超薄絕緣三五族金氧半場效電晶體與負電容場效電晶體之量子次臨界模型建立

Abstract

本論文針對超薄絕緣金氧半場效電晶體與負電容場效電晶體建立兩個量子次臨界解析模型。藉由解析模型與數值模擬交相驗證，我們探討並比較了不同三五族與矽材料之超薄絕緣金氧半場效電晶體的本質汲極誘發能障降低特性。我們的研究驗證了，本質汲極誘發能障降低特性會受到三個因素影響：通道介電常數，內建的等效基板偏壓以及量子侷限效應。對於通道厚度相當薄的三五族超薄絕緣金氧半場效電晶體，其汲極誘發能障降低效應會被量子侷限效應改善並可與矽通道電晶體的汲極誘發能障降低效應相抗衡。此外，藉由解析模型搭配Landau-Khalatnikov方程式，我們也探討了超薄絕緣金氧半負電容場效電晶體在次臨界的特性。我們的研究指出，雖然在底層的金氧半場效電晶體的次臨界斜率會因為通道長度下降而惡化，但是對於負電容場效電晶體的次臨界斜率來說，反而有所改善。當負電容場效電晶體的通道長度相當短時，我們觀察到次臨界斜率會隨著不同閘極偏壓而有所變化的特性。

This thesis provides two analytical quantum-mechanical (QM) subthreshold models for ultra-thin-body (UTB) III-V-on-insulator MOSFETs and for UTB negative capacitance FETs (NCFETs). Using the analytical model corroborated with TCAD numerical simulation, the intrinsic drain-induced-barrier-lowering (DIBL) characteristics of various UTB III-V-OI and SOI MOSFETs are investigated and benchmarked. Our study confirms that the DIBL of the III-V-OI devices can be affected by three factors: the permittivity, the built-in effective body-bias effect and the quantum-mechanical effect. With a smaller channel thickness, the DIBL of III-V-OI devices can be improved by the QM effect and can become comparable to Si devices. In addition, the subthreshold characteristics of UTB NCFETs are investigated us-ing the analytical model coupled with the Landau-Khalatnikov equation. Our study indicates that, albeit the gate-length scaling would degrade the subthreshold swing (S.S.) for the under-lying UTB MOSFETs, it can improve the S.S. for the UTB NCFETs. Besides, for UTB NCFETs with much shorter gate-length, gate-bias dependent S.S. characteristics are found.