Etching solution, method for etching metal-containing layer, and method for forming metal wiring

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

[Technical Field]

[0001] The present invention relates to an etching solution, a method for etching a metal-containing layer, and a method for forming metal wiring. [Background technology]

[0002] The manufacturing process of semiconductor devices consists of various multi-stage processing steps, including the patterning of semiconductor layers and electrodes by etching, etc. Metal materials used for wiring, etc. include molybdenum (Mo), copper (Cu), cobalt (Co), nickel (Ni), and tungsten (W).

[0003] Known etching solutions used in processes for forming metal wiring such as molybdenum include aqueous hydrogen peroxide solutions, mixed solutions of phosphoric acid, nitric acid, and acetic acid, mixed solutions of nitric acid, hydrofluoric acid, and acetic acid, and alkaline aqueous solutions of sodium hydroxide, sodium carbonate, ammonium hydroxide, and sodium phosphate. Furthermore, an etching solution containing hydrogen peroxide, a fluorine-free inorganic acid, an organic acid, an amine compound, an azole compound, and a hydrogen peroxide stabilizer has been proposed as an etching solution for multilayer thin films containing copper and molybdenum layers (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5051323 Summary of the Invention [Problem to be solved by the invention]

[0005] In the etching process of metal surfaces, it is necessary to reduce the roughness of the metal surface after etching (surface roughness), but until now there has been no etching solution that can sufficiently reduce surface roughness. If the surface roughness is not reduced sufficiently, problems may occur in subsequent processes, resulting in a decrease in yield. Furthermore, in devices with a semiconductor stacked structure, current leakage can be a problem when connecting upper and lower wirings to plugs due to the proximity of the upper wiring. To prevent this, micro-etching of the wiring using a recess process is required. In such micro-etching, etching with reduced surface roughness is required to prevent defects at the plug junctions.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an etching solution, an etching method using the etching solution, and a method for forming metal wiring, which are capable of reducing surface roughness after etching. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention employs the following configuration.

[0008] A first aspect of the present invention is an etching solution for use in etching a metal-containing layer, which contains hydrogen peroxide and chitosan and has a pH of 0.1 or more and 4.0 or less.

[0009] A second aspect of the present invention is an etching solution for use in etching a metal-containing layer, the etching solution comprising hydrogen peroxide, chitosan, and an organic acid.

[0010] A third aspect of the present invention is a method for etching a metal-containing layer, comprising the step of contacting the metal-containing layer with the etching solution of the first or second aspect.

[0011] A third aspect of the present invention is a method for forming metal wiring, comprising the step of etching a metal-containing layer using the etching solution of the first or second aspect. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide an etching solution capable of reducing surface roughness after etching, an etching method using the etching solution, and a method for forming metal wiring. DETAILED DESCRIPTION OF THE INVENTION

[0013] (etchant) An etching solution according to one embodiment of the present invention is used for etching a metal-containing layer. The etching solution according to this embodiment contains hydrogen peroxide and chitosan.

[0014] <Hydrogen peroxide> The etching solution of this embodiment contains hydrogen peroxide (H2O2). In the etching solution of this embodiment, hydrogen peroxide functions as an oxidizing agent.

[0015] In the etching solution of this embodiment, the content of hydrogen peroxide is not particularly limited as long as it can etch the metal to be etched. Examples of the hydrogen peroxide content include 0.05 to 40 mass% relative to the total mass of the etching solution. Examples of the lower limit of the hydrogen peroxide content include 0.1 mass% or more, 0.5 mass% or more, 1 mass% or more, 2 mass% or more, 3 mass% or more, 4 mass% or more, or 5 mass% or more relative to the total mass of the etching solution. When the hydrogen peroxide content is equal to or greater than the lower limit, the etching rate for the metal to be etched is improved. Examples of the upper limit of the hydrogen peroxide content include 35 mass% or less, 30 mass% or less, 25 mass% or less, 20 mass% or less, 18 mass% or less, or 15 mass% or less relative to the total mass of the etching solution. When the hydrogen peroxide content is equal to or less than the upper limit, the surface roughness of the metal after etching is easily reduced. The upper and lower limits can be arbitrarily combined.

