Cleaning composition and method of cleaning mask by using the same

A cleaning composition comprising:

• an inorganic acid or salt thereof;
• an organic acid;
• and
• deionized water, wherein
• the organic acid has a first acid dissociation constant (Pka1) and a second acid dissociation constant (Pka2),
• Pka1 is less than Pka2,
• Pka1 is about 1 to about 3,
• Pka2 is about 4 to about 7, and
• the inorganic acid or salt thereof includes at least one of sulfuric acid, salt of sulfuric acid, nitric acid, or salt of nitric acid.

A method of cleaning a mask, the method comprising:

• providing an extreme ultraviolet (EUV) mask used in a EUV lithography process;
• and
• at least partially removing, by using a cleaning composition, tin or tin oxide formed on the EUV mask in the EUV lithography process, wherein
• the cleaning composition includes an inorganic acid or salt thereof and an organic acid,
• the organic acid has a first acid dissociation constant (PKa1) and a second acid dissociation constant (PKa2),
• PKa1 is less than PKa2,
• PKa1 is about 1 to about 3,
• PKa2 is about 4 to about 7,
• in the cleaning, the inorganic acid or salt thereof combines with the tin and allows the tin to be soluble in water, and
• in the cleaning, the organic acid chelates with the tin oxide and forms a chelate compound with tin of the tin oxide.