I guess first question would be why not get wafers without the epi.
The easiest way to remove the Epi would be to Polish it off and can be
done relatively cheap and with some level of control, assuming that the
thickness is known. to remove with etch, KOH or Acid type etch would be
needed, and then removal would be on both sides if back is bare as well.

Ken

aslam muhammad wrote:

> i have got silicon <100> wafers with EPI layer of Ar.
> I want to etch through the silicon wafer to make some
> windows but EPI works as etch stop(i think).  How can
> I etch EPI layer with wet etchant like TMAH.  If i
> keep on etching the wafer, EPI layer etches very
> slowly but my mask ( SiO2 ) etches rapidly as compared
> to EPI layer.  Is there any body to help, Please.
>
> Thanks
>
> M. Aslam



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