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모델링 및 실험적 접근에 따른 SiC 용액성장 Full-cycle 공정기술개발

Development of Full-cycle Process for Top Seeded Solution Growth of SiC Single Crystals Using Modeling and Experiments,

하민탄 (何明新, 경상대학교 대학원 세라믹공학전공)

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초록/요약moremore
As the saving energy material is becoming the trend of study in the 21st century, silicon carbide (SiC) gets much attention due to its wide band-gap coupled with excellent physical properties and chemical inert. It is suitable for the fabrication of high-efficiency power devices and working in harsh...
As the saving energy material is becoming the trend of study in the 21st century, silicon carbide (SiC) gets much attention due to its wide band-gap coupled with excellent physical properties and chemical inert. It is suitable for the fabrication of high-efficiency power devices and working in harsh environments such as high voltage, high temperature, high frequency, or intense radiation. Therefore, SiC single crystal is the target material to study in this thesis. Among methods to grow bulk SiC single crystal, top seeded solution growth (TSSG) is a promissory method to grow very high quality SiC single crystal. However, mastering TSSG for SiC is still a challenge at this time. Thus, this thesis shows our efforts to understand and develop the TSSG for SiC single crystal. This thesis is divided into six chapters: The first chapter briefly introduces the SiC single crystal, such as its microstructure and properties. Then the overview of bulk growth methods for SiC single crystal, including top-seeded solution growth (TSSG) which is the focused method in this study. In chapter 2, the numerical analysis is introduced. After that, the governing physics are discussed and implement to COMSOL multiphysics to modeling the TSSG process. After that, the simulation data was validated with experimental data. Chapters 3, 4, and 5 are the main content of the thesis. They present the process design of full-cycle TSSG of SiC single crystal through the understanding of physicochemistry properties in the melt obtained by both simulation and experiments. In chapter 3, the effect of temperature distribution in the melt into the quality of the grown crystal is discussed. From that revealing, a stable experimental setup was proposed to obtain good quality crystal and stable growth process. Chapter 4 shows the investigation into the fluid flow in the melt, which is a crucial factor to influence the growth rate of SiC crystal by TSSG method. From information collected through simulation, the growth rate was improved and predicted. Chapter 5 presents the study on the formation of a residual droplet on the surface of SiC crystal and the stress conducted by the droplet. Post-growth heat treatment was proposed to eliminate the droplet. The last chapter summaries the achievement in this thesis and suggests some prospects work in TSSG.
목차moremore
Chapter 1. INTRODUCTION AND MOTIVATION 5
1.1. SiC single crystal overview 5
1.1.1. Micro-structure and poly-types of SiC 5
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Chapter 1. INTRODUCTION AND MOTIVATION 5
1.1. SiC single crystal overview 5
1.1.1. Micro-structure and poly-types of SiC 5
1.1.2. Physical and electrical properties 9
1.1.3. Chemical properties 11
1.1.4. Application capabilities 12
1.2. Methods for bulk growth of SiC single crystal 14
1.2.1. Physical vapor transport 16
1.2.2. High temperature chemical vapor deposition 17
1.2.3. Top seeded solution growth 19
1.3. The motivation of the thesis 26
Chapter 2. MULTIPHYSICS SIMULATION OF SOLUTION GROWTH OF SiC SINGLE CRYSTAL 29
2.1. Overview of numerical analysis methods 30
2.2. Finite element method procedure 33
2.3. TSSG modeling procedure 35
2.3.1. Physics conducted in TSSG modeling 35
2.3.2. Boundary conditions and meshing 38
2.4. Simulation validation 41
2.4.1. Temperature verification 41
2.4.2. Fluid flow verification 42
Chapter 3. HOTZONE DESIGN OF THE TSSG REACTOR AND TEMPERATURE GRADIENT IN THE MELT 45
3.1. The length of the hot zone 45
3.1.1. Simulation results 46
3.1.2. Experimental results 52
3.2. The position of graphite reflector 57
3.2.1. Simulation results 59
3.2.2. Experimental result 62
3.3. Chapter conclusion 66
Chapter 4. EFFECT OF MELT FLOW TO THE CRYSTAL GROWTH RATE 67
4.1. A comprehensive investigation of fluid flow in the melt 68
4.1.1. General of carbon transport in the melt 68
4.1.2. Comparison of convective flow in the melt 69
4.1.3. Further discussion about electromagnetic convection 76
4.2. Implementation of flow modifiers 80
4.3. Growth rate analysis 86
4.3.1. Model for carbon distribution near the growth front 86
4.3.2. Numerical result 88
4.4. Chapter conclusion 91
Chapter 5. RESIDUAL Si DROPLET ON THE SURFACE OF GROWN SiC CRYSTAL 93
5.1. Simulation of residual Si droplet on the crystal surface 94
5.1.1. The shape of liquid Si droplet 94
5.1.2. Solidification process 96
5.1.3. Thermal shrinkage 97
5.2. Post-growth heat treatment 98
5.3. Chapter conclusion 101
Chapter 6. GENERAL CONCLUSION 102
종합결론 105
References 108