Enhanced Surface Passivation of Subnanometer Silicon Dioxide Films by Superacidic Treatments
Enhanced Surface Passivation of Subnanometer Silicon Dioxide Films by Superacidic Treatments
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DOI：
10.1021/acsaem.1c02935
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发表时间：
2022-01-24
影响因子：
6.4
通讯作者：
Murphy, John D.
中科院分区：
文献类型：
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作者：
Grant, Nicholas E.;Pain, Sophie L.;Murphy, John D.
亚纳米级二氧化硅（SiO2）薄膜经常在硅器件加工之前、过程中和之后出现，但它们的表面钝化程度最低，可能对后续加工步骤产生不利影响。在这里，我们开发了一种工艺，通过使用超强酸双（三氟甲烷）磺酰亚胺（TFSA，有时是TFSI）进行简单的室温处理，纳米和亚纳米SiO2薄膜的表面钝化程度提高了2个数量级。通过精确模拟超强酸处理SiO2样品的有效寿命曲线，我们确定了钝化的增强主要是由于Si/SiO2界面缺陷密度（D-it）的降低，负电荷的存在也有一小部分贡献。经过处理的SiO2薄膜的x射线光电子能谱显示氟的存在，并且氟和氢是Si/SiO2界面缺陷化学钝化的有力候选者。处理后，SiO2薄膜表现出短时间尺度的电子不稳定性，在1-10小时内观察到降解，然后恢复，这归因于D-it的变化，这是根据我们对注射依赖寿命数据的分析确定的。在不稳定期之后，表面钝化在几天内保持相对稳定。超酸基溶液的核磁共振测量表明，应避免使用电子给体溶剂，因为它们会加剧表面钝化不稳定性。结果表明，简单的策略可以大大提高超薄膜的钝化性能，在纳米技术时代，这可以为包括太阳能电池和电池在内的一系列应用中的器件性能带来好处。
Subnanometer-scale silicon dioxide (SiO2) films are frequently present before, during, and after silicon device processing, yet they offer minimal surface passivation and can detrimentally impact subsequent processing steps. Here we develop a process whereby the surface passivation of nanometer and subnanometer SiO2 films is enhanced by up to 2 orders of magnitude by a simple room temperature treatment using the superacid bis(trifluoromethane)sulfonimide (TFSA, sometimes TFSI). By accurately modeling the effective lifetime curves corresponding to the superacid treated SiO2 samples, we have determined that the enhanced passivation is mainly due to a reduction in the interface defect density (D-it) at the Si/SiO2 interface, with a minor contribution also arising from the presence of negative charge. X-ray photoelectron spectroscopy of the treated SiO2 films reveals the presence of fluorine, and this, along with hydrogen, is a strong candidate for the chemical passivation of defects at the Si/SiO2 interface. Post treatment, the SiO2 films show short time scale electronic instability, whereby a degradation and then recovery are observed over a period of 1-10 h which is attributed to variations in the D-it, as determined from our analysis of the injection-dependent lifetime data. Following the instability period, the surface passivation remains relatively stable for days. Nuclear magnetic resonance measurements of superacid-based solutions reveal that electron-donating solvents should be avoided, as they exacerbate surface passivation instabilities. The results presented demonstrate that simple strategies can be used to enhance the passivation properties of ultrathin films greatly, which in the age of nanotechnology could offer benefits to device performance in a range of applications including solar cells and batteries.