Characterization of the Interfaces between IV-IV Semiconductors and Ultra-Thin Oxide films

为了寻找适合SiC mosfet的氧化工艺，我们采用椭偏光谱法和光电子能谱法研究了氧化膜与SiC的界面，氧化膜形成后经过各种热处理后界面结构的变化及其电学性能的关系。为了了解超薄氧化膜的形成过程和界面的微观结构，我们开发了原位椭偏光谱系统。结果表明，氧化初期形成的氧化膜的组成与化学计量SiO_2不同，界面层的折射率随热处理而降低，但比SiC和SiO_2的折射率大。为了弄清界面折射率与界面态密度之间的关系，我们对γ射线辐照后界面态密度增加的SiC MOS结构进行了光谱椭偏和C-V测量。我们发现界面层的折射率随着伽马射线的照射而增加，这表明光谱椭偏测量得到的折射率与界面态密度密切相关，而界面态密度影响着SiC MOSFET的沟道迁移率。采用角度分辨x射线光发射光谱和紫外光发射光谱分析了热处理后氧化物/碳化硅界面成分和键合状态的变化。此外，我们已经使用微红外反射光谱来表征SiC块体晶体的电学性能，并证明了在没有电接触的情况下，SiC晶圆中的职业浓度和迁移率分布可以被〓〓〓地无损地确定。本研究对氧化硅/碳化硅界面的结构有了更深入的了解，揭示了光谱椭偏法是一种很好的表征技术，适用于器件过程中的监测工具。少

We have used spectroscopic ellipsometry, together with photoelectron spectroscopy, to investigate the interfaces between the oxide film and SiC, structural changes in the interfaces by various kinds of heat treatment after the oxide film formation, and the correlation with their electrical properties, in order to search appropriate oxidation process good for SiC MOSFETs.We have developed in-situ spectroscopic ellipsometry system to acquire the knowledge for clarifying the formation process of ultra-thin oxide films on SiC and microstructure of the interfaces. It is found that the composition of the oxide film formed in the initial stage of oxidization is different from that of stoichiometric SiO_2 and that the refractive indices of the interface layers, which are larger than that of SiC and SiO_2, decrease with heat treatment. In order to make clear the relation between the refractive indices of the interfaces and interface state density, we have carried out spectroscopic ellipsometry … More and C-V measurements for the SiC MOS structures whose interface state density is increased by gamma ray irradiation. We have found that the refractive indices of the interface layers increase with gamma ray irradiation, which suggest that the refractive indices obtained by spectroscopic ellipsometry are closely related to the interface state density, which affects the channel mobility in SiC MOSFET. Angle-resolved x-rays photoemission spectroscopy and ultraviolet photoemission spectroscopy were performed to clarify the change of composition and bonding state at the oxide/SiC interfaces by heat treatment. In addition, we have used micro infrared reflection spectroscopy to characterize the electrical properties of SiC bulk crystals and demonstrated that the distribution of the career concentration and mobility in SiC wafers can be 〓〓〓〓sured nondestructively without electric contacts.This research project brings about a better understanding of the structures of oxide/SiC interfaces and reveals that spectroscopic ellipsometry is an excellent characterization technique and is applicable to monitoring tool during device processes. Less