wet etching method

Abstract

This invention provides a wet etching method, which involves pretreating a metal-containing film on a substrate using a surface-modifying solution, followed by etching using an etching solution. The etching solution is a solution containing a β-diketone bonded with trifluoromethyl and carbonyl groups and an organic solvent. The metal-containing film contains a metal element capable of forming a complex with the β-diketone. The surface-modifying solution contains an oxidizing agent for the metal element. The wet etching method includes: a first step in which the surface-modifying solution is brought into contact with the metal-containing film to form an oxide film of the metal element on the surface of the metal-containing film; and a second step in which the etching solution is brought into contact with the metal-containing film having the oxide film.

Description

[Technical Field]

[0001] This invention relates to a wet etching method or etching solution for etching a metal-containing film on a substrate used in semiconductor manufacturing processes. [Previous Technology]

[0002] In the manufacturing process of semiconductor devices, an etching process is performed to form the desired pattern on the metal film and metal compound film (hereinafter sometimes referred to as metal-containing film) formed on the substrate, such as metal film as metal gate material, electrode material or magnetic material, or metal compound film as piezoelectric material, LED (Light Emitting Diode) light-emitting material, transparent electrode material or dielectric material.

[0003] As a step in the manufacturing of semiconductor devices, the etching method for metal-containing films on a substrate includes wet etching using chemical solutions. Patent Document 1 discloses an etching method in which a mixture of ammonia water and hydrogen peroxide water with a pH value adjusted to 8-10 or 9-10 is brought into contact with a copper film to form a copper oxide film. Subsequently, an acid or alkali is used as an etching solution to etch the copper oxide film, thereby selectively removing the copper oxide film from the copper film. Patent Documents 2 and 3 disclose methods using etching solutions containing inorganic or organic acids and oxidizing substances. Patent Document 4 discloses a method for smoothing the surface of the etched metal at the atomic level during the etching of metal-containing films on a substrate. Patent Document 5 discloses a method for selectively etching Ti using an etching solution containing organic amine compounds, alkaline compounds, and oxidants in an aqueous medium with a pH value of 7-14. Furthermore, Patent Document 6 discloses an etching solution containing a β-diketone bonded with trifluoromethyl and carbonyl groups and an organic solvent, replacing the previous etching solution containing inorganic or organic acids and oxidizing substances. (Prior Art Documents, Patent Documents)

[0004] Patent Document 1: Japanese Patent Application Publication No. 2001-210630; Patent Document 2: Japanese Patent Publication No. 2008-541447; Patent Document 3: Japanese Patent Publication No. 2008-512869; Patent Document 4: Japanese Patent Re-publication No. 2013-161959; Patent Document 5: Japanese Patent Application Publication No. 2013-033942; Patent Document 6: Japanese Patent Application Publication No. 2017-028257 [Summary of the Invention]

[0005] The applicant has discovered that while the etching solution disclosed in Patent Document 6 etches materials containing metals that form complexes with β-diketones, it does not etch silicon-based semiconductor materials or silicate glass materials that do not form complexes with β-diketones. Therefore, it can selectively etch only the metal-containing film on the substrate. Furthermore, when there are two or more metal-containing films on the substrate, it is also possible to selectively etch a certain metal-containing film relative to another metal-containing film by utilizing the difference in etching rates based on the metals they contain. However, the etching rate is not sufficient.

[0006] In the manufacturing process of semiconductor devices, etching technology requires high precision. Regarding the etching process, if the surface roughness is compared with that before the process, and the roughness of the patterned surface after the process is greater, it may have a significant impact on the characteristics of the semiconductor device. Therefore, it is also important to maintain a low roughness while etching.

[0007] The present invention relates to wet etching of a metal-containing film on a substrate used in semiconductor manufacturing processes, etc., and aims to provide a method for etching that increases the etching speed and maintains a small difference in surface roughness of the metal-containing film before and after wet etching.

[0008] The wet etching method disclosed in this invention pretreats a metal-containing film on a substrate using a surface-modifying liquid, and then etches it using an etching solution. The etching solution is a solution containing a β-diketone bonded with trifluoromethyl and carbonyl groups and an organic solvent. The metal-containing film contains a metal element that can form a complex with the β-diketone. The surface-modifying liquid contains an oxidizing agent for the metal element. The wet etching method includes: a first step in which the surface-modifying liquid is brought into contact with the metal-containing film to form an oxide film of the metal element on the surface of the metal-containing film; and a second step in which the etching solution is brought into contact with the metal-containing film having the oxide film.

[0009] According to the method disclosed in the present invention, the method can improve the etching speed by maintaining the difference in surface roughness of the metal-containing film before and after wet etching of the metal-containing film on the substrate to a small extent.

Implementation Method

[0011] (Wet Etching Method for Metal-Containing Films) In the wet etching method of the present invention, after a pretreatment step (step 1) in which a metal oxide film is formed on the surface of a metal-containing film on a substrate by pretreating the metal-containing film with a surface-modifying liquid containing an oxidizing substance, an etching step (step 2) is performed in which the metal-containing film having the metal oxide film is etched with an etching solution containing a β-diketone with a trifluoromethyl group and a carbonyl group.

