臺灣博碩士論文加值系統

摘要
在本實驗中，我們利用射頻磁控濺鍍法製作不同結構的鈦酸鍶鋇(BST)薄膜電容器及場效電晶體，在實驗的製程條件下，成長厚度為50nm到150nm的薄膜，探討其基本電性及深入的漏電流機制。
在基本電性量測方面，BST薄膜在經過XRD分析後，確定薄膜具有鈣鈦礦結構的成相，膜厚為96nm的MIS電容器經過電容-電壓(C-V)量測在低頻100赫茲下，介電常數值約有77，在高頻1百萬赫茲下大約在47左右。
在漏電流機制的探討方面，金屬/絕緣層/半導體(MIS)電容器在我們所量測的溫度範圍內(305K~470K)，低場屬於歐姆傳導電流機制，高場為蕭基發射。由歐姆傳導機制可以計算出費米能階的位置在傳導帶底部以下0.2eV的地方，在鈦酸鍶鋇薄膜內的電子移動率μ=2.28×10-5 cm2/V-sec，熱平衡少數載子濃度大約為1.57×1017 cm-3；並且由蕭基發射得到BST及Al的位能障高為0.63eV，由此可以畫出Al/BST/Si的MIS結構之能帶圖。
對於電晶體的量測上，其電性上的表現如：由IDS-VDS，IDS-VGS等圖，可以發現臨界電壓(VT)約是-0.13V，次臨界斜率(St)是125.9 mV/dec和電子遷移率約為187 cm2/V-sec，已具有MOSFET的基本效能。經臨界電壓計算其單位面積氧化層固定電荷為3.35×10-7C/cm-2，並進而算出氧化層內單位面積固定電荷的數量為2.09×10-12cm-2。經次臨界斜率計算介面補捉缺陷態電荷密度為3.3×1012cm-2eV-1，發覺表面特性BST跟矽基板的介面特性比二氧化矽的差，所以仍有許多進步的空間。

Abstract
In this work , the electrical characteristics of Al/BST/Si (P-type) (MIS) capacitors and n-channel metal gate metal-oxide-semiconductor field effect transistors (MOSFET) with (BaxSr1-x)TiO3 (BST) gate dielectric are investigated. The BST thin films are deposited by magnetron control RF sputtering. The perovskite phase was confirmed by X-Ray Diffraction spectra. The dielectric constant of 96nm thick BST thin film is around 47 at 1MHz and 77 at 100Hz. The I-V and C-V characteristics of MIS capacitors are discussed.
The conduction current mechanism of BST films at different temperatures is studied. For MIS structure, Ohmic conduction is dominant at high temperature under low electrical field, when the device is negative biased (operated in accumulation region). The EC-EF is 0.2eV, the mobility in BST thin film is 2.28×10-5 cm2/V-sec, and the thermal equilibrium concentration of free electrons in BST thin film is 1.57×1017 cm-3 extracted from ohmic conduction. Schottky emission is observed at high temperature under high electrical field. At higher electrical field (>150kV/cm) and with the Si/Al electrode positively biased, the Al/BST forms a Schottky barrier with a barrier height of 0.63eV in the temperature range from 340 to 430 K.
The IDS-VDS and IDS—VGS characteristics are measured from MOSFET with BST gate dielectric. The electron mobility obtained from gm versus VG plot was about 187 cm2/V·s. The subthreshold swing was 125.9 mV/dec. The interface trap density and fixed oxide charge measured from Vt and St are 2.091×1012cm-2, 3.3×1012cm-2ev-1, respectively. Comparison with conventional MOSFETs with SiO2 gate oxide was made. It shows that the surface properties of BST transistors are worse than SiO2 transistors. For BST transistors, there are still many places for improvement in the future.

目 錄
第一章 緒論
1.1 簡介 1
1.2 研究動機 1
1.3 鐵電材料鈦酸鍶鋇的基本特性 2
1.3.1 鈦酸鍶鋇簡介 2
1.3.2 鈦酸鍶鋇薄膜應用主要有兩大方面 3
1.4鈦酸鍶鋇電容器在未來應用上可能遭遇的問題 4
1.4.1溫度的相依性 4
1.4.2漏電流的影響 4
1.4.3介電質崩潰 4
1.4.4依時性介電崩潰 5
第二章 元件製作流程
2.1射頻磁控濺鍍法（RF Magnetron Sputtering）的簡介 6
2.2 MIM結構電容器的設備與製程 7
2.2.1 基板及下電極的製作 7
2.2.2 鈦酸鍶鋇薄膜的成長 7
2.2.3 鈦酸鍶鋇試片之熱處理 8
2.2.4 上電極的製作 8
2.3 MIS結構電容器的設備與製程 9
2.4 鈦酸鍶鋇薄膜電晶體的製備 10
2.4.1 製作流程 10
2.4.1.1 清洗晶圓與成長場氧化層之製作 10
2.4.1.2 開源極/汲極 11
2.4.1.3 鈦酸鍶鋇薄膜的製作 11
2.4.1.4 接觸洞(contact hole)的蝕刻 12
2.4.1.5 鋁蒸鍍與金屬蝕刻 12
2.4.1.6 金屬蝕刻後熱退火處理 12
2.5 量測儀器以及實驗儀器介紹 13
第三章 薄膜基本電性分析
3.1 X-ray繞射分析 14
3.2電流-電壓(I-V)特性曲線量測 14
3.2.1 MIS結構正負偏壓下的電流特性 14
3.2.2崩潰電場特性 15
3.2.3極化電流特性 16
3.3電容-電壓(C-V)特性曲線量測 17
3.3.1相對介電常數 17
3.3.2介電特性 18
第四章 漏電流機制探討與溫度效應
4.1電流傳導機制簡介 20
4.1.1 歐姆傳導 21
4.1.2蕭基發射 21
4.1.3普爾-法蘭克效應 22
4.2 MIS電容器電流對電壓特性量測分析
4.2.1 歐姆傳導 23
4.2.2 蕭基發射 24
第五章 電晶體基本電性量測
5.1 IDS-VDS、IDS-VGS圖的特性 26
5.2 臨界電壓(VT) 27
5.3 探討IDS-VGS圖的特性 29
5.4次臨界斜率(Subthreshold Swing) 29
5.5遷移率的探討(Mobility) 30
第六章 結論 6.1鈦酸鍶鋇薄膜電容器的討論 33
6.2鈦酸鍶鋇薄膜場效應電晶體的討論 33
附錄
參考文獻(reference)
附錄 A — 光罩圖
附錄 B - 濺渡機操作手冊

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