Background: I'm a statistician working with a design of experiments example regarding plasma etching of circuits, and unfortunately, the author does not define what is meant by the units used for the etch rate ($\mathring{A}$/min). A google search has proved fruitless due to the specialized symbol and the fact that other texts also assume you already know what the $\mathring{A}$ symbol means (which is probably true for those who work in this field, but not for the rest of us).

Question: What does the $\mathring{A}$ unit mean in a plasma etching experiment, for "Etch rate ($\mathring{A}$/min)."

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    $\begingroup$ $\AA$ is the symbol for an Angstrom, $10^-10$ meters. $\endgroup$
    – Carlton
    Feb 6, 2016 at 15:13
  • $\begingroup$ For the record, the best way to render this symbol here might be with the Unicode character (i.e., $\unicode{x212b}$ --> $\unicode{x212b}$) since there's an open issue describing the inability of MathJax to render \AA. That said, it makes sense to leave the question as it is in case people use "mathring" in a search query. $\endgroup$
    – Air
    Feb 11, 2016 at 18:25

1 Answer 1


Anisotropic etching is a linear process, like welding, so presumably the units would be distance per time. Unlike welding it is at a small scale. See this slideshare. In this case units are Angstroms per minute. One Angstrom is $10^{-10}\ \textrm{m}$, indicating the process is on an atomic scale. Since it appears to be used for integrated circuit fabrication, those units are sensible depending on the scale.


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