Molecular Mechanism of Thermal Dry Etching of Iron in a Two-Step Atomic Layer Etching Process: Chlorination Followed by Exposure to Acetylacetone
Molecular Mechanism of Thermal Dry Etching of Iron in a Two-Step Atomic Layer Etching Process: Chlorination Followed by Exposure to Acetylacetone
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DOI：
10.1021/acs.jpcc.0c10556
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发表时间：
2021-03-26
影响因子：
3.7
通讯作者：
Teplyakov, Andrew
中科院分区：
文献类型：
--
作者：
Konh, Mahsa;Janotti, Anderson;Teplyakov, Andrew
控制磁性随机存取存储器制造中使用的过渡金属薄膜的厚度和形态是一个主要的挑战。热干蚀刻已成为制备所需薄膜的首选方法;然而，底层表面过程的机制非常难以评估。在这项工作中，热干法刻蚀金属铁通过使用顺序暴露于氯气和2，4-戊二酮（乙酰丙酮，acacH）进行了研究。acacH与氯改性的铁表面反应的机制进行了研究，通过以下的片段从表面解吸的程序升温脱附实验中的半周期过程，比较氯化，氧化，混合（Cl和O），和清洁（溅射）铁膜。在每个蚀刻步骤后，每个样品的原位俄歇电子能谱和非原位X射线光电子能谱证实，表面被氯活化，然后含氯的铁物种从样品的顶层被除去，从而产生金属铁表面。用acacH没有观察到清洁（溅射）表面的蚀刻。acacH与氯化铁样品反应的完整机理是复杂的，并且蚀刻产物可以包含Fe 2+和Fe 3+。然而，一些主要的结论，包括形成的表面中间体和蚀刻的最终产品，主要是去除Fe（acac）（x）Cl-y，推断通过比较这些实验的结果与使用密度泛函理论计算的选定的表面过程的计算调查。
Controlling thickness and morphology of transition-metal thin films used in magnetic random-access memory fabrication is a major challenge. Thermal dry etching has emerged as a method of choice for preparing the desired films; however, the mechanisms of the underlying surface processes are very difficult to assess. In this work, thermal dry etching of metallic iron by using sequential exposure to chlorine gas and 2,4-pentanedione (acetylacetone, acacH) was investigated. The mechanism of reacting acacH with chlorine-modified iron surface was studied by following the fragments desorbing from the surface in temperature-programmed desorption experiments in half-cycle processes that compared the chlorinated, oxidized, mixed (Cl and O), and clean (sputtered) iron films. In situ Auger electron spectroscopy and ex situ X-ray photoelectron spectroscopy of each sample after each etching step confirmed that the surface is activated by chlorine and then the chlorine-containing iron species are removed from the top layer of the sample, resulting in a metallic iron surface. No etching of clean (sputtered) surface was observed with acacH. The complete mechanism of acacH reaction with chlorinated iron samples is complicated, and etch products can contain both Fe2+ and Fe3+. However, a number of major conclusions, including the formation of surface intermediates and the final products of etching, primarily removal of Fe(acac)(x)Cl-y, are inferred by comparing the results of these experiments with the computational investigation of selected surface processes using density functional theory calculations.