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

本文从表面处理和高温氧化两个方面研究了碳化硅（SiC）晶体物理化学性质的各向异性。1. SiC的氧化通过测量样品上氧化层厚度，研究了CVD SiC和单晶SiC在573 ~ 1273 K和345.6ks温度范围内，在含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面以及先前报道的氧气氛中的氧化速率。对SiC单晶氧化速率的测定表明，氧化速率的大小顺序为（0001^^_）>（12^^_10）>（101^^_0）>（0001）。这个顺序很好地对应于单个面上的碳密度。与干氧或湿氧等氧化气氛相比，臭氧气氛中（0001）Si面的氧化速率相对增加。这一结果表明，在半导体器件制造过程中使用臭氧气体作为氧化剂，可能是有效的，在低温下快速氧化。2.在SiC单晶中引入了SiC负晶体的表面工艺。在2473 K下测量了负晶体的形状变化。负晶体的小面化表明{0001}是稳定面，是武尔夫形状的一部分，而{121 ^^_0}是不稳定面，不是武尔夫形状的一部分。将实验中得到的负晶体的形状变化率与用表面化学势差作为形状变化驱动力的模型计算的形状变化率进行了比较。在轴向面，形状变化的速率控制过程是表面附着限制动力学（SALK），而在轴向面，形状变化的速率控制过程是表面附着限制动力学（SALK）。对于离轴面，提出了表面扩散对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.