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Reactive Magnetron Sputtering에 의한 p-type SnO TFT의 저온공정 제작 및 특성 연구

  • 한광희 (대학원 전기전자공학과 반도체 및 나노전공)

초록/요약

The best fabrication condition and transition were investigated about the p-type SnO thin-film transistors (TFTs) using tin-oxide with different deposition temperature and oxygen partial pressure. At first, to analysis the chemical and electrical properties of SnOx channel layers, SnO thin films were deposited on Si substrate (i.e. 100 oriented) with difference oxygen partial pressure ( = 3 to 12 %) by DC magnetron reactive sputter. From the x-ray photoelectron spectroscopy (XPS) data, it is demonstrated that the phase of tin oxide partially transforms from SnO to SnO2 with an increasing oxygen partial pressure ( = 3 to 12 %). From this data, It is concluded that the analysis show that the deposition conditions of = 6 % (SnO = 80.0 %) is the most optimal conditions for fabricating SnO thin-film. In this study, SnOx thin films were deposited with low temperature ( = 50 to 250 °C) without post annealing process. By reducing the step of fabrication process about active layer, It is expect to save time and cost to fabricate the TFT. In addition, It is distinguished from other studies by the fact that the thickness of the thin film is relatively thin at 5 nm. As a result of SEM analysis, It is confirmed that the crystalline increases rapidly at 250 °C. However, no significant difference in crystalline was observed at temperatures below 250 °C. This is probably due to the small size of the crystals of SnOx. From XRD data as the deposition temperature increases, which is mainly attributed to the increase the crystal structures. The origin of holes that determine the mobility of p-type SnO semiconductors is known to originate from the tin vacancy. This is a natural phenomenon in the case of sputtering deposition, which is caused by the binding of Sn metal ions and oxygen. It is confirmed about this phenomenon through thin-film analysis and analyzed the correlation of electrical characteristics. After SnOx thin film analysis, SnO-TFT devices were fabricated which is Staggered Bottom-Gate structure. As a result of the field-effect mobility() is 0.85 /Vs, at = 225 °C and on/off ratio of , and a sub-threshold swing of 14 V/decade, at = 200 °C. However field-effect mobility() is 0.29 /Vs, and on/off ratio of at = 250 °C (over the melting point of Tin, 239.1 °C).

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Abstract ⅰ
목차 ⅳ
그림 목차 ⅶ
표 목차 ⅹ
기호 및 약호 목록 ⅺ

제 1장. 서 론 1

제 2장. 이론적 배경 3
2.1. SnO (Tin(Ⅱ) oxide) 3
2.1.1. SnO의 구조적 특성과 상태도 3
2.1.2. SnO의 밴드 구조 6
2.2. 박막 트랜지스터(Thin Film Transistor : TFT) 12
2.2.1. 박막 트랜지스터의 구조 12
2.2.2. 박막 트랜지스터의 동작 특성 14
2.2.3. 박막 트랜지스터의 성능 파라미터 16
2.2.3.1. 드레인 전류(Drain current, IDS) 16
2.2.3.2. 문턱전압 (Threshold voltage, VTH) 18
2.2.3.3. SS (Subthreshold swing) 19
2.2.3.4. 전류점멸비 (Ion/off current ratio) 19
2.3. 박막과 스퍼터링 21
2.3.1. 박막 형성의 기본 개념 21
2.3.2. Sputtering 원리 23
2.3.3. Sputtering 종류 25
2.3.3.1. DC Sputtering 25
2.3.3.2. RF Sputtering 27
2.3.3.3. Magnetron Sputtering 29
2.3.3.4. Reactive Sputtering 31

제 3장. 실험 및 분석 방법 32
3.1. SnO(Tin monoxide) 박막 증착 32
3.2. 전극 형성 34
3.3. 박막 특성 분석 37
3.3.1. Atomic Force Microscopy (AFM) 37
3.3.2. Scanning Electron Microscope (SEM) 38
3.3.3. X-ray Photoelectron Spectroscopy (XPS) 39
3.3.4. Hall Effect measurement 40
3.3.5. X-Ray Diffraction (XRD) 42

제 4장. 결과 및 고찰 43
4.1. SnO 박막 특성 분석 43
4.1.1. 박막의 화학 결합 분석 43
4.1.1.1 산소 분압에 따른 화학 결합 분석 43
4.1.1.2 증착 온도에 따른 화학 결합 분석 48
4.1.2. 박막의 표면 거칠기 분석 52
4.1.3. 박막의 표면 형상 분석 54
4.1.4. 박막의 홀 측정 56
4.1.5. 박막의 결정성 분석 58
4.2. SnO TFT의 전기적 특성 분석 61
4.2.1. 증착 온도에 따른 p-type SnO TFT의 I-V 특성 61

제 5장. 결 론 66

참고문헌 68

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