Selectively Etching Al over GaAs

Jenny Hu jennyhu at
Mon Sep 1 22:59:54 PDT 2008

Hi Wet Bench GaAs Users,


 I have patterned resist over 100nm Aluminum over GaAs, and I would like to
etch the aluminum without etching the GaAs beneath.  It seems most chemicals
that etch Al (H3PO4, HCl, KOH, NaOH) also etch GaAs.

I tried etching using AL-11 etchant at 40C, but my GaAs surface was also
etched and the surface was roughened. The timing was very hard to control,
so I wasn't able to stop at exactly the Al/GaAs interface.  I tried a lower
temperature, but I was still not able to remove my sample in time.   


Does anyone have any experience with this?  Any suggestions would also be
very helpful.


Thank you very much for your help.



Jenny Hu

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