Anisotropy of silicon carbide crystal : Approaches in terms of surface process and high-temperature oxidation

从表面处理和高温氧化两个方面研究了碳化硅晶体的物理和化学性质的各向异性。1.通过测量样品的氧化层厚度，评价了CVD-碳化硅和单晶碳化硅在573~1273K到345.6K的臭氧气氛中的氧化动力学。(0001)C面在含臭氧气氛中的氧化速率远高于(0001)Si面以及在氧气气氛中的氧化速率。对单晶碳化硅氧化速率的测定表明，其氧化速率大小顺序为：(0001)&(0001)&(0001)&(0001)。这一顺序与个体面部的碳密度很好地对应。在含臭氧气氛中，(0001)Si面上的氧化速率比在干氧或湿氧气氛中的氧化速率相对较大。这一结果表明，在半导体器件制备过程中使用臭氧气体作为氧化剂可能是一种有效的低温快速氧化方法。2.在碳化硅单晶中引入了氮化硅负性晶体的表面工艺。在2473K测量了负极晶体的形状变化，负极晶体的刻面表明，{0001}是稳定面，属于Wulff形状，而{121^0}是不稳定面，不是Wulff形状的一部分。将实验得到的负极晶体的变形率与假设表面化学势差为变形力的模型计算的变形率进行了比较。形状变化的速率控制过程是轴向面上的表面附着限制动力学(SALK)，而表面附着限制动力学(SALK)是轴向表面的表面附着限制动力学。提出了表面扩散对离轴工作面速率控制过程的贡献。

The anisotropy of physical and chemical properties of silicon carbide (SiC) crystal was investigated with the approaches in terms of surface process and high-temperature oxidation.1.Oxidation of SiCOxidation kinetics of CVD-SiC and single crystalline SiC in ozone-containing atmospheres at temperatures from 573 to 1273K up to 345.6ks were evaluated by the measurement of oxide thickness on the specimen. The oxidation rate of (0001^^_) C face in the ozone-containing atmospheres was much higher than that of (0001) Si face as well as in oxygen atmosphere previously reported. The measurement of the oxidation rates of single crystalline SiC revealed that the order of the oxidation rates was (0001^^_)> (12^^_10) >(101^^_0)> (0001). This order well corresponds to the density of carbon on the individual face. The oxidation rate on (0001) Si face in the ozone-containing atmospheres relatively increased compared with that in other oxidation atmospheres such as dry oxygen or wet oxygen. This result suggests that the use of ozone gas as oxidant in semiconductor device fabrication process might be effective for rapid oxidation at low temperatures.2.Surface process in SiCNegative crystal was introduced into the SiC single crystal. The shape change of the negative crystal was measured at 2473 K. The faceting of the negative crystal suggested that {0001} was stable face, a part of the Wulff shape, while {121^^_0} was unstable face, not a part of Wulff shape. The rate of shape change of the negative crystals obtained in the experiments was compared with that calculated using the model, in which the driving force of shape change assumed to be the difference of chemical potential on the surface. The rate controlling process of shape change was the surface attachment limited kinetics (SALK) for on-axis face, while the. contribution of surface diffusion on the rate controlling process was suggested for off-axis face.