[0012] In the wet etching method of the present invention, the metal-containing film to be etched contains a metal element that can form a complex with the aforementioned β-diketone. Examples of metal elements included in the metal-containing film include: Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al, Ga, In, Sn, Pb, and As. These metals can form complexes with β-diketones, form complexes with β-diketones in the etching solution, and dissolve in the etching solution. Furthermore, the metal elements contained in the metal-containing film are preferably Ti, Zr, Hf, V, Cr, Mn, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Zn, Al, Ga, In, Sn, Pb, and As, more preferably Ti, Zr, Hf, Cr, Fe, Ru, Co, Ni, Pt, Cu, Zn, Al, Ga, In, Sn, and Pb. Cu is particularly preferred. Moreover, the metal-containing film etched using the wet etching method of the present invention can be a combination of several metal-containing films.

[0013] The metal-containing film is preferably any one of the following: a film containing a single elemental metal, an alloy film containing multiple elements, or a compound film containing elements. Such films can be fabricated using sputtering, chemical vapor deposition (CVD), or plating methods to achieve a low surface roughness. As for the alloy film containing multiple elements, it can be not only an alloy film such as NiCo, CoFe, CoPt, MnZn, NiZn, CuZn, or FeNi, but also an alloy film doped with other elements, such as CoFeB. Furthermore, examples of the compound film containing elements include: nitride films such as GaN and AlGaN; silicate films such as NiSi, CoSi, and HfSi; arsenide films such as InAs, GaAs, and InGaAs; and phosphide films such as InP or GaP. Moreover, regarding the metal-containing film containing multiple elements, the composition ratio of each element can be any value that can be manufactured.

[0014] Furthermore, in this invention, there are no particular limitations on the substrate, as long as it is suitable for forming a metal-containing film and is made of a material that does not react with the etching solution during wet etching. For example, substrates made of silicon-based semiconductor materials such as monocrystalline silicon, silicon oxide, polycrystalline silicon, silicon nitride, silicon oxynitride, and silicon carbide, or substrates made of silicate glass materials such as soda-lime glass, borosilicate glass, and quartz glass can be used. In addition to metal-containing films, the substrate may also have films of silicon-based semiconductor materials.

[0015] In this invention, the surface-modifying liquid used in the pretreatment step refers to a liquid that can modify the outermost surface of the metal-containing film by contacting it with the metal-containing film on the substrate. Here, "modification" refers to the alteration of the crystal grains or grain boundaries on the surface of the metal-containing film through a chemical reaction caused by corrosion, thereby enabling rapid interleaving in the subsequent etching step. It can also be achieved by combining the metal on the outermost surface of the metal-containing film with oxygen to oxidize the metal.

[0016] That is, the surface-modifying liquid of the present invention refers to a liquid that can form a metal oxide layer on the outermost surface of a metal-containing film by contacting it with a metal-containing film on a substrate (here, "oxidation" refers to the operation of combining metal with oxygen through a chemical reaction, thereby increasing the valence of the metal element). The metal oxide film is formed on the outermost surface of the metal-containing film by contacting the surface-modifying liquid of the present invention with the metal-containing film.

[0017] Thus, by pretreatment, the outermost surface of the metal-containing film can be made into an oxide film of a certain thickness of the metal. Therefore, in the next etching step, the metal contained in the oxide film and the β-diketone containing trifluoromethyl and carbonyl groups contained in the etching solution form a complex, and the oxide film can be removed. In this way, the etching of a metal-containing film of a certain thickness on the substrate can be promoted.

[0018] Here, the removal of the oxide film formed on the outermost surface of the metal-containing film using an etching solution may be a part or all of the oxide film. Even when only a part of the oxide film is removed, as shown in the embodiments described later, the entire oxide film can be removed by repeatedly performing the etching process.

[0019] Furthermore, when the entire oxide film is removed by etching, the following situation occurs: if the etching solution comes into contact with the oxide film, trace amounts of oxygen in the gas dissolve in the etching solution, thereby further oxidizing the unoxidized metal-containing film surface. Therefore, by immediately rinsing the etching solution adhering to the substrate with PGMEA (Propylene glycol monomethyl ether acetate), IPA (Iso-propyl alcohol), ultrapure water, etc., after removing the substrate from the etching solution, and then performing a drying operation using a blower, the etching solution and the aforementioned mixture are removed. By performing this operation, further oxidation of the metal-containing film can be suppressed, and the roughness of the metal surface after etching can be reduced.

[0020] Furthermore, the surface-modifying liquid of the present invention contains an oxidizing substance. The term "oxidizing substance" here is not particularly limited to any substance that, by bringing the surface-modifying liquid containing the oxidizing substance into contact with a metal-containing film on a substrate, can form an oxide on the outermost surface of the metal-containing film. Specifically, examples include: oxygen, ozone, hydrogen peroxide, dialkyl peroxide, hydrogen peroxide, urea, and other peroxides; sulfuric acid, nitric acid, permanganic acid, potassium permanganate, and other oxidizing acids or their salts; hexafluoropropane persulfonic acid, methane persulfonic acid, trifluoromethane persulfonic acid, or p-toluene persulfonic acid, and other persulfonic acids or their salts; peracetic acid, sodium percarbonate, and other percarbonic acids or their salts; ammonium persulfate, sodium persulfate, tetramethylammonium persulfate, potassium persulfate, and potassium peroxysulfate, and other persulfonic acids or their salts; periodic acid, ammonium periodate, or tetramethylammonium periodate, and other periodic acids or their salts. Among them, oxygen, ozone, peroxide, and oxidizing acid are preferred, and oxygen, ozone, hydrogen peroxide, nitric acid, and sulfuric acid are even more preferred.

