JP2023048527A - Etching liquid, method for etching metal-containing layer and method for forming metal wiring - Google Patents

Abstract

To provide an etching liquid capable of reducing roughness of a surface after etching, an etching method using the etching liquid and a method for forming metal wiring.SOLUTION: There is provided an etching liquid which contains hydrogen peroxide and chitosan, has a pH of 0.1 or more and 4.0 or less and is used for etching of a metal-containing layer. Further, there is provided an etching liquid which contains hydrogen peroxide, chitosan and an organic acid and is used for etching of a metal-containing layer. Furthermore, there is provided a method for etching a metal-containing layer which comprises a step of bringing the etching liquid into contact with a metal-containing layer. In addition, there is provided a method for producing metal wiring which comprises a step of etching a metal-containing layer using the etching liquid.SELECTED DRAWING: None

Description

The present invention relates to an etchant, a method for etching a metal-containing layer, and a method for forming metal wiring.

2. Description of the Related Art A semiconductor device manufacturing process is composed of various multi-step processing steps. Such a processing step includes a process of patterning semiconductor layers, electrodes, etc. by etching or the like. Molybdenum (Mo), copper (Cu), cobalt (Co), nickel (Ni), tungsten (W), and the like are used as metal materials for wiring and the like.

Etching solutions used in metal wiring formation processes such as molybdenum include aqueous hydrogen peroxide solution; mixed solution of phosphoric acid, nitric acid and acetic acid; mixed solution of nitric acid, hydrofluoric acid and acetic acid; sodium hydroxide, sodium carbonate and ammonium hydroxide. and an alkaline aqueous solution of sodium phosphate. In addition, an etching solution containing hydrogen peroxide, an inorganic acid not containing fluorine atoms, an organic acid, an amine compound, an azole compound, and a hydrogen peroxide stabilizer is proposed as an etching solution for a multilayer thin film containing a copper layer and a molybdenum layer. (Patent Document 1).

Japanese Patent No. 5051323

In etching processes for metal surfaces, it is required to reduce the roughness (surface roughness) of the metal surface after etching, but so far there has been no etchant that can sufficiently reduce the surface roughness. If the surface roughness is not sufficiently reduced, problems may occur in post-processes, resulting in a decrease in yield.
In addition, in a device having a semiconductor laminated structure, current leakage due to proximity between upper and lower wirings becomes a problem in plug junctions of upper and lower wirings. In order to prevent this, fine etching of the wiring by the recess process is required. In such micro-etching, etching with reduced surface roughness is required so as not to cause defects in the plug junction.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an etchant, an etching method using the etchant, and a method for forming metal wiring, which are capable of reducing surface roughness after etching. do.

In order to solve the above problems, the present invention employs the following configurations.

A first aspect of the present invention is an etchant used for etching a metal-containing layer, containing hydrogen peroxide and chitosan and having a pH of 0.1 or more and 4.0 or less.

A second aspect of the present invention is an etchant used for etching a metal-containing layer, containing hydrogen peroxide, chitosan, and an organic acid.

A third aspect of the present invention is a method for etching a metal-containing layer, comprising the step of bringing the metal-containing layer into contact with the etching solution of the first or second aspect.

A third aspect of the present invention is a method for forming a metal wiring, comprising the step of etching a metal-containing layer using the etching solution of the first or second aspect.

ADVANTAGE OF THE INVENTION According to this invention, the etching liquid which can reduce the surface roughness after an etching, the etching method using the said etching liquid, and the formation method of metal wiring can be provided.

(Etching liquid)
An etchant according to one embodiment of the present invention is used for etching a metal-containing layer. The etchant according to this embodiment contains hydrogen peroxide and chitosan.

<Hydrogen peroxide>
The etchant of this embodiment contains hydrogen peroxide (H ₂ O ₂ ). In the etching liquid of this embodiment, hydrogen peroxide functions as an oxidizing agent.

In the etching solution of the present embodiment, the content of hydrogen peroxide is not particularly limited as long as the metal to be etched can be etched. The content of hydrogen peroxide is, for example, 0.05 to 40% by mass with respect to the total mass of the etchant. The lower limit of the content of hydrogen peroxide is, for example, 0.1% by mass or more, 0.5% by mass or more, 1% by mass or more, 2% by mass or more, 3% by mass or more with respect to the total mass of the etching solution. , 4% by mass or more, or 5% by mass or more. When the content of hydrogen peroxide is at least the lower limit, the etching rate for the metal to be etched becomes better. The upper limit of the hydrogen peroxide content is, for example, 35% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 18% by mass or less, or 15% by mass with respect to the total mass of the etching solution. % or less. When the content of hydrogen peroxide is equal to or less than the upper limit, the surface roughness of the etched metal is likely to be reduced. The upper limit value and the lower limit value can be combined arbitrarily.

