나노압입시험을 이용한연질 박막에서의 점착력 평가

학위논문 (석사)-- 서울대학교 대학원 : 재료공학부, 2017. 2. 권동일.계면은 이종소재간의 접합 등으로 나타나며, 박막과 모재에 비해 상대적으로 기계적 특성이 취약한 부분이다. 그 중 증착으로 인해 발생하는 박막의 점착력은 박막시스템의 신뢰성을 평가하기 위한 주요 요소 중 하나이다. 그 동안 박막의 점착력을 평가하고자 한 시험법들은 대개 파괴적인 방식을 이용하였다. 그래서 비파괴적인 시험법인 압입시험으로 점착력을 평가하는 기존 모델을 소개하고 이를 기초로 더 발전시킬 방법을 연구하였다. 기존 모델에서는 계면의 점착력으로 인해 상대적으로 연질의 재료의 소성변형역이 구속된다고 보았다. 그래서 박막과 기판의 소성변형역을 각기 구하고, 박막, 기판, 복합물의 경도로 계면인자를 구하였다. 이후 계면인자와 상대적 연질 재료의 경도와의 관계로 점착력을 구할 수 있다. 이렇게 하여 기존 모델에서는 같은 재료로 공정 과정을 다르게 하여 그 점착력을 비교할 수 있었다. 그러나 기판의 소성변형역을 구할 때 박막과의 관계를 고려하지 않았기 때문에 다른 재료끼리 점착력을 비교할 때에는 기존 모델을 사용할 수 없다. 그렇기 때문에 실제 복합물의 압입과정에서 박막 내부에 수압 부분이 생긴다는 연구를 바탕으로 하여, 간접적으로 기판의 소성변형역을 구할 수 있었다. 경질의 기판 위에 서로 다른 연질 박막, 서로 다른 경질 기판 위에 연질 박막을 제작하여 스크래치 테스트와 비교하였다. 그 결과 서로 다른 경질 기판 위에 연질 박막의 점착력을 정성적으로 비교하는 것에 새로 제시한 모델을 쓰는 것이 적합함을 확인할 수 있었다. 같은 재료, 다른 공정을 이용할 때에만 기존 모델로 비교할 수 있었다는 한계에서 벗어나, 연질의 박막을 증착한다면 서로 다른 재료에서도 점착력 비교가 가능하게 되었다는 점에서 모델의 의의를 갖는다.1. 서론 1 2. 이론적 배경 3 2.1. 점착력 측정 방법들 3 2.2.나노압입시험법 5 3. 나노압입시험을 이용한 박막의 점착력 평가 11 3.1. 모델의 기본 개념 11 3.2. 계면인자와 점착력 14 3.3. 기존 모델의 실험 방법 및 의의와 한계 16 4. 연질 박막 복합물에서 소성변형역 모델 21 4.1. 복합물에서의 기판이 받는 힘과 소성변형역 21 4.2. 모델링 구체화 24 5. 시편 제작 및 분석 29 5.1. 시편 제작 과정 및 실험 방법 29 5.2. 스크래치 테스트 31 5.3. 실험 결과 및 분석 32 6. 결론 45 참고문헌 46 Appendix 48 Abstract 53Maste

Channel-Stacked NAND Flash Memory with High-κ Charge Trapping Layer for High Scalability

