Low-Temperature CVD for Microelectronics: Utilizing Surface Reactions to Afford ALD-Like Conformality

技术：提出的工作将发展低温化学气相沉积（CVD）的方法，以提供均匀、光滑和无针孔的薄膜在基片上具有高宽高比的开孔，如深沟和过孔。这种薄膜是各种先进技术所需要的，例如，集成电路中与铜金属化相关的扩散屏障。CVD方法也可以以合理的速率完全填充这些特征。迄今为止的例子包括用HfB2或MgO薄膜涂覆和填充直径为100nm的高纵横比（30:1）通孔。采用三种实验方法获得了优异的涂层性能。(1)独特的CVD前驱体分子具有高蒸气压，在薄膜生长表面产生位点阻断效应，使表面反应性较低，但生长速度可接受。（ii）在生长过程中加入抑制剂来改变表面反应性：H原子撞击并强烈结合在最暴露的（上）表面，导致自下而上的薄膜生长；NH3或dme等分子物种均匀地降低生长速率，使a ？非保形?前驱体将提供高保形膜。（iii）抑制剂种类用于通过降低相对于新核形成的速率的第一次形成的核的生长速率来增强底物上核的密度。这样可以大大平滑几纳米厚度的薄膜，并消除针孔。这些方法在薄膜生长领域具有变革性的潜力。本研究采用表面科学技术和动力学建模，以获得高保形化学气相沉积薄膜表面反应的机理理解。跨学科的智力综合？表面物理，表面化学和薄膜材料科学为指导共形CVD的进一步发展提供了科学知识。例如，它提供了前体分子和抑制剂种类的必要性质和行为的定量度量。非技术：该项目涉及与技术相关的材料科学专题领域的基础研究问题，并有望为跨学科领域的研究生和本科生培训提供独特的机会。预期这一研究项目还将通过培训这一研究领域的科学家和通过出版物广泛传播这一研究成果而产生更广泛的影响。PI将在小组中指导一名REU学生和一至两篇本科毕业论文。来自代表性不足群体的研究生和本科生通过伊利诺伊大学的项目SURGE（工程领域代表性不足群体的支持）和WISE（科学和工程领域的女性）招收。在撰写本文时，一名女博士生正在参与这个项目。定期的新闻报道也报道了这些进展，并引用了美国国家科学基金会在发现过程中的关键作用。

Technical: The proposed work will develop methods of low temperature chemical vapor deposition (CVD) to afford uniform, smooth, and pinhole free thin films on substrates that have high aspect-ratio openings such as deep trenches and vias. Such films are required for a wide variety of advanced technologies, e.g., diffusion barriers associated with copper metallization in integrated circuits. The CVD method can also completely fill these features at reasonable rates. Examples to date include the coating and filling of high aspect ratio (30:1) vias, 100 nm in diameter, with HfB2 or MgO films.Three experimental approaches are used to achieve excellent coating properties. (i) Unique CVD precursor molecules with high vapor pressure produce a site-blocking effect on the film growth surface, such that the surface reactivity is low but the growth rate is acceptable. (ii) Inhibitor species are added to the growth process to modify the surface reactivity: H atoms impinge on, and bind strongly to the most exposed (upper) surfaces and lead to bottom-up film growth; molecular species such as NH3 or dme uniformly lower the growth rate such that a ?non conformal? precursor will afford a highly conformal film. (iii) Inhibitor species are used to enhance the density of nuclei on a substrate by reducing the growth rate of the first-formed nuclei with respect to the rate at which new nuclei form. This has the effect of greatly smoothing films of few-nm thickness, and of eliminating pinholes. The approaches have transformative potential in the field of thin film growth.This research employs surface science techniques and kinetic modeling to obtain a mechanistic understanding of the surface reactions involved in highly conformal chemical vapor deposition of thin films. That intellectual synthesis across disciplines ? surface physics, surface chemistry, and thin film materials science provides enabling scientific knowledge to guide further development of conformal CVD. For example, it affords quantitative metrics for the necessary properties and behavior of precursor molecules and inhibitor species.Non-technical: The project addresses basic research issues in a topical area of materials science with technological relevance, and is expected to provide unique opportunities for graduate and undergraduate training in an interdisciplinary field. This research project is also expected to have broader impacts through the training of scientists in this research field and through the wide dissemination of the findings of this research through publications. The PI will mentor a REU student and one or two undergraduate senior theses in the group. Graduate students and undergraduates from under-represented groups are recruited via the University of Illinois programs SURGE (Support ofUnder-Represented Groups in Engineering) and WISE (Women in Science and Engineering). One woman Ph.D. student is associated with this project at the time of writing. Periodic news stories also report the developments and cite the crucial role of the National Science Foundation in the process of discovery.