Judith:

If you can dilute your HBr with Ar or He you should see a big jump in
selectivity between the Si and the SiO2 mask.  You might also consider
reducing the HBr flow.  A 3:1 mix with 30 sccm Ar or He and 10 sccm HBr
should yield better results.  You should see a more vertical profile as
well.

Regards,
Robert

On Jun 9, 2011 5:20 AM, "Judith Linacero Blanco" 
wrote:
> Hi Andrew,
>
> I try to etch 300nm in Si. With the process that I explain you, I etched
> 180nm in silicon, and now I'm trying to change the parameters.
> I use 25sccm HBr, 30mt and 150W with short and repetitive processes.
>
> I use samples with thermal SiO2 than we buy in a Siltronix Company, but
now
> we have a new evaporator (thermal, e-beam and sputtering) and I would like
> to evaporate our samples, but I don´t know if I can use all kind of
process,
> Could you recommend me something? Does the RIE etching change?
>
> Thanks a lot
>
> *JUDITH NOEMÍ LINACERO BLANCO*