We show that the functionalization of a SiN_x surface with benzaldehyde can be used to increase the overall SiO₂ to SiN_x etch selectivity during atomic layer etching (ALE). The surface reactions, composition, as well as film thickness during ALE are monitored using in situ surface infrared spectroscopy and in situ four-wavelength ellipsometry. Prior to ALE, we show that benzaldehyde can selectively populate a plasma-deposited SiN_x surface with benzene rings through a self-limiting reaction with surface —NH_x (x = 1, 2) groups, while no reaction occurs with —OH groups on a plasma-deposited SiO₂ surface. Using alternating cycles of a C₄F₈/Ar and an rf-biased Ar plasma, ALE is performed on bare and benzaldehyde-exposed SiN_x and SiO₂. Over the first 16 ALE cycles, the SiO₂ to SiN_x etch selectivity increases from ∼2.1 to ∼4.5 due to the selective functionalization of the SiN_x surface with benzaldehyde. A detailed analysis of the infrared spectra of the bare and benzaldehyde-functionalized SiN_x surfaces shows that benzaldehyde promotes the formation of a more graphitic hydrofluorocarbon film on the SiN_x surface, which inhibits etching.

中文翻译：

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SiNx 与苯甲醛的气相表面功能化以提高原子层蚀刻中 SiO2 对 SiNx 蚀刻的选择性

我们表明，在原子层蚀刻 (ALE) 过程中，使用苯甲醛对 SiN _x表面进行功能化可用于增加整体 SiO ₂到 SiN _x蚀刻选择性。使用原位表面红外光谱和原位四波长椭偏仪监测 ALE 过程中的表面反应、组成以及薄膜厚度。在 ALE 之前，我们表明苯甲醛可以通过与表面 -NH _x ( x  = 1, 2) 基团的自限反应选择性地填充带有苯环的等离子体沉积的 SiN _x表面，而与表面上的 -OH 基团不发生反应等离子沉积的 SiO ₂表面。使用 C ₄ F ₈ /Ar 和 rf 偏置 Ar 等离子体的交替循环，对裸露和苯甲醛暴露的 SiN _x和 SiO ₂进行 ALE 。在前 16 个 ALE 循环中，由于苯甲醛对 SiN _x表面的选择性功能化，SiO ₂对 SiN _x蚀刻的选择性从~2.1 增加到~4.5 。裸和苯甲醛官能Sin的红外光谱的详细分析_X面显示，苯甲醛促进了更多的石墨氢氟烃膜的氮化硅上形成_X表面，其抑制蚀刻。