Atomic layer etching (ALE) techniques are growing in popularity due to their various benefits such as low damage, high selectivity, and precise and controlled etching. In ALE, surface modification is typically achieved by chemisorption of radicals generated in a plasma followed by ion assisted removal of the modified surface. A surface modification process assisted by a plasma may lead to unwanted side effects such as excessive polymerization or spontaneous etching. In this work, the authors demonstrate the feasibility of atomic layer etching of silicon nitride by physisorption of hydrofluorocarbon gas precursors [CH_xF_(4−x), x = 1−4] in the absence of a plasma. Self-limited SiN etching was observed for all hydrofluorocarbon gases, with the largest etch depth per cycle observed for CF₄ and CHF₃ adsorption (∼15 Å/cycle), and smallest etch depth per cycle observed using CH₃F adsorption (∼6 Å/cycle). Etch precursor availability on the surface was manipulated by varying absolute pressure, partial pressure of the adsorbate, and adsorption time. The results of these experiments indicated that of physisorption of precursors is enough to modify the surface, leading to its removal in the subsequent plasma assisted desorption step.

中文翻译：

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物理吸附在氮化硅原子层蚀刻中的作用

原子层蚀刻（ALE）技术由于其各种优点（例如低损坏，高选择性以及精确且受控的蚀刻）而越来越受欢迎。在ALE中，通常通过化学吸附等离子体中产生的自由基，然后离子辅助去除修饰的表面来实现表面修饰。由等离子体辅助的表面改性过程可能导致不良的副作用，例如过度聚合或自发蚀刻。在这项工作中，作者证明了在不存在等离子体的情况下，通过物理吸附氢氟烃气体前体[CH _x F _（4-x），x = 1-4]进行氮化硅原子层蚀刻的可行性。在所有氢氟烃气体中均观察到了自限SiN刻蚀，CF的每个循环的刻蚀深度最大₄和CHF ₃吸附（〜15Å/循环），使用CH ₃ F吸附（〜6Å/循环）观察到的每个循环的最小蚀刻深度。通过改变绝对压力，被吸附物的分压和吸附时间来控制表面上蚀刻剂前体的可用性。这些实验的结果表明，前体的物理吸附足以修饰表面，从而在随后的等离子体辅助解吸步骤中将其除去。