Tetramethylammonium hydroxide (TMAH or TMAOH) is a quaternary ammonium salt with the molecular formula N(CH3)4+ OH−. It is commonly encountered as concentrated solutions in water or methanol. The solid and solutions are colorless, or yellowish if impure.

Application

TMAH solution is widely used in the electronics industry as a developer or cleaner. TMAH is typically one of several ingredients in etching / stripping mixtures, although it may also be used as a pure chemical. It is often used in solution in water, and less frequently, in methanol.