動態臨限電壓場效電晶體之零溫度係數點模型研究

Abstract

在本論文中，我們提供三種金氧半場效電晶體的操作模式，分別是 DT-A 模式、DT-B 模式以及傳統操作模式。每種操作模式皆搭配三種不同閘級材料，即polysilicon、TiN 以及 TaC，用以比較不同操作模式以及不同閘極材料對元件的性能的影響。其中，DT-B 模式搭配金屬閘極可以得到非常優良的電性，例如：它能夠提供最佳的臨限電壓變化特性(threshold voltage roll-off)、減少汲極產生的位勢降低量(DIBL) 以及接近理想值的次臨限擺動(subthreshold swing)。然而，在同樣的閘極條件下，DT-A模式則能擁有最佳化的驅動電流(drive current)。此外，在廣泛的操作溫度範圍下[223K，398K]，我們進一步地從理論及實驗層面去分探討臨限電壓、汲極產生的位勢降低量以及次臨限擺盪對溫度的相依性。 為了能夠在低溫操作下得到較高的電流增益，我們推演出動態臨限電壓金氧半場效電晶體的零溫度係數點(zero temperature coefficient point) 模型，並且將零溫度係數點在線性區與飽和區的預測理論值與實驗值做比較。在這個縝密的模型分析過程中，我們不僅考慮基板偏壓效應(body bias effect )，還修正了飽和區理想電流公式中的次方項。因此，不論是在線性區或者飽和區，我們都得到非常小的誤差值(<5%)。

In this work, we provide three operation modes of MOSFET, respectively DT-A mode, DT-B mode, and normal mode, and three gate materials, namely polysilicon, TiN and TaC, to compare their performance. Although DT-B mode accompanied with metal gate shows the excellent characteristics, such as the lowest threshold voltage roll-off, better DIBL and the near ideal value of subthreshold swing, the DT-A mode counterpart exhibits the optimized drive current. Furthermore, the temperature dependence of threshold voltage, DIBL and subthreshold characteristics are investigated both theoretically and experimentally over the wide operation temperature ranges from 223K to 398K. In addition, in order to obtain high current gain at low operation temperature, we develop a zero temperature coefficient (ZTC) point model for DTMOS to compare with experimental results in the linear and saturation regions. The analysis takes in to the consideration of body bias effect and the modification of ideal square-law condition in the saturation region to obtain very small error (<5%) no matter in the linear or nonlinear region.