[0021] The surface-modifying solution is prepared by diluting the aforementioned oxidizing substance with a solvent. The solvent used to dilute the oxidizing substance can be water, organic solvents described later, or mixtures thereof; there are no particular limitations as long as it dissolves the oxidizing substance, and previously known solvents can be used. Considering the stability of the surface-modifying solution, water is preferably used as the main solvent for dilution. Furthermore, "main solvent" means that it contains 50% by weight or more relative to 100 parts by weight of the diluent. Considering the duration of contact with the surface-modifying solution and the improvement in the roughness of the metal-containing film after wet etching, the content of the aforementioned oxidizing substance, while also depending on the relationship between the oxidizing power of the metal in the metal-containing film and the oxidizing substance, is preferably 0.01 to 50% by weight, more preferably 0.02 to 20% by weight, and even more preferably 0.05 to 10% by weight, relative to 100 parts by weight of the surface-modifying solution.

[0022] The etching solution of the present invention is a solution containing a β-diketone bonded with trifluoromethyl and carbonyl groups and an organic solvent. Compared with β-diketones without trifluoromethyl and carbonyl groups, β-diketones bonded with trifluoromethyl (CF3) and carbonyl (C=O) groups can achieve high-speed etching, and the complexes with metals are less likely to aggregate and precipitate as solids. There are no particular limitations on the β-diketone contained in the etching solution, as long as it contains the trifluoromethyl (CF3) and carbonyl (C=O) group (trifluoroacetyl). For example, it is preferably selected from hexafluoroacetyl acetone (1,1,1,5,5,5-hexafluoro-2,4-pentanedione, sometimes referred to as "HFAc" in this specification), trifluoroacetyl acetone (1,1,1-trifluoro-2,4-pentanedione), 1,1,1,6,6,6-hexafluoroacetyl acetone. One or a combination of the group consisting of 2,4-hexanedione, 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione, 4,4,4-trifluoro-1-phenyl-1,3-butanedione, 1,1,1,5,5,5-hexafluoro-3-methyl-2,4-pentanedione, 1,1,1,3,5,5,5-heptafluoro-2,4-pentanedione, and 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione. Hexafluoroacetyl acetone is particularly preferred.

[0023] As for the organic solvent used in the above-mentioned etching solution, any previously known organic solvent may be used without particular restriction, as long as it can dissolve the β-diketone and cause minimal damage to the surface of the workpiece. Suitable organic solvents include, for example, alcohols, hydrocarbons, esters, ethers, ketones, halogen-containing solvents, sulfoxides, lactones, carbonates, polyol derivatives, nitrogen-containing solvents, silicones, or mixtures thereof. Hydrocarbons, esters, ethers, halogen-containing solvents, polyol derivatives without OH groups, or mixtures thereof may be used. Using these solvents improves the stability of the etching solution, which is preferable.

[0024] Examples of the aforementioned alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, tributanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 2-methyl-2-butanol, 3-methyl-2-butanol, 1-hexanol, 2-hexanol, 3-hexanol, 2-methyl-1-pentanol, 3-methyl-1-pentanol, 4-methyl-1-... -Pentanol, 2-methyl-2-pentanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 2-methyl-3-pentanol, 3-methyl-3-pentanol, 2,2-dimethyl-1-butanol, 3,3-dimethyl-1-butanol, 3,3-dimethyl-2-butanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 4-heptanol, benzyl alcohol, 1-octanol, isooctanol, 2-ethyl-1-hexanol, etc.

[0025] Examples of the aforementioned hydrocarbons include n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tetradecane, n-hexadecane, n-octadecane, n-eicosane, and branched hydrocarbons corresponding to the number of carbon atoms thereon (e.g., isododecane, isohexadecane, etc.), cyclohexane, methylcyclohexane, decahydronaphthalene, benzene, toluene, xylene, (o-, m-, or p-)diethylbenzene, 1,3,5-trimethylbenzene, naphthalene, etc.

[0026] Examples of the above-mentioned esters include ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isopentyl acetate, n-hexyl acetate, n-heptyl acetate, n-octyl acetate, n-pentyl formate, n-butyl propionate, ethyl butyrate, n-propyl butyrate, isopropyl butyrate, n-butyl butyrate, methyl octanoate, methyl decanoate, methyl pyruvate, ethyl pyruvate, n-propyl pyruvate, methyl acetoacetate, ethyl acetoacetate, ethyl 2-butyrate, dimethyl adipate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, ethyl ethoxyacetate, etc.

