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

在973 K氧-臭氧气氛中研究了硅和碳化硅的氧化动力学，探讨了硅基材料的氧化机理。使用干燥氧气作为源气体，通过无声放电臭氧发生器系统产生氧气-臭氧混合气体（臭氧气体分压：2-7 kPa，总压：0.1MPa）。氧化温度为973 K。在固定折射率（1.462）下通过椭圆偏振法测量在样品上形成的氧化物膜的厚度。结果与讨论（1）氧化动力学在973 K下，在O_2-O_3混合气体中，SiC C面、Si面和Si的氧化均表现出抛物线行为。硅和碳化硅的氧化速率远高于纯氧中的氧化速率。臭氧气体离解提供的原子氧似乎是氧化速率增加的原因，原子氧通过氧化硅膜的扩散是氧化速率的控制过程，因为抛物线速率常数随臭氧气体分压线性增加。(2)SiC C面的高氧化速率碳化硅C面在含臭氧气氛中的氧化速率高于Si面和硅。用西姆斯检测到C面氧化速率高于硅表面氧化速率，这可能是由于C面氧化膜中的碳所引起的。

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.