The wet chemical cleaning of a magnetic tunnel junction (MTJ) stack after dry etching was carried out to eliminate the redeposited materials on the sidewall of the MTJ and to examine the effect on the properties of the MTJ. Wet cleaning may result in the degradation of electrical properties of a MTJ. The resistance (R)-magnetic field (H) curve after cleaning showed that CoFe pinned layer was switched at low magnetic field. It was proved from transmission electron microscopy that CoFe and IrMn layers were attacked and the interface between the two layers was damaged due to the reaction with cleaning solutions. (C) 2004 The Electrochemical Society.