[0027] Examples of the above-mentioned ethers include di-n-propyl ether, ethyl-n-butyl ether, di-n-butyl ether, ethyl-n-pentyl ether, di-n-pentyl ether, ethyl-n-hexyl ether, di-n-hexyl ether, di-n-octyl ether, and diisopropyl ether, diisopentyl ether, which have branched hydrocarbon groups corresponding to the number of carbons of the above-mentioned ethers, as well as dimethyl ether, diethyl ether, methyl cyclopentyl ether, diphenyl ether, tetrahydrofuran, dialkyl, methyl perfluoropropyl ether, methyl perfluorobutyl ether, ethyl perfluorobutyl ether, methyl perfluorohexyl ether, ethyl perfluorohexyl ether, etc.

[0028] Examples of the above-mentioned ketones include acetone, acetone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, 2-heptanone, 3-heptanone, cyclohexanone, isophorone, etc.

[0029] Examples of solvents containing the aforementioned halogen elements include perfluorooctane, perfluorononane, perfluorocyclopentane, perfluorocyclohexane, hexafluorobenzene, and other perfluorocarbons; 1,1,1,3,3-pentafluorobutane, octafluorocyclopentane, 2,3-dihydrodecafluoropentane; Zeorora H (manufactured by Zeon Corporation of Japan), and other hydrofluorocarbons; methyl perfluoroisobutyl ether, methyl perfluorobutyl ether, ethyl perfluorobutyl ether, ethyl perfluoroisobutyl ether; Asahiklin AE-3000 (manufactured by Asahi Glass Co., Ltd.); Novec 7100; Novec 7200; Novec 7300; Novec... 7600 (all manufactured by 3M) and other hydrofluoroethers, tetrachloromethane and other chlorocarbons, chloroform and other hydrochlorocarbons, dichlorodifluoromethane and other chlorofluorocarbons, 1,1-dichloro-2,2,3,3,3-pentafluoropropane, 1,3-dichloro-1,1,2,2,3-pentafluoropropane, 1-chloro-3,3,3-trifluoropropene, 1,2-dichloro-3,3,3-trifluoropropene and other hydrochlorofluorocarbons, perfluoroethers, perfluoropolyethers, etc.

[0030] Examples of the aforementioned urethanes include dimethyl urethane. Examples of the aforementioned lactones include β-propiolactone, γ-butyrolactone, γ-valerolactone, γ-caprolactone, γ-heptanolactone, γ-octanolactone, γ-nonanolactone, γ-decanolactone, γ-undecanolactone, γ-dodecanolactone, δ-valerolactone, δ-caprolactone, δ-octanolactone, δ-nonanolactone, δ-decanolactone, δ-undecanolactone, δ-dodecanolactone, ε-caprolactone, etc.

[0031] Examples of the above-mentioned carbonates include dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and propylene carbonate.

[0032] Examples of the above-mentioned polyol derivatives include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol monopropyl ether, tetraethylene glycol monobutyl ether, propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ... Propylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, tetrapropylene glycol monomethyl ether, butanediol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol diacetate, diethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, diethylene glycol diethyl ether, diethylene glycol butyl methyl ether, diethylene glycol dibutyl ether, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol diacetate, triethylene glycol Dimethyl ether, triethylene glycol diethyl ether, triethylene glycol dibutyl ether, triethylene glycol butyl methyl ether, triethylene glycol monomethyl ether acetate, triethylene glycol monoethyl ether acetate, triethylene glycol monobutyl ether acetate, triethylene glycol diacetate, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol dibutyl ether, tetraethylene glycol monomethyl ether acetate, tetraethylene glycol monoethyl ether acetate, tetraethylene glycol monobutyl ether acetate, tetraethylene glycol diacetate, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol dibutyl ether, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, propylene glycol diacetate Dipropylene glycol dimethyl ether, dipropylene glycol methyl propyl ether, dipropylene glycol diethyl ether, dipropylene glycol dibutyl ether, dipropylene glycol monomethyl ether acetate, dipropylene glycol monoethyl ether acetate, dipropylene glycol monobutyl ether acetate, dipropylene glycol diacetate, tripropylene glycol dimethyl ether, tripropylene glycol diethyl ether, tripropylene glycol dibutyl ether, tripropylene glycol monomethyl ether acetate, tripropylene glycol monoethyl ether acetate, tripropylene glycol monobutyl ether acetate, tripropylene glycol diacetate, tetrapropylene glycol dimethyl ether, tetrapropylene glycol monomethyl ether acetate, tetrapropylene glycol diacetate, butanediol dimethyl ether, butanediol monomethyl ether acetate, butanediol diacetate, glyceryl triacetate, etc.

[0033] Examples of nitrogen-containing solvents mentioned above include methylamine, N,N-dimethylmethylamine, N,N-dimethylacetamide, N-diethylacetamide, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-propyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-diisopropyl-2-imidazolidinone, alkylamines, dialkylamines, trialkylamines, pyridine, etc.

[0034] Examples of the aforementioned silicones include hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, dodecylpentasiloxane, etc.

[0035] Furthermore, from the viewpoint of the stability of the etching solution, the aforementioned organic solvents are preferably hydrocarbons, esters, ethers, solvents containing halogen elements, carbonates, and polyol derivatives that do not have OH groups. Among these, from the viewpoint of cost or environmental impact, esters, ethers, and polyol derivatives that do not have OH groups are preferred, and propylene glycol monoalkyl ether acetate is even more preferred, especially propylene glycol monomethyl ether acetate.

