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研究生：	蔡秉翰 Tsai, Ping-Han
論文名稱：	低導通電阻β相氧化鎵金氧半場效電晶體之研製 Low On-resistance β-Ga2O3 Metal-Oxide-Semiconductor Field Effect Transistor
指導教授：	王永和 Wang, Yeong-Her
學位類別：	碩士 Master
系所名稱：	電機資訊學院 - 微電子工程研究所 Institute of Microelectronics
論文出版年：	2022
畢業學年度：	110
語文別：	英文
論文頁數：	118
中文關鍵詞：	氧化鎵、β相氧化鎵金氧半場效電晶體、四甲基氫氧化銨溶液、原子層沉積法、氧化鋁、鉑閘極、極寬能隙
外文關鍵詞：	Ga2O3, β-Ga2O3 MOSFET, TMAH treatment, Atomic layer deposition (ALD), Al2O3, Pt gate, Ultra-wide bangap
相關次數：	點閱：166 下載：0
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β相氧化鎵金氧半場效電晶體在製作高功率元件上有很大的潛力，因為它具有4.4-4.9 eV的極寬能隙，比氮化鎵和碳化矽的能隙都大。然而最關鍵的議題是要如何降低由寬能隙能障所導致的接觸電阻並得到好的歐姆接觸特性。在這篇論文中，我們利用高溫沉積後快速熱退火來取代已被普遍提出的方法，即在離子佈值之後以470度進行沉積後快速熱退火。如此一來我們可以得到傑出的導通電阻，範圍在35到70Ω．mm之間。此外，高功函數的鉑閘極被用來提升閘極能障高度並降低閘極漏電流。這樣一來就可以達成合理的開關比。TMAH表面處理以及閘極沉積後退火被用來改善表面粗糙度並降低缺陷和表面能態。接受TMAH表面處理以及閘極沉積後退火的鉑閘極β相氧化鎵金氧半場效電晶體在閘極電壓7V的時候最大電流密度可以達到210 mA/mm此時的導通電阻是65.3 Ω．mm。它的最大轉導密度達到8.59 mS/mm並且有10的5次方的開關比。此元件的崩潰電壓達到394V，大約是同維度平面氮化鎵金氧半高電子遷移率電晶體的三倍。

β-Ga2O3 metal–oxide–semiconductor field effect transistors (MOSFETs) show great potential in fabricating high power devices because of their ultra wide bandgap reaching 4.4-4.9 eV, which is larger than that of GaN and SiC. Nevertheless, the most crucial issues include lowering contact resistance caused by the wide bandgap barrier and obtaining good ohmic contact behavior. In this study, we use high temperature post deposition rapid thermal annealing (RTA) to substitute the commonly proposed method of ion implantation followed by post deposition 470°C RTA. Thus, the outstanding on-resistance(Ron) ranging from 35-70 Ω．mm is obtained. In addition, the high work function Pt gate is used in enhancing the gate barrier height and lowering the gate leakage current to achieve a reasonable on-off ratio. Tetramethylammonium hydroxide(TMAH) treatment and post gate annealing(PGA) are adopted to improve surface roughness and decrease defects and surface states. The Pt gate β-Ga2O3 MOSFET exhibits a maximun drain current density of 210 mA/mm at VG=7V. Its on-resistance(Ron) is 65.3 Ω．mm. The maximum transconductance(Gm) of 8.59 mS/mm and the on-off ratio up to 10 to 5 are achieved. The off-state breakdown voltage is 394V, which is nearly three times larger than the same dimension planar GaN MOS-HEMT.

中文摘要	I
Abstract	III
CONTENTS	VII
List of Tables	XI
List of Figures	XII
Chapter 1 Introduction	1
1-1 Background	1
1-2 Motivation	7
1-3 Organization	12
Chapter 2 Principle of β-Ga2O3 MOSFETs	13
2-1 Crystal Structure of Ga2O3	13
2-1-1 Five Different Polymorphs of Ga2O3	13
2-1-2 Lattice Structure of β-Ga2O3	17
2-2 Epitaxial Structure of β-Ga2O3 MOSFET	18
2-3 Etching of β-Ga2O3	23
2-3-1 Wet etching of β-Ga2O3	24
2-3-2 Dry etching of β-Ga2O3	25
2-4 Ohmic Contact Formation in β-Ga2O3	27
2-5 The Concepts of the Gate Barrier Height and the Field Plate	32
Chapter 3 Experiments and Device Fabrication	34
3-1 Experimental Equipment	34
3-1-1 Ultrasonic Cleaner、Hot Plate and Oven	34
3-1-2 Spin Coater	36
3-1-3 Mask Aligner with Mercury Lamp	37
3-1-4 ICP Plasma Etching System	38
3-1-5 RIE System	39
3-1-6 Alpha Step	40
3-1-7 Electron Beam Evaporator	41
3-1-8 DC Sputter	41
3-1-9 Rapid Thermal Annealing System	43
3-1-10 Atomic Layer Deposition(ALD) System	44
3-1-11 Semiconductor and Power Analyzer	45
3-1-12 FIB and TEM	46
3-1-13 Atomic Force Microscope(AFM)	48
3-2 Device Fabrication	49
3-2-1 Wafer Cleaning	50
3-2-2 Mesa Isolation	51
3-2-3 Source /Drain Ohmic Contact Pad	53
3-2-4 Deposition of Gate Insulator	55
3-2-5 Schottky Gate Definition and Deposition	56
3-3 Schematics of the Fabrication Process	58
Chapter 4 Results and Discussion	61
4-1 Surface Roughness Issue of the β-Ga2O3 wafer	61
4-2 Physical Properties of the β-Ga2O3 MOSFET	65
4-2-1 Transmission Electron Microscopy	65
4-2-2 Energy-Dispersive X-ray Spectroscopy(EDS)	69
4-3 Planar β-Ga2O3 MOSFET Performance	72
4-3-1 Ohmic Contact Behavior	72
4-3-2 ID-VD Output Characteristics	77
4-3-3 ID-VG Transfer Characteristics	80
4-3-4 Subthreshold ID-VG and On-Off Ratio	82
4-3-5 Gate Leakage Current	86
4-3-6 DC-Pulse ID-VD Dispersion	88
4-3-7 Off-State Breakdown Voltage	91
4-4 Double-gate Structure Performance	93
4-4-1 ID-VD Output Characteristics	94
4-4-2 ID-VG Transfer Characteristics	96
4-4-3 Subthreshold ID-VG and On-Off Ratio	98
4-4-4 Gate Leakage Current	101
4-4-5 DC-Pulse ID-VD Dispersion	103
Chapter 5 Conclusion	105
Chapter 6 Future Work	109
Reference	110
                                    

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