[0016] <Chitosan> The etching solution of this embodiment contains chitosan. In the etching solution of this embodiment, chitosan functions as a surface roughness suppressor. Chitosan is a polysaccharide composed of the following repeating units:

[0017] [ka]

[0018] In the etching solution of this embodiment, the chitosan content is not particularly limited as long as it can etch the metal to be etched. Examples of the chitosan content include 0.0001 to 10% by mass, relative to the total mass of the etching solution. Examples of the lower limit of the hydrogen peroxide content include 0.0005% by mass or more, 0.001% by mass or more, 0.005% by mass or more, 0.01% by mass or more, 0.03% by mass or more, or 0.05% by mass or more, relative to the total mass of the etching solution. When the chitosan content is equal to or greater than the lower limit, the surface roughness of the metal after etching is further reduced. Examples of the upper limit of the chitosan content include 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, 3% by mass or less, 2% by mass or less, 1.5% by mass or less, or 1% by mass or less, relative to the total mass of the etching solution. When the chitosan content is equal to or less than the upper limit, the etching rate is improved. The upper and lower limits can be combined in any desired manner.

[0019] <Acid component> The etching solution of this embodiment preferably contains an acid component. In the etching solution of this embodiment, the acid component can function as a stabilizer for chitosan. When the etching solution contains an acid component, chitosan is stabilized in the etching solution, and surface roughness of the metal after etching is likely to be reduced.

[0020] The acid component is not particularly limited as long as it stabilizes chitosan. The acid component may be an organic acid or an inorganic acid. Examples of inorganic acids include sulfuric acid, nitric acid, hydrochloric acid, phosphoric acid, hypophosphorous acid, carbonic acid, and sulfamic acid. Among these, phosphoric acid is preferred as the inorganic acid.

[0021] Examples of organic acids include carboxylic acids. The carboxylic acid may be a monocarboxylic acid or a polycarboxylic acid, with monocarboxylic acids being preferred. The carboxylic acid may be an aliphatic carboxylic acid or an aromatic carboxylic acid, with aliphatic carboxylic acids being preferred. The number of carbon atoms in the aliphatic carboxylic acid may be, for example, 1 to 18, preferably 1 to 14, more preferably 1 to 10, still more preferably 1 to 6, and particularly preferably 1 to 3. The number of carbon atoms in the aromatic carboxylic acid may be 6 to 10.

[0022] Examples of aliphatic carboxylic acids include aliphatic monocarboxylic acids such as 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, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid; aliphatic dicarboxylic acids such as tartaric acid, succinic acid, malic acid, maleic acid, fumaric acid, glutaric acid, itaconic acid, and adipic acid; and aliphatic tricarboxylic acids such as citric acid, propanetricarboxylic acid, and trans-aconitic acid. Examples of 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 these, the organic acid is preferably an aliphatic monocarboxylic acid, and more preferably acetic acid, glycolic acid, or lactic acid. The etching solution of this embodiment may be free of organic acids other than carboxylic acids, or may be free of one or more of the components exemplified above as the acid component. For example, the etching solution of this embodiment may be free of one or more of aromatic carboxylic acids, polycarboxylic acids, dicarboxylic acids, tricarboxylic acids, and tetracarboxylic or higher carboxylic acids.

[0023] The acid component may be used alone or in combination of two or more. In the etching solution of this embodiment, the content of the acid component is not particularly limited as long as it can etch the metal to be etched. Examples of the content of the acid component include 0.05 to 40% by mass, relative to the total mass of the etching solution. Examples of the lower limit of the content of the acid component include 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% by mass or more, relative to the total mass of the etching solution. When the content of the acid component is equal to or greater than the lower limit, the surface roughness of the metal after etching is likely to be reduced. Examples of the upper limit of the content of the acid component include 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, 12% by mass or less, or 10% by mass or less, relative to the total mass of the etching solution. When the content of the acid component is equal to or less than the upper limit, the etching rate is likely to be maintained at a good level. The upper and lower limits can be arbitrarily combined.

[0024] The acid component may be used to adjust the pH of the etching solution. For example, after dissolving other components of the etching solution in water, the acid component may be added to achieve 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 stopped when the desired pH is achieved. In the etching solution of this embodiment, the content of the acid component may be an amount necessary to adjust the pH of the etching solution to a desired range.

