LOW-TEMPERATURE GROWTH OF 3C-SIC FILMS ON SI SUBSTRATE

在Si衬底上生长的立方碳化硅（3C-SiC）质量很差，主要原因是sic与Si之间存在约20%的晶格失配，热膨胀系数相差较大，约8%，并且Si衬底在1000℃以上的高温下会损耗。为了帮助克服这些问题，在SiC生长之前，通过碳化衬底和溅射SiC靶材在Si衬底表面制备了SiC缓冲层。SiC缓冲层防止了衬底的损耗，但并不能完全解决Si和SiC之间晶格失配和热膨胀系数差异的问题。最近，C与Si和Si_<1-x>Ge_x的合金化由于能够控制与Si晶格失配相关的应变而引起了人们的关注。C、Si和Ge在共价半径、键长和键强方面存在较大差异。因此，如果在SiC生长前制备Ge_<1-x>C_x层，则有可能通过原子自组织相互扩散来释放SiC/Si界面上晶格失配引起的应变。例如，C扩散到Si中，Ge扩散到SiC中，可能导致SiC和Si之间晶格失配的减少。在这个项目中，我们研究了一种在Si衬底上生长3C-SiC的新技术。在600℃下，在Si衬底上制备了厚度为5 nm的Ge_<1-0.63>C_<0.63>缓冲层，在相同温度下，在氢气气氛中退火30 min， 850℃下可在衬底上生长出3C-SiC。c - sic薄膜的结晶度很大程度上取决于缓冲层的厚度。在缓冲层厚度约为5 nm时，观察到3C-SiC薄膜的最大x射线衍射强度。SiC薄膜结晶度的提高与SiC薄膜生长过程中缓冲层中SiC/Si界面应变的释放有关。Si（001）衬底对SiC薄膜外延生长的影响在缓冲层中得到放松。SiC晶粒“自由”生长，即其生长不受Si衬底的影响。碳化硅晶粒的取向取决于碳化硅晶粒的成核和生长的自由能。因此，由于（111）取向SiC核在低温下的自由能较小，因此（111）取向SiC晶粒优先生长在薄膜中。少

The quality of the cubic silicon carbide (3C-SiC) grown on a Si substrate was very poor due to the large lattice mismatch of about 20 % between 3C-SiC and Si, the relatively large difference in thermal expansion coefficients of about 8 %, and the loss of the Si substrate at high growth temperatures above 1000℃. To help overcome these problems, a SiC buffer layer was prepared on the surface of a Si substrate by carbonization of the substrate and sputtering of a SiC target before the SiC growth. The SiC buffer layer prevented the loss of the substrate, but did not solve completely the problems of lattice mismatch and difference in thermal expansion coefficients between Si and SiC.Recently, the alloying of C with Si and Si_<1-x>Ge_x has attracted attention because of its ability to control the strain associated with the lattice mismatch to Si. There are large differences in covalent radius, bond length, and bond strength among C, Si and Ge. Therefore, it is possible to release the strains … More due to lattice mismatch at the SiC/Si interface by atomic self-organized interdiffusion if a Ge_<1-x>C_x layer is prepared before the SiC growth. For example, the diffusions of C into Si and Ge into SiC may result in the decrease in lattice mismatch between SiC and Si.In this project, we studied a new growth technique for 3C-SiC on a Si substrate. The Ge_<1-0.63>C_<0.63> buffer layer with a thickness of 5 nm was prepared on the Si substrate at 600℃, and was annealed at the same temperature in hydrogen atmosphere for 30 min. 3C-SiC can be grown on the substrate with the buffer layer at 850℃.The crystallinity of the 3C-SiC film depends strongly on the thickness of the buffer layer. The maximum X-ray diffraction intensity of the 3C-SiC film at a buffer thickness of about 5 nm is observed. The improved crystallinity of the SiC film is related to the release of the SiC/Si interface strains in the buffer layer during the growth of the SiC film.The effects of the Si(001) substrate on epitaxial growth of the SiC film are relaxed in the buffer layer. The SiC grains grow 'freely', that is, its growth is not affected by the Si substrate. The orientation of the SiC grains depends on free energies for nucleation and growth of the SiC grains. Therefore, the (111) oriented SiC grains are preferentially grown in the film because of smaller free energy of the (111)-oriented SiC nuclei at low temperature. Less