量子侷限效應對超薄絕緣鍺與砷化銦鎵金氧半場效電晶體的次臨界與後端閘極偏壓調變臨界電壓特性之理論研究

Abstract

藉由使用Schrödinger方程式的解析解並與元件數值模擬進行驗證，本論文理論性地探討在超薄絕緣鍺與砷化銦鎵元件中量子侷限效應對於次臨界擺幅與後端閘極偏壓調變之臨界電壓特性的影響。 對於高載子遷移率通道之超薄層元件而言，我們的研究發現量子侷限效應可以改善次臨界擺幅，特別是當載子重心較靠近後端閘極界面的情形下，例如在作用正的後端閘極偏壓用以進行多臨界電壓操作的情況下。對於短通道超薄層元件而言，我們發現量子侷限效應可以抑制由於通道厚度變化而造成的次臨界擺幅變異程度。此外，在考慮了量子侷限效應後，長通道超薄層元件對於後端閘極偏壓的臨界電壓靈敏度會有所提高。由於量子侷限效應而有所抑制的臨界電壓衰變在後端閘極順偏壓下，抑制效應會變得更加顯著。另外，我們已經將波函數穿透效應合併考量在我們的量子侷限模型中，以適用於有著高介電常數閘極介電材料的超薄層金氧半場效電晶體。因為鍺、砷化銦鎵和矽通道顯示出不同的量子侷限程度(因為不同的量子化有效質量)，所以當一對一比較這些超薄層元件特性時，量子侷限效應的影響必須被納入考量。本論文希望能夠提供在使用先進超薄絕緣鍺與砷化銦鎵的工藝技術時，對於先進超薄絕緣鍺與砷化銦鎵金氧半場效電晶體的多臨界電壓元件或電路設計有更多的了解。

This thesis theoretically investigates the impact of quantum confinement on subthreshold swing and backgate-bias modulated Vth characteristics for UTB GeOI and InGaAs-OI devices using an analytical solution of Schrödinger equation verified with device simulation. Our study indicates that the quantum confinement effect may improve the subthreshold swing of high mobility channel UTB devices especially when the carrier centroid is closer to the backgate interface, for example, applying positive backgate bias (Vbg) for multi-Vth application. Due to the quantum confinement effect, the subthreshold swing variation due to channel thickness variation for short-channel UTB devices can be suppressed. Besides, the sensitivity of Vth to Vbg increases after considering the quantum confinement effect for UTB devices with triangular potential well. The suppressed Vth roll-off effect due to quantum confinement becomes more significant under forward backgate bias. In addition, we have incorporated the wavefunction penetration effect into our quantum-confinement model for UTB MOSFETs with high-k gate dielectric. Since Ge, InGaAs, and Si channels exhibit different degree of quantum confinement (due to different quantization effective mass), the impact of quantum confinement has to be considered when one-to-one comparisons among UTB GeOI, InGaAs-OI and SOI MOSFETs are made. Our study may provide insights for multi-Vth device/circuit designs using advanced UTB GeOI and InGaAs-OI technologies.