| CPC C09K 13/08 (2013.01) | 20 Claims |

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1. An etchant comprising:
persulfate;
a fluorine-containing compound;
a chlorine-containing compound; a cyclic amine compound;
an inorganic acid;
a first compound; and water,
wherein the first compound is a compound comprising:
a sulfonic group, a sulfonic acid group, or a combination thereof; and
an amine group, and
an interfacial permeation inhibition index (Y) of the etchant is a value of at least about 0.10 and not more than about 0.35, the interfacial permeation inhibition index (Y) being a value calculated by <Equation 1>:
Y=1.4×10−4×M(X1)+1.3×10−4×M(X2)+1.45×10−3×M(X3)+1.5×10−5×M(X1)×M(X2)+1.6×10−3×M(X1)×M(X3)+6.5×10−4×M(X2)×M(X3), Equation 1
wherein, in Equation 1,
M(X1) indicates wt % of the first compound with respect to 100 wt % in total of the etchant,
M(X2) indicates wt % of the chlorine-containing compound with respect to 100 wt % in total of the etchant, and
M(X3) indicates wt % of the water with respect to 100 wt % in total of the etchant.
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