Thermal atomic layer etch (ALE), facilitating the removal of up to one monolayer of material per cycle, is growing in importance for thin-film processing. The number of available ALE processes is much smaller than for atomic layer deposition, its complementary growth process. Quantum chemical simulations are a key approach in the development of new thermal ALE processes, however, methodologies and workflows need to be developed. In this regard, the present paper reports a simulation-based approach toward the development of new thermal ALE processes using metallic cobalt as a test case. We demonstrate a predictive process discovery approach for ALE in which target volatile etch products and the corresponding gas phase reactants are chosen from the literature, an overall ALE cycle for each combination of reactant is investigated for thermochemical favorability, and the detailed mechanisms of the individual reaction steps in the proposed ALE processes are studied using density functional theory. From these results, we derive a temperature-pressure process window for each combination of reactants at typical reactant and product pressures allowing the selection of an ALE process window. For Co ALE, we investigated propene, butyne, silane, and trimethyl silane as a first pulse reactant and CO as the second pulse reactant. We propose propene and CO as the best combination of reactants for Co ALE. Propene adsorbs with sufficient strength to the target Co atom at temperatures below the CO decomposition temperature of 440 K, which results in the lowest energy etch species. This approach is equally relevant for the ALE process design of elemental, binary, and ternary materials.

中文翻译：

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钴的热原子层蚀刻工艺的计算机设计

热原子层蚀刻（ALE）有助于在每个循环中去除多达一层单层材料，对于薄膜处理而言，其重要性日益提高。可用的ALE工艺的数量比原子层沉积（其互补的生长工艺）要少得多。量子化学模拟是开发新的热ALE工艺的关键方法，但是，需要开发方法和工作流程。在这方面，本论文报告了一种基于仿真的方法，该方法以金属钴为测试案例，用于开发新的热ALE工艺。我们展示了一种针对ALE的预测性过程发现方法，其中从文献中选择了目标挥发性蚀刻产物和相应的气相反应物，研究了每种反应物组合的整个ALE循环的热化学适应性，并使用密度泛函理论研究了拟议ALE方法中各个反应步骤的详细机理。从这些结果中，我们得出了典型反应物和产物压力下每种反应物组合的温度-压力过程窗口，从而可以选择ALE过程窗口。对于Co ALE，我们研究了丙烯，丁炔，硅烷和三甲基硅烷作为第一脉冲反应物，而CO作为第二脉冲反应物。我们建议将丙烯和一氧化碳作为Co ALE的最佳反应物组合。丙烯在低于440 K的CO分解温度的温度下以足够的强度吸附到目标Co原子上，这导致最低的能量蚀刻种类。