The wet-chemical acidic treatment of silicon wafer surfaces is very important in photovoltaic, microelectronic and further industries. Recent works report on new mixtures for acidic anisotropic etching mixtures based on hydrofluoric acid HF and hydrochloric acid HCl with an added oxidant. The aim of this work was to get an insight into the reactions during the etching process of silicon in the system HF-HCl-Cl₂. The etching mixtures, gaseous reaction products, as well as the generated silicon surfaces were investigated by ¹⁹F, ²⁹Si, and ³⁵Cl NMR, ion chromatography (IC), iodometric titration, FT-IR spectroscopy, diffuse reflectance FT-IR spectroscopy (DRIFT) as well as scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDX). A reaction scheme for the anisotropic dissolution of silicon in chlorine containing aqueous HF-solutions is proposed, which involves dissolved Cl₂ as the oxidizing agent, coordination of fluoride/chloride ions and formation of a hydrophilic surface. These steps are similar to the well known alkaline anisotropic etching of silicon.

中文翻译：

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硅在含氟氢氟酸溶液中各向异性溶解的机理研究

硅片表面的湿化学酸性处理在光伏，微电子和其他行业中非常重要。最近的工作报道了基于氢氟酸HF和盐酸HCl并添加了氧化剂的酸性各向异性蚀刻混合物的新混合物。这项工作的目的是深入了解系统HF-HCl-Cl ₂中硅的蚀刻过程中的反应。用¹⁹ F，²⁹ Si和³⁵研究了腐蚀混合物，气态反应产物以及生成的硅表面。Cl NMR，离子色谱（IC），碘量滴定，FT-IR光谱，漫反射FT-IR光谱（DRIFT）以及扫描电子显微镜和能量色散X射线光谱（SEM-EDX）。提出了一种将硅各向异性地溶解在含氯的HF水溶液中的反应方案，该方案涉及溶解的Cl ₂作为氧化剂，配位氟化物/氯离子和形成亲水性表面。这些步骤类似于众所周知的硅的碱性各向异性蚀刻。