Composition and method for treating substrate

A composition comprising:

• at least one iodic acid compound selected from the group consisting of periodic acid, iodic acid, and salts thereof;
• a chloride ion;
• and
• a compound represented by Formula (1),
• in Formula (1), R1 to R4 each independently represent an alkyl group which may have a substituent, R1 to R4 do not represent the same group all together, Xn− represents a hydroxide ion, a chloride ion, or a fluoride ion, and n represents an integer of 1,
• wherein a content of the compound represented by Formula (1) is 0.001% to 2.00% by mass with respect to the total mass of the composition, and
• the compound represented by Formula (1) includes at least one compound selected from the group consisting of a diethyldimethylammonium salt, a methyltriethylammonium salt, a trimethyl(hydroxyethyl)ammonium salt, a methyltributylammonium salt, a dimethyldipropylammonium salt, a benzyltrimethylammonium salt, a benzyltriethylammonium salt, a triethyl(hydroxyethyl)ammonium salt, a methyltri(hydroxyethyl)ammonium salt, a benzyltrimethylammonium salt, a triethyl(hydroxyethyl)ammonium salt, a bishydroxyethyldimethylammonium salt, a trimethylpropylammonium salt, an isopropyltrimethylammonium salt, a butyltrimethylammonium salt, a triethylpropylammonium salt, an isopropyltriethylammonium salt, a butyltriethylammonium salt, a methyltripropylammonium salt, an ethyltripropylammonium salt, a butyltripropylammonium salt, an ethyltributylammonium salt, a propyltributylammonium salt, a diisopropyldimethylammonium salt, a dibutyldimethylammonium salt, a diethyldipropylammonium salt, a diethyldiisopropylammonium salt, a diethyldibutylammonium salt, an ethylmethylpropylbutylammonium salt, an ethylmethylisopropylbutylammonium salt, an ethylmethyldipropylammonium salt, an ethylmethyldiisopropylammonium salt, a dimethylbis(2-hydroxyethyl)ammonium salt, a methyltris(2-hydroxyethyl)ammonium salt, and an ethylmethyldibutylammonium salt.