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

技术：建议的工作将开发低温化学气相沉积(CVD)方法，以在具有高纵横比开口的衬底上获得均匀、光滑和无针孔的薄膜，例如深沟槽和通孔。这种薄膜是各种先进技术所需要的，例如与集成电路中铜金属化相关的扩散阻挡层。CVD方法也可以以合理的速度完全填充这些特征。到目前为止的例子包括用HfB2或MgO薄膜涂覆和填充直径为100 nm的大长宽比(30：1)通孔。三种实验方法被用来获得优异的涂层性能。(I)具有高蒸汽压的独特的CVD前体分子在薄膜生长表面产生位置阻塞效应，使得表面反应性较低，但生长速度是可以接受的。(Ii)在生长过程中加入抑制物物种以改变表面反应性：H原子撞击并强烈结合到最暴露的(上)表面，导致自下而上的薄膜生长，分子物种如NH3或DME均匀地降低了生长速度，使得a？非共形？先驱体将提供高度适形的薄膜。(3)抑制物种类用于通过降低第一次形成的核相对于新核形成的速率的增长速度来提高底物上的核的密度。这具有极大地平滑几纳米厚的薄膜并消除针孔的效果。这些方法在薄膜生长领域具有变革的潜力。本研究利用表面科学技术和动力学模型，从机理上了解高共形化学气相沉积薄膜所涉及的表面反应。这种跨学科的智力合成？表面物理、表面化学和薄膜材料科学为指导共形化学气相沉积的进一步发展提供了科学知识。例如，它为前体分子和抑制剂物种的必要性质和行为提供了定量的衡量标准。非技术性：该项目解决了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。预计这一研究项目还将通过培训这一研究领域的科学家以及通过出版物广泛传播这项研究的结果，产生更广泛的影响。PI将指导小组中的一名REU学生和一到两篇本科高级论文。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(支持工程学中的弱势群体)和WISE(科学和工程领域的女性)招募。在撰写本文时，一名女博士生参与了这个项目。定期的新闻报道也会报道这一进展，并引用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.