Resist is not allowed either. Masks are usually nitride, although there is a moderately slow oxide etch rate. Chemicals used in the TMAH-KOHhood are corrosive and toxic, and care must be taken in handling them. Besides the smock, hood, booties and vinyl gloves, which must be worn at all times in EML, you must also wear the face shield, latex gloves, vinyl sleeve protectors and splash apron, when using the hood. Know the location of the eye wash and safety shower, and become familiar with the MSDS for any chemical you use.
Contamination control is of the utmost importance.
Make sure you are using the correct KOH or TMAH labware, that it is clean and stored correctly at the beginning and end of your process. Be especially diligent in making sure NO inadvertent use of EML labware or tools is made, as EML processes are expressly forbidden from entering ICL or TRL, ever. After using any item, rinse it three times with DI water, and let it dry on fabwipes or N2 blow-dry it before putting away. Any process surface, such as wafer carriers, thermometers, or tweezers must not be allowed to touch any counter surface, but need be rested on clean fabwipes instead. Put plastic evaporator balls in the water, and the wire rack to keep the beaker off the bottom of the water bath, if they are not already in the bath.