Theoretical study of penetration reaction of fluorine atoms and ions into hydrogen-terminated Si(111) thin film

On The Mechanism of the Anisotropic Dissolution of Silicon in Chlorine Containing Hydrofluoric Acid Solutions

“…A second signal at −129.15 ppm, appearing after dissolving silicon powder, can be assigned to hexafluorosilicate ions [SiF 6 ] 2− . This species was also characterized by 29 Si-NMR which shows a signal at −188.16 ppm (Figure 2). 35 Cl-NMR-spectra show a signal at 14.65 ppm which can be assigned to chloride ions.…”

“…The concentration of dissolved chlorine was determined by iodometric titration to be 18 g L −1 . The etching mixtures were characterized before and after etching silicon by 19 F-NMR, 29 Si-NMR, and 35 Cl-NMR measurements. The 19 F-NMR spectrum ( Figure 1) shows a signal at −168.21 ppm indicating hydrofluoric acid.…”

“…By FT-IR spectroscopy, silicon tetrafluoride SiF 4 was observed as only gaseous reaction product. SiF 4 is dissolved by HF to form hexafluorosilicic acid [SiF 6 ] 2− , observed by 19 F and 29 Si NMR spectroscopy. The amount of chlorine consumed during the etching process was monitored by iodometric titration, two Cl 2 molecules are required for oxidizing one Si surface atom.…”

“…However, as it was pointed out by one of the referees, that EDX does not have sufficient sensitivity to observe even a full monolayer of F atoms. Besides, it is well known [27][28][29] that F diffuses into the Si lattice and it is this F doped near surface region that must be responsible for the EDX signal. Thus, when etching a silicon wafer in the system HF-HCl-Cl 2 , a hydrophilic, OH-, F-, and Cl-terminated surface is generated.…”

“…The aim of this work is to get an insight on the reactions during the etching process of silicon in the system HF-HCl-Cl 2 . The HF-HCl-Cl 2 z E-mail: Kroke@chemie.tu-freiberg.de etching mixtures, gaseous reaction products, as well as the generated silicon surfaces are investigated by 19 F, 29 Si, and 35 Cl 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).…”