基于使用 HF/H2 和 CF4/H2 等离子体的氟化氢与氢化 SiN 薄膜相互作用的蚀刻机制,ACS Applied Electronic Materials

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基于使用 HF/H2 和 CF4/H2 等离子体的氟化氢与氢化 SiN 薄膜相互作用的蚀刻机制
ACS Applied Electronic Materials ( IF 4.3 ) Pub Date : 2023-12-12 , DOI: 10.1021/acsaelm.3c01258
Shih-Nan Hsiao ₁ , Nikolay Britun ₁ , Thi-Thuy-Nga Nguyen ₁ , Makoto Sekine ₁ , Masaru Hori ₁

Affiliation

在双频电容耦合等离子体反应器中研究了使用CF ₄ /H ₂和HF/H ₂等离子体的SiN薄膜的蚀刻特性，其中H ₂百分比从5%增加到34%。_{CF 4} /H ₂中的蚀刻速率降低了35％，HF/H ₂中的蚀刻速率降低了10％。通过光发射光度测定法测量的 F 密度在两种等离子体中均降低了约 70%，但仅凭它无法解释蚀刻速率的降低。表面分析表明，当向两种等离子体中添加H ₂时，形成了(NH ₄ ) ₂ SiF ₆，一种氟硅酸氨(AFS)相。提出了一种模型，其中无水 HF 气体直接与氢化 SiN 表面反应形成 AFS 相。在HF/H ₂等离子体中，蚀刻速率的降低较小，但F密度显着降低。在CF ₄ /H ₂等离子体中，即使缺乏F自由基，从碳氟化合物层释放的HF蚀刻剂仍然可以与氢化SiN表面反应。观察结果表明，AFS 的形成不一定会抑制蚀刻，并且可以在足够高的偏压下辅助 SiN 蚀刻。这些结果凸显了 HF 形成及其与氢化 SiN 表面在使用氢和含氟等离子体蚀刻的 SiN 中的重要作用。

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Etching Mechanism Based on Hydrogen Fluoride Interactions with Hydrogenated SiN Films Using HF/H2 and CF4/H2 Plasmas

The etch characteristics of SiN films using CF₄/H₂ and HF/H₂ plasmas were investigated in a dual-frequency capacitively coupled plasma reactor with increasing an H₂ percentage from 5 to 34%. The etch rate decreased by 35% in CF₄/H₂ and 10% in HF/H₂. F density, measured by optical emission actinometry, decreased by approximately 70% in both plasmas, but it alone could not explain the etch rate reduction. Surface analysis revealed the formation of (NH₄)₂SiF₆, an ammonia fluorosilicate (AFS) phase, when H₂ was added to both plasmas. A model is proposed where anhydrous HF gas directly reacts with a hydrogenated SiN surface to form the AFS phase. In the HF/H₂ plasma, the decrease in etch rate was small, but the F density decreased significantly. In the CF₄/H₂ plasma, HF etchants released from the fluorocarbon layer can still react with the hydrogenated SiN surface, even with a deficiency of F radicals. The observations suggest that the formation of AFS does not necessarily inhibit etching and can assist in SiN etching with a sufficiently high voltage bias. These results highlight the significant role of HF formation and its reactions with the hydrogenated SiN surface in SiN etching using hydrogen and fluorine-containing plasmas.

更新日期：2023-12-12

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