Oxidation mechanism of silicon and silicon-based ceramics in ozone-containing atmosphere.

本文研究了硅和碳化硅在973 K氧-臭氧气氛下的氧化动力学，并对硅基材料可能的氧化机理进行了探讨。实验氧化试验的样品有单晶硅、多晶碳化硅（CVD）和单晶α(6H)-碳化硅。以干氧为气源，采用静音排放臭氧发生器系统生成臭氧混合气（臭氧气体分压2-7 kPa，总压0.1 MPa）。氧化温度为973 K。在固定折射率（1.462）下，用椭偏仪测量样品上氧化膜的厚度。采用二次离子质谱（SIMS）对氧化膜进行了表征。结果与讨论(1)在973 K的氧-臭氧混合气体中，观察了碳化硅c面、硅面和硅的氧化动力学抛物行为。硅和碳化硅的氧化速率远高于纯氧中的氧化速率。臭氧气体解离提供的原子氧似乎引起氧化速率的增加，原子氧通过二氧化硅膜的扩散是一个速率控制过程，因为抛物线速率常数随着臭氧气体分压的增加而线性增加。(2)碳化硅c面氧化率高碳化硅c面在含臭氧环境中的氧化率高于硅面和硅面。c -面氧化速率高于硅的原因可能是SIMS检测到c -面形成的硅膜中含有碳。

IntroductionThe oxidation kinetics of silicon and silicon carbide were investigated in an oxygen-ozone atmosphere at 973 K, and the possible oxidation mechanism of silicon-based materials is discussed.ExperimentalThe samples used for oxidation tests were single crystalline silicon, polycrystalline silicon carbide (CVD), and single crystalline α(6H)-silicon carbide. An oxygen-ozone mixture gas (ozone gas partial pressure : 2-7 kPa, total pressure : 0.1 MPa) was generated with a silent discharge ozonizer system using dry oxygen as a source gas. Oxidation temperature was 973 K.Thickness of the oxide film formed on a sample was measured by ellipsometry at a fixed refractive index (1.462). The oxide films were examined by secondary ion mass spectroscopy (SIMS).Results and discussion(1) Oxidation kineticsParabolic behavior was observed at 973 K in oxygen-ozone mixture gas for the oxidation of silicon carbide C-face, Si-face and silicon. The oxidation rates of silicon and silicon carbide were much higher than those in pure oxygen. Atomic oxygen supplied by the dissociation of ozone gas seems to cause the increasing of oxidation rates, and the atomic oxygen diffusion through silica film is a rate-controlling process for oxidation because parabolic rate constant increased linearly with ozone gas partial pressure.(2) High oxidation rate of SiC C-faceThe oxidation rates of silicon carbide C-face in ozone-containing atmospheres are higher than those of Si-face and silicon. The higher oxidation rates of C-face than those of silicon may be caused by carbon in silica film formed on C-face detected with SIMS.