In-situ X-ray Studies of Surface Structure during Plasma Processing

该项目解决了电子材料等离子体加工中与表面结构及其与等离子体环境的关系有关的基本问题。该方法是利用实时、原位、基于同步加速器的X射线衍射仪来研究经过氯基等离子体处理的硅和化合物半导体(GaAs和GaN)的表面和近表面结构。在获得了在加工过程中使用实时x射线散射来了解硅表面结构的经验之后，将讨论化合物半导体，GaAs(100)/(110)和GaN(0001)(即极性表面与非极性表面)。在暴露于等离子体期间，将检查表面的原子结构，包括在这种环境下化合物半导体中表面重建的程度的问题。利用掠入射小角X射线散射(GISAXS)研究了等离子体处理过程中表面形貌的演变。化合物半导体表面的阶跃结构(聚束与反聚束)在暴露于等离子体期间的演变将被作为衬底错切尺寸和方向的函数来研究。此外，还将研究逐层移除和逐级回缩的情况，以更好地了解它们与表面结构的关系。用x射线荧光实时跟踪GaAs表面化学计量比的演变。在硅中，将研究损坏的氯化表面层的密度和深度，并与现有的模拟进行比较。在拟议工作的X射线部分进行的实验结果将与在北卡罗来纳大学和NRL进行的独立表征工作相关联。后处理后的表面形态将用原子力显微镜进行检查。还将使用C-V测量、传输线测量加工表面的接触电阻和光反射光谱来异地表征表面损伤。所提出的研究计划集中在等离子体处理条件与原子表面结构之间的关系这一基本问题上，并有望推动理论和模拟的进一步发展。所获得的新知识将对未来合理开发新的加工技术，特别是在新材料方面具有重要意义。%该项目解决具有技术相关性的电子材料科学领域的基础研究问题。该项目的一个重要特点是高度重视教育，并将研究与教育相结合。该研究计划提供了在使用尖端科学设备方面的实践经验的绝佳机会。广泛的资源和协作方面，为从事跨学科前沿研究的研究生和本科生提供了特殊的教育和培训机会。***

This project address fundamental issues associated with surface structure and its relationship to the plasma environment in plasma-based processing of electronic materials. The approach is to use real-time, in-situ, synchrotron- based x-ray diffraction to investigate the surface and near-surface structure of silicon and compound semiconductors (GaAs and GaN) undergoing chlorine-based plasma processing. After gaining experience using real-time x-ray scattering to understand silicon surface structure during processing, compound semiconductors, GaAs(100)/(110) and GaN(0001) (i.e. polar surface vs. non-polar surfaces) will be addressed. The atomic structure of the surfaces will be examined during exposure to the plasma, including questions of the extent to which surface reconstruction remains in the compound semiconductors in this environment. The evolution of the surface morphology during plasma processing will be investigated using grazing-incidence small-angle x-ray scattering (GISAXS). The evolution of step structure (bunching vs. anti-bunching) on the compound semiconductor surfaces during exposure to the plasma will be studied as a function of substrate miscut size and direction. In addition, regimes of layer-by-layer removal vs. step retraction will be examined to better understand their relationship to the surface structure. The evolution of the GaAs surface stoichiometry will be followed in real time with x-ray fluorescence. In silicon, the density and depth of the damaged chlorinated surface layer will be studied and compared with existing simulations. The results of experiments performed in the x-ray portion of the proposed work will be correlated to independent characterization efforts performed at BU and NRL. Post- processing surface morphology will be examined with AFM. Surface damage will also be characterized ex-situ using C-V measurements, transmission line measurements of contact resistances to processed surfaces and photoreflectance spectroscopy. The proposed research program focuses on the fundamental questions of the relation between plasma processing conditions and atomic surface structure and is expected to serve as a stimulus for further development of theory and simulation. The new knowledge gained will be important for future rational development of new processing techniques, especially in novel materials.%%% The project addresses fundamental research issues in areas of electronic materials science having technological relevance. An important feature of the project is the strong emphasis on education, and the integration of research and education. The research program provides excellent opportunities for hands-on experience in the use of sophisticated scientific equipment. The broad resources, and collaborative aspects, provide special opportunities for education and training of graduate and undergraduate students involved in interdisciplinary forefront research. ***