Leakage reduction and reliability enhancement of high-k dielectrics for next-generation memories

국문 초록 (Abstract)

고유전율 박막은 결정 결함 및 산소 공공 형성에 기인하는 신뢰성 문제가 발생하기 쉽다. 하지만, 기존 공정은 낮은 열 처리 온도 제한과 함께 원자층 증착으로 만들어진 고유전율 박막의 결함으로 인한 성능 저하라는 중요한 문제에 직면해 있다. 본 연구에서는 자외선 오존 저온 열 처리와 산소 분위기 열 처리를 결합한 새로운 공정, 라디칼 유도 산소 확산 및 비정질 유지 (RODA) 공정을 제안한다. RODA 공정은 자외선 오존 저온 열 처리 공정을 통해 고활성 산소 라디칼을 생성하고, 이를 하프늄 옥사이드 표면에 흡착시켜 산소 공공과 결합하여 결함을 치유하는 효과를 활용한다. 특히 RODA 공정은 단순히 결함을 완화하는 것 뿐만 아니라, 산소 분위기의 열 처리 공정 단계에서 산소 간질 원자를 박막 안으로 적극적으로 확산시켜 구조적 이완을 유도하고 안정적인 비정질 구조를 유지하여 박막의 전체적인 안정성을 향상시킨다. 가속 수명 시험 결과, RODA 공정을 통해 산화막 무결성이 크게 향상됨을 실험적으로 입증하였다. 엑스선 회절 분석은 넓게 분포한 비정질 산란 강도의 미세한 증가를 보여주며, 비정질 상과 단거리 질서가 유지되고 있음을 나타낸다. 엑스선 광전자 분광법 및 정전용량-전압 간 이력 현상 분석을 통해 RODA 공정이 과산화 결합 및 격자 산소와 관련된 다양한 결함 수준을 생성함을 확인했다. 이러한 정밀한 결함 화학 제어를 통해 박막 신뢰성이 크게 향상된다. 본 혁신적인 방법은 단순한 표면 처리를 넘어 박막 내부까지 제어하며, 원자층 증착으로 만들어진 고유전율 박막의 성능을 최대한 끌어낼 수 있는 새로운 결함 관리 방식을 제시한다. 이 연구 결과는 열 처리 온도 제한을 극복하고, 집적 회로의 소형화 추세를 지속할 수 있도록 RODA 공정의 가능성을 보여준다.

다국어 초록 (Multilingual Abstract)

High-k films often suffer from reliability issues stemming from crystalline defects and oxygen vacancy formation. However, conventional processes face a critical challenge: limited thermal budgets and defect-related degradation of atomic layer deposited (ALD) high-k films. This work introduces the Radical induced Oxygen Diffusion and Amorphous retention (RODA) process—a unique combination of UV-O3 Low-Temperature Annealing (LTA) followed by Oxygen atmosphere thermal annealing (PDA). RODA leverages the synergistic effect of generating highly active oxygen radicals through UV-O3 LTA, which are initially adsorbed onto the HfO2 surface and bond with oxygen vacancies, initiating defect healing. Importantly, RODA doesn't simply mitigate defects; the O2 PDA step actively drives Oi into the bulk, inducing structural relaxation and maintaining a remarkably stable, amorphous structure, enhancing the film’s overall stability. Experimental results demonstrate significant enhancements in oxide integrity under accelerated testing. GI-XRD confirms a slight increase in broad halo intensity, indicating the persistence of an amorphous phase and short-range order. XPS and C-V measurements reveal that RODA facilitates the diffusion of oxygen interstitials into the bulk, effectively passivating oxygen vacancies associated with lattice oxygen and thereby reducing trap density, leading to enhanced oxide reliability. This novel approach provides a paradigm shift in defect engineering, extending beyond surface treatments to achieve deep-bulk control and unlock the full potential of ALD-deposited high-k materials. These findings highlight RODA’s potential to overcome thermal budget limitations and enable continued scaling of integrated circuits.