<Chitosan>
The etching solution of this embodiment contains chitosan. In the etching solution of the present embodiment, chitosan functions as an inhibitor of surface roughness. Chitosan is a polysaccharide composed of the following repeating units.

In the etching solution of the present embodiment, the content of chitosan is not particularly limited as long as the metal to be etched can be etched. The content of chitosan is, for example, 0.0001 to 10% by mass with respect to the total mass of the etching liquid. The lower limit of the hydrogen peroxide content is, for example, 0.0005% by mass or more, 0.001% by mass or more, 0.005% by mass or more, 0.01% by mass or more with respect to the total mass of the etching solution, 0.03% by mass or more, or 0.05% by mass or more. When the content of chitosan is at least the lower limit, the surface roughness of the etched metal is further reduced. The upper limit of the content of chitosan is, for example, 9% by mass or less, 8% by mass or less, 7% by mass or less, 6% by mass or less, 5% by mass or less, 4% by mass or less, based on the total mass of the etching solution. 3% by mass or less, 2% by mass or less, 1.5% by mass or less, or 1% by mass or less. When the content of chitosan is equal to or less than the upper limit, the etching rate becomes better. The upper limit value and the lower limit value can be combined arbitrarily.

<Acid component>
The etching solution of the present embodiment preferably contains an acid component. In the etching solution of the present embodiment, the acid component can function as a stabilizing agent for chitosan. When the etchant contains an acid component, chitosan is stabilized in the etchant, and the surface roughness of the metal after etching is easily reduced.

The acid component is not particularly limited as long as chitosan can be stabilized. The acid component may be an organic acid or an inorganic acid. Inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, hypophosphorous acid, carbonic acid, sulfamic acid and the like. Among them, the inorganic acid is preferably phosphoric acid.

Organic acids include, for example, carboxylic acids. The carboxylic acid may be a monocarboxylic acid or a polyvalent carboxylic acid, but is preferably a monocarboxylic acid. The carboxylic acid may be either an aliphatic carboxylic acid or an aromatic carboxylic acid, preferably an aliphatic carboxylic acid. The number of carbon atoms in the aliphatic carboxylic acid includes, for example, 1 to 18 carbon atoms, preferably 1 to 14 carbon atoms, more preferably 1 to 10 carbon atoms, and more preferably 1 to 6 carbon atoms. Preferred are those with 1 to 3 carbon atoms. The number of carbon atoms in the aromatic carboxylic acid includes 6 to 10 carbon atoms.

Examples of aliphatic carboxylic acids include formic acid, acetic acid, propionic acid, lactic acid, glycolic acid, diglycolic acid, pyruvic acid, butyric acid, hydroxybutyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, lauric acid, and myristic acid. , palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, etc.; tartaric acid, succinic acid, malic acid, maleic acid, fumaric acid, glutaric acid, itaconic acid, adipic acid, etc. Acids; aliphatic tricarboxylic acids such as citric acid, propanetricarboxylic acid, trans-aconitic acid, and the like.
Aromatic carboxylic acids include aromatic monocarboxylic acids such as benzoic acid, salicylic acid and mandelic acid; and aromatic dicarboxylic acids such as phthalic acid, isophthalic acid and terephthalic acid.
Among them, as the organic acid, aliphatic monocarboxylic acids are preferable, and acetic acid, glycolic acid, and lactic acid are more preferable.
The etching solution of the present embodiment may contain no organic acid other than carboxylic acid, or may contain no one or more of the components exemplified as the acid components. The etching solution of the present embodiment may not contain, for example, any one or more of aromatic carboxylic acid, polycarboxylic acid, dicarboxylic acid, tricarboxylic acid, and tetravalent or higher carboxylic acid.

