Conditioning of Si-interfaces by wet-chemical oxidation: Electronic interface properties study by surface photovoltage measurements
Conditioning of Si-interfaces by wet-chemical oxidation: Electronic interface properties study by surface photovoltage measurements
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DOI：
10.1016/j.apsusc.2014.05.087
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发表时间：
2014-09
影响因子：
6.7
通讯作者：
H. Angermann
中科院分区：
文献类型：
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作者：
H. Angermann
利用场调制表面光电压（SPV）方法测定了湿化学氧化和蚀刻硅（Si）界面的电子界面性质。通过对抛光后的Si（111）和Si（100）衬底进行同时光谱椭偏仪（SE）测量，研究了制备诱导的表面微粗糙度和非化学计量氧化物对表面电荷、能量分布dit (E)和密度dit、可充电态的影响。基于以往的发现和新的研究，建立了传统和新开发的湿化学氧化方法的研究，将所涉及的氧化和蚀刻溶液与初始衬底形态之间的相互作用与最终的表面调理联系起来。它显示了湿化学氧化和氧化物去除的顺序，必须结合起来，以实现原子光滑，氢终止表面，以及在平面，锯损伤蚀刻和有纹理的Si衬底上具有低密度可充电状态的超薄氧化层，如通常应用于硅器件和太阳能电池制造。这些传统的湿化学预处理策略主要是基于浓缩溶液。因此，特别注意发展更环保的工艺，例如利用低氧或低盐酸和低臭氧含量的热纯水，在环境温度下工作。根据我们的研究结果，这些方法可以替代目前使用液体化学物质制备疏水性Si衬底表面和超薄钝化氧化层的方法，是一种高质量和低成本的替代方法。如所选择的例子所示，优化的湿化学预处理可以在随后的软等离子体增强化学气相沉积中保留硅氧化物（SiOx）或非晶材料(如Si (a-Si:H)，氮化硅（a-SiNx:H）， AlOx/a-SiNxand碳化硅（a-SiC:H）的效果，并提高异质结硅太阳能电池的能量转换效率。
The field-modulated surface photovoltage (SPV) method, a very surface sensitive technique, was utilized to determine electronic interface properties on wet-chemically oxidized and etched silicon (Si) interfaces. The influence of preparation-induced surface micro-roughness and un-stoichiometric oxides on the resulting the surface charge, energetic distributionDit(E), and densityDit,minof rechargeable states was studied by simultaneous, spectroscopic ellipsometry (SE) measurements on polished Si(111) and Si(100) substrates.Based on previous findings and new research, a study of conventional and newly developed wet-chemical oxidation methods was established, correlating the interactions between involved oxidizing and etching solutions and the initial substrate morphology to the final surface conditioning. It is shown, which sequences of wet-chemical oxidation and oxide removal, have to be combined in order to achieve atomically smooth, hydrogen terminated surfaces, as well as ultra-thin oxide layers with low densities of rechargeable states on flat, saw damage etched, and textured Si substrates, as commonly applied in silicon device and solar cell manufacturing. These conventional strategies for wet-chemical pre-treatment are mainly based on concentrated solutions. Therefore, special attention was put on the development of more environmentally acceptable processes, utilizing e.g. hot pure water with low contents of oxygen or hydrochloric acid, and of ozone, working at ambient temperatures. According to our results, these methods could be a high quality and low cost alternative to current approaches with liquid chemicals for the preparation of hydrophobic Si substrate surfaces and ultra-thin passivating oxide layers.As demonstrated for selected examples, the effect of optimized wet-chemical pre-treatments can be preserved during subsequent soft plasma enhanced chemical vapor depositions of Si oxides (SiOx), or amorphous materials such as Si (a-Si:H), Si nitride (a-SiNx:H), AlOx/a-SiNxand Si carbide (a-SiC:H) and enhance the energy conversion efficiency of heterojunction silicon solar cells.