[0025] <ph> The pH of the etching solution of this embodiment is not particularly limited, but is preferably 0.1 or more and 4.0 or less. When the pH of the etching solution is within this range, chitosan in the etching solution is stabilized, and surface roughness is likely to be 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, and 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, and 3.5 or less. The upper and lower limits can be combined in any manner.

[0026] <Optional ingredients> The etching solution of this embodiment may contain other components in addition to the above components, as long as the effects of the present invention are not impaired. Examples of other components include water, polar organic solvents, amine compounds, azoles, hydrogen peroxide stabilizers, pH adjusters, and surfactants.

[0027] ≪Water≫ The etching solution of this embodiment preferably contains water as a solvent for the above components. The water may contain trace components that are inevitably mixed in. The water used in the etching solution of this embodiment is preferably purified water such as distilled water, ion-exchanged water, or ultrapure water, and more preferably ultrapure water commonly used in semiconductor manufacturing. The content of water in the etching solution of the present embodiment is not particularly limited, but may be 30 to 99 mass % based on the total mass of the etching solution. The content of water may be adjusted to achieve desired contents of other components.

[0028] Polar organic solvents The etching solution of this embodiment may contain a polar organic solvent as long as the effects of the present invention are not impaired. Examples of 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, 1,4-butanediol, diethylene glycol, dipropylene glycol, furfuryl alcohol, and 2-methyl-2,4-pentanediol), dimethyl sulfoxide, and ethers (e.g., ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and propylene glycol dimethyl ether). One polar organic solvent may be used alone, or two or more may be used in combination. The etching solution of the present embodiment may not contain a polar solvent, or may not contain one or more of the polar solvents exemplified above.

[0029] <Amine compounds> 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 the amine compound 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, and N-methyl Polyamines such as ethylenediamine, N,N-dimethylethylenediamine, trimethylethylenediamine, N-ethylethylenediamine, N,N-diethylethylenediamine, triethylethylenediamine, 1,2,3-triaminopropane, hydrazine, tris(2-aminoethyl)amine, tetra(aminomethyl)methane, diethylenetriamine, triethylenetetramine, tetraethylpentamine, heptaethyleneoctamine, nonaethylenedecamine, and 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-2-ol, 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-methylpentan-1-ol, 2-aminohexane-1-ol Examples of the amine compound include alkanolamines such as 1,2-diaminopropan-3-ol, 2-aminopropan-1,3-diol, 3-aminoheptan-4-ol, 1-aminooctan-2-ol, 5-aminooctan-4-ol, 1-aminopropane-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-(2-aminoethylamino)ethanol, and diglycolamine. One type of amine compound may be used alone, or two or more types may be used in combination. The etching solution of the present embodiment may not contain an amine compound, or may not contain one or more of the amine compounds exemplified above.

[0030] <Azoles> The etching solution of this embodiment may contain an azole to the extent that the effects of the present invention are not impaired. Examples of azoles include triazoles such as 1H-benzotriazole, 5-methyl-1H-benzotriazole, and 3-amino-1H-triazole; tetrazoles such as 1H-tetrazole, 5-methyl-1H-tetrazole, 5-phenyl-1H-tetrazole, and 5-amino-1H-tetrazole; imidazoles such as 1H-imidazole and 1H-benzimidazole; and thiazoles such as 1,3-thiazole and 4-methylthiazole. One type of azole may be used alone, or two or more types may be used in combination. The etching solution of the present embodiment may not contain any azoles, or may not contain any one or more of the azoles exemplified above.

[0031] <Hydrogen peroxide stabilizer> The etching solution of this embodiment may contain a hydrogen peroxide stabilizer as long as the effect of the present invention is not impaired. The 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, allylurea, 1,3-dimethylurea, and thiourea; phenylacetic acid amide; and phenylethylene glycol. One type of hydrogen peroxide stabilizer may be used alone, or two or more types may be used in combination. The etching solution of the present embodiment may not contain a hydrogen peroxide stabilizer, or may not contain one or more of the hydrogen peroxide stabilizers exemplified above.

