Hi, I am trying to etch the AlGaAs under a GaAs layer using HCl. The AlGaAs
is exposed to the etchant at the sidewall of a trech. To protect the most
part of the trench, I covered the whole thing with photoresist AZ4330. There
is only a small opening left to let the echant in. However, what I found is,
somehow, the etchant creeped along the interface between the photoresist and
the sidewall. And etch away the material they are not supposed to. I have
tried both wet etch are RIE to make the sidewall, it doesn't change much.
Anyone has any idea, or similar experience? Is there something wrong with
the sidewall or the recipe of the photoresist?

Thanks a lot for your help

Qingwei

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Mo, Qingwei                                              *
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