(A) Study on Thermal Stability of Ni-Silicide and Characteristics of Junction Leakage Current Using Cluster Carbon Co-implanted Source/Drain for Nano-scale MOSFETs

다국어 초록 (Multilingual Abstract)

One of the key challenges for future CMOS technology nodes is to form source/drain junctions with very small parasitic series resistance. This requires fundamentally new junction and contact formation technologies to produce ultra-shallow junctions with super abrupt doping profiles, above equilibrium dopant activation and contact resistivity.
Generally, Cobalt was used for contact material for Source/Drain and gate of MOSFET. At present, it is believed that Ni silicide will replace current CoSi2 for nano-scale MOSFET because Ni silicide has several advantages over CoSi2. But poor thermal stability is a main obstacle to be applied on the nano-scale CMOSFET. In this study, the nickel silicide (NiSi) on different substrates (cluster carbon, and boron cluster (B18H22) co-implanted substrate) was investigated in the point of improving the thermal stability and analysis of junction leakage current. To improve the thermal stability, Thermal stability improvement of the NiSi based on boron cluster (B18H22) implanted substrate is investigated using Ni-Pd(5%) alloy and Yb/Ni/TiN structures. The proposed Ni-Pd(5%) alloy and Yb/Ni/TiN structures technology exhibits low temperature silicidation with a wide temperature window for rapid thermal process (RTP). Moreover, sheet resistance shows stable characteristics in spite of the high temperature post-silicidation annealing up to 700 ℃ for 30 min. Second, various metal alloys were used. Also post-silicidation annealing condition was split as N2 ambient and vacuum. Thermal stability improvement of the NiSi based on boron cluster (B18H22) implanted substrate is investigated using different annealing ambient of N2 and vacuum. In case of a vacuum ambient, the sheet resistance and cross-sectional profile showed more stable characteristics than N2 ambient, because the Ni and boron diffused less than N2 ambient annealing. Agglomeration was suppressed though the vacuum annealing with reduction of the boron and nickel diffusion. A B18H22 implant was compared with a BF2 and B11 case. B18H22 doped substrate shows lower junction leakage current than BF2 and B11 doped substrates. Therefore, boron cluster (B18H22) ion implantation is promising for ultra shallow junction for nano-scale CMOSFETs as the thermal stable NiSi can be formed on the B18H22 implanted source/drain. Different implant sequences have been compared in which B18H22 and C16H10 have been combined with pre-amorphization and co-implants. Co-implantation schemes using C16+B18H22 results in shallow and abrupt junctions. Finally, although C16 can increases leakage current it is still attractive as it increases the thermal stability of junctions in post-processing anneals.

목차 (Table of Contents)

• 1. 서 론 1
• 2. 이론적 배경 7
• 2.1. Nickel을 이용한 실리사이드 7
• 2.1.1. Nickel-silicide 7
• 2.1.2. Heavy dopant (B18H22) 9
• 2.1.3.BF2 의 문제점들 10
• 2.1.4. SOI 에서 Nickel-silicide의 특성 11
• 2.2.junction leakage current 특성 12
• 2.2.1.Poole-Frenkel barrier lowering 13
• 2.2.2. Schottky barrier lowering 15
• 2.2.3. Schottky barrier diode 누설전류 17
• 2.2.4. 터널링에 의한 누설전류 19
• 2.3.Nickel Germanosilicide 및 Selective eching of RE-Germanide 21
• 3. 실험 및 측정방법 23
• Nickel silicide 형성 과정 및 열안정성 평가 23
• Diode 제작과정 25
• Silicide의 물리적, 전기적 특성 평가 27
• 4. 실험결과 및 고찰 28
• 4.1. Cluster carbon 에서의 silicide 특성 28
• 4.1.1.Boron cluster(B18H22)와다른 dopants들과의 비교 28
• 4.1.2. 주입 Energy 변화에 따른 B18H22의 silicide 특성 변화 35
• 4.1.3.Boron cluster과 다른 dopants과의 Reverse leakage current 분석 41
• 4.1.4.Cluster carbon 적용 시 다른 dopants들과의 비교 43
• 4.1.5.Cluster carbon 적용 시 Boron cluster (B18H22) silicide 특성 49
• 4.1.6.Carbon 적용 시 Boron cluster (B18H22)의 leakage current분석 57
• 4.2. Ni-Pd(5%)/TiN 을 적용한 Boron cluster (B18H22)의 특성 개선 59
• 4.2.1. Ni-Pd(5%)/TiN을 적용한 Boron cluster (B18H22)물리적, 전기적 특성 59
• 4.2.2. Ni-Pd(5%)/TiN 을 적용 시 Reverse leakage current 비교분석 67
• 4.3. Yb/Ni/TiN을 적용한 Boron cluster (B18H22)의 특성 개선 69
• 4.3.1. Yb/Ni/TiN을 적용한 Boron cluster (B18H22)열 안정성 개선 69
• 4.3.2. Yb/Ni/TiN을 Cluster carbon에 적용한 열 안정성 개선 77
• 4.3.3. Yb/Ni/TiN을 적용 시 Reverse leakage current 비교분석 84
• 4.4. SOI에 적용된 Boron cluster (B18H22) Ni-silicide의 특성 86
• 4.5. Vacuum Anneal을 통한 열 안정성 개선 89
• 4.6. Junction leakage current 대한 분석 96
• 4.7. Selective eching of RE-Germanide 102
• 4.7.1. RE-Germanide의 Etching 대한 실험 102
• 4.7.2. TiN 대신 Ti 사용 한 경우 RTP 와 Anneal 진행 후 특성 비교 110
• 5. 결론 117
• 6. 참고문헌 119
• 7. 영문 요약문 124