量子電容效應於超薄單閘極與雙閘極及閘極全包覆式三五族金氧半場效電晶體 閘極反轉層電容値之比較與模型建立

Abstract

我們透過理論模型比較量子電容對於超薄單閘極與雙閘極以及閘極全包覆式三五族電晶體的反轉層電容值的影響。藉由數值模擬與理論分析的交互印證我們了解到，由於三五族材料具有較小的電子有效質量及較低的能態密度，量子電容將嚴重衰減三五族電晶體反轉層電容值。我們觀察到量子電容效應在雙閘極三五族電晶體帶來的影響大於超薄單閘極三五族電晶體，而這個結果可以由等效模型的差異來解釋。此外我們也會討論如何去改善閘極全包覆式三五族電晶體的理論模型準確度。參照ITRS 2018至2024年的參數來設計元件，我們的研究指出對於不同元件結構下為補償反轉層電荷量下降所需的最低載子移動率增益。最後我們的研究表示，在完全彈道傳輸的情況下，三五族材料的效能將低於矽。然而隨著通道長度的增加，在接近彈道傳輸的情況下，三五族材料的效能將有機會優於矽。

This work models and compares the impact of quantum capacitance (Cq) on inversion capacitance (Cinv) of double-gate (DG), ultra-thin-body (UTB), and gate-all-around (GAA) III-V n-MOSFETs. Through TCAD quantum-mechanical simulation corroborated by model calculation, our study indicates that Cq will significantly impact the characteristics of Cinv and lead to degradation of Cinv for devices with In0.53Ga0.47As channel. Moreover, the impact of Cq on In0.53Ga0.47As DG devices is larger than the UTB counterpart, and this can be explained by the difference of the equivalent circuit model. Besides, how to improve the model accuracy of Cinv calculation for GAA devices is also discussed. Based on the ITRS 2018 to 2024 technology nodes, our study indicates that the mobility enhancement should be at least ~2X for the UTB device, ~2.7X for the DG device, and ~3.73X for the GAA device, respectively, to compensate the inversion-charge loss due to the Cq. Finally, our study indicates that the performance of III-V channel materials is no better than the Si counterpart under the fully ballistic condition. However, it can be superior than the Si device as the gate length increases.