A composition for cleaning a phase shift mask is provided to effectively remove sulfate ion inducing haze and to reduce phase change and transmittance change generated with damage of a phase shift layer. A composition for cleaning a phase shift mask comprises ammonium salts of organic acids of which the ionization constant(Kb) of ammonium salts is greater than the ionization constant(Ka) of organic acid ions; hydrogen peroxide; and water. A method for cleaning a phase shift mask comprises the steps of: (S10) performing a first cleaning process on a substrate formed with the phase shifting mask by using a first cleaning solution including an sulfuric acid to remove photoresist and etching byproducts; and (S40) performing a second cleaning process by using the composition for cleaning the phase shift mask to remove sulfate ion remaining on the substrate without the damage of the phase shifting mask.
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