[0036] Furthermore, if β-diketone forms a hydrate, it is easy to precipitate out in solid form. Therefore, the water content in the etching solution is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 1% by mass or less, relative to 100 parts by weight of the etching solution.

[0037] Furthermore, the concentration of β-diketone in the above-mentioned etching solution is preferably 0.5 to 15% by mass, more preferably 1 to 12% by mass, and even more preferably 2 to 10% by mass. If there is too much β-diketone, the price of the etching solution becomes too high, since β-diketone is generally more expensive than organic solvents. Also, if it is higher than 10% by mass, there is a tendency for the surface roughness to deteriorate. On the other hand, if the β-diketone is less than 1% by mass, there is a tendency for etching to be impossible.

[0038] Furthermore, as long as it does not cause adverse effects on the object being processed, the etching solution may also contain additives such as citric acid, formic acid, acetic acid and trifluoroacetic acid in order to increase the etching speed or improve the etching selectivity.

[0039] The amount of the above-mentioned additive is adjusted within a range that does not adversely affect the object being treated. For example, it may be added in the range of 0.01 to 20% by mass, 0.1 to 15% by mass, and further 0.5 to 10% by mass relative to the etching solution. The above-mentioned etching solution may be substantially composed of a β-diketone bonded with trifluoromethyl and carbonyl groups and an organic solvent.

[0040] The wet etching method of the present invention, by including a first step of contacting the surface-modifying liquid with the metal-containing film and a second step of contacting the etching liquid with the metal-containing film modified by the surface-modifying liquid, can perform etching without increasing the roughness of the metal-containing film. The wet etching method can also be performed by adding a surface-modifying liquid and / or an etching liquid to an apparatus such as an etching device that has a metal-containing film on a substrate, thereby contacting the surface-modifying liquid and / or the etching liquid with the metal-containing film of the object to be processed, and wet etching the metal-containing film.

[0041] As long as an apparatus is used that can hold the aforementioned surface-modifying liquid and / or the aforementioned etching liquid on the surface of the object to be treated, there are no particular limitations on the apparatus or method for applying the wet etching liquid of the present invention. For example, examples include a single-plate method using a rotating apparatus that holds the substrate approximately horizontally and rotates it while supplying liquid to the vicinity of the rotation center to process the substrate one by one, or a batch method using an apparatus that concentrates multiple substrates in a tank for immersion treatment. Furthermore, as for the form of the etching liquid when supplying it to the surface of the object to be treated, there are no particular limitations as long as it remains liquid when held on the object to be treated, such as liquid, steam, etc.

[0042] The first step and the second step described above may be discontinuous. Preferably, a cleaning step is provided between the first step and the second step to rinse the surface of the metal-containing film with the surface modification solution adhering to it. By providing the cleaning step, the content of the oxidizing substances contained in the etching solution can be reduced, and thus, contact with the metal-containing film can be avoided.

[0043] As an example of the above-described cleaning step, water or an organic solvent can be brought into contact with the metal-containing film to remove the oxidizing substances from the metal-containing film. As for the organic solvent used in the cleaning step, any previously known organic solvent can be used without particular limitation, as long as it can dissolve the etching solution and / or the oxidizing substances. For example, organic solvents used in etching solutions can be used. Furthermore, from the viewpoint of the solubility of the surface-modifying solution, water, alcohol, or polyol derivatives are preferred. Also, the solvent of the surface-modifying solution is preferred. Furthermore, multiple rinsings can be performed using water or an organic solvent in the cleaning step. For example, there are methods such as rinsing with the solvent of the surface-modifying solution followed by rinsing with the solvent of the etching solution. A preferred rinsing method is when the solvent of the surface-modifying solution reacts with the β-diketone contained in the etching solution.

[0044] Furthermore, when the solvent of the surface modification solution and the solvent of the etching solution are immiscible, it is preferable to use a solvent that is dissolved in both for rinsing. For example, as shown in the embodiments described below, one preferred embodiment is to rinse with ultrapure water, 2-propanol, and propylene glycol-1-monomethyl ether-2-acetic acid after contact with the surface modification solution, and then contact with the etching solution.

[0045] The first step and the second step described above can be repeated. If repeated, the etching amount can be increased without worsening the surface roughness.

[0046] Furthermore, when repeatedly performing the first step and the second step described above, one preferred approach is to rinse the substrate that has been removed after contact with the etching solution using ultrapropylene glycol-1-monomethyl ether-2-acetic acid, 2-propanol or ultrapure water, and then bring it into contact with a surface modification solution.

[0047] The oxidizing substance contained in the etching solution of the present invention is preferably 0.01% by mass or less, more preferably 0.005% by mass or less, relative to 100 parts by mass of the etching solution. Furthermore, as long as it is within this range, it is not necessary to set a washing step between the first step and the second step to rinse the surface of the metal-containing film with the surface modification solution attached. However, by rinsing, the amount of the oxidizing substance can be adjusted to 0.001% by mass or less, thereby minimizing the roughness of the etched metal surface.

