The surface chemistry of the atomic layer deposition of ruthenium on aluminum and tantalum oxide surfaces

IF 2.1 4区 化学 Q3 CHEMISTRY, PHYSICAL
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Abstract

The surface chemistry of Ru atomic layer deposition (ALD) processes based on the use of tris(2,2,6,6-tetramethyl-3,5-heptanedionato)ruthenium(III) (Ru(tmhd)3) and either molecular oxygen or atomic hydrogen on aluminum oxide films was characterized by a combination of surface-sensitive techniques. The thermal decomposition of the Ru metalorganic precursor was determined, by using a combination of reflection-absorption infrared spectroscopy (RAIRS), temperature programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS), to start below 400 K and to take place in a stepwise fashion over a wide range of temperatures. Gas-phase products from this chemistry include 2,2,6,6-tetramethyl-3,5-heptanedione (the protonated ligand, Htmhd; in a TPD peak at 520 K), isobutene (540 K; indicating the fragmentation of the organic ligands), and other products from isomerization and/or aldol condensation (650 and 730 K). This chemistry is accompanied by the reduction of the Ru3+ ions in two stages, involving the loss of some of their ligands and their direct bonding to the substrate first (between 500 and 600 K) and a full reduction to a metallic state later on (600–700 K). ALD cycles using either molecular oxygen or atomic hydrogen resulted in the slow build-up of Ru on the surface, but the co-deposition of carbon could not be avoided, at least in the initial cycles, while the alumina surface was still exposed. With O2, the Ru atoms alternate between partially-oxidized (after the O2 exposures) and zero-valent (after the Ru(tmhd)3 doses) states, and some Ru loss in the form of the volatile RuO4 oxide was seen after the second half of the ALD cycles; neither the Ru oxidation state alternation nor the elimination of some Ru from the surface were observed when using H·. The deposited Ru was determined, by combining results from angle-resolved XPS (ARXPS) and low-energy ion scattering (LEIS) experiments, to grow as 3D nanoparticles rather than as a layer-by-layer 2D film, presumably because the Ru precursor preferentially adsorbs (and decomposes more cleanly) on the metal surface. A discussion is provided of the implications of these results for the design of ALD processes.

Abstract Image

铝和钽氧化物表面原子层沉积钌的表面化学反应
通过结合使用表面敏感技术,对基于三(2,2,6,6-四甲基-3,5-庚二酮酸)钌(III) (Ru(tmhd)3)和分子氧或原子氢在氧化铝薄膜上的 Ru 原子层沉积 (ALD) 过程的表面化学性质进行了表征。通过结合使用反射吸收红外光谱(RAIRS)、温度编程解吸(TPD)和 X 射线光电子能谱(XPS),确定 Ru 金属有机前体的热分解始于 400 K 以下,并在广泛的温度范围内逐步进行。这种化学反应产生的气相产物包括 2,2,6,6-四甲基-3,5-庚二酮(质子化配体 Htmhd;在 520 K 时出现 TPD 峰)、异丁烯(540 K;表明有机配体发生了破碎)以及异构化和/或醛醇缩合(650 和 730 K)产生的其他产物。伴随着这种化学反应,Ru3+ 离子的还原过程分为两个阶段,首先是失去部分配位体并与基底直接结合(500 至 600 K 之间),然后完全还原为金属态(600 至 700 K)。使用分子氧或原子氢的 ALD 循环可使 Ru 在表面上缓慢沉积,但碳的共沉积无法避免,至少在最初的循环中,氧化铝表面仍然暴露在外。使用 O2 时,Ru 原子在部分氧化(O2 暴露后)和零价(Ru(tmhd)3 剂量后)状态之间交替,在 ALD 循环的后半段后,可以看到一些 Ru 以挥发性 RuO4 氧化物的形式流失;使用 H- 时,既没有观察到 Ru 氧化状态的交替,也没有观察到一些 Ru 从表面消失。结合角度分辨 XPS(ARXPS)和低能离子散射(LEIS)实验的结果,可以确定沉积的 Ru 是以三维纳米颗粒的形式生长,而不是以逐层二维薄膜的形式生长,这可能是因为 Ru 前驱体优先吸附在金属表面(并且分解得更干净)。本文讨论了这些结果对 ALD 工艺设计的影响。
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来源期刊
Surface Science
Surface Science 化学-物理:凝聚态物理
CiteScore
3.30
自引率
5.30%
发文量
137
审稿时长
25 days
期刊介绍: Surface Science is devoted to elucidating the fundamental aspects of chemistry and physics occurring at a wide range of surfaces and interfaces and to disseminating this knowledge fast. The journal welcomes a broad spectrum of topics, including but not limited to: • model systems (e.g. in Ultra High Vacuum) under well-controlled reactive conditions • nanoscale science and engineering, including manipulation of matter at the atomic/molecular scale and assembly phenomena • reactivity of surfaces as related to various applied areas including heterogeneous catalysis, chemistry at electrified interfaces, and semiconductors functionalization • phenomena at interfaces relevant to energy storage and conversion, and fuels production and utilization • surface reactivity for environmental protection and pollution remediation • interactions at surfaces of soft matter, including polymers and biomaterials. Both experimental and theoretical work, including modeling, is within the scope of the journal. Work published in Surface Science reaches a wide readership, from chemistry and physics to biology and materials science and engineering, providing an excellent forum for cross-fertilization of ideas and broad dissemination of scientific discoveries.
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