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2016. 2. 박병국.Exploding demands for mobile devices induce the drastic expansion of the market of NAND flash memory as high density storage devices. Three-dimensional (3D) NAND flash memory paved a new way of increasing the memory capacity by stacking cells in three-dimension. For stacked NAND flash memory, the thickness of ONO (memory dielectric layers) is a roadblock in scaling-down of the minimum feature size, because channel diameter can be scaled down to < 20 nm. However, it is challenging to reduce the thickness of oxide-nitride-oxide (ONO) layer, since the charge trapping properties degrade when the Si3N4 is made thinner. .In this thesis, the channel stacked NAND flash memory array (CSTAR) with high-κ charge trapping layer for high scalability is proposed. To adopt high-κ layer into 3D NAND, its memory characteristics were evaluated with capacitors and gate-all-around flash memory devices. Finally, 4-layer channel stacked memory with high-κ layer was successfully fabricated and characterized. Recent trend of nonvolatile memories are introduced and the overview of 3D stacked NAND flash memory technology is presented in Chapter 1 and 2. In Chapter 3, the memory characteristics of high-κ layer were evaluated with fabricated capacitors and flash memory devices. In Chapter 4, fabrication process and electrical characteristics of CSTAR with high-κ are shown. With the comparison with previous works using ONO layer, CSTAR with high-κ is evaluated. In Chapter 5, the novel operation method of CSTAR is presented. Using TCAD and measurement, a newly designed operation method is verifiedChapter 1 Introduction 1 1.1 Flash Memory Technology 1 1.2 Flash Memory Unit Cell and Array Structure 6 1.3 NAND Cell Operation 13 1.4 Charge Trap Flash Memory 25 Chapter 2 3-D Stacked NAND Flash Memory 28 2.2 Examination of Previous 3-D Stacked NAND Flash 28 2.2.1 Gate Stack Type 3-D NAND Flash Memory 28 2.2.2 Channel Stack Type 3-D NAND Flash Memory 36 2.2.3 Comparison between the Gate Stack Type and the Channel Stack Type 45 Chapter 3 Channel Stacked NAND Flash Memory with high- Charge Trapping Layer 48 3.1 Introduction 48 3.2 Memory Characteristics of HfO2 52 3.3 Fabrication of Nanowire Memory Devices with high-κ Dielectric Layer 56 Chapter 4 Fabrication of Channel Stacked NAND Flash Memory with High-κ 66 4.1 Introduction 66 4.2 Fabrication Method 67 4.3 Key Process Steps of CSTAR with high-κ 72 4.3.1 Single Crystalline Silicon Channel 72 4.3.2 Fin Patterning 74 4.3.3 Stacked Nanowires 76 4.4 Measurement Results 81 4.5 Comparison with Previous Works 88 Chapter 5 Novel Program Operation in CSTAR 92 5.1 Introduction. 92 5.2 Simulation Results 93 5.3 Measurement Results 103 Chapter 6 Conclusions 106 Bibliography 108 Abstract in Korean 116 List of Publications 118Docto

