Area-Selective Chemical Vapor Deposition of Thin Films: Suppression of Nucleation on Oxides by Amine Adsorption

先进的微电子芯片，无论是民用还是军用，都应该更快，执行更多的数据操作，消耗更少的电力。 为了实现这些目标，未来设备的尺寸将被减小，例如，晶体管的有效宽度将小于10纳米（百万分之0.4英寸）。 传统的芯片制造工艺涉及多个步骤，其中在整个区域上沉积诸如金属的材料薄层，然后在该层上形成对应于器件的图案，并且通过化学蚀刻去除不需要的材料。 然而，在如此小的尺寸下，图案化步骤变得非常困难和昂贵，因为图案必须与其下方的部分制造的器件精确对准。作为回应，该项目开发了一种方法，该方法避免了许多图案化和蚀刻步骤的需要：开发化学气相沉积路线使得材料层选择性地沉积在已经存在的图案特征的顶部上，但不会存款在不需要的表面上。 它还可以制造新的三维晶体管结构和微电子之外的其他类型的纳米级器件结构。 因此，该项目的结果提高了美国高科技产业的制造能力和经济竞争力，这对国家繁荣至关重要，也是我们国防系统所需的。科学和技术成果在主要的专业会议、同行评审文献和主要微电子行业的研讨会上报告。 该项目还支持发展多样化的美国劳动力通过研究生研究助理的培训，谁执行这项研究作为他们的论文的中心焦点。 通过化学气相沉积的薄金属膜的区域选择性沉积在将合适的胺分子（例如氨）添加到前体原料（例如羰基金属分子）中时发生。 然后，在生长所需厚度的金属膜所需的时间期间，金属膜（例如钴或钌）沉积在导电衬底特征上，但不沉积在氧化物表面（例如二氧化硅、二氧化钛、氧化铝或氧化镁）上。 胺的作用是抑制氧化物表面上的金属成核，特别是具有酸性羟基的那些，否则金属岛将在其上形成。 该项目测试关于胺与氧化物表面和吸附前体的相互作用的机制假设，包括位点阻断和表面从酸性到碱性特征的转化的作用。 实验变量包括不同的氧化物表面的改性，使用不同的吸附剂-胺组合，生长温度和分压。 分析方法是原位傅里叶变换红外光谱法检测吸附物的身份，椭圆偏振光谱法检测成核的开始，以及吸附物键合和数量的非原位微观结构探针。 对潜在机制的科学确定将使这种方法在先进器件制造中的可靠使用成为可能，并将其扩展到其他前体、胺和表面。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Advanced microelectronic chips, for both civilian and military applications, should be faster, perform more data operations, and consume less electrical power. To meet these goals, the size of future devices will be reduced, e.g., the active width of a transistor will be less than 10 nanometers (0.4 millionths of an inch). Conventional chip fabrication processes involve multiple steps in which a thin layer of material, such as metal, is deposited over the entire area, then a pattern corresponding to the devices is formed over that layer, and unwanted material is removed by chemical etching. However, at such small size the patterning step becomes significantly difficult and costly because the pattern must align precisely with the partially fabricated device below it. In response, this project develops an approach that obviates the need for many of the patterning and etching steps: a chemical vapor deposition route is developed such that a layer of material deposits selectively on top of already-existing pattern features, but does not deposit on surfaces where it is not wanted. It can also enable the fabrication of new, three-dimensional transistor structures and other types of nanoscale device structures beyond microelectronics. Thus, the results of the project boost the manufacturing capabilities and economic competitiveness of the U.S. high technology industry critical to national prosperity and needed for our national defense systems. The scientific and technical results are reported at major professional conferences, in the peer-reviewed literature, and by seminars at major microelectronic industries. The project also supports the development of a diverse U.S. workforce through training of graduate student research assistants, who perform this research as the central focus of their dissertation. Area-selective deposition of thin metal films by chemical vapor deposition occurs when a suitable amine molecule, such as ammonia, is added to the precursor feedstock, such as a metal carbonyl molecule. The metal film, such as cobalt or ruthenium, then deposits on conductive substrate features but not on oxide surfaces such as silica, titania, alumina, or magnesia during the time required to grow the desired thickness of metal film. The role of the amine is to suppress metal nucleation on oxide surfaces, especially those with acidic hydroxyl groups, on which metal islands would otherwise form. This project tests mechanistic hypotheses concerning the interaction of the amine with the oxide surface and with adsorbed precursor, including the roles of site-blocking and conversion of the surface from acidic to basic character. Experimental variables include modification of different oxide surfaces, the use of different precursor-amine combinations, growth temperature, and partial pressures. Analytical methods are in-situ Fourier transform IR spectroscopy to detect the identity of adsorbates, and spectroscopic ellipsometry to detect the onset of nucleation, and ex-situ microstructural probes of adsorbate bonding and quantity. The scientific determination of underlying mechanisms will enable the reliable use of this approach for advanced device fabrication, as well as its extension to other precursors, amines and surfaces.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.