[0032] <pH adjuster> The etching solution of this embodiment may contain a pH adjuster other than the acid component, as long as the effect of the present invention is not impaired. Examples of the pH adjuster include basic compounds. The basic compound may be an organic basic compound or an inorganic basic compound. Examples of inorganic basic compounds include inorganic compounds containing alkali metals or alkaline earth metals and salts thereof, such as lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, and cesium hydroxide. Examples of the organic basic compound include quaternary ammonium salts, alkylamines (trimethylamine, triethylamine, etc.), etc. Examples of the quaternary ammonium salt include tetramethylammonium hydroxide (TMAH), bis(2-hydroxyethyl)dimethylammonium hydroxide, tetraethylammonium hydroxide (TEAH), tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, methyltriethylammonium hydroxide, trimethyl(hydroxyethyl)ammonium hydroxide, and triethyl(hydroxyethyl)ammonium hydroxide. The pH adjusters may be used alone or in combination of two or more. The etching solution of the present embodiment may not contain any pH adjuster other than the acid component, or may not contain any one or more of the pH adjusters exemplified above.

[0033] <Surfactants> The etching solution of the present embodiment may contain a surfactant within a range that does not impair the effects of the present invention. Examples of the surfactant include a nonionic surfactant, an anionic surfactant, a cationic surfactant, and an amphoteric surfactant.

[0034] Examples of nonionic surfactants include polyalkylene oxide alkyl phenyl ether surfactants, polyalkylene oxide alkyl ether surfactants, block polymer surfactants consisting of polyethylene oxide and polypropylene oxide, polyoxyalkylene distyrene-substituted phenyl ether surfactants, polyalkylene tribenzyl phenyl ether surfactants, and acetylene polyalkylene oxide surfactants.

[0035] Examples of anionic surfactants include alkyl sulfonic acids, alkyl benzene sulfonic acids, alkyl naphthalene sulfonic acids, alkyl diphenyl ether sulfonic acids, fatty acid amide sulfonic acids, polyoxyethylene alkyl ether carboxylic acids, polyoxyethylene alkyl ether acetic acids, polyoxyethylene alkyl ether propionic acids, alkyl phosphonic acids, and salts of fatty acids. Examples of "salts" include ammonium salts, sodium salts, potassium salts, and tetramethylammonium salts.

[0036] Examples of cationic surfactants include quaternary ammonium salt surfactants and alkylpyridium surfactants.

[0037] Examples of amphoteric surfactants include betaine surfactants, amino acid surfactants, imidazoline surfactants, and amine oxide surfactants.

[0038] The surfactant may be used alone or in combination of two or more kinds. The etching solution of the present embodiment may not contain a surfactant, or may not contain one or more of the surfactants exemplified above.

[0039] <Other> 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, it may contain various additives that are known as additives for etching solutions. The etching solution of this embodiment may or may not contain a slurry such as that used in a CMP (Chemical Mechanical Polishing) process. The etching solution of this embodiment may or may not contain an abrasive. Examples of the abrasive include metal oxide particles (alumina, silica, titania, ceria, zirconia, etc.).

[0040] <Object to be treated> The etching solution of this embodiment is used for etching a metal-containing layer. The etching solution of this embodiment is used to etch a workpiece 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 substrates having a metal-containing layer. The substrate is not particularly limited, and examples include various substrates such as semiconductor wafers, glass substrates for photomasks, glass substrates for liquid crystal displays, glass substrates for plasma displays, substrates for FEDs (Field Emission Displays), substrates for optical disks, substrates for magnetic disks, and substrates for magneto-optical disks. The substrate is preferably a substrate used for manufacturing semiconductor devices. The substrate may include layers other than the metal-containing layer as appropriate. The substrate may have various structures in addition to the layer structure. The substrate may have, for example, metal wiring, a gate structure, a source structure, a drain structure, an insulating layer, a ferromagnetic layer, and a nonmagnetic layer. The uppermost layer on the device surface of the substrate does not necessarily have to be a metal-containing layer; for example, an intermediate layer in a multilayer structure may be a metal-containing layer. The size, thickness, shape, layer structure, etc. of the substrate are not particularly limited and can be appropriately selected depending on the purpose.