One type of acid component may be used alone, or two or more types may be used in combination.
In the etching solution of the present embodiment, the content of the acid component is not particularly limited as long as the metal to be etched can be etched. The content of the acid component is, for example, 0.05 to 40% by mass with respect to the total mass of the etchant. The lower limit of the content of the acid component is, for example, 0.01% by mass or more, 0.05% by mass or more, 0.1% by mass or more, 0.5% by mass or more, or 1 mass % or more is mentioned. When the content of the acid component is at least the lower limit, the surface roughness of the etched metal is likely to be reduced. The upper limit of the content of the acid component is, for example, 35% by mass or less, 30% by mass or less, 25% by mass or less, 20% by mass or less, 15% by mass or less, or 12% by mass or less with respect to the total mass of the etching solution. , or 10% by mass or less. When the content of the acid component is equal to or less than the above upper limit value, the etching rate is likely to be favorably maintained. The upper limit value and the lower limit value can be combined arbitrarily.

An acid component may be used to adjust the pH of the etchant. For example, after dissolving other components of the etchant in water, an acid component may be added so as to obtain a desired pH. In this case, the acid component may be added to the etching solution while measuring the pH of the etching solution, and the addition of the acid component may be terminated when the desired pH is reached. In the etchant of the present embodiment, the content of the acid component may be an amount necessary to adjust the pH of the etchant to a desired range.

<pH>
Although the pH of the etching solution of the present embodiment is not particularly limited, it is preferably from 0.1 to 4.0. When the pH of the etchant is within the above range, chitosan in the etchant is stabilized and the surface roughness is easily reduced. Examples of the lower limit of the pH of the etching solution include 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.6 or more, 0.7 or more, or 0.8 or more. . Examples of the upper limit of the pH of the etching solution include 3.9 or less, 3.8 or less, 3.7 or less, 3.6 or less, or 3.5 or less. The upper limit value and the lower limit value can be combined arbitrarily.

<Optional component>
The etching solution of the present embodiment may contain other components in addition to the above components within a range that does not impair the effects of the present invention. Other components include, for example, water, polar organic solvents, amine compounds, azoles, hydrogen peroxide stabilizers, pH adjusters, and surfactants.

≪Water≫
The etching solution of the present embodiment preferably contains water as a solvent for the above components. The water may contain trace ingredients which are unavoidably included. The water used in the etching solution of the present embodiment is preferably purified water such as distilled water, ion-exchanged water, and ultrapure water, and ultrapure water generally used in semiconductor manufacturing is used. is more preferred.
The content of water in the etching solution of the present embodiment is not particularly limited, but may be 30 to 99% by mass with respect to the total mass of the etching solution. The water content may be adjusted to achieve the desired content of other ingredients.

≪Polar organic solvent≫
The etching solution of the present embodiment may contain a polar organic solvent as long as the effects of the present invention are not impaired. Polar organic solvents include alcohols (e.g., methanol, ethanol, n-butanol, isobutanol, tert-butanol, ethylene glycol, propylene glycol, glycerin, 1,3-propanediol, 1,3-butanediol, 1,3-butanediol, 4-butanediol, diethylene glycol, dipropylene glycol, furfuryl alcohol, and 2-methyl-2,4-pentanediol, etc.), dimethyl sulfoxide, ethers (e.g., ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, propylene glycol dimethyl ether) and the like. A polar organic solvent may be used individually by 1 type, and may use 2 or more types together.
The etching solution of the present embodiment may contain no polar solvent, or may contain no one or more of the polar solvents exemplified above.

