실리콘 기판과 CoSi2 버퍼층 위에 HVPE로 저온에서 형성된 GaN의 에피텍셜 성장 연구
GaN epitaxy growth by low temperature HVPE on CoSi2 buffer/Si substrates
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초록
실리콘 기판에 GaN 에피성장을 확인하기 위해, P형 Si(100), Si(111) 기판 전면에 버퍼층으로 40 nm 두께의 코 발트실리사이드를 형성시켰다. 형성된 코발트실리사이드 층에 연속으로 HVPE(hydride vapor phase epitaxy)로 하나는 850 o C-12분 + 1080 o C-30분(공정I)과, 또 하나 조건은 557 o C-5분 + 900 o C-5분(공정II) 조건으로 각각 나누어 진행하여 보았다. GaN의 에피성장을 광학현미경, 주사전자현미경, 주사탐침현미경, 그리고 HR-XRD로 확인하였다. 공정I로는 GaN의 에피성 장이 진행되지 않았으며, 공정II에서는 에피성장이 진행되었다. 특히 공정II는 열팽창에 의해 실리콘 기판과의 자가정렬적 인 기판분리 현상을 보였으며, XRD로 GaN의 0002 방향의 결정성 (crystallinity)을 ω-scan으로 확인한 결과 (100)면 방향의 실리콘과 코발트실리사이드를 버퍼층으로 활용하고 저온에서 HVPE를 진행한 조합이 GaN의 에피성장에 유리하였다.
Abstract
We fabricated 40 nm-thick cobalt silicide (CoSi2) as a buffer layer, on p-type Si(100) and Si(111) substrates to investigate the possibility of GaN epitaxial growth on CoSi2/Si substrates. We deposited GaN using a HVPE (hydride vapor phase epitaxy) with two processes of process I (850 o C-12 minutes + 1080 o C-30 minutes) and process II (557 o C-5 minutes + 900 o C-5 minutes) on CoSi2/Si substrates. An optical microscopy, FE-SEM, AFM, and HR-XRD (high resolution X-ray diffractometer) were employed to determine the GaN epitaxy. In case of process I, it showed no GaN epitaxial growth. However, in process II, it showed that GaN epitaxial growth occurred. Especially, in process II, GaN layer showed selfaligned substrate separation from silicon substrate. Through XRD ω-scan of GaN <0002> direction, we confirmed that the combination of cobalt silicide and Si(100) as a buffer and HVPE at low temperature (process II) was helpful for GaN epitaxy growth.
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