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研究生:蘇俊龍
研究生(外文):Jun-Long Su
論文名稱:Al.32Ga.68N/GaN異質結構場效電晶體之研製
論文名稱(外文):Investigation and Fabrication of Al.32Ga.68N/GaN Heterostructure Field Effect Transistor
指導教授:許渭州
指導教授(外文):Wei-Chou Hsu
學位類別:碩士
校院名稱:國立成功大學
系所名稱:微電子工程研究所碩博士班
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2004
畢業學年度:92
語文別:中文
論文頁數:63
中文關鍵詞:氮化鋁鎵異質結構場效電晶體
外文關鍵詞:HFETGaNEtchAlGaN
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  • 下載下載:42
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  本論文中,我們分別利用氯氣、三氯化硼和氬氣的混和氣體作為感應耦合電漿源,對氮化鋁鎵做蝕刻特性探討。首先,我們以氯氣和氬氣的混合氣體作電漿實驗,得到當氯氣和氬氣含量分別為30及10sccm(即3:1)時會有最大蝕刻速率620nm/min,並且在感應耦合電漿功率提高的狀況下,也能獲得較高的蝕刻速率。而在氯氣、三氯化硼和氬氣的混合電漿中,當氯氣含量增加時,能得到較高的蝕刻速率,這是因為在三種混合氣體的蝕刻機制中,氯為主宰蝕刻反應的主要離子,其次為氬離子,最後才是三氯化硼離子。因此,如果想利用較低的蝕刻速率在製程上,可以使用純三氯化硼的電漿,其蝕刻速率為70nm/min。另外,蝕刻表面經過退火後表面粗糙度亦可大幅改善。

  此外,我們也成功的製作出氮化鋁鎵異質結構電晶體,並分析其直流和高頻特性。我們磊晶成長了三種不同通道厚度的結構來探討其特性的變化,其中通道厚度分別為1800Å、1500 Å和1200 Å。在直流方面,由於通道厚度1800Å為三者中最大所以通道內載子量為最多,使得其在三者中擁有最大飽和電流密度160mA/mm和最高轉導74mS/mm。我們也利用了嵌入埋藏鎂摻雜氮化鎵和氮化鋁鎵來做絕緣層以降低漏電流的發生,因此而得到相當好的截止特性。高頻特性方面,1800Å和1500Å結構的單一增益截止頻率分別為1.82GHz和1.69GHz。另外我們也做了一組變溫的量測,發現隨著溫度升高,轉導值和飽和電流都會因為高溫造成雜質散射效應降低了電子移動率而下降。不過當溫度達200oC時,仍保有很好的電晶體特性且轉導值仍有48mS/mm,證明這材料適於高溫的應用。
  In this thesis, we utilized Cl2, BCl3 and Ar mixtures as the inductively coupled plasma source to research the etching characteristics of AlGaN. At first, we used Cl2 and Ar mixtures as inductively coupled plasma, and we obtained the result that the highest etching rate 620nm/min can be got when the flow rate Cl2 : Ar = 30 : 10 sccm (3:1). Furthermore, we can get higher etching rate at higher ICP power. Besides, in the Cl2, BCl3 and Ar mixed plasma, the ratio of Cl2 increase, the higher etching rate can be obtained. This is because during the etching mechanism of the three mixed plasma, the dominant ion of the whole etching reaction is Cl, the next is Ar, and BCl3 is the weakest in the reaction. Therefore, if someone wants to make use of the lower etching rate in fabrication process, the pure BCl3 plasma is a very good choice, and the etching rate is about 70nm/min. In addition, the surface roughness of the etched samples can be substantially improved after RTA annealing.
  Besides, we have successfully fabricated the AlGaN/GaN heterostructure field effect transistor and analyzed the DC and RF characteristics. We grew three kinds of heterostructures with different channel thickness to discuss the characteristic variations of them. In DC characteristics, the maximum drain current density (Idss) 160mA/mm and the highest transconductance (Gm Max) 74 mS/mm can be obtained in the structure of channel thickness 1800Å. In addition, we inserted the Mg-doped insulating GaN layer to eliminate the leakage current. In RF characteristics, the unity gain cut-off frequency of structure 1800Å and 1500Å are 1.82GHz and 1.69GHz, respectively. Moreover, we also measured the DC characteristics at different temperatures and found that transconductance and drain current density decreased with the increase of temperatures. However, the device can still normally operate at 200oC with transconductance 48mS/mm. It proves that this material suits the applications at high temperature.
Contents
Abstract (Chinese)
Abstract (English)
Chapter 1 Introduction
1.1 The background research on GaN 1
1.2 Organization 2
Chapter 2 Measurement Techniques and Instruments 4
2.1 Photoluminescence (PL) measurement 4
2.2 Inductively coupled plasma reactive ion etching (ICP-RIE) 4
2.3 Atomic force microscope (AFM) 5
2.4 Rapid thermal annealing (RTA) 6
2.5 Alpha step measurement system 7
Chapter 3 LP-MOCVD System and Epitaxy Procedures 8
3-1 System introduction 8
3-1-1 The gas handling system 9
3-1-2 The bypass pipe line 10
3-1-3 The reaction chamber and heating system 10
3-1-4 The automatic pressure control (APC) system 11
3-1-5 The gas exhaust system 12
3-2 Epitaxy growth 12
Chapter 4 Inductively coupled plasma (ICP) on AlGaN 14
4.1 Introduction 14
4.2 Experiment arrangement 15
4.3 Results and discussion 16
4.4 Conclusions 18
Chapter 5 Fabrication and characteristics of AlGaN/GaN HEMT 19
5.1 Introduction 19
5.2 Epitaxy growth 20
5.3 Fabrication processes 20
5.3-1 Mesa definition 20
5.3-2 Source-drain definition 21
5.3-3 Gate definition 22
5.4 Device structure 22
5.5 Characterization and discussion 23
5.6 The RF characteristic of AlGaN/GaN HEMT 25
Chapter 6 Conclusions and Further works 26
6.1 Conclusions 26
6.2 Future works 28
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[32]. 國立成功大學碩士論文 ”Investigation and Fabrication of AlGaN/GaN MODFET by ICP System” by Tzu-hsuan Hsu.
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