> We are in the process of acquiring bulk etch high doped Si,
> using KOH or TMAH. But as we know high doped Si will cause
> etch stop, how to solve the problem?
>
> Any suggestion will be really appreciated. Thanks!

Use heavily-doped n-type silicon (phosphorus or arsenic doping).

Etching with KOH or TMAH is slowed by a lack of electrons,
which is why greater p-type doping reduces the etch rate.
N-type doping does not have the same effect.

        --Kirt Williams Agilent Technologies