GENERATING AND OBSERBATING OF SiC SUPPER LATTICE AND EXTRA SMOOTH SURFACE

单晶碳化硅（SiC）是一种极有潜力的用于恶劣环境下精密结构的材料，如X射线反射镜。但由于其硬度高，很难通过使用传统的切割和/或磨削工艺来实现高精度。我们将分子束磊晶（MBE）技术应用于原子层级的表面修饰制程。我们将这种工艺从硅衬底上的硅的同质外延扩展到硅衬底上的SiC的异质外延。以往对分子束外延相关研究的动机不是应用于加工过程，而是对物理或电学性质的兴趣，因此，分子束外延尚未被确立为表面光滑过程。本研究尝试在实验上探讨Si基底上SiC异质磊晶成长的过程，目的是建立一个平滑化的过程。然而，所获得的SiC表面的性质，如化学成分和粗糙度，是不令人满意的。本研究探讨了在硅衬底上异质外延碳化硅时，改善碳化硅表面性质的适宜条件。衬底温度在1023 ~ 1373 K之间变化，对外延生长有很大影响，当衬底温度为1073- 1173 K时，可以在保持晶体结构的同时，使粗糙度提高到1.4 nm。

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.