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I have the following equation, based on the reaction of $\ce{SiO2}$ with $\ce{HF}:$

$$\ce{SiO2 + HCl -> SiCl4 + 2 H2O}$$

I want to know if this reaction is indeed feasible, what conditions may be needed to induce it, or if it isn't possible why that's the case.

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    $\begingroup$ No, HCl does not etch SiO2 appreciably. $\endgroup$
    – Jon Custer
    Jun 26, 2019 at 18:39
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    $\begingroup$ You can store HCl in a glass bottle. Please don't do that with HF. $\endgroup$
    – Jon Custer
    Jun 26, 2019 at 18:43
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    $\begingroup$ Well, Cl is very much not like F. For this reason, the reaction is totally impossible. Or rather, it will go quite readily, only backwards. $\endgroup$
    – Ivan Neretin
    Jun 26, 2019 at 18:53
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    $\begingroup$ @faissaloo - in grad school somebody really messed up a hood by being lazy and pouring HF waste into the (glass) waste bottle sitting there (for aluminum etchant). What a mess to clean up! $\endgroup$
    – Jon Custer
    Jun 26, 2019 at 19:03
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    $\begingroup$ The reaction works with a high efficiency in the opposite sense : $\ce{SiCl_4}$ reacts quite easily with the slightest amount of water to produce huge fumes of silica + HCl. This reaction has been used in war times for hiding tanks advancing in the direction of the enemy. $\endgroup$
    – Maurice
    Apr 9, 2020 at 17:02

1 Answer 1

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According to the paper by Chung and Sturm [1], $\ce{HCl}$ will do a very small amount of etching at high enough temperatures (525 °C will give you about 1 nm/min), but the presence of hydrogen limits the reaction because the formation of $\ce{HCl}$ is preferred to the formation of $\ce{SiCl4}.$

References

  1. Chung, K. H.; Sturm, J. C. Chlorine Etching for In-Situ Low-Temperature Silicon Surface Cleaning for Epitaxy Applications. In ECS Transactions; ECS: Chicago, Illinois, 2007; Vol. 6, pp 401–407. DOI: 10.1149/1.2727426.
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