB NCFET) with the aid of TCAD numerical simulation coupled with 1D Landau equation. Our study indicates that, while the SS of conventional MOSFETs degrades as Lg decreases, the SS of NCFETs improves as Lg decreases. This is because the gate-voltage amplification of the NCFET becomes higher with decreasing gate-length due to stronger drain coupling. In addition, the impact of the ferroelectric material on the overall gate capacitance (C_GG) of the NCFET is also investigated. Our study indicates that, albeit the C_GG of the NCFET is amplified, the intrinsic delay of the NCFET can still be improved. Besides, the switching performance of the NCFET improves as Lg decreases.