[0048] Furthermore, in the second step, in order to prevent the oxidizing substances contained in the etching solution from contacting the aforementioned metal-containing film, it is ideal to repeatedly rinse until the content of the oxidizing substances becomes 0% by mass. In order to perform the cleaning step efficiently, the detection limit for the content of the oxidizing substances can be set as a lower limit. Also, with 0.0001% by mass as the lower limit, rinsing can be repeated until it becomes more than 0.0001% by mass and less than 0.001% by mass. Furthermore, when the amount of oxidizing substances dissolves into the etching solution in an amount exceeding 0.01% by mass relative to 100 parts by mass of the etching solution, it is not easy to reduce the difference in surface roughness of the metal-containing film before and after etching.

[0049] The step of contacting the etching solution, which can etch the metal-containing film, with the metal-containing film can be performed before the first step described above. The metal-containing film may have its outermost surface naturally oxidized due to the effects of steps prior to treatment with the surface-modifying solution or exposure to the atmosphere. It is preferable to perform the contact step with the etching solution first, as this can remove the natural oxide on the outermost surface. The etching solution used in the second step can be used here.

[0050] In the wet etching method of the present invention, the temperature of the surface modifier is not particularly limited as long as it is the temperature at which the surface modifier is kept in a liquid state. It can be appropriately set within a range of approximately -10 to 60°C, taking into account the length of contact time with the surface modifier and the roughness of the metal-containing film after etching. Similarly, the temperature of the etching solution is not particularly limited as long as it is the temperature at which the etching solution is kept in a liquid state. It can be appropriately set within a range of approximately -10 to 100°C, taking into account the length of contact time with the etching solution and the roughness of the metal-containing film after etching.

[0051] There is no particular limitation on the length of contact time with the surface modifier solution, but considering the efficiency of the semiconductor device manufacturing process, it is preferably within 60 minutes, more preferably within 10 minutes, and even more preferably within 2 minutes. Similarly, there is no particular limitation on the length of contact time with the etching solution, but considering the efficiency of the semiconductor device manufacturing process, it is preferably within 60 minutes, more preferably within 10 minutes, and even more preferably within 2 minutes. Here, the length of contact time with the surface modifier solution or etching solution refers to, for example, the time for spraying the liquid into the substrate being processed, the time for immersing the substrate, or the time for introducing the etching solution into the processing chamber where the substrate is disposed until the etching solution is subsequently discharged from the processing chamber to conclude the etching process.

[0052] If the wet etching method of the present invention is used, the metal-containing film of the etchable object can be etched without etching the substrate or silicon-based semiconductor material film other than the metal element that does not contain a metal element that forms a complex with β-diketone. Furthermore, if the wet etching method of the present invention is used, a wet etching apparatus that is more economical than a dry etching apparatus can be used to improve the roughness of the metal-containing film after etching, thereby improving the quality of the semiconductor device.

[0053] (Device) A high-performance device can be manufactured using the wet etching method of the present invention. The device of the present invention can be manufactured economically by using a metal-containing film etched using the wet etching method of the present invention. Examples of such devices include: solar cells, hard disks, integrated circuits (ICs), microprocessors, dynamic random access memory (DRAM), phase-change memory, ferroelectric memory, magnetoresistive memory, resistive-change memory, and MEMS (Microelectromechanical systems). Examples

[0054] Hereinafter, the present invention will be described in detail by way of embodiments, but the present invention is not limited to these embodiments.

[0055] The following describes the evaluation method, solution preparation, etching treatment and evaluation results.

[0056] [Evaluation Method] (Determination of Etching Amount) The etching amount is calculated based on the change in mass of the substrate before and after immersion in the etching solution. At this time, the specific gravity of Cu used as the metal-containing film is set to 8.94 g / cm³. The etching rate is determined by the etching amount [nm] / immersion time [sec]. (Determination of Surface Roughness) The surface of the metal-containing film before etching (initial state) and after etching is measured using an AFM (SHIMADZU SPM-9700: scanning range 1.00 μm, scanning speed 1.0 Hz). The centerline average surface roughness Ra (nm) is calculated, and the Ra difference (ΔRa) before and after etching is determined. Furthermore, Ra is the centerline average roughness defined in JIS B 0601, three-dimensionally expanded, and is calculated according to the following formula in the form of "the value obtained by averaging the absolute value of the deviation from the reference surface to the specified surface". [Chemistry 1] Here, XL, XR, YB, and YT represent the measurement ranges of the X and Y coordinates, respectively. S0 is the area of ​​the measurement surface when it is ideally a plane, denoted as (XR - XL) × (YB - YT). Also, F(X, Y) represents the height of the measurement point (X, Y), and Z0 represents the average height within the measurement surface. (Observation of Surface Shape) The surface shape was observed using a SEM (Scanning Electron Microscope) (SU8010 manufactured by Hitachi: accelerating voltage 10.0 KV, emission 20 μA).