<<Amine compound>>
The etching solution of the present embodiment may contain an amine compound within a range that does not impair the effects of the present invention. Examples of amine compounds include ethylenediamine, trimethylenediamine, tetramethylenediamine, 1,2-propanediamine, 1,3-propanediamine, N,N-dimethyl-1,3-propanediamine, N,N-diethyl- 1,3-propanediamine, 1,3-diaminobutane, 2,3-diaminobutane, pentamethylenediamine, 2,4-diaminopentane, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, N- methylethylenediamine, N,N-dimethylethylenediamine, trimethylethylenediamine, N-ethylethylenediamine, N,N-diethylethylenediamine, triethylethylenediamine, 1,2,3-triaminopropane, hydrazine, tris(2-aminoethyl)amine, tetra Polyamines such as (aminomethyl)methane, diethylenetriamine, triethylenetetramine, tetraethylpentamine, heptaethyleneoctamine, nonaethylenedecamine, diazabicycloundecene; ethanolamine, N-methylethanolamine, N-methyldiethanolamine, N -ethylethanolamine, N-aminoethylethanolamine, N-propylethanolamine, N-butylethanolamine, diethanolamine, triethanolamine, 1-amino-2-propanol, N-methylisopropanolamine, N-ethylisopropanolamine, N-propylisopropanolamine, 2-aminopropan-1-ol, N-methyl-2-amino-propan-1-ol, N-ethyl-2-amino-propan-1-ol, 1-aminopropan-3- ol, N-methyl-1-aminopropan-3-ol, N-ethyl-1-aminopropan-3-ol, 1-aminobutan-2-ol, N-methyl-1-aminobutan-2-ol, N- Ethyl-1-aminobutan-2ol, 2-aminobutan-1-ol, N-methyl-2-aminobutan-1-ol, N-ethyl-2-aminobutan-1-ol, 3-aminobutan-1-ol, N -methyl-3-aminobutan-1-ol, N-ethyl-3-aminobutan-1-ol, 1-aminobutan-4-ol, N-methyl 1-aminobutan-4-ol, N-ethyl-1-aminobutan- 4-ol, 1-amino-2-methylpropan-2-ol, 2-amino-2-methylpropan-1-ol, 1-aminopentan-4-ol, 2-amino-4-methylpentane-1- ol, 2-aminohexan-1-ol, 3-aminoheptan-4-ol, 1-aminooctan-2-ol, 5-aminooctan-4-ol, 1-aminobutane-2,3-diol, 2- aminopropane-1,3-diol, tris(oxymethyl)aminomethane, 1,2-diaminopropan-3-ol, 1,3-diaminopropan-2-ol, 2-(2-aminoethoxy)ethanol, 2 Alkanolamine such as -(2-aminoethylamino)ethanol and diglycolamine. An amine compound may be used individually by 1 type, and may use 2 or more types together.
The etching solution of the present embodiment may contain no amine compound, or may contain no one or more of the amine compounds exemplified above.

<<Azoles>>
The etching solution of the present embodiment may contain azoles as long as the effects of the present invention are not impaired. Examples of azoles include triazoles such as 1H-benzotriazole, 5-methyl-1H-benzotriazole, 3-amino-1H-triazole; 1H-tetrazole, 5-methyl-1H-tetrazole, 5-phenyl-1H -tetrazole and 5-amino-1H-tetrazole; imidazoles such as 1H-imidazole and 1H-benzimidazole; thiazoles such as 1,3-thiazole and 4-methylthiazole. Azoles may be used singly or in combination of two or more.
The etching solution of the present embodiment may contain no azoles, or may contain no one or more of the azoles exemplified above.

≪Hydrogen peroxide stabilizer≫
The etching solution of the present embodiment may contain a hydrogen peroxide stabilizer within a range that does not impair the effects of the present invention. A hydrogen peroxide stabilizer is a substance that inhibits the decomposition of hydrogen peroxide. Examples of hydrogen peroxide stabilizers include urea-based hydrogen peroxide stabilizers such as phenylurea, allyl urea, 1,3-dimethylurea and thiourea; phenylacetamide; phenylethylene glycol and the like. The hydrogen peroxide stabilizers may be used singly or in combination of two or more.
The etching solution of the present embodiment may contain no hydrogen peroxide stabilizer, or may contain no one or more of the hydrogen peroxide stabilizers exemplified above.

≪pH adjuster≫
The etching solution of the present embodiment may contain a pH adjuster other than the acid component within a range that does not impair the effects of the present invention. Examples of pH adjusters include basic compounds. The basic compound may be an organic basic compound or an inorganic basic compound.
Inorganic basic compounds include inorganic compounds containing alkali metals or alkaline earth metals and salts thereof. Examples include lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide.
Examples of organic basic compounds include quaternary ammonium salts and alkylamines (trimethylamine, triethylamine, etc.). Examples of quaternary ammonium salts include tetramethylammonium hydroxide (TMAH), bis(2-hydroxyethyl)dimethylammonium hydroxide, tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, methyltriethylammonium hydroxide, trimethyl(hydroxyethyl)ammonium hydroxide, triethyl(hydroxyethyl)ammonium hydroxide and the like.
One of the pH adjusters may be used alone, or two or more of them may be used in combination.
The etching solution of the present embodiment may contain no pH adjuster other than the acid component, or may contain no one or more of the pH adjusters exemplified above.

