Wet Etching Method

Abstract

The present disclosure provides a wet etching method wherein a metal-containing film on a substrate is pretreated with a surface modification liquid, and subsequently etched with use of an etching liquid. With respect to this wet etching method, the etching liquid is a solution that contains an organic solvent and a β-diketone wherein a trifluoromethyl group and a carbonyl group are bonded to each other; the metal-containing film contains a metal element which is capable of forming a complex together with the β-diketone; the surface modification liquid contains an oxidizing substance which is oxidizing with respect to the metal element. This wet etching method comprises: a first step wherein an oxide film of the metal element is formed on the surface of the metal-containing film by bringing the surface modification liquid into contact with the metal-containing film; and a second step wherein the etching liquid is brought into contact with the metal-containing film, on which the oxide film has been formed.

Description

[Technical Field]

[0001] The present disclosure relates to a wet etching method and etching solution for a metal-containing film on a substrate used in semiconductor manufacturing processes and the like. [Background technology]

[0002] In the manufacturing process of semiconductor devices, metal films and metal compound films (hereinafter sometimes referred to as metal-containing films) formed on substrates, such as metal films as metal gate materials, electrode materials, or magnetic materials, and metal compound films as piezoelectric materials, LED light-emitting materials, transparent electrode materials, or dielectric materials, are subjected to an etching process to form a desired pattern.

[0003] Wet etching using chemical solutions is known as a method for etching metal-containing films on substrates during the manufacturing process of semiconductor devices. Patent Document 1 discloses an etching method in which a mixture of aqueous ammonia and aqueous hydrogen peroxide adjusted to a pH of 8-10 or 9-10 is brought into contact with a copper film to form a copper oxide film, and the copper oxide film is then selectively removed from the copper film using an acid or alkali etching solution. Patent Documents 2 and 3 disclose methods using an etching solution containing an inorganic acid, an organic acid, and an oxidizing substance. Patent Document 4 discloses a method for etching a metal-containing film on a substrate, smoothing the metal surface at the atomic level after etching. Patent Document 5 discloses a method for selectively etching Ti using an etching solution containing an organic amine compound, a basic compound, and an oxidizing agent in an aqueous medium and having a pH of 7-14. Patent Document 6 also discloses an etching solution containing a β-diketone bonded to a trifluoromethyl group and a carbonyl group, and an organic solvent, instead of the conventional etching solution containing an inorganic acid, an organic acid, or an oxidizing substance. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-210630 [Patent Document 2] Special Publication No. 2008-541447 [Patent Document 3] Special Publication No. 2008-512869 [Patent Document 4] Republished Publication No. 2013-161959 [Patent Document 5] Japanese Patent Application Laid-Open No. 2013-033942 [Patent Document 6] Japanese Patent Application Publication No. 2017-028257 Summary of the Invention

[0005] The etching solution disclosed by the present applicant in Patent Document 6 etches materials containing metals that form complexes with β-diketones, but does not etch silicon-based semiconductor materials or silicate glass materials that do not form complexes with β-diketones, and therefore can selectively etch only metal-containing films relative to substrates. Furthermore, when two or more types of metal-containing films are present on a substrate, it is also possible to selectively etch one metal-containing film relative to another by utilizing the difference in etching rate due to the metals contained therein. However, the etching rate was not sufficient.

[0006] In the manufacturing process of semiconductor devices, etching technology requires high precision. If the roughness of the pattern surface after etching is greater than the surface roughness before processing, it can have a significant impact on the characteristics of the semiconductor device. Therefore, it is also important to perform etching while maintaining low roughness.

[0007] The present disclosure aims to provide a method for wet etching of a metal-containing film on a substrate used in a semiconductor manufacturing process or the like, which method improves the etching rate and performs etching while maintaining a small difference in surface roughness of the metal-containing film before and after wet etching.

[0008] The wet etching method presented in the present disclosure is a wet etching method in which a metal-containing film on a substrate is pretreated with a surface modification liquid and then etched using an etching liquid, wherein the etching liquid is a solution containing a β-diketone having a trifluoromethyl group and a carbonyl group bonded thereto and an organic solvent, the metal-containing film contains a metal element capable of forming a complex with the β-diketone, and the surface modification liquid contains an oxidizing substance for the metal element, and the method includes a first step of contacting the surface modification liquid 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 of contacting the etching liquid with the metal-containing film having the oxide film.