[0057] [Example 1] (Preparation of Solution) A surface-modifying solution was prepared by mixing hydrogen peroxide water and ultrapure water (H2O) to a hydrogen peroxide concentration of 1% by mass. An etching solution was prepared by mixing hexafluoroacetate acetone (HFAc) and propylene glycol-1-monomethyl ether-2-acetate (PGMEA) as a solvent to a HFAc concentration of 5% by mass. Furthermore, the water content in the etching solution was 1% by mass or less. (Wet Etching Process) A silicon substrate having a Cu film (1 μm thick, centerline average surface roughness Ra = 6 nm) prepared by plating was selected as the processing object. An oxide film was formed on the outermost surface of Cu by immersing the substrate in the surface-modifying solution obtained above at 24°C for 20 seconds as a pretreatment step. Subsequently, the surface-modifying solution adhering to the substrate surface was rinsed off. The rinsing process involves immersing the substrate in ultrapure water, 2-propanol (IPA), and PGMEA at 24°C for 20 seconds each. Next, the substrate is immersed in the aforementioned etching solution at 24°C for 20 seconds to perform the etching step. Afterward, the etching solution adhering to the substrate surface is rinsed off. The rinsing process involves immersing the substrate in PGMEA, IPA, and ultrapure water at 24°C for 20 seconds each. Finally, the surface is dried using an air blower for 10 seconds.

[0058] [Examples 2-4] Surface modification solution and etching solution were prepared in the same manner as in Example 1. Using the same silicon substrate as in Example 1 as the treatment object, the series of operations of pretreatment step → rinsing → etching step → rinsing were repeated 2, 5, and 10 times. Finally, the surface was dried for 10 seconds using an air blower. Otherwise, wet etching was performed using the same method as in Example 1.

[0059] [Example 5] A surface-modifying solution and an etching solution were prepared in the same manner as in Example 1. Before immersion in the surface-modifying solution, a silicon substrate identical to that in Example 1 was immersed in the etching solution at 24°C for 20 seconds, and then the etching solution adhering to the substrate surface was rinsed off. The rinsing was performed by immersion in PGMEA, IPA, and ultrapure water at 24°C for 20 seconds each. Subsequently, wet etching was performed using the same method as in Example 1.

[0060] [Example 6] A surface-modifying solution was prepared in the same manner as in Example 1. Propylene glycol monomethyl ether (PGME) was used as the solvent, and the etching solution was prepared in the same manner as in Example 1. In the wet etching process, a silicon substrate identical to that in Example 1 was immersed in the surface-modifying solution at 24°C for 20 seconds. Afterwards, without rinsing off the surface-modifying solution adhering to the substrate surface, the substrate was immersed in the etching solution at 24°C for 20 seconds with the surface-modifying solution still attached. This operation was repeated 10 times, after which the etching solution adhering to the substrate surface was rinsed off. The rinsing was performed by immersion in PGME, IPA, and ultrapure water at 24°C for 20 seconds each. Finally, the surface was dried using an air blower for 10 seconds. That is, in this embodiment, the etching solution contains a trace amount of the surface modifier solution, and 0.003% by mass of hydrogen peroxide is dissolved relative to the total amount of the etching solution and the dissolved surface modifier solution.

[0061] [Comparative Example 1] An etching solution was prepared in the same manner as in Example 1. A silicon substrate identical to that in Example 1 was immersed in the etching solution at 24°C for 20 seconds, and then immersed in PGMEA and 2-propanol (IPA) at 24°C for 20 seconds each. Finally, the surface was dried using an air blower for 10 seconds. Otherwise, wet etching was performed using the same method as in Example 1. That is, in this comparative example, the pretreatment step of immersion in a surface-modifying solution was omitted.

[0062] [Comparative Example 2] In the etching step, the sample was immersed in the etching solution at 24°C for 40 seconds. Otherwise, wet etching was performed using the same method as in Comparative Example 1.

[0063] [Comparative Example 3] In the etching step, the sample was immersed in the etching solution at 24°C for 80 seconds. Otherwise, wet etching was performed using the same method as in Comparative Example 1.

[0064] [Comparative Example 4] An etching solution was prepared by mixing 98% sulfuric acid and IPA in such a way that the sulfuric acid was 5% by mass. Except for using the etching solution, wet etching was performed using the same method as in Example 1.

[0065] [Comparative Example 5] An etching solution was prepared by mixing 25% ammonia and IPA in such a way that NH3 was 2% by mass. Otherwise, wet etching was performed using the same method as in Example 1.

[0066] [Comparative Example 6] In the etching step, the sample was immersed in the etching solution at 24°C for 40 seconds. Otherwise, wet etching was performed using the same method as in Comparative Example 5.

[0067] [Comparative Example 7] In the etching step, the sample was immersed in the etching solution at 24°C for 80 seconds. Otherwise, wet etching was performed using the same method as in Comparative Example 5.

[0068] <Etching Amount [nm] and ΔRa [nm]> The results are shown in Tables 1-2 for Examples 1-6 and Comparative Examples 1-3. The etching method of the present invention can increase the etching rate when etching metal-containing films containing specific metal elements and suppress the increase of ΔRa. Furthermore, the etching amount can be increased according to the number of etching cycles, and the increase of ΔRa can be suppressed even when the etching amount is increased. In Comparative Examples 4-7, where acid or alkali is used instead of β-diketone in the etching solution, ΔRa is significantly increased. Figure 1 is a SEM image of the Cu surface after 5 etching cycles of Example 3. The Cu surface after etching is smooth, and no large roughness was found.

