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

奖：CBET-0650992标题：使用新的旋转衬底对动态表面上的等离子体反应进行系统研究首席研究员：文森特·M·唐纳利研究所：休斯顿大学休斯顿分校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堆壁的重要相互作用。等离子体放电被用来沉积薄膜，最重要的是，用来蚀刻硅集成电路中的精细特征。在未来几十年里，对这些等离子刻蚀过程的控制将是实现未来自上而下纳米技术的关键。在理解和控制等离子体刻蚀和沉积过程方面的许多科学和技术挑战涉及在等离子体/反应堆壁边界发生的复杂化学物质。高能等离子体电子与工艺气体氯(Cl2)碰撞产生的等离子体中的氯原子等反应性自由基物种，需要促进包括硅在内的电子材料的选择性和定向刻蚀。这些反应物在血浆中达到的浓度部分是由等离子体-壁边界的损失反应建立的，产生的反应产物较少。一个很好的例子是由两个氯原子结合而形成的Cl2。表面反应的速度取决于表面的性质，而表面的性质又取决于被蚀刻的材料的成分和工艺的持续时间。因此，反应物浓度随着时间的推移而漂移，使得控制等离子体过程变得困难。即使是简单的壁面反应也大多缺乏基本知识，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存在挑战。在这里，我们将把已建立的质谱学和俄歇电子能谱表面科学诊断技术引入等离子体环境，使人们能够识别和研究等离子体-壁边界上的反应。这是通过用圆柱形衬底代替反应堆壁的一小段中空部分来实现的。一个容纳这些诊断工具的腔室被密封在反应堆壁的另一侧。基片快速旋转；因此，其表面的一部分周期性地在等离子体中，然后在非常短的时间后面对诊断探头。连接到中空等离子体壁和诊断室上的大型真空泵可以去除从等离子体中泄漏的气体。以这种方式，防止了等离子体气体和带电物种扭曲诊断方法，并且可以分离和鉴定在等离子体壁上形成和从等离子体壁上射出的产物。等离子体曝光和分析之间的时间也可以通过改变衬底转速来改变，从而允许提取反应速率。这项拟议的工作将产生有关等离子体表面相互作用的基本知识，并将为改善未来制造纳米器件所需的先进等离子体工艺的控制提供关键信息。拟议的工作将提供丰富的科学和教育回报，以及技术进步。这些研究将产生的基本知识，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中的壁面反应、催化、燃烧和大气化学以及基础表面科学在内的不同领域具有广泛的影响和潜在的影响。计划开展若干外联活动，包括与等离子体科学联盟合作，提高公众对半导体等离子体加工的社会效益的认识。

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.