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系統識別號 U0026-2707201515271100
論文名稱(中文) 後閘極退火與不同閘汲極間距 於高電子遷移率電晶體之研究
論文名稱(英文) Investigation of AlGaN/GaN HEMT by Post gate annealing and various gate-drain spacing
校院名稱 成功大學
系所名稱(中) 微電子工程研究所
系所名稱(英) Institute of Microelectronics
學年度 103
學期 2
出版年 104
研究生(中文) 李承軒
研究生(英文) Cheng-Hsuan Li
學號 Q16021018
學位類別 碩士
語文別 英文
論文頁數 93頁
口試委員 召集委員-周榮泉
口試委員-王欽戊
指導教授-許渭州
口試委員-李景松
口試委員-王水進
口試委員-劉文超
口試委員-林育賢
中文關鍵字 氮化鋁鎵/氮化鎵  高電子遷移率電晶體  超音波霧化熱裂解法  後閘極退火  閘汲極間距。 
英文關鍵字 AlGaN/GaN  high electron mobility transistor  ultrasonic spray pyrolysis deposition  post gate annealing  different gate drain spacing. 
學科別分類
中文摘要 本論文主要研究不同的閘源極間距和不同的鈍化層並且應用在氮化鋁鎵/氮化鎵高電子遷移率電晶體之研究。且探討利用後閘極退火的方式進一步改善元件特性。 鈍化層部分,選用二氧化矽和氧化鋁當作鈍化層材料,最後應用雙疊鈍化技術去獲得最佳元件特性。
為了解氧化層之特性,我們選用原子力顯微鏡觀察表面粗糙度和薄膜均勻度。我們可以看到用超音波霧化熱裂解法沉積氧化鋁在表面粗糙度和薄膜均勻度上都非常的好。採用穿透式電子顯微鏡可以觀察到成長薄膜和預計的成長厚度相當接近,比較退火前後可以發現,氧化層退完火後氧化層厚度有稍微下降,代表退火有效的修復氧化層表面和氧缺陷。接著用化學分析電子儀分析氧化層組成,可得知氧化層組成成分確實為氧化鋁而且經過後退火,氧和鋁之間的比例接近氧化鋁的比例。 在霍爾量測中發現氧化鋁鈍化處理完片電子濃度有所上升而電子遷移率有些許下降,在經過後閘極退火處理之後片電子濃度有所上升而電子遷移率有些許下降,代表元件在經過退火之後特性可以再進步。接著進行電容電壓實驗後可以得知在經過氧化層鈍化處理之後,元件的遲滯效應與表面狀態密度會大幅進步,代表鈍化層處理可以有效的解決表面狀態的問題,再加上後閘極退火之後元件的陷阱和表面狀態可以得到改善。
在進行後閘極退火之後元件特性會更進步。由於氧化層經過退火之後元件的氧空缺和表面狀態密度會改善,陷阱減少元件的二維電子氣可以增加,使得後退火完的元件特性可以再進步。
比較不同的鈍化層特性可以發現利用雙疊式的鈍化技術可以得到一個最佳的特性。其中氧化鋁可以有效的改善表面狀態,氧化矽可以保護元件,進一步改善元件特性,且可有良好的保護。
再不同的閘源極間距比較。5µm 間距的元件有最好的電流特性但是在崩潰和漏電流部分就相對比較差。在20µm 間距的元件和5µm 間距的元件的特性相反,電流特性較差,但是元件的漏電和崩潰比起來就進步不少。
結合不同閘源極間距和使用雙疊技術的元件後,再進行後閘極退火進一步改善元件特性之後,我們可以獲得一個特性優良的元件。不同閘源極間距可以獲得不同元件特性可以應用在不同需求的高功率元件應用上。
英文摘要 This research proposed the investigation of different gate-drain spacing and different passivation layers on the AlGaN/GaN high electron mobility transistors (HEMTs). We adopt SiO¬2 and Al2O3 to be the passivation layers. Comparison with different passivation layers, we observed that the Stack-passivated HEMTs had better performance.
