Hi Judith,

If you are not concerned with the anisotropy of the etching you can try XeF2
gas etching. It is selective to SiO2 up to 500.



On Mon, Jun 6, 2011 at 4:05 PM, Judith Linacero Blanco
wrote:

> Hi all,
>
> Does anybody know how to etch Si with a SiO2 mask? Because I use 50sccm
> HBr, 30mT and 200W in the RIE system, but the selectivity isn't good.
> I only have 20nm of SiO2 to etch silicon.
>
> Thanks a lot,
> Judith