GENERATING AND OBSERBATING OF SiC SUPPER LATTICE AND EXTRA SMOOTH SURFACE

单晶碳化硅是制作X射线反射镜等恶劣环境下精密结构的潜在材料之一。但由于其高硬度，使用传统的切割和/或磨削工艺很难获得高精度。我们已经将分子束外延(MBE)这一真空晶体生长技术应用于原子水平的表面精加工。我们将这一过程从硅衬底上的同质外延扩展到硅衬底上的异质外延。以往有关分子束外延的研究动机并不是应用于加工过程，而是出于对物理或电学性质的兴趣，因此，分子束外延并不是一种表面光滑工艺。本研究尝试对硅衬底上的碳化硅异质外延生长过程进行实验研究，旨在将其确定为一种平滑的生长过程。然而，所获得的碳化硅表面的化学成分和粗糙度等性能并不令人满意。本研究探讨了在硅衬底上异质外延碳化硅时改善其表面性能的适宜条件。生长过程中的衬底温度在1023~1373K之间变化，衬底温度对外延生长过程有很大影响。研究发现，在保持良好晶体结构的前提下，合适的衬底温度为1073~1173K，可使薄膜的粗糙度提高到1.4 nm Ra。

Single crystal silicon carbide (SiC) is one of the potential materials for the precise structures in severe environment, such as X-ray mirrors. But it is difficult to achieve high accuracy by using conventional cutting and/or grinding processes because of its high hardness. We have been applying molecular beam epitaxy (MBE), which is one of the crystal growth techniques in vacuum, to the surface finishing process in atomic level. We were extending this process from homo-epitaxy of silicon on silicon substrate to hetero-epitaxy of SiC on silicon substrate. The motivations of previous studies related to MBE were not the application to machining process but the interest in physical or electric property, thus, MBE has not been established as a surface smoothing process. This study tried to investigate the SiC hetero-epitaxial growth process on Si substrate experimentally, aiming to establish it as a smoothing process. However, the properties of the obtained SiC surface, such as chemical composition and roughness, are not satisfactory. In this study, the proper conditions were investigated to improve the surface properties in hetero-epitaxy of silicon carbide on silicon substrate. The substrate temperature during the process, which strongly affects the epitaxial growth process, was changed between 1023K and 1373K.It is found that the proper substrate temperature, 1073-1173K in this case, improves the roughness up to 1.4 nm Ra while keeping good crystal structure.