Lorenzo,

I etch both 15% and 70% AlGaAs.  If you have any air leaks in your system
your etch will be terrible.
Cl2 makes everything rough but etches GaAs very fast.
The solution for etching through my epi structure containing may different
layers and getting a smooth etch was to switch to BCl3 and Ar.  I use a 2
and 8 sccm flows at 20 or 40 watts depending on what speed I want.  Air
leaks are not much of a consideration anymore with this gas.

Hope this helps,

Brent

Lorenzo Sirigu wrote:

> Hello,
> I'm trying to etch by RIE very deep pillars (16 um) in a GaAs/AlGaAs
> superlattice (30% Al content) with SiCl4/Cl2/Ar sources.
> The result is often not very good since sometimes I have filaments with
> a resulting rough surface. I've been told that one problem could be an
> excess of Cl in the mixture but its reduction did not lead always to
> better results.
> Do you have some ideas?
> Is it maybe a kind of contamination or leak in the chamber?
> Thank you
>
> Lorenzo
>
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