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研究生：	黃同雋 Huang, Tong-Jyun
論文名稱：	以液相沉積法在氮化鎵上沉積鈦酸鍶膜之研究 Characterization of Liquid-phase-deposited SrTiO3 on GaN
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：	2009
畢業學年度：	97
語文別：	英文
論文頁數：	69
中文關鍵詞：	液相沉積法、鈦酸鍶、氮化鎵
外文關鍵詞：	Liquid Phase Deposition (LPD), SrTiO3, GaN
相關次數：	點閱：77 下載：3
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二氧化鈦膜具有高介電係數，加入鍶形成鈦酸鍶膜之後會增加其介電係數，因此我們研究以液相沉積法來成長鈦酸鍶膜，經過多次的實驗我們發現鈦酸鍶膜不但具有高介電係數，也能經由改善來提升其良好的介面品質。
在本文中，藉由使用液相沉積法我們成功的將鈦酸鍶薄膜沉積於氮化鎵材料上，液相沉積法是一種相當便宜又容易使用的氧化層沉積技術，並且可於室溫下使用，沉積的速率約可達到每小時45奈米。為了分析液相沉積法所沉積之二氧化鈦薄膜，我們使用X光譜儀、二次離子質譜儀與能量散佈分析儀來分析氧化層的化學組成成分和元素鍵結，掃描電子顯微鏡及原子力顯微鏡則用來觀察薄膜的表面狀態。當我們成長100奈米厚的氧化層時，氧化層漏電流密度可達到10-4A/cm2而電場約為-5MV/cm，崩潰電場則可以達到-6MV/cm以上。在經過高純度氮氣環境下的退火處理後，藉由X光繞射我們觀察到二氧化鈦氧化層由非晶相轉換至銳鈦礦及金紅石相且結晶顆粒增大，表面粗糙度也有所改善，在600℃退火處理後，最高的相對介電常數可以達到36。在經過400℃退火處理後，二氧化鈦氧化層漏電流密度可達到4.3×10-5A/cm2而電場約為-4MV/cm，崩潰電場則可以達到-6.3MV/cm，而它的相對介電常數可以達到29。

Titanium dioxide shows a high dielectric constant for dielectric applications. Besides, strontium can create additional oxygen vacancies that can enhance dielectric constant. In this study, we prepared SrTiO3 film by liquid phase deposition which is a novel material considered to have high dielectric constant. From several characteristic measurements, we found that SrTiO3 with exhibiting higher dielectric constant and well interface state.
SrTiO3 oxide has been deposited on GaN material through the liquid phase deposition method (LPD) which provides a low-cost and low-complex method in forming oxide layers at room temperature. The deposition rate is about 45nm/hr. X-ray photoelectron spectroscopy (XPS), second ion mass spectrometer (SIMS), and energy-dispersive spectrometer (EDS) are used to analyze chemical composition. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) are likewise used to observe the surface of the LPD-STO film. The leakage current is about 10-4A/cm2 at -5MV/cm and the breakdown field is more than -6MV/cm when the oxide thickness is 100nm. Upon annealing under an atmosphere of high purity N2, it is observed that the crystal phase of SrTiO3 transformed from the amorphous to the anatase and rutile phases and the crystal size increased by X-ray diffraction (XRD). Moreover, surface roughness improved significantly after thermal treatment, and the highest relative dielectric constant is 36 after annealing at 600℃. It is observed that the leakage current is about 4.3×10-5A/cm2 at -4MV/cm electric field and the breakdown field can reach -6.3MV/cm after annealing at 400℃ for 30 minutes, and the relative dielectric constant is 29.

