Etchant and method of etching
A fine wiring line profile with satisfactory precision is formed from a multilayer film containing a first layer made of an aluminum alloy and a second layer formed thereon made of a molybdenum-niobium alloy, by simultaneously etching the two layers constituting the multilayer film through only one etching operation while preventing the upper layer from forming overhangs. An etchant for etching a multilayer film containing an aluminum alloy layer formed over a substrate and a molybdenum-niobium alloy layer formed thereon having a niobium content of 2-19% by weight contains an aqueous solution of an acid mixture containing phosphoric acid, nitric acid, and an organic acid; and a method of etching is carried out with this etchant. The etchant preferably has a phosphoric acid concentration N p of 50-75% by weight, a nitric acid concentration N n of 2-15% by weight, and an acid ingredient concentration defined by N p +(98/63)N n of 55-85% by weight.
1 . An etchant for etching a multilayer film comprising an aluminum alloy layer formed over a substrate and a molybdenum-niobium alloy layer formed thereon having a niobium content of 2-19% by weight,
comprising an aqueous solution of an acid mixture comprising phosphoric acid, nitric acid, and an organic acid.
2 . The etchant as claimed in claim 1 , characterized by having
a phosphoric acid concentration N p of 50-75% by weight,
a nitric acid concentration N n of 2-15% by weight, and
an acid ingredient concentration defined by N p +(98/63)N n of 55-85% by weight.
3 . The etchant as claimed in claim 2 , characterized in that the organic acid is acetic acid or an alkylsulfonic acid.
4 . The etchant as claimed in claim 2 , characterized in that the organic acid is acetic acid and the concentration thereof is 1-30% by weight.
5 . The etchant as claimed in claim 2 , characterized in that the organic acid is methanesulfonic acid, ethanesulfonic acid or both of them and the concentration thereof is 0.5-20% by weight.
6 . A method of etching with an etchant a multilayer film comprising an aluminum alloy layer formed over a substrate and a molybdenum-niobium alloy layer formed thereon having a niobium content of 2-19% by weight, wherein
the etchant comprises an aqueous solution of an acid mixture comprising phosphoric acid, nitric acid, and an organic acid, and
the ratio of the etching rate of the molybdenum-niobium alloy layer to the etching rate of the aluminum alloy layer, (etching rate of the molybdenum-niobium alloy layer)/(etching rate of the aluminum alloy layer), is in the range of 0.7-1.3.
7 . The method of etching as claimed in claim 6 , characterized in that the multilayer film further has a lower layer interposed between the aluminum alloy layer and the substrate, the lower layer comprising a molybdenum-niobium alloy having a niobium content of 2-19% by weight.
8 . The method of etching as claimed in claim 6 , characterized in that the aluminum alloy is an aluminum-copper alloy having a copper content of 0.05-3% by weight or an aluminum-neodymium alloy having a neodymium content of 1.5-15% by weight.
9 . The method of etching as claimed in claim 6 , characterized in that the ratio of the thickness of the upper molybdenum-niobium alloy layer t M to the thickness of the underlying aluminum alloy layer t A , t M /t A , is from 0.1 to 1.
10 . The method of etching as claimed in claim 6 , characterized by having
a phosphoric acid concentration Np of 50-75% by weight,
a nitric acid concentration Nn of 2-15% by weight, and
an acid ingredient concentration defined by N p +(98/63)N n of 55-85% by weight.
11 . The method of etching as claimed in claim 6 , characterized in that the organic acid is acetic acid or an alkylsulfonic acid.
12 . The method of etching as claimed in claim 6 , characterized in that the organic acid is acetic acid and the concentration thereof is 1-30% by weight.
13 . The method of etching as claimed in claim 6 , characterized in that the organic acid is methanesulfonic acid, ethanesulfonic acid or both of them and the concentration thereof is 0.5-20% by weight.