PVT法生长6H-SiC单晶中平面六方空洞缺陷研究

Hexagonal Voids in 6H-SiC Single Crystal by PVT

平面六方空洞是SiC晶体中一种典型的体缺陷,其存在严重影响了晶片的质量。因此,研究和去除平面六方空洞缺陷对提高晶片质量有重要意义。使用物理气相输运法(physical vapor transport,PVT)制备了4块6H-SiC单晶,使用光学显微镜观察了平面六方空洞的分布和形貌特征,并研究其形成机制。结果表明,平面六方空洞的形成主要由籽晶背向分解造成的。籽晶背向分解存在两个必要条件:籽晶背面存在与其相接触的气孔;气孔内与籽晶背面相接触的区域比其他区域温度高。籽晶背面的TaC致密膜层能够抑制籽晶背面的分解。结合使用在籽晶背面生成致密TaC膜层和粘结固定两种措施,有效地抑制了籽晶的背面分解,得到了无平面六方空洞缺陷的SiC晶体。

Hexagonal voids defect was a kind of typical bulk defects in the SiC boules grown by physical vapor transport method （PVT）, which seriously affected the quality of the SiC wafers. Therefore, it is significant to study and remove the hexagonal voids to improve the wafer quality. In this paper, four SiC boules were grown by PVT method with different seed mounting methods. The char- acteristics of distribution and morphology and the formation of the voids in the boules were studied by means of optical microscopy. The results showed that the evaporation of back-seed was the main cause of hexagonal voids. Two reasons of back-seed evaporation were summed up ： the existence of air bubbles attached to the backside surface of the seed crystal and the higher temperature in the place at- tached to it than the other places in the air bubbles. Dense tantalum carbide film on the backside of the seed could restrain the evaporation of back-seed. When the TaC-coated seed was fixed on the seed holder by adhesive, SiC crystal with little hexagonal voids was obtained.