Systematic Studies of Plasma Reactions on Dynamic Surfaces, Using a Novel Rotating Substrate

题目：使用新型旋转基板在动态表面上等离子体反应的系统研究首席研究员：Vincent M. donnelli机构：休斯顿大学TXA将采用一种新的方法来研究气体等离子体与等离子体反应器壁的重要相互作用。等离子体放电用于沉积薄膜，最重要的是，用于蚀刻硅集成电路的精细特征。控制这些等离子体蚀刻过程将是未来几十年实现自上而下纳米技术的关键。在理解和控制等离子体蚀刻和沉积过程中，许多科学和技术挑战涉及等离子体/反应器壁边界发生的复杂化学反应。在等离子体中，通过高能等离子体电子与过程气氯（Cl2）的碰撞产生的反应物自由基，如氯原子，是促进包括硅在内的电子材料的选择性和定向刻蚀所必需的。这些反应物在等离子体中达到一定的浓度，部分是由等离子体壁边界的损失反应建立的，产生较少的反应产物。一个很好的例子就是两个Cl原子结合生成Cl2。表面反应的速率取决于表面的性质，而表面的性质又取决于被蚀刻材料的组成和过程的持续时间。因此，反应物浓度随时间漂移，使等离子体过程难以控制。即使是简单的壁反应的基本知识也大多缺乏，这在很大程度上是因为在恶劣的等离子体条件下应用可靠的分析方法是一项挑战。在这里，我们将把已建立的表面科学诊断技术质谱和俄歇电子能谱带到等离子体环境中，使等离子体壁边界的反应能够被识别和研究。这是通过用一个圆柱形衬底代替一个小的、空心的反应器壁来实现的。装有这些诊断工具的一个腔室被密封在反应堆壁的另一边。基底快速旋转；因此，其表面的一部分周期性地在等离子体中，然后在很短的时间内面对诊断探针。连接在空心等离子体壁和诊断室上的大型真空泵可除去从等离子体中泄漏的气体。通过这种方式，可以防止等离子体气体和带电物质扭曲诊断方法，并且可以分离和识别在等离子体壁上形成和从等离子体壁上演化的产物。等离子体暴露和分析之间的时间也可以通过改变底物旋转速度来改变，从而可以提取反应速率。提出的工作将产生等离子体表面相互作用的基本知识，并将为改进对先进等离子体过程的控制提供关键信息，这些过程将用于制造未来的纳米器件。拟议的工作将提供丰富的科学和教育回报，以及技术进步。从这些研究中产生的基本知识，特别是分离这种复杂反应的新方法，对包括等离子体聚变反应堆壁反应、催化、燃烧和大气化学以及基础表面科学在内的各个领域都有广泛的影响和潜在的影响。计划开展几项外联活动，包括与等离子体科学联盟合作，提高公众对等离子体加工半导体的社会效益的认识。

Award: CBET-0650992Title: Systematic Studies of Plasma Reactions on Dynamic Surfaces Using a Novel Rotating SubstratePrincipal Investigator: Vincent M. DonnellyInstitution: University of Houston, Houston TXA novel approach will be taken to study the important interactions of gaseous plasmas with plasma reactor walls. Plasma discharges are used to deposit thin films, and most importantly, to etch fine features in silicon integrated circuits. Control of these plasma etching processes will be critical in enabling future top-down nano-technology in the coming decades. Many of the scientific and technological challenges in understanding and controlling plasma etching and deposition processes involve the complex chemistry occurring at the plasma/reactor wall boundary. Reactant radical species such as chlorine atoms that are generated in the plasma by collisions of energetic plasma electrons with the process gas chlorine (Cl2) are required to promote selective and directional etching of electronic materials including silicon. These reactants reach a concentration in the plasma that is established in part by loss reactions at the plasma-wall boundary, which produce less reactive products. A good example would be the formation of Cl2 from combination of two Cl atoms. The rate of surface reactions depends on the nature of the surface, which in turn depends on the composition of the materials being etched and the duration of the process. Consequently, reactant concentrations drift over time, making it difficult to control plasma processes. A basic knowledge of even simple wall reactions is mostly lacking, in large part because of the challenge in applying reliable analytical methods under hostile plasma conditions. Here we will bring the established surface-science diagnostic techniques of mass spectrometry and Auger electron spectroscopy to the plasma environment, allowing reactions at the plasma-wall boundary to be identified and studied. This is accomplished by substituting a cylindrical substrate for a small, hollow section of the reactor wall. A chamber housing these diagnostic tools is sealed to the other side of the reactor wall. The substrate is rotated rapidly; consequently, a portion of its surface is periodically in the plasma and then faces the diagnostic probe a very short time thereafter. Large vacuum pumps attached to the hollow plasma wall and on the diagnostics chamber remove the gas that leaks from the plasma. In this manner, the plasma gas and charged species are prevented from distorting the diagnostic methods, and the products formed on and evolving from the plasma wall can be isolated and identified. The time between plasma exposure and analysis can also be varied by changing the substrate rotation speed, allowing reaction rates to be extracted. The proposed work will yield basic knowledge of plasma surface interactions and will also provide critical information for improving control of advanced plasma processes that will be called upon for fabrication of future nano-devices.The proposed work will provide rich scientific and educational payoffs, as well as technological advances. The basic knowledge that will emerge from these studies, and in particular, the new method for isolating such complex reactions has broad implications for and potential impact on diverse areas including wall reactions in plasma fusion reactors, catalysis, combustion, and atmospheric chemistry, as well as basic surface science. Several outreach activities are planned, including a collaboration with the Coalition for Plasma Science to increase public awareness for societal benefits of plasma processing of semiconductors.