應用第一原理理論計算研究本質,矽摻雜,及釔摻雜二氧化鉿之介電性質與相穩定性

Dielectric properties and phase stability of pure, Si-doped, and Y-doped hafnium dioxide from ab initio calculations

洪佑銘(Yu-Ming Hung)

指導教授 ： 郭光宇

國立臺灣大學/理學院/物理研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.03178

摘要

在過去幾年來，隨著互補式金氧半元件(CMOS)的尺寸不斷的縮小，傳統的閘極介電材料(SiO2)的厚度越來越薄。然而不幸的是當厚度越來越薄的時候,減少閘極漏電流就變得越來越困難了。所以找尋新的材料來取代傳統的閘極介電材料(SiO2)就變的很重要了。
由於二氧化鉿(HfO2)是高介電係數材料，所以它被認為是取代傳統的閘極介電材料的最佳選擇之一。在這篇論文當中,我們研究了本質及矽摻雜二氧化鉿(HfO2)之介電性質與相穩定性。
首先,我們計算二氧化鉿(HfO2)的立方晶(cubic)、正方晶(tetragonal)以及單斜晶(monoclinic)的結構係數。第二,利用第一原理有限電場的方法計算立方晶(cubic)、正方晶(tetragonal)以及單斜晶(monoclinic)的波恩有效電荷和介電張量。我們發現介電常數會隨著不同的結構而劇烈變動。然而在常溫常壓下單斜晶是最穩定的結構但是它的介電常數卻是最低的。因此,調查三個不同相間的相對穩定性是必須的。我們發現如果二氧化鉿(HfO2)摻雜適當濃度的矽原子或釔原子分別可以使正方晶及立方晶變成最穩定的相而且使介電常數升高。

關鍵字

介電材料 ； 第一原理

並列摘要

For decades, the downscaling of CMOS (Complementary Metal-Oxide-Semiconductor) devices has resulted in the reduction of the thickness of the traditional gate dielectric, SiO2. Unfortunately, stopping the undesired current leakage becomes more difficult as the thickness is reduced. Therefore, it is necessary to search for a replacement for the traditional gate dielectric, SiO2.
Hafnium dioxide (HfO2) with high permittivity (high-k) is considered to be one of the promising replacements for SiO2 as a gate dielectric material. In this thesis,the dielectric properties and phase stability of pure, Si-doped, and Y-doped HfO2 are investigated.
First, the structure parameters of HfO2 in the cubic, tetragonal and monoclinic phases are carefully studied using ab initio method. Second, we obtain the Born effective charge and the dielectric tensor of HfO2 in the cubic, tetragonal and monoclinic phases by the ab intio finite electric field method. We find that the dielectric constant varies dramatically with three different phases. However, the monoclinic phase, with the lowest dielectric constant, is the stable phase under ambient condition. Therefore, relative stability of three different structures is investigated here. We find that Si doping and Y doping with appropriate concentration stabilize tetragonal phase and cubic phase, respectively, and enhance the dielectric constant.

並列關鍵字

hafnium dioxide ； high permittivity ； ab initio

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