[0069] Furthermore, in Examples 1 to 5, the surface roughness after etching did not change significantly compared to the Cu film surface before the surface modifier solution came into contact with the metal-containing film and the Cu oxide film surface before etching. However, compared to Example 6, where the surface modifier solution was not removed by rinsing, the surface roughness after etching in Examples 1 to 5 was smaller.

[0070] [Table 1] Metal-containing film Surface Modifying Liquid Etching solution peroxide solvent Immersion time [sec] β-Diketone solvent other Soaking time [sec] type concentration type concentration type concentration Example 1 Cu H2O2 1% of mass H2O 20 HFAc 5% of quality PGMEA - - 20 Example 2 Cu H2O2 1% of mass H2O 20 HFAc 5% of quality PGMEA - - 20 Example 3 Cu H2O2 1% of mass H2O 20 HFAc 5% of quality PGMEA - - 20 Example 4 Cu H2O2 1% of mass H2O 20 HFAc 5% of quality PGMEA - - 20 Example 5 Cu H2O2 1% of mass H2O 20 HFAc 5% of quality PGMEA - - 20 Example 6 Cu H2O2 1% of mass H2O 20 HFAc 5% of quality PGME - - 20 Comparative Example 1 Cu - - - - HFAc 5% of quality PGMEA - - 20 Comparative Example 2 Cu - - - - HFAc 5% of quality PGMEA - - 40 Comparative Example 3 Cu - - - - HFAc 5% of quality PGMEA - - 80 Comparative Example 4 Cu H2O2 1% of mass H2O 20 - - IPA / H2O H2SO4 5% of quality 20 Comparative Example 5 Cu H2O2 1% of mass H2O 20 - - IPA / H2O NH3 2% of mass 20 Comparative Example 6 Cu H2O2 1% of mass H2O 20 - - IPA / H2O NH3 2% of mass 40 Comparative Example 7 Cu H2O2 1% of mass H2O 20 - - IPA / H2O NH3 2% of mass 80 [Table 2] Processing order Rinsing between pretreatment and etching Etching amount [nm] Surface roughness Ra [nm] ∆Ra [nm] Before etching After etching Example 1 Pretreatment → Etching have 6 6 5 -1 Example 2 (Pretreatment → Etching) ×2 have 14 6 5 -1 Example 3 (Pretreatment → Etching) ×5 have 26 6 6 0 Example 4 (Pretreatment → Etching) × 10 have 45 6 6 0 Example 5 Etching → Pretreatment → Etching have 12 6 5 -1 Example 6 (Pretreatment → Etching) × 10 none 29 6 9 3 Comparative Example 1 Etching - 0 6 5 -1 Comparative Example 2 Etching - 1 6 6 0 Comparative Example 3 Etching - 1 6 6 0 Comparative Example 4 Pretreatment → Etching have 30 6 18 12 Comparative Example 5 Pretreatment → Etching have 3 6 17 11 Comparative Example 6 Pretreatment → Etching have 7 6 19 13 Comparative Example 7 Pretreatment → Etching have 15 6 25 19 [Simplified Explanation of the Diagram]

[0010] Figure 1 is a SEM image of a Cu surface using the wet etching method of the present invention (Example 3).

Claims

1. A wet etching method comprising pretreating a metal-containing film on a substrate using a surface-modifying solution, and then etching using an etching solution, wherein the etching solution comprises a solution of a β-diketone bonded with trifluoromethyl and carbonyl groups and an organic solvent, the metal-containing film comprises a metal element capable of forming a complex with the β-diketone, the surface-modifying solution comprises an oxidizing agent for the metal element, and the wet etching method includes: The first step involves contacting the surface-modifying solution with the metal-containing film to form an oxide film of the metal element on the surface of the metal-containing film; and the second step involves contacting the etching solution with the metal-containing film having the oxide film. Between the first and second steps is a cleaning step of the substrate surface. The concentration of β-diketone in the etching solution is 0.5 to 15% by mass. The surface-modifying solution contains 0.01% to 20% by mass of an oxidizing agent relative to 100 parts by weight of the surface-modifying solution. The oxidizing agent is at least one selected from the group consisting of oxygen, ozone, peroxides, oxidizing acids, or their salts.

2. The wet etching method of claim 1, wherein in the second step described above, the oxidizing substance is not allowed to come into contact with the metal-containing film.

3. The wet etching method of claim 1, wherein the contact time between the surface modification solution and the metal-containing film is less than 2 minutes, and the contact time between the etching solution and the metal-containing film having the oxide film is less than 2 minutes.

4. The wet etching method of claim 1, wherein the oxidizing substance contained in the etching solution is less than 0.01% by mass relative to 100 parts by mass of the etching solution.

5. The wet etching method of claim 1, wherein the oxidizing substance is selected from at least one of the group consisting of persulfonic acid or its salt, percarbonic acid or its salt, peracetic acid, persulfate or its salt, perchloric acid or its salt, and periodic acid or its salt.

6. The wet etching method of claim 1, wherein the oxidizing substance is selected from at least one of the group consisting of oxygen, ozone, hydrogen peroxide, nitric acid and sulfuric acid.

7. The wet etching method of any one of claims 1 to 6, wherein the material of the substrate is a silicon-based semiconductor material or a silicate glass material.

Images