Etching of Dielectrics: Fundamental Plasma-Surface Interactions Through Mass-Filtered, Energy-Tuned Ion Beams

总结本研究旨在了解负责硅，二氧化硅（二氧化硅），和其他新的电介质材料（氧化锆，多孔氧化硅，黑金刚石）在氟碳等离子体或其他适当的化学蚀刻的基本等离子体表面相互作用。 为此，使用与散射和表面诊断相结合的独特离子束线，将可调节能量的等离子体提取的、质量过滤的离子束引导到上述介电材料的表面。 相同或不同化学组成的中性自由基也以不同的中性离子比同时供应。 发射的反应产物由飞行时间四极质谱原位和真实的时间监测。 使用表面分析技术分析相互作用的稳定表面产物。 比较在硅表面的散射，以了解硅上的电介质材料的选择性蚀刻。 具体目标包括：理解与半导体工业相关的表面上的高能、惰性和反应性离子的散射动力学;碳氟化合物等离子体中硅和二氧化硅之间的蚀刻选择性的原因;区分非热反应途径并测量它们相对于热反应对蚀刻的贡献;监测由离子轰击促进的表面改性的程度和化学性质，作为离子的平移能和化学特性的函数;测量作为射弹离子的平移能量和入射角的函数的蚀刻产率，并开发所观察到的依赖性的唯象模型;使用用于射束散射的蚀刻产率模型来模拟轮廓演变;进行受控离子束表面实验，目标是在高密度等离子体中蚀刻硅、二氧化硅和新型电介质材料时发生的基本相互作用。 的散射相互作用的详细图片，包括蚀刻产率和反应产物作为入射能量和角度的函数。 采用了在氧化物和低k电介质的蚀刻中使用的典型的复合碳氟化合物化学的复合离子[CFx+和SiFx+（x=1-3）]。 对多种离子在蚀刻各种材料中的作用进行快速筛选。这建立了一种新的范例来选择等离子体化学物质以实现期望的蚀刻速率和蚀刻轮廓，这与现在工业上通过试错法进行的耗时且昂贵的配方开发形成对比。这些实验被用来验证分子动力学模拟的结果，以提高理解，并产生行业所需的散射的唯象模型，以实现真正的预测轮廓演变。表面相互作用，并且足够实用以在选择允许蚀刻工具的快速优化的化学和操作条件时对工艺工程师有用。 一个新的范例，在蚀刻工艺的发展建立了通过基本的光束散射实验和蚀刻轮廓演化模拟相结合。 所获得的知识和理解被纳入等离子体表面相互作用的课程和教程中，以教育学生和工程师了解化学反应动力学的基本原理。一个新的，低成本的实验，涉及大气微等离子体直接图案化的硅，介绍等离子体表面相互作用的本科生。

SummaryThis research seeks to understand the fundamental plasma-surface interactions responsible for the etching of silicon, silicon dioxide (silica), and other novel dielectric materials (zirconia, porous silicon oxide, black diamond) in fluorocarbon plasmas or other appropriate chemistries. To this end, plasma-extracted, mass-filtered ion beams of adjustable energy are directed at surfaces of the aforementioned dielectric materials using a unique ion beamline combined with scattering and surface diagnostics. Neutral radicals of the same or different chemical composition are also supplied simultaneously at varying neutral to ion ratios. The emitted reaction products are monitored by time-of-flight quadrupole mass spectrometry in situ and in real time. The stable surface products of the interaction are analyzed using surface analysis techniques. Comparisons are made with scattering at silicon surfaces to understand selective etching of dielectric materials over silicon. Specific goals include the understanding of the scattering dynamics of energetic, inert, and reactive ions on surfaces of relevance to the semiconductor industry; the reasons for etch selectivity between silicon and silica in fluorocarbon plasmas; distinguishing non-thermal reaction pathways and measuring their contribution to etching relative to that of thermal reactions; monitoring the extent and chemical nature of the surface modification facilitated by the ion bombardment as a function of the translational energy and chemical identity of the ions; measurement of etch yields as functions of translational energy and incident angle of the projectile ions and developing phenomenological models of the observed dependencies; using the etch-yield models for beam scattering to simulate profile evolution; and performing etch experiments in the beam path for comparison and validation purposes.Controlled ion-beam surface experiments are performed that target the fundamental interactions occurring when etching silicon, silicon dioxide, and novel dielectric materials in high-density plasmas. A detailed picture of the scattering interaction is produced, including etch yields and reaction products as functions of incident energy and angle. Complex ions [CFx+ and SiFx+ (x=1-3)] typical of the complex fluorocarbon chemistries employed in the etching of oxides and low-k dielectrics are employed. A rapid screening of the role of a number of ions in etching various materials is performed. This establishes a new paradigm to select the plasma chemistry to achieve a desired etch rate and etch profile in contrast to the time-consuming and costly recipe development by trial-and-error now practiced by industry. The experiments are used to validate results from molecular dynamics simulations for improved understanding and to produce phenomenological models of scattering needed by the industry for truly predictive profile evolution.Broader impactThe results produced are fundamental enough to be used by theorists in the validation of simulations of beam-surface interactions and practical enough to be useful to process engineers in the selection of chemistries and operating conditions that permit rapid optimization of etch tools. A new paradigm in etch process development is established through a combination of fundamental beam-scattering experiments and etch-profile-evolution simulations. The knowledge and understanding obtained is incorporated in courses and tutorials on plasma-surface interactions to educate students and engineers on the underlying principles of chemical reaction dynamics. A new, low-cost experiment involving atmospheric microplasmas in direct patterning of silicon is developed to introduce plasma-surface interactions to undergraduates.