決定高效能蕭特基金氧半場效應電晶體傳輸參數的新實驗方法

Abstract

在近年來，蕭特基金氧半場效應電晶體以金屬矽化物取代源極和汲極的方式受 到了許多關注，因為它具有優越的Ion/Ioff 比例及壓制短通道效應的能力，但是蕭特基 介面和通道間形成的蕭特基位障卻降低了它的效能。為了減輕蕭特基位障的影響並增 進效能，□雜物隔離式蕭特基金氧半場效應電晶體因而被提出來，且觀察到載子速度 的提升，這個現象被認為是擁有強烈的速度過衝機制所導致。然而，這個機制並未對 所觀察到的速度增強有一個完整及詳細的探討。因此，對元件做傳輸效率的分析是必 要的。 彈道理論可以被用來延伸做為準彈道現象來探討傳輸效率。在本論文裡，我們 提出一個名為速度飽和模型的新方法，以實驗量測來研究□雜物隔離式蕭特基金氧半 場效應電晶體的彈道效率以及射入速度。我們一開始先引入□雜物隔離式蕭特基金氧 半場效應電晶體的基本特性，包含元件結構、工業用製程、操作原理以及電性，然後 再分別以溫度相依法和速度飽和模型來討論及比較彈道效率。相對於溫度相依法 (Temperature Dependent Method)，透過速度飽和模型，我們獲得了合理的結果。實 ii 驗結果顯示□雜物隔離式蕭特基金氧半場效應電晶體在通道長度愈短時，會有更高的 彈道效率促使它的效能增強，不同於溫度相依法所得的結果。除此之外，我們也用接 觸蝕刻停止層型式的應變矽元件做一驗證，結果清楚顯示由於通道的應變力引起低的 等效載子質量使其擁有高的射入速度以增進元件的效能。 最後，我們得出了幾個結論：（1）隨著通道長度的縮短，□雜物隔離式蕭特基 金氧半場效應電晶體展現其高效能，（2）經由速度飽和模型所決定的彈道效率，應用 在□雜物隔離式蕭特基金氧半場效應電晶體上，顯示出比溫度相依法有更可靠的結 果，（3）□雜物隔離式蕭特基金氧半場效應電晶體，在通道長度縮短下的效能增益是 因為彈道效率的強烈增加，（4）接觸蝕刻停止層型式的應變矽元件的效能改善是由於 其高的射入速度所引起的。因此，速度飽和模型提供了我們一個比溫度相依法更精確 及可靠的彈道傳輸的分析。

In recent years, SBMOS with metal-silicided source/drain has received much attention for its better Ion/Ioff ratio and the immunity to short channel effect but has shown a worse performance due to Schottky junction at the silicide and the channel. In order to alleviate the barrier height of S/D Schottky junction and to improve the performance, Dopant-Segregated SBMOS (DSS) is introduced, and a better enhancement on the carrier velocity has also been observed because of the strong velocity overshoot phenomenon. However, it has been not clear on the mechanism of the enhancement in overshoot velocity. Thus, the analysis of the transport efficiency is mandatory. The ballistic theory has been extended to explore the transport efficiency in quasiballistic regime. In this thesis, a new approach called Velocity Saturation Model (VSM), based on experimental measurements, is developed to study the ballistic efficiency, Bsat, and injection velocity (vinj) for DSS. We first introduce the basic properties of DSS including structure of device, manufacturing process, operating principle, and electrical characteristics. Then, we discuss and compare the ballistic efficiency extracted by the TDM(Temperature Dependent Method) and VSM respectively. For VSM, we obtain a reasonable relationship of performance, compared to TDM. Moreover, the experimental results showed that the value of Bsat is improved with reducing the channel length, resulting in a better enhancement of the performance, but not agreed with the results of TDM. Additionally, the strained-Si device with CESL is further discussed. It demonstrates that the vinj dominates the improvement of the performance since the strained channel induces a low effective mass. iv Finally, it was concluded that: (1) with the shrinkage of channel length, the DSS exhibits high performance; (2) the determination of Bsat by VSM is applied to DSS, which offers more reliable results than TDM; (3) the enhancement in DSS increases with decreasing channel length because of the increase of the Bsat; (4) the improvement of performance in strained-Si device with CESL is induced by high vinj. Consequently, the VSM provides us more accurate and reliable results than the TDM ones.