Charleston,

I have successfully etched about 100 µm GaAs/AlGaAs with an ICP tool.  We used a
thick photoresist mask (10 µm or so) and it worked because of the backside
cooling of the wafer in the ICP and the selectivity was about 15:1.  Still, it
took over an hour to etch with an etch rate under 2 µm/min.  1 mm is 10x more
etching, and I'm not sure it can be done strictly with DRIE.  The chemistry used
is typically Cl based (either Cl2 or BCl3), and your tool and facility needs to
be set up to handle the hazardous gases.  This type of  etch tends to form nasty
byproducts that contaminate the chamber and the vacuum systems, so additional
maintenance is required.

Good luck,

Brad Cantos
brad.cantos@holage.com
http://holage.com




On Jan 11, 2010, at 8:18 AM, Charleston LEE wrote:

> I have one more question. If the etch depth is 1mm, what's the DRIE recipe of
GaAs? And what mask should be used?
>
> Thanks very much!
>
> LEE