運用氧化鉿鋁鐵電薄膜搭配應變閘極增進的負電容電晶體於超低功耗應用

Abstract

在這篇論文中，我們運用氧化鉿鋁鐵電材料在電晶體上，此元件在低操作電壓下，搭配負電容效應，可以達到陡峭之次臨界擺幅。藉此可以達到最低功率的操作並進一步得到省電的效果。為了局部分析材料上的特性，像是在結晶的方向和反鐵電效應的電性上，鋁原子含量影響，最後搭配著閘極應力變化，找出最佳化的實驗條件完成。 在製程電晶體前，將氧化鉿鋁鐵電材料透過X光繞射儀量測晶向，以確保晶向是否維持在斜方晶體。透過XPS分析鋁在氧化鉿比例，搭配著我們預期的濃度做驗證，也運用EDX做元素分析，再次加以確認材料的分佈。另外在電性分析，將氧化鉿鋁鐵電材料製作成電容，在此結構上對於不同熱退火條件做極化量測來驗證反鐵電效應，漏電流的量測確保是否耐得住高溫，最後在電容值做分析材料的K值、等效微縮的厚度。在應變閘極上，我們在材料分析上驗證了不同氮含量影響晶向的變化，搭配在電性上得到最佳的氮含量條件，因而得到最好的極化量。 綜合各項最佳化條件套入到電晶體上，為此我們成功展示負電容電晶體，此元件電流開關比約為8個數量級，電量測條件為汲極電壓0.2伏特，漏電流約在負15次方，次臨界擺幅達到20mV/decade。

In this thesis, we demonstrated ferroelectric HfAlO thin film in MOSFET. Low operation voltage with low subthreshold swing can be achieved by the negative capacitance effect. In addition, the NCFET also reduces the power consumption. The characteristics of ferroelectric material HfAlO thin film are analyzed with the variation of Al contents, such as the phase of crystallization and anti-ferroelectric phenomenon in HfAlO capacitor. Furthermore, the metal strained-gate on ferroelectric will be discussed in this study too. The material analyses of HfAlO thin film are demonstrated by lots of measurement instrument. The concentration of elements was measured by XPS and EDX. The orthorhombic phase crystallization and exact thickness of ferroelectric HfAlO thin film were measured by X-Ray diffraction pattern and TEM respectively. In electrical characteristic, the thermal dynamic influence on HfAlO thin film that remanent polarization becomes larger and leakage current also maintains its stability in higher temperature. The permittivity and CET of HfAlO MOSCap structure were extracted from C-V measurement. Moreover, high metal strained-gate on HfAlO thin film is under investigation simultaneously. The results show that it could enhance the orthorhombic phase crystallization and remanent polarization. To sum up, the large 108 on/off ratio, ultra-low 20mV/decade subthreshold swing, small 0.2V supply voltage and quite low 4.7x10-15A/mm off current are all achieved by HfAlO NCFET in this thesis.