[0009] The method disclosed in the present disclosure has the effect of improving the etching rate while maintaining a small difference in surface roughness of a metal-containing film before and after wet etching of the metal-containing film on a substrate. [Brief explanation of the drawings]

[0010]

Figure 1

[0011] (Method for wet etching of metal-containing film) In the wet etching method of the present disclosure, a pretreatment step (first step) is performed in which a metal-containing film on a substrate is pretreated with a surface modification liquid containing an oxidizing substance to form an oxide film of the metal on the surface of the metal-containing film, followed by an etching step (second step) in which the metal-containing film having the oxide film of the metal is etched using an etching solution containing a β-diketone having a trifluoromethyl group and a carbonyl group bonded thereto.

[0012] The metal-containing film to be etched by the wet etching method of the present disclosure contains a metal element capable of forming a complex with the β-diketone. Examples of metal elements contained 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-diketone, form complexes with the β-diketone 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, and more preferably Ti, Zr, Hf, Cr, Fe, Ru, Co, Ni, Pt, Cu, Zn, Al, Ga, In, Sn, and Pb. Cu is particularly preferred. Note that the metal-containing film etched by the wet etching method of the present disclosure may be a combination of multiple types of metal-containing films.

[0013] The metal-containing film is preferably a film of a single metal element, an alloy film containing multiple metal elements, or a compound film containing a metal element. These films can be formed with low surface roughness using techniques such as sputtering, chemical vapor deposition (CVD), or plating. The alloy film containing multiple metal elements includes alloy films such as NiCo, CoFe, CoPt, MnZn, NiZn, CuZn, and FeNi, as well as alloy films doped with other elements, such as CoFeB. Examples of compound films containing metal elements include nitride films such as GaN and AlGaN, silicide films such as NiSi, CoSi, and HfSi, arsenide films such as InAs, GaAs, and InGaAs, and phosphide films such as InP and GaP. In a metal-containing film containing multiple elements, the composition ratio of each element can be any value that can be manufactured.

[0014] In the present disclosure, the substrate is not particularly limited as long as it is made of a material that can form a metal-containing film and does not react with the etching solution during wet etching, and examples of substrates that can be used include silicon-based semiconductor material substrates such as single crystal silicon, silicon oxide, polysilicon, silicon nitride, silicon oxynitride, and silicon carbide, and silicate glass material substrates such as soda-lime glass, borosilicate glass, and quartz glass. In addition to the metal-containing film, the substrate may have a silicon-based semiconductor material film or the like on it.

[0015] In the present disclosure, the surface modification liquid used in the pretreatment step refers to a liquid that can modify the outermost surface of a metal-containing film on a substrate by contacting the metal-containing film. The "modification" referred to here refers to an operation of changing the crystal grains and grain boundaries on the surface of the metal-containing film through a corrosion action by a chemical reaction, thereby facilitating complexation in the subsequent etching step. The metal on the outermost surface of the metal-containing film may be oxidized by combining with oxygen.

[0016] That is, the surface modification liquid of the present disclosure is a liquid that can form a metal oxide layer on the outermost surface of a metal-containing film on a substrate by contacting the liquid with the metal-containing film ("oxidation" here refers to a process in which the metal is combined with oxygen through a chemical reaction, thereby increasing the valence of the metal element). By contacting the surface modification liquid of the present disclosure with a metal-containing film, an oxide film of the metal is formed on the outermost surface of the metal-containing film.

[0017] In this way, the outermost surface of the metal-containing film can be converted into an oxide film of the metal of a certain thickness by pretreatment. In the subsequent etching step, the metal contained in this oxide film forms a complex with a β-diketone containing a trifluoromethyl group and a carbonyl group in the etching solution, which then removes the oxide film, thereby facilitating etching of the metal-containing film of a certain thickness on the substrate.

[0018] Here, the oxide film formed on the outermost surface of the metal-containing film may be partially or entirely removed by the etching solution. Even when only a portion of the oxide film is removed, the entire oxide film can be removed by repeating the etching process as shown in the examples described later.

