Etchant composition

An etchant composition for an etching treatment of a layer to be etched that contains molybdenum,

• the etchant composition comprising an etching inhibitor, an acid including a phosphoric acid, an acetic acid, and a nitric acid, and water and having a pH of 1 or less,
• wherein the etching inhibitor has an average molecular weight of 1,200 or more and is a nitrogen-containing compound with a percentage of etching inhibition of 30% or more, which is determined under the following conditions:
• the percentage of etching inhibition is calculated by subtracting a relative rate A from 100, where the relative rate A is obtained by determining an etching rate measured using the etchant composition with respect to an etching rate measured using a mixed acid aqueous solution, which is taken as 100;
• the mixed acid aqueous solution consists of a phosphoric acid, an acetic acid, a nitric acid, and water;
• a mass ratio of added amounts of the phosphoric acid, the acetic acid, and the nitric acid in the mixed acid aqueous solution is the same as that of added amounts of the phosphoric acid, the acetic acid, and the nitric acid in the etchant composition;
• a total added amount of the phosphoric acid, the acetic acid, and the nitric acid in the mixed acid aqueous solution is 86% by mass;
• and the mixed acid aqueous solution is used for etching at a predetermined temperature for a predetermined time so that the etching rate is measured.

An etching method comprising:

• etching a layer to be etched that contains molybdenum with an etchant composition,
• the etchant composition comprising an etching inhibitor, an acid including a phosphoric acid, an acetic acid, and a nitric acid, and water and having a pH of 1 or less,
• wherein the etching inhibitor is polyalkyleneimine having an average molecular weight of 1,200 or more,
• a blending amount of the etching inhibitor is 0.1% by mass or more and 5% by mass or less.

An etching method comprising:

• etching a layer to be etched that contains molybdenum with an etchant composition,
• the etchant composition comprising an etching inhibitor, an acid including a phosphoric acid, an acetic acid, and a nitric acid, and water and having a pH of 1 or less,
• wherein the etching inhibitor has an average molecular weight of 1,200 or more and is a nitrogen-containing compound with a percentage of etching inhibition of 30% or more, which is determined under the following conditions:
• the percentage of etching inhibition is calculated by subtracting a relative rate A from 100, where the relative rate A is obtained by determining an etching rate measured using the etchant composition with respect to an etching rate measured using a mixed acid aqueous solution, which is taken as 100;
• the mixed acid aqueous solution consists of a phosphoric acid, an acetic acid, a nitric acid, and water;
• a mass ratio of added amounts of the phosphoric acid, the acetic acid, and the nitric acid in the mixed acid aqueous solution is the same as that of added amounts of the phosphoric acid, the acetic acid, and the nitric acid in the etchant composition;
• a total added amount of the phosphoric acid, the acetic acid, and the nitric acid in the mixed acid aqueous solution is 86% by mass;
• and the mixed acid aqueous solution is used for etching at a predetermined temperature for a predetermined time so that the etching rate is measured.