I've had decent results with a CF4/CHF3 RIE, though I don't have the recipe
handy.

Alternatively, if you want to stick to wet etches, have you tried buffered HF?
The Kirt Williams etch rate bible mentions 5:1 NH4F:HF for etching Pyrex, though
I have no personal experience with it.

-Mike

On Jun 8, 2011, at 2:13, Ned Flanders wrote:

> Hi all,
>
> I need to etch 100 nm of borosilicate glass. I used a diluted HF + HCl
> recepy - but it seems that when diluted, this doesn't create a very
> smooth etch surface. However, I cannot use it in a more concentrated
> form, as it has an etch rate of about 8 um/min and I need to control
> the etch depth with a higher degree of precision. I need 100 nm +/- 20
> nm
>
> Any suggestions?
>
> thanks
>
> m