奈米場效電晶體之通道逆向散射實驗

Abstract

最近幾年有一個簡易的通道逆向散射理論被學術界引進用來解釋矽通道的載子傳輸機制，這個新理論將逆向散射係數代替傳統電流－電壓特性關係中的載子遷移率參數。藉由引進這個簡易的散射模型，我們能夠輕易地理解在奈米級場效電晶體中所隱含的基礎物理原理。 在奈米場效電晶體中，逆向散射係數在解釋載子傳輸過程中扮演著重要的角色，因此我們利用兩種不同方式來直接求取散射係數。一個方式是對於通道長度短到75奈米及1.7奈米氧化層厚度的N型金氧半導體作低溫變壓實驗，同時我們也建立了一個溫度版本的逆向散射實驗模型。在這個新模型中，我們可以直接萃取出逆向散射係數，而這些係數和閘道長度、閘極電壓和汲極電壓呈現了不同程度的關係。另外一個方式是電流特性的萃取方法，我們利用以逆向散射理論為基礎的電流－電壓模型來直接獲得係數，而係數也和各種閘道長度和電壓參數呈現了和之前溫度實驗相同的關係。最後從結論中可以發現，這兩項的實驗結果更加確立了散射理論的主軸架構，並且可以利用其結果來預測未來更短通道長度的散射係數及半導體傳輸特性。

In recent years, there has been a simple channel backscattering theory dedicated to explaining carrier transmission mechanism in the silicon channel. As a result current–voltage (I-V) characteristics are expressed in terms of backscattering parameters instead of mobility. The fundamental physics of nanoFETs can thus be comprehended easily by introducing this simple scattering model. The backscattering coefficient plays a main role for explaining carrier transmission in nanoFETs. Therefore we perform two methods to extract this coefficient directly. One method is the temperature experiment (-40 oC to 25 oC) on 17Å thick gate oxide NMOSFETs down to 75-nm mask gate length under different bias conditions, along with a temperature version of backscattering model built together. In this new model, we can extract the backscattering coefficients immediately which exhibit different dependencies on gate length, drain voltage and gate voltage. The other one is electrical characterization method, that is, I-V model based on backscattering theory to extract these coefficients. The results also reveal the same dependencies on the dimensions and bias parameters as the first method. The efforts in this work strongly confirm the original concept of backscattering theory.