≪Surfactant≫
The etching solution of the present embodiment may contain a surfactant within a range that does not impair the effects of the present invention. Surfactants include nonionic surfactants, anionic surfactants, cationic surfactants, amphoteric surfactants, and the like.

Examples of nonionic surfactants include polyalkylene oxide alkylphenyl ether surfactants, polyalkylene oxide alkyl ether surfactants, block polymer surfactants composed of polyethylene oxide and polypropylene oxide, and polyoxyalkylene distyrenated surfactants. Phenyl ether-based surfactants, polyalkylenetribenzylphenyl ether-based surfactants, acetylene polyalkylene oxide-based surfactants, and the like are included.

Examples of anionic surfactants include alkylsulfonic acids, alkylbenzenesulfonic acids, alkylnaphthalenesulfonic acids, alkyldiphenyl ether sulfonic acids, fatty acid amidosulfonic acids, polyoxyethylene alkyl ether carboxylic acids, polyoxyethylene alkyl ether acetic acids, polyoxyethylene Alkyl ether propionic acids, alkyl phosphonic acids, fatty acid salts and the like can be mentioned. "Salts" include ammonium salts, sodium salts, potassium salts, tetramethylammonium salts and the like.

Examples of cationic surfactants include quaternary ammonium salt-based surfactants and alkylpyridium-based surfactants.

Examples of amphoteric surfactants include betaine surfactants, amino acid surfactants, imidazoline surfactants, amine oxide surfactants, and the like.

One type of surfactant may be used alone, or two or more types may be used in combination.
The etching solution of the present embodiment may contain no surfactant, or may contain no one or more of the surfactants exemplified above.

≪Others≫
The etching solution of the present embodiment may contain any component other than the components exemplified above as long as the effects of the present invention are not impaired. For example, various additives known as additives for etching liquids may be contained.
The etchant of the present embodiment may or may not contain slurry as used in a CMP (Chemical Mechanical Polishing) process. The etching solution of this embodiment may or may not contain an abrasive. Examples of abrasives include metal oxide particles (alumina, silica, titania, ceria, zirconia, etc.).

<Object to be processed>
The etchant of this embodiment is used for etching a metal-containing layer. The etching solution of the present embodiment is intended for etching an object including a metal-containing layer. Examples of metals to be etched include molybdenum, copper, cobalt, nickel, and tungsten.
Specific examples of the object to be processed include a substrate having a metal-containing layer. The substrate is not particularly limited, and includes semiconductor wafers, photomask glass substrates, liquid crystal display glass substrates, plasma display glass substrates, FED (Field Emission Display) substrates, optical disk substrates, magnetic disk substrates, and magneto-optical substrates. Various substrates such as disk substrates can be used. The substrate is preferably a substrate used for fabricating semiconductor devices. The substrate may optionally include layers other than metal-containing layers. The substrate may comprise various structures in addition to the layered structure. The substrate may have, for example, metal lines, gate structures, source structures, drain structures, insulating layers, ferromagnetic layers, non-magnetic layers, and the like. The topmost layer on the device side of the substrate need not be the metal-containing layer; for example, the intermediate layer of the multilayer structure may be the metal-containing layer.
The size, thickness, shape, layer structure, etc. of the substrate are not particularly limited and can be appropriately selected according to the purpose.

The metal-containing layer preferably contains at least one metal selected from the group consisting of molybdenum, copper, cobalt, nickel, and tungsten. The metal-containing layer is preferably a metal film, more preferably a metal film containing at least one metal selected from the group consisting of molybdenum, copper, cobalt, nickel, and tungsten. The thickness of the metal-containing layer on the substrate is not particularly limited, and can be appropriately selected according to the purpose. Examples of the thickness of the metal-containing layer include 1 to 500 nm, 1 to 300 nm, 1 to 200 nm, 1 to 100 nm, or 1 to 50 nm.
The metal-containing layer may have a single layer structure or a multilayer structure. The metal-containing layer may be, for example, a multi-layer structure in which layers made of different kinds of metals are laminated. The multilayer structure may include, for example, two or more metal layers selected from the group consisting of molybdenum layers, copper layers, cobalt layers, nickel layers, and tungsten layers.
be able to.

The etchant of the present embodiment may be used to etch the metal-containing layer to form metal wiring. For example, metal-containing layers including molybdenum, copper, cobalt, nickel, or tungsten can be etched to form metal interconnects including molybdenum, copper, cobalt, nickel, or tungsten.