[0041] 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 depending on 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, and 1 to 50 nm. The metal-containing layer may have a single-layer structure or a multilayer structure. For example, the metal-containing layer may have a multilayer structure in which layers formed of different types of metals are stacked. The multilayer structure may include, for example, two or more metal layers selected from the group consisting of a molybdenum layer, a copper layer, a cobalt layer, a nickel layer, and a tungsten layer. It is possible.

[0042] The etching solution of the present embodiment may be used to etch a metal-containing layer to form metal wiring. For example, a metal-containing layer containing molybdenum, copper, cobalt, nickel, or tungsten may be etched to form metal wiring containing molybdenum, copper, cobalt, nickel, or tungsten.

[0043] The etching solution of the present embodiment contains hydrogen peroxide and chitosan, and therefore, the metal-containing layer can be etched while suppressing surface roughness. It is presumed that the chitosan in the etching solution protects the surface of the metal-containing layer, thereby suppressing an increase in surface roughness due to etching. If the metal surface after etching is highly rough, there is a risk of defects occurring in subsequent processes, current leakage at the junctions between upper and lower wirings, or poor connection at plug junctions. In particular, reduction of surface roughness is required in recess etching. The etching solution of this embodiment can form a metal surface with reduced metal roughness, and therefore can be suitably used for etching for forming metal wiring, particularly recess etching.

[0044] (Metal-containing layer etching method) A method for etching a metal-containing layer according to one embodiment of the present invention includes a step of bringing a metal-containing layer into contact with the etching solution of the above embodiment.

[0045] In the etching method of this embodiment, the metal-containing layer to be etched may be the same as that described above. The metal-containing layer preferably contains at least one metal selected from the group consisting of molybdenum, copper, cobalt, nickel, and tungsten.

[0046] The method for bringing the metal-containing layer into contact with the etching solution is not particularly limited, and examples of such methods include, but are not limited to, spraying, immersion, puddling, and pouring. In the spray method, for example, the metal-containing layer is transported or rotated in a predetermined direction, and the etching solution is sprayed into the space between the metal-containing layer and the etching solution, so that the etching solution comes into contact with the metal-containing layer. If necessary, the etching solution may be sprayed while rotating the substrate using a spin coater. In the immersion method, the metal-containing layer is immersed in an etching solution to bring the etching solution into contact with the metal-containing layer. At this time, the metal-containing layer may be immersed in the etching solution while stirring it, if necessary. In the puddle method, an etching solution is poured onto the metal-containing layer, and the metal-containing layer is brought into contact with the etching solution. These etching methods can be appropriately selected depending on the structure, material, etc. of the metal-containing layer. In the case of the spray method or the puddle method, the amount of etching liquid supplied to the metal-containing layer may be an amount that sufficiently wets the surface of the metal-containing layer to be treated with the etching liquid. In the liquid pouring method, the substrate having the metal-containing layer is rotated at a rotation speed as required, and an etching solution is ejected onto the metal-containing layer in an amount sufficient to wet the layer.

[0047] The temperature of the etching treatment is not particularly limited, and may be any temperature at which the metal to be etched dissolves in the etching solution. Examples of the etching temperature include 20 to 60°C. In the case of any of the spray method, immersion method, and puddle method, increasing the temperature of the etching solution increases the etching rate. The etching temperature can be appropriately selected taking into consideration the etching rate, changes in the composition of the etching solution, workability, safety, cost, and the like.

[0048] The etching time may be appropriately selected depending on the purpose of the etching, the amount of metal to be removed by etching (for example, the thickness of the metal-containing layer), and the etching conditions.

[0049] The purpose of the etching treatment is not particularly limited, and may be to finely process a metal-containing layer (e.g., a metal-containing layer on a substrate), to remove metal-containing deposits adhering to a workpiece (e.g., a substrate having a metal-containing layer), or to clean a metal-containing layer (e.g., a metal-containing layer on a substrate). When the purpose of the etching treatment is to microfabricate the metal-containing layer, the metal-containing layer may be brought into contact with the etching solution after covering the areas that should not be etched with a mask. When the purpose of the etching process is to remove metal-containing deposits adhering to the workpiece, the metal-containing deposits are dissolved by bringing the etching solution into contact with the workpiece, and the metal deposits can be removed from the workpiece. When the purpose of the etching treatment is to clean the metal-containing layer, impurities such as particles adhering to the surface of the metal-containing layer can be removed in a short time by bringing the etching solution into contact with the metal-containing layer.