아밀로수크레이스와 메뚜기콩 검을 이용한 지소화성 전분의 제조 및 물리화학적 특성

학위논문 (석사)-- 서울대학교 대학원 : 농생명공학부, 2011.2. 문태화.Maste

한 농촌지역 인구 집단에서 미세알부민뇨에 독립적으로 영향을 미치는 BaPWV 상승에 관한 연구

학위논문 (석사)-- 서울대학교 보건대학원 : 보건학과 보건학 전공, 2016. 2. 조성일.Objectives Microalbuminuria is used to a predictor for cardiovascular morbidity and mortality due to cardiovascular diseases. Also, microalbuminuria is a marker of generalized endothelial dysfunction resulting from arterial stiffness or insulin resistance. However, the mechanism of microalbuminuria is unclear. Therefore, it is important to evaluate the relationship between arterial stiffness or insulin resistance and microalbuminuria. Meanwhile, brachial-ankle pulse wave velocity (baPWV) is a good measure of arterial stiffness. Thus, baPWV is a useful measure for explain the relationship between arterial stiffness and microalbuminuria. This study aimed to investigate whether elevated baPWV is independently associated with microalbuminuria. Methods This study included 1,648 individuals aged over 40 who participated in baseline Multi-Rural Cohort Study conducted in Korean rural communities between 2005 and 2006. The participants were classified into: less than 30mg/g as normoalbuminuria or 30-300mg/g as microalbuminuria using urinary albumin creatinine ratio (UACR). BaPWV data were transformed to a normal distribution using natural logarithms to improve normality. Multivariate logistic regression analyses were performed to determine associations with baPWV and microalbuminuria and odds ratios were calculated. Results The median and Q1-Q3 baPWV values were significantly higher in the microalbuminuric group both in men (1538, 1370-1777 cm/s vs. 1776, 1552-2027 cm/s, p<0.001) and in women (1461, 1271-1687cm/s vs. 1645, 1473-1915cm/s, p<0.001). Five models were used to estimate the relation between baPWV and microalbuminuria. The baPWV was independently associated with microalbuminuria in both genders after adjusting for heart rate, fasting blood glucose, triglyceride, homeostatic model assessment insulin resistance and history of hypertension and diabetes. Fasting blood sugar and HOMAIR were judged they had nothing to do with multicolinearity (r=0.532, p<0.001). Log(baPWV) (OR15.813, 95%CI2.629-95.119) was the only independent risk factor in men, while log(baPWV) (OR5.399, 95%CI1.157-25.205) and fasting blood glucose (OR1.011, 95%CI1.002-1.020) were significant in women by adjusting for all significant variables in the univariate analyses. Conclusion BaPWV was the only factor examined that was independently associated with microalbuminuria in both genders and in all the models examined. Elevated baPWV is independently associated with microalbuminuria regardless of insulin resistance among rural subjects over 40 yr. However, baPWV cant be a very good indicator considering relatively low explanatory power representing for adjusted R2 value. It means that many factors contribute to microalbuminuria except baPWV as well as other factors used this study. However, in consideration of not only the ease of the measurement of baPWV but results of this study, it may be a useful screening tool for predicting cardiovascular complications.Introduction 1 Background 1 Literature Review and Necessity of this study 2 Objectives 4 Materials and Methods 5 Subjects and General characteristics variables 5 Study Modeling 8 Brachial-ankle pulse wave velocity 11 Microalbuminuria 13 Blood pressure and blood chemistry 13 Statistical analysis 16 Results 17 General characteristics of the study population 17 Age-adjusted characteristics according to baPWV quartiles 20 UACR levels and distribution of microalbuminuria of study population according to baPWV quartiles 25 Comparison of the normoalbuminuric and microalbuminuric group 29 Odds ratios and 95% Confidence intervals of microalbuminuria stratified by diseases status 34 The relation between baPWV and microalbuminuria 37 Discussion 42 Discussion on Results 42 Limitations and Strengths 46 Conclusion 47 References 49 국문초록 55Maste

Channel Stacked Array NAND Flash Memory With Vertically Stacked String Selection Line (SSL)

학위논문 (석사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2012. 8. 박병국.Three-dimensional (3D) stacked memory devices are representative solutions that can lead to reduce bit cost of NAND flash memories. Recently, many groups have proposed various types of 3D stacked NAND flash memory devices. In this thesis, we propose a novel 3-D STacked Array (STAR) NAND flash memory featuring Gate-All-Around (GAA) structure with single crystalline Si channel. In Chapter 1 and 2, we introduce a newly designed structure, compact STAR, and address the advantages of compact STAR over other types of 3D stacked NAND flash memories. By using TCAD simulation, we demonstrate that the proposed array structure can support fully compatible device operation with conventional NAND array. In Chapter 3 and 4, we investigate the advantages of metal gates in a 3D stacked NAND flash memory compared with poly-Si gates in terms of the variation of dopant concentration. Also, we show the fact that NAND flash memory cells featuring a GAA structure are less sensitive to the variation of the gate dimensions than cells featuring a DG structure. In Chapter 5, we investigate the cell characteristics with respect to physical dimensions of channel and gate experimentally. Poly-Si channel with GAA structure flash memory cells are successfully fabricated.Abstract i Contents iii 1. Introduction 1 2. Compact Channel Stacked Array 5 2. 1 Concept 5 2. 2 Fabrication Process 8 2. 3 Summary 13 3. Poly Depletion Effect in 3D NAND Flash Array 14 3. 1 Introduction 14 3. 2 Simulation Results 15 3. 3 Summary 19 4. Effect of the Variation of Gate Dimensions on Program Characteristics in 3D NAND Flash Array 20 4. 1 Introduction 20 4. 2 Simulation Results 21 4. 3 Summary 29 5. Fabrication of poly-Si Channel Stacked Array 30 5. 1 Introduction 30 5. 2 Fabrication Process 31 5. 3 Measurement Results 36 6. Conclusion 41 Bibilography 43 Abstract in Korean 49Maste