Since the etching solution of the present embodiment contains hydrogen peroxide and chitosan, it is possible to etch the metal-containing layer while suppressing surface roughness. It is presumed that the chitosan in the etchant protects the surface of the metal-containing layer, thereby suppressing an increase in surface roughness due to etching.
If the roughness of the metal surface after etching is large, there is a risk of problems occurring in the post-process, current leakage at the joints of the upper and lower wirings, poor connection at the plug joints, and the like. Especially in recess etching, reduction of surface roughness is required. Since the etching solution of the present embodiment can form a metal surface with reduced metal roughness, it can be suitably used for etching for forming metal wiring, particularly recess etching.

(Etching method for metal-containing layer)
A method for etching a metal-containing layer according to one embodiment of the present invention includes the step of bringing the metal-containing layer into contact with the etching solution of the embodiment.

In the etching method of this embodiment, the metal-containing layer to be etched includes the same ones as those described above. The metal-containing layer preferably contains at least one metal selected from the group consisting of molybdenum, copper, cobalt, nickel, and tungsten.

The method of bringing the metal-containing layer into contact with the etchant is not particularly limited. Examples of such methods include, but are not limited to, a spray method, a dipping method, a liquid heaping method, and a liquid pouring method.
In the spray method, for example, the metal-containing layer is conveyed or rotated in a predetermined direction, and the etchant is sprayed into the space to bring the etchant into contact with the metal-containing layer. If necessary, the etchant may be sprayed while rotating the substrate using a spin coater.
In the immersion method, the metal-containing layer is immersed in an etchant to bring the metal-containing layer into contact with the etchant. At this time, the metal-containing layer may be immersed while stirring the etchant as necessary.
In the liquid deposition method, an etchant is applied to the metal-containing layer, and the metal-containing layer and the etchant are brought into contact with each other.
These etching methods can be appropriately selected according to the structure, material, etc. of the metal-containing layer. In the case of the spray method or the liquid immersion method, the amount of the etchant supplied to the metal-containing layer may be an amount that sufficiently wets the surface of the metal-containing layer to be processed with the etchant.
Further, in the liquid pouring method, while rotating the base material having the metal-containing layer at a necessary rotation speed, the metal-containing layer is discharged and brought into contact with the etching liquid in an amount sufficient to wet the metal-containing layer.

The temperature of the etching treatment is not particularly limited, and may be any temperature at which the metal to be etched is dissolved in the etchant. The temperature of the etching process is, for example, 20 to 60.degree. In any of the spray method, the immersion method, and the liquid filling method, the etching rate increases by increasing the temperature of the etchant. The temperature of the etching treatment can be appropriately selected in consideration of the etching rate, changes in the composition of the etchant, workability, safety, cost, and the like.

The etching treatment time may be appropriately selected according to the purpose of the etching treatment, the amount of metal to be removed by etching (for example, the thickness of the metal-containing layer), and the etching treatment conditions.

The purpose of the etching treatment is not particularly limited, and may be microfabrication of a metal-containing layer (for example, a metal-containing layer on a substrate). It may be removal of deposits or cleaning of a metal-containing layer (eg, a metal-containing layer on a substrate).
When the purpose of the etching treatment is microfabrication of the metal-containing layer, the metal-containing layer and the etchant may be brought into contact with the etching solution after covering the portions that should not be etched with a mask.
When the purpose of the etching treatment is to remove metal-containing deposits that adhere to the object to be processed, the metal-containing deposits are dissolved by bringing the etchant into contact with the object to be processed, and the metal deposits are removed from the object to be processed. can be removed.
When the purpose of the etching treatment is to clean the metal-containing layer, by bringing the etchant into contact with the metal-containing layer, impurities such as particles adhering to the surface of the metal-containing layer can be removed in a short period of time.

According to the etching method of this embodiment, the metal-containing layer is etched using the etchant of the above embodiment. Therefore, it is possible to satisfactorily etch while suppressing an increase in surface roughness. This makes it possible to obtain a metal-containing layer with reduced surface roughness after etching.

(Method for forming metal wiring)
A method for forming a metal wiring according to one embodiment of the present invention includes a step of etching a metal-containing layer using the etching solution of the above embodiment.

<Etching process>
Examples of the metal-containing layer include those similar to those described above. The metal-containing layer preferably contains at least one metal selected from the group consisting of molybdenum, copper, cobalt, nickel, and tungsten.