We used the atomic force microscopy (AFM) to observe the root mean square (RMS) and the surface roughness. We found that the Al2O3 layer had better RMS before and after annealing. And we utilized the transmission electron microcopy (TEM) to analyze the oxide thickness. The results showed that the oxide layers were approaching the oxide thickness which we designed. We also utilized the Electron spectroscopy for chemical analysis (ESCA) to observe that the oxide composition. The oxide layer before and after annealing showed that annealing could effectively reduce the traps and the oxygen vacancies. Finally, we utilized Hall measurement method to confirm the DC characteristics improved. The sheet concentration was increased and the electron mobility slightly reduced by passivation layer.
C-V measurement showed that the k constants, hysteresis, and interface state density. And the results showed that the passivation layers could effectively reduce the traps.
Post gate annealing was an effectively method to improve performance by repairing the oxide traps and oxygen vacancies. The traps decreased made the performance improved.
The different passivation layer could improve the performance by removing the interface state density and the 2DEG concentration increased. And comparison with different passivation layers, we found that the stack-passivated layer had the best performance.
Comparison with different gate-drain spacing, we found that the spacing would influence the characteristics. 5 µm spacing, the DC characteristics was better but the breakdown was worst. 20 µm spacing, the results was opposite with 5 µm.
The stack-passivated HEMT had the best performance compared with other passivation layers. Combination the different gate-drain spacing, different passivation layer, and post gate annealing, we could obtain the different characteristics. And this different characteristics could be applied in different high power applications.
論文目次 摘要................................................................................................................................................ I
Abstract................................................................................................................................III
Contents..............................................................................................................................VII
Figure Captions IX
Table Captions XV
Chapter 1 INTRODUCTION 1
1-1 Motivation 1
1-2 Organization of Thesis 4
Chapter 2 CHARACTERIZATION OF AlGaN/GaN 5
2-1 Group III-Nitride Semiconductors 5
2-2 Principle of AlGaN/GaN 6
Chapter 3 MATERIAL GROWTH AND DEVICES FABRICATION 8
3-1 Epitaxy Structure 8
3-2 Fabrication Process 8
3-2-1 Mesa Isolation 9
3-2-2 Source and Drain Ohmic Contact 11
3-2-3 Gate Schottky Contact 12
3-2-4 Plasma-Enhanced Chemical Vapor Deposition (PECVD) 13
3-2-5 Ultrasonic Spray Pyrolysis Deposition (USPD) 14
3-2-6 Post-gate Annealing 14
3-2-7 Metal-Insulator-Semiconductor (M-I-S) Diode Fabrication 15
Chapter 4 RESULTS AND DISCUSSION 16
4-1 Materials Analysis 16
4-1-1 Atomic Force Microscopy 16
4-1-2 Hall measurement 17
4-1-3 Transmission Electron Microscopy 18
4-1-4 Electron Spectroscopy for Chemical Analysis 19
4-2 Capacitance-Voltage measurement 20
4-2-1 Dielectric Constant 20
4-2-2 Hysteresis 21
4-2-3 Interface State Density (Dit) 21
4-3 Direction Current Characteristics 22
4-3-1 Post-gate Annealing with annealing Time and Temp.-dependent 22
4-3-2 Output Characteristics 24
4-3-3 Transfer Characteristics 25
4-3-4 Leakage current Characteristics 27
4-3-5 Three-terminal Drain-source Breakdown Characteristics 28
4-4 Temperature-Dependent DC Characteristics 29
4-4-1 Temperature-Dependent Output Characteristics 29
4-4-2 Temperature-Dependent Transfer Characteristics 32
4-4-3 Temperature-Dependent Leakage Current Characteristics 34
4-5 Microwave Characteristics 39
4-5-1 Pulse Characteristics 39
Chapter 5 CONCLUSION 42
References 43
Figures..................................................................................................................................48
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