[0019] Furthermore, if the oxide film is completely removed by the etching process, trace amounts of oxygen in the atmosphere may dissolve in the etching solution if the etching solution is in contact with the oxide film, which may cause further oxidation of the unoxidized metal-containing film surface. Therefore, immediately after removing the substrate from the etching solution, the etching solution adhering to the substrate is rinsed with PGMEA, IPA, ultrapure water, or the like, and then dried with a gas blower or the like to remove the etching solution and the complex. 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] The surface modification liquid of the present disclosure also contains an oxidizing substance. The oxidizing substance referred to here is not particularly limited as long as it can form an oxide on the outermost surface of a metal-containing film on a substrate when the surface modification liquid containing the oxidizing substance comes into contact with the metal-containing film. Specific examples include oxygen, ozone, peroxides such as oxygen, ozone, hydrogen peroxide, dialkyl peroxide, and urea hydrogen peroxide; oxidizing acids or salts thereof such as sulfuric acid, nitric acid, permanganic acid, and potassium permanganate; persulfonic acids or salts thereof such as hexafluoropropanepersulfonic acid, methanepersulfonic acid, trifluoromethanepersulfonic acid, and p-toluenepersulfonic acid; percarbonates or salts thereof such as peracetic acid and sodium percarbonate; persulfuric acids or salts thereof such as ammonium persulfate, sodium persulfate, tetramethylammonium persulfate, potassium persulfate, and potassium peroxysulfate; perchloric acids or salts thereof such as sodium perchlorate, potassium perchlorate, ammonium perchlorate, and tetramethylammonium perchlorate; and periodic acids or salts thereof such as periodic acid, ammonium periodate, and tetramethylammonium periodate. Among these, oxygen, ozone, peroxides, and oxidizing acids are preferred, and oxygen, ozone, hydrogen peroxide, nitric acid, and sulfuric acid are particularly preferred.

[0021] The surface modification liquid is prepared by diluting the oxidizing substance with a solvent. The solvent for diluting the oxidizing substance may be water, an organic solvent as described below, or a mixture thereof. Any solvent that dissolves the oxidizing substance may be used without any particular limitation. In consideration of the stability of the surface modification liquid, the main solvent for dilution is preferably water. The main solvent is a solvent in which the dilution solvent is 100%. Mass % 50 against Mass Considering the length of time for which the surface modifying liquid is in contact with the metal-containing film and the effect of improving the roughness of the metal-containing film after wet etching, the content of the oxidizing substance is determined to be 100% by volume of the surface modifying liquid, although it also depends on the relationship between the metal in the metal-containing film and the oxidizing power of the oxidizing substance. Mass % The content is preferably 0.01 to 50% by mass, more preferably 0.02 to 20% by mass, and particularly preferably 0.05 to 10% by mass.

[0022] The etching solution of the present disclosure is a solution containing a β-diketone in which a trifluoromethyl group and a carbonyl group are bonded, and an organic solvent. β-diketones in which a trifluoromethyl group (CF3) and a carbonyl group (C=O) are bonded can be etched at a higher speed than β-diketones in which a trifluoromethyl group and a carbonyl group are not bonded, and further, the complex with the metal is less likely to aggregate and solids are less likely to precipitate. The β-diketone contained in the etching solution is not particularly limited as long as it contains a moiety in which a trifluoromethyl group (CF3) and a carbonyl group (C=O) are bonded (a trifluoroacetyl group). Examples of the β-diketone include hexafluoroacetylacetone (1,1,1,5,5,5-hexafluoro-2,4-pentanedione, sometimes referred to as "HFAc" in this specification), trifluoroacetylacetone (1,1,1-trifluoro-2,4-pentanedione), 1,1,1,6,6,6-hexafluoroacetylacetone, and 1,1,1,6,6,6-hexafluoroacetylacetone. Preferably, the fluorocarbon ester is one or a combination of fluorocarbon esters selected from the group consisting of 1,1,1,5,5,5-hexafluoro-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. Hexafluoroacetylacetone is particularly preferred.

[0023] The organic solvent used in the etching solution is not particularly limited, and any conventionally known organic solvent can be used 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, polyhydric alcohol derivatives, nitrogen-containing solvents, silicones, and mixtures thereof. Among these, hydrocarbons, esters, ethers, halogen-containing solvents, and polyhydric alcohol derivatives that do not have an OH group, or mixtures thereof, can be used. The use of these solvents is preferred because they improve the stability of the etching solution.

[0024] Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutanol, tert-butanol, 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, 5-methyl-1-pentanol, 6-methyl-1-pentanol, 7-methyl-1-pentanol, 8-methyl-1-pentanol, 9-methyl-1-pentanol, 10-methyl-1-pentanol, 11-methyl-1-pentanol, 12-methyl-1-pentanol, 13-methyl-1-pentanol, 14-methyl-1-pentanol, 15-methyl-1-