목차 (Table of Contents)

• Chapter 1. INTRODUCTION 1
• 1. Background and Motivation 1
• 2. Research Objectives and Scope 15
• A. Academic Contributions 15
• B. Technological Contributions 16
• C. Core Research Content 17
• 3. Distinctive Aspects and Expected Outcomes of the Research 18
• A. Distinctive Aspects of the Research 18
• B. Expected Outcomes 20
• 4. Dissertation Structure and Flow 21
• Chapter 2. Theoretical Background 22
• 1. Properties and Crystallization Mechanisms of High-k Thin Films 22
• A. The Evolution of Dielectrics and the Need for High-k Materials 22
• B. Key Characteristics of High-k Materials 27
• C. High-k Thin Film Crystallization Process and Reliability Degradation Factors 29
• D. Comparison with Existing Technologies and Advantages of UV-O3 Low-Temperature Annealing 32
• 2. Atomic Layer Deposition (ALD) 42
• A. ALD Principles and Mechanism 42
• B. ALD Process Variables and Their Influence on Film Properties 45
• C. Limitations of ALD and Supplementation with UV-O3 Low-Temperature Annealing 45
• 3. UV-O3 Low-Temperature Annealing 46
• A. Principles and Effects of UV-O3 Low-Temperature Annealing 46
• B. UV-O3 Treatment and Frenkel Pair Formation 47
• C. Impact of UV-O3 Low-Temperature Annealing Process Parameters on Film Properties 55
• D. Advantages and Limitations of UV-O3 Low-Temperature Annealing 55
• 4. Thermal Annealing Process 56
• A. Thermal Annealing Conditions (Temperature, Gas Atmosphere, and Time) 57
• B. Influence of Thermal Annealing on Thin Film Properties 57
• 5. Electrode Materials 60
• A. Characteristics and Types of Metallic Electrode Materials 60
• B. Electrode-Dielectric Interface Characteristics and Interactions with High-k Films 62
• Chapter 3. Experimental Methods 63
• 1. High-k Film Fabrication Process 63
• A. Film Structure and Deposition Parameters for AZA and HZAZA structures 64
• B. Thermal Annealing 64
• C. UV-O3 Low-Temperature Annealing Process 64
• 2. Thin Film Structure Analysis (X-ray Diffraction, XRD) 65
• 3. High-Resolution Transmission Electron Microscopy (HR-TEM) and Atomic Force Microscopy (AFM) 67
• 4. X-ray Photoelectron Spectroscopy (XPS) 67
• 5. Electrical Characterization (C-V, C-F, TZDB, TDDB) 68
• A. Time-Zero Dielectric Breakdown (TZDB) 69
• B. Time-Dependent Dielectric Breakdown (TDDB) 69
• 6. Reliability Analysis Methods 70
• A. Weibull Probability Analysis 70
• B. Lifetime Prediction Models 71
• Chapter 4. Interface Engineering for High-k Thin Film Structure and Process Optimization 73
• 1. Research Background and the Importance of Interface Engineering 74
• A. Performance Degradation Factors in High-k Thin Film Devices and the Significance of Interfaces 74
• B. Concept of Interface Engineering and its Impact on High-k Thin Film Device Performance 74
• C. Novel Structural Design for Enhanced Reliability: Thin Film Stack Engineering 77
• D. Differentiation through Interface Engineering: A Holistic Approach 77
• 2. Exploratory Study of AZA Structures: Initial Stage of Interface Engineering Application 78
• A. AZA Structure Design and Process Conditions 78
• B. Electrical and Physical Characterization of AZA Structures 80
• 3. Introduction to RODA process and Design implications for HZAZA 109
• A. Radical induced Oxygen Diffusion and Amorphous retention (RODA): A Proactive Defect Engineering 109
• B. Analysis of AZA Structure and Design Direction for HZAZA Structure and Process 111
• C. Oxide integrity test for Optimized RODA : Sequence and Process Optimization using TZDB and TDDB 117
• D. XPS results and discussion for RODA Sequence 126
• E. XRD analysis for amorphous retention of HZAZA with RODA sequences 131
• F. Capacitance Measurements of RODA Effect in HZAZA 133
• Chapter 5. Conclusion and Future Work 143
• 1. Summary of Research Findings 143
• 2. Contributions of the Research 145
• 3. Future Research Directions 146
• References 148
• Korean Abstract 153