[0050] According to the etching method of the present embodiment, the metal-containing layer is etched using the etching solution of the above embodiment. Therefore, etching can be performed satisfactorily while suppressing an increase in surface roughness. As a result, a metal-containing layer with reduced surface roughness after etching can be obtained.

[0051] (Metal wiring formation method) A method for forming 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.

[0052] <Etching process> Examples of the metal-containing layer include the same 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.

[0053] The etching of the metal-containing layer can be carried out in the same manner as described above. The etching of the metal-containing layer may be carried out after covering the areas that should not be etched 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. The resist film is then developed with a developer to form a resist pattern in which the pattern is transferred. The metal-containing layer is etched using this resist pattern as a mask, thereby forming a desired wiring pattern in the metal-containing layer. The etching for forming the metal wiring may be recess etching.

[0054] <Optional process> The method for manufacturing metal wiring according to this embodiment may include optional steps in addition to the etching step. The optional steps may include, without limitation, known steps carried out when forming metal wiring. Examples of such steps include, but are not limited to, steps for forming structures such as gate structures, source structures, drain structures, insulating layers, ferromagnetic layers, and nonmagnetic layers (layer formation, etching other than the above-mentioned etching treatments, chemical mechanical polishing, modification, etc.), resist film formation, exposure, development, heat treatment, cleaning, and inspection. These optional steps may be carried out before or after the etching step, as needed.

[0055] According to the method for manufacturing a metal wiring of this embodiment, the metal-containing layer is etched using the etching solution of the above embodiment, so that a metal wiring having reduced surface roughness can be obtained. [Example]

[0056] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0057] <Preparation of etching solution> Example 1 16.7 g of a 30 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 the etching solution of Example 1. The pH of the etching solution was measured at 25°C using a pH meter (Horiba, Ltd.).

[0058] (Examples 2 to 13, Comparative Examples 1 and 2) Etching solutions for each example were obtained in the same manner as in Example 1, except that the compositions shown in Table 1 were used.

[0059] [Table 1]

[0060] <Etching process> The substrate used was a silicon wafer on which a molybdenum film was formed to a thickness of 50 nm. The etching solution of each example was placed in a 200 mL beaker and stirred at 300 rpm using a stirrer. A substrate was immersed in the stirring etching solution and removed after a predetermined time. Next, the substrate was washed with running water using a 5% by mass aqueous solution of acetic acid. Next, the substrate was washed with running pure water and spray-dried.

[0061] [Etching rate evaluation] The thickness of the molybdenum coating on the substrate before and after the etching treatment was measured using an X-ray fluorescence analyzer (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 as the "etching rate" in Table 2.

[0062] [Surface roughness evaluation] The surface of the substrate after the etching treatment was observed using an AFM (atomic force microscope, manufactured by Takano Corporation) to determine the root mean square height (surface roughness) Rq (nm) per 1 μm square. Similarly, the surface roughness Rq0 (nm) of the surface of the substrate that had not been subjected to etching treatment was determined. Rq / Rq0 was calculated, and this was shown in Table 2 as "surface roughness [Rq / Rq0]."

[0063] [Table 2]

[0064] As shown in Table 2, in Examples 1 to 13, the surface roughness was suppressed compared to Comparative Examples 1 and 2. In addition, the etching rate was also good. From the above results, it was confirmed that by using the etching solution of the example, it is possible to reduce the surface roughness while maintaining a good etching rate.< / ph>

Claims

1. An etching solution for use in etching a metal-containing layer containing molybdenum, comprising hydrogen peroxide, chitosan, and an organic acid selected from monocarboxylic acids.

2. The etching solution according to claim 1, having a pH of 0.1 or more and 4.0 or less.

3. The etching solution according to claim 1 or 2, which is used for forming metal wiring.

4. A method for etching a metal-containing layer, comprising the step of contacting a metal-containing layer containing molybdenum with the etching solution according to any one of claims 1 to 3.

5. A method for forming metal wiring, comprising the step of etching a metal-containing layer containing molybdenum with the etching solution according to claim 3.

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