Contents

Abstract
List of Tables
List of Figures
Chapter 1  Introduction	1
1.1   Motivation	1
1.2   High Dielectric Constant Materials	4
1.3   Organization	5
Chapter 2  LPD System	7
2.1   Introduction of the STO film Material	7
2.2   LPD System	10
2.3   Experimental Procedures	12
Chapter 3  Properties of the SrTiO3 Oxide Films	16
3.1   Introduction	16
3.2   Physical and Chemical Properties	17
3.2.1 Thickness and deposition rate	17
3.2.2 SIMS depth profile	21
3.2.3 EDS analysis	23
3.2.4 XPS spectra	25
3.3   Surface Morphology	28
3.3.1 SEM analysis	28
3.3.2 AFM analysis	30
3.4   Electrical Characteristics	34
3.4.1 Introduction	34
3.4.2 Current-Voltage (I-V) measurement	36
3.4.3 Capacitance-Voltage (C-V) measurement	39
Chapter 4  Annealing Effects on the LPD-STO film	41
4.1   Introduction	41
4.2   Annealing Effects on the Physical and Chemical Properties	41
4.2.1 Thickness and deposition rate	42
4.2.2 XRD analysis	44
4.3   Annealing Effects on Surface Morphology	46
4.3.1 AFM analysis	46
4.4   Annealing Effects on Electrical properties	50
4.4.1 Relative dielectric constant	50
4.4.2 Current-Vltage (I-V) characteristic	53
4.5   Performance of the AlGaN/GaN MOS-HFETs	57
4.5.1 The saturated drain current	57
4.5.2 The transconductance	59
4.5.3 The gate leakage current and breakdown voltage	61
4.5.4 Summary	61
Chapter 5  Conclusions & Future Work	63
References:	65


List of Tables

Table  1 Material properties of GaN and several conventional semiconductors	3
Table  2 Surface Roughness of different temperature and LPD-STO film	33

List of Figures

Chapter 1
Fig. 1- 1 The organization chart of this thesis	6
Chapter 2
Fig. 2- 1 Relationship between the bandgap and the permittivity for simple dielectrics	9
Fig. 2- 2 Schematic diagram of the apparatus for preparing LPD-STO film	14
Fig. 2- 3 Procedure of preparing LPD solution	15
Chapter 3
Fig. 3- 1 Dependence of oxide thickness and refractive index on deposition	19
Fig. 3- 2 The plot for oxide thickness deposition time with different growth temperature and 4ml Sr(NO3)2	20
Fig. 3- 3 SIMS depth profiles of LPD-STO film on GaN	22
Fig. 3- 4 EDS analysis of LPD-STO film on GaN	24
Fig. 3- 5 XPS spectra of the LPD-STO film on GaN	26
Fig. 3- 6 XPS spectra of (a)Ti (b)O and (c)Sr in LPD-STO films grown on GaN	27
Fig. 3- 7 Surface of as-deposited LPD-STO film oxide on GaN	29
Fig. 3- 8 (a)AFM 2d image of GaN (b)AFM 3d image of GaN	31
Fig. 3- 9 (a)AFM 2d image of as-deposited STO film	32
Fig. 3- 10 (a)AFM 2d image of as-deposited STO film	32
Fig. 3- 11 The fabrication procedure of MOS structure	35
Fig. 3- 12 I-V characteristic of as-deposited LPD-STO film in 40 and 60℃	37
Fig. 3- 13 The leakage current density of STO film below -6 MV/cm	38
Fig. 3- 14 C-V characteristic of as-deposited LPD-STO film in 40 and 60℃	40
Chapter 4
Fig. 4- 1 The normalized thickness of the annealed STO film oxide as a function of annealing temperature	43
Fig. 4- 2 X-Ray diffraction analysis of LPD-STO film annealing at different temperature for 30 minutes	45
Fig. 4- 3 AFM image of LPD-STO film annealing at 400℃ on GaN and deposition temperature is 40 ℃	47
Fig. 4- 4 AFM image of LPD-STO film annealing at 600℃ on GaN and deposition temperature is 40 ℃	47
Fig. 4- 5 AFM image of LPD-STO film annealing at 400℃ on GaN and deposition temperature is 60 ℃	48
Fig. 4- 6 AFM image of LPD-STO film annealing at 600℃ on GaN and deposition temperature is 60 ℃	48
Fig. 4- 7 Surface roughness RMS value of LPD-STO film annealing at different temperature on GaN and deposition temperature is 40℃ and 60℃	49
Fig. 4- 8 C-V characteristic of LPD-STO film after N2 annealing at 400 and 600℃	51
Fig. 4- 9 The plot of relative dielectric constant versus annealing temperature	52
Fig. 4- 10 I-V characteristics of LPD-STO film annealing at 400 and 600℃	54
Fig. 4- 11 The leakage current density of LPD-STO film annealing at 400 and 600℃	55
Fig. 4- 12 The breakdown electric field of LPD-STO film annealing at 400 and 600℃	56
Fig. 4- 13 The measured IDS-VDS characteristics of conventional HFET and MOS-HFET.	58
Fig. 4- 14 The measured transconductance and the drain current density versus VGS of conventional HFET and MOS-HFET.	60
Fig. 4- 15 The reverse gate leakage current versus VGS for conventional HFET	62
                                    

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