The mechanism of thermal dry etching of cobalt films is discussed for a thermal process utilizing sequential exposures to chlorine gas and a diketone [either 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (hexafluoroacetylacetone, hfacH) or 2,4-pentanedione (acetylacetone, acacH)]. The process can be optimized experimentally to approach atomic layer etching (ALE); a sequential exposure to Cl2 and hfacH dry etchants at 140 °C is shown to proceed efficiently. The use of acacH as a diketone does not result in ALE with chlorine even at 180 °C, but the decrease of surface chlorine concentration and chemical reduction of cobalt is noted. However, thermal desorption analysis suggests that the reaction of chlorinated cobalt surface exposed to the ambient conditions (oxidized) with hfacH does produce volatile Co-containing products within the desired temperature range and the products contain Co3+. The effect of adsorption of ligands on the energy required to remove surface cobalt atoms is evaluated using the density functional theory.

中文翻译：

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连续暴露于分子氯和二酮的钴原子层蚀刻的分子机制


讨论了利用连续暴露于氯气和二酮[1,1,1,5,5,5-六氟-2,4-戊二酮（六氟乙酰丙酮，hfacH）的热处理过程中钴膜热干法蚀刻的机理。或2,4-戊二酮（乙酰丙酮，acacH）]。该工艺可以通过实验进行优化以接近原子层蚀刻（ALE）；在 140 °C 下连续暴露于 Cl2 和 hfacH 干蚀刻剂被证明可以有效进行。即使在 180 °C 下，使用 acacH 作为二酮也不会导致与氯发生 ALE，但注意到表面氯浓度的降低和钴的化学还原。然而，热解吸分析表明，暴露于环境条件（氧化）的氯化钴表面与 hfacH 的反应确实在所需温度范围内产生挥发性含 Co 产物，且产物含有 Co3+。使用密度泛函理论评估配体吸附对去除表面钴原子所需能量的影响。