수직 구조 발광 다이오드에서 열 방출 향상과 Sn 확산 방지층에 대한 연구
Enhanced Heat Dissipation and Sn Diffusion Barrier in Vertical Light Emitting Diodes
- 주제(키워드) dissipation , V-LED , Sn , diffusion barrier
- 발행기관 포항공과대학교 일반대학원
- 지도교수 이종람
- 발행년도 2014
- 학위수여년월 2014. 2
- 학위명 석사
- 학과 및 전공 일반대학원 첨단재료과학부
- 세부전공 전자재료
- 원문페이지 61
- 실제URI http://www.dcollection.net/handler/postech/000001678700
- 본문언어 영어
- 저작권 포항공과대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
We demonstrated the GaN based vertical light emitting diodes with enhanced heat dissipation. This device had a new utilizing receptor which was the Cu extreme flat substrate. GaN based V-LED occurs much higher temperatures so we could design to extract much heat with Cu extreme flat substrate which has much higher thermal conductivity, 401 W/m•K. As the result, the forward voltage of Cu (Vf=3.15V) was lower than Mo (Vf=3.21V) and Si (Vf=3.28V) and this result could be connected with a reliability test. After all, the Cu substrate device (more than 600 hour) could be lost lasting than Mo (450 hour) and Si (530 hour) substrate. However, wafer bowing is a big problem in some metals with high thermal expansion coefficient. So we suggest a low temperature bonding with Au-Sn(1:9). But, there was still the Sn diffusion problem so we could need to design new Sn diffusion barrier. In this dissertation, Ni/Cu and W/Mo diffusion barriers had a hopeful outlook. More than 7 multi layers of Ni/Cu and W/Mo could block Sn diffusion at the V-LED structure. Consequently, Ni/Cu and W/Mo multi layers were confirmed a distinct possibility as a Sn diffusion barrier. In conclusion, these results clearly represent enhanced V-LED characteristics, heat dissipation and reducing wafer bow with a low temperature bonding.
more목차
1. Introduction 1
2. Theoretical background 4
2.1. Light emitting diodes 4
2.1.1. Principle of LEDs 4
2.1.2. Conventional planar LEDs 6
2.1.3. Vertical LEDs 7
2.2. GaN wafer bowing 8
2.2.1. Principle 8
2.2.2. Bowing causes and results 9
2.2.3. Main factors of wafer bowing 10
2.3. Wafer bonding and laser lift off (LLO) 11
2.3.1. Wafer-bonding 11
2.3.2. Laser lift off (LLO) 12
2.4. Diffusion barrier 14
2.4.1. Solid state diffusion 14
2.4.2. Thermal diffusion model 15
2.4.3. The Kirkendall effect in solid state diffusion 16
3. Experimental 17
3.1. Device fabrication 17
3.2. Device measurement 18
3.2.1. Integrating sphere 18
3.3. Receptor (Cu extreme flat substrate) fabrication 20
4. Results and discussion 22
4.1. Cu metal substrate for enhanced heat dissipation 22
4.2. Wafer bowing and low temperature bonding 27
4.3. Optimizing wafer bonding conditions 30
4.4. Analysis of the V-LED structure between Cu substrate and bonding layer 37
4.5. Designing Sn diffusion barrier 41
4.5.1. Ti/Ni diffusion barrier 44
4.5.2. Ni/Cu diffusion barrier 45
4.5.3. W/Mo diffusion barrier 46
5. Conclusion 47
Reference 49