Etching of the metal-containing layer can be performed in a manner similar to that described above. Etching of the metal-containing layer may be performed after areas not to be etched are covered with a mask. The mask may be formed of a resist film. For example, a resist film is formed on the metal-containing layer using a resist composition and exposed through a desired pattern mask. Next, by developing the resist film with a developing solution, a resist pattern is formed by transferring the pattern. By etching the metal-containing layer using this resist pattern as a mask, a desired wiring pattern can be formed in the metal-containing layer.
The etching for forming the metal wiring may be recess etching.

<Optional process>
The method for manufacturing a metal wiring according to the present embodiment may include arbitrary steps in addition to the etching step. The optional process can include, for example, known processes that are performed when forming metal wiring without particular limitation. Such steps include, for example, steps of forming each structure such as a gate structure, a source structure, a drain structure, an insulating layer, a ferromagnetic layer, and a nonmagnetic layer (layer formation, etching other than the above etching, chemical mechanical polishing, metamorphic etc.), a resist film formation process, an exposure process, a development process, a heat treatment process, a cleaning process, an inspection process, etc., but are not limited to these. These optional steps can be appropriately performed before or after the etching step as required.

According to the metal wiring manufacturing method of the present embodiment, since the metal-containing layer is etched using the etchant of the above-described embodiment, a metal wiring with reduced surface roughness can be obtained.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

<Preparation of etching solution>
(Example 1)
16.7 g of 30% by mass aqueous hydrogen peroxide solution, 5 g of acetic acid, 1 g of chitosan, and 77.3 g of pure water were added to a 200 mL beaker and dissolved by stirring to obtain an etching solution of Example 1. The pH of the etchant was measured at 25° C. with a pH meter (Horiba, Ltd.).

(Examples 2-13, Comparative Examples 1-2)
An etchant for each example was obtained in the same manner as in Example 1, except that the compositions shown in Table 1 were used.

<Etching treatment>
The substrate used was a silicon wafer on which a molybdenum film was formed to a thickness of 50 nm.
The etchant of each example was placed in a 200 mL beaker and stirred with a stirrer at 300 rpm. A substrate was immersed in the etching solution being stirred, and then pulled out after a predetermined period of time. Next, the substrate was washed with running water in a 5 mass % acetic acid aqueous solution. Then, the substrate was washed with running pure water and spray-dried.

[Evaluation of etching rate]
The film thickness of the molybdenum coating on the substrate before and after the <etching treatment> was measured using an X-ray fluorescence spectrometer (XRF) (ZSX Primus manufactured by Rigaku Corporation). The etching rate was calculated from the measured film thickness before and after the etching treatment. This is shown in Table 2 as "etching rate".

[Evaluation of surface roughness]
The surface of the substrate after the above <etching treatment> is observed with an AFM (atomic force microscope: manufactured by Takano Co., Ltd.), and the root mean square height (surface roughness) Rq (nm) per 1 μm square is obtained. rice field. Similarly, the surface roughness Rq0 (nm) of the surface of the substrate not subjected to the etching treatment was obtained. Rq/Rq0 was determined and shown in Table 2 as "surface roughness [Rq/Rq0]".

As shown in Table 2, in Examples 1-13, the surface roughness was suppressed as compared with Comparative Examples 1-2. Also, the etching rate was good.
From the above results, it was confirmed that the surface roughness can be reduced while maintaining a good etching rate by using the etching solution of the example.

Claims (8)

An etchant used for etching a metal-containing layer, containing hydrogen peroxide and chitosan and having a pH of 0.1 or more and 4.0 or less. The etching solution according to claim 1, further comprising an organic acid. An etchant used for etching a metal-containing layer, containing hydrogen peroxide, chitosan, and an organic acid. The etching liquid according to claim 3, having a pH of 0.1 or more and 4.0 or less. The etching solution according to any one of claims 1 to 4, wherein the metal-containing layer contains at least one metal selected from the group consisting of molybdenum, copper, cobalt, nickel, and tungsten. The etching solution according to any one of claims 1 to 5, which is used for forming metal wiring. A method for etching a metal-containing layer, comprising the step of bringing the metal-containing layer into contact with the etching solution according to any one of claims 1 to 6. A method of forming a metal wiring, comprising the step of etching a metal-containing layer using the etchant according to claim 6 .