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

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.

中文翻译:

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

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。
更新日期:2023-12-12
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