Demonstration of crack-free c-axis sapphire crystal growth using the vertical Bridgman method

Vertical Bridgman growth of sapphire crystals, with thin-neck formation process

“…It was confirmed as previously reported [6] that the size of the gap between the crystal periphery and the inner wall of the crucible is large enough to allow release due to the different thermal shrinkage of sapphire and the crucible material. No correlation was found between the difficulty of release and the conical shape as the diameter increased from the thin neck to the main body, as shown in Fig.…”

“…3(b3), but not those with diameters less than 20 mm. It is considered that the seed release differences between Mo and W crucibles were due to their different contraction during cooling [6].…”

“…We have applied the traditional vertical Bridgman (VB) technique to c-axis sapphire crystal growth [6]. The one difference between the HE method [3] and the VB method [6] is in the seeding process.…”

“…The one difference between the HE method [3] and the VB method [6] is in the seeding process. The seed crystal placed in the crucible bottom is kept from melting by a cooling flow of He gas in the former method.…”

Analysis of thermal stress through finite element analysis during vertical Bridgman crystal growth of 2 inch sapphire

“…VB 공정은 기존 HEM과 비교하여 hot zone 내 온도구배와 결정성장 속도의 제어가 용이하 며 [7][8][9], 성장시 hot zone 하단에 저온부가 형성되므로 CZ, KY 등의 공정과 비교하여 대류의 영향에서 자유로 운 장점이 있다. 또한 기판에 쓰이는 c-축 방향으로 직 접 성장이 가능하고 대구경화에 용이하여 향후 LED용 사파이어 기판 제조에 적극 활용될 것으로 기대된다 [10].…”