hi,
the following is a general procedure to decontaminate substrate and labware
from KOH ions. However, I can not assure you that this process will give a
full y cmos compatible device, you need to try and tyest it. good luck

20min of inmersion in a self-heating solution of 1:1:1 H2O:H2O2:HCl in volume.
First pour H2O, followed by a 30%H2O2 and finally a 38%HCl. Pour the HCl
slowly and be carefull the solution will self-heat up an boils.  Place your
wafer and the labware you used to etch with KOH into this solution for 20min.
remove them and rinse thoroughly.
Do not use PP or pyrex beakers for this cleaning process.  You can use quartz,
teflon and HDPE plastc that can stand high temperatures.
however, if you plan to do some cmos process after you etching I'll advise you
to better work with TMAH instead of KOH.

Good luck
Giancarlo