奈米場效電晶體的通道次能階和彈道傳輸之研究

Abstract

當通道長度越來越短, 縮短到100奈米甚至更短時, 傳統金氧半場效電晶體模型的基本假設便逐漸失去它的正確性. 未來的金氧半場效電晶體可能會以接近它們彈道傳輸的極限來運作. 因此, 了解彈道傳輸元件的物理機制和如何達到類似彈道傳輸的運作是非常重要的。 實際上,金氧半場效電晶體都是以低於它們彈道傳輸的極限來運作, 因為載子在傳輸時會遇到散射. 我們可使用最近提出來的通道散射理論來探索載子在奈米場效電晶體傳輸的介觀特性。接近熱平衡的平均自由路徑 □ 與 KT 層寬度l 的比例是了解奈米場效電晶體的通道散射特性的重要關鍵. 為了清楚的了解基本的介觀傳輸機制, □ 與 l 必須被分開. 我們用一維的量子力學模擬器和通道散射理論的溫度模型來分離 □ 與 l. 我們可由分離出來的l 與 l 來了解它在不同偏壓下和不同通道長度下的介觀特性. 同時我們也藉由重現不同通道長度下的飽和電流電壓特性來確認我們分離的方法。

As channel lengths shrink towards 100 nm and below, the underlying assumptions of the conventional MOSFET model are rapidly losing validity. Future MOS transistors may operate near their ballistic limit, and it is important to understand ballistic device physics and the prospect of achieving quasi-ballistic operation. In practice, current MOSFETs operate below the ballistic limit because of carrier scattering within the device. Channel backscattering theory has recently been introduced to explore mesoscopic aspects of carrier transport in nanoFETs. The ratio of near-equilibrium mean-free-path □ to KT layer width l is key to channel backscattering characteristics in nanoFETs. To make clear underlying mesoscopic transport mechanisms, □ and l must be separately addressed. Separation of □ and l is achieved by means of a 1-D quantum mechanical numerical simulator on a MOS system, followed by a temperature dependent experiment on backscattering coefficient assessment. The resulting □ and l reveal their mesoscopic behaviors as applied bias or gate length changes. Reproduction of saturation I-V characteristics with mask gate lengths down to 75 nm is further achieved adequately, confirming the validity of the separation process in a consistent manner.