Journal of the Korean Crystal Growth and Crystal Technology (한국결정성장학회지)

The Korea Association of Crystal Growth (한국결정성장학회)
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Analysis of melt flows and remelting phenomena through numerical simulations during the kyropoulos sapphire single crystal growth

전산해석을 통한 키로플러스 사파이어 단결정 성장공정의 유동 및 remelting 현상 분석

  • Kim, Jin Hyung (Dongnam Regional Division, Korea Institute of Industrial Technology) ;
  • Park, Yong Ho (Department of Materials Science and Engineering, Pusan National University) ;
  • Lee, Young Cheol (Dongnam Regional Division, Korea Institute of Industrial Technology)
  • 김진형 (한국생산기술연구원 동남권지역본부) ;
  • 박용호 (부산대학교 재료공학부) ;
  • 이영철 (한국생산기술연구원 동남권지역본부)
  • Received : 2013.05.10
  • Accepted : 2013.06.07
  • Published : 2013.06.30
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Abstract

Sapphire wafers are used as an important substrate for the production of blue LED (light emitting diode) and the LED's performance largely depends on the quality of the sapphire single crystals. There are several crystal growth methods for sapphire crystals and Kyropoulos method is an efficient way to grow large diameter and high-quality sapphire single crystals with low dislocation density. During Kyropoulos growth, the convection of molten melt is largely influenced by the hot zone geometry such as crucible shape, heater and refractory arrangements. In this study, CFD (computational fluid dynamics) simulations were performed according to the bottom/side ratios (per unit of the crucible surface area) of heaters. And, based on the results of analysis, the molten alumina flows and remelting phenomena were analyzed.

사파이어($Al_2O_3$) 단결정 웨이퍼는 청색 LED(light emitting diode) 제작을 위한 핵심 소재로 사용되고 있으며, 사파이어 단결정의 품질에 따라 LED의 성능이 크게 좌우하게 된다. 여러 가지 사파이어 단결정 제조방법 중 키로플러스(Kyropoulos)법은 도가니 직경에 근접한 크기로 잉곳 생산이 가능하며, 내부 전위밀도가 낮아 고품질의 대구경 사파이어 잉곳 제작이 가능하다. 키로플러스법 공정에서 용융 알루미나의 유동은 seed의 성장 형태, 도가니 및 단열재의 형상에 영향을 받으며, 유동양상에 따라 단결정 사파이어 잉곳의 품질이 좌우된다. 특히 온도구배는 hot-zone 내부의 히터 구조와 밀접한 관련이 있으므로 본 연구에서는 도가니 단위표면적당 하부와 측면 히터의 발열비율에 따른 CFD(computational fluid dynamics) 해석을 실시하고, 해석결과를 토대로 각각 용융 알루미나의 유동 및 remelting 현상에 대해 분석하였으며, 이상적인 히터 발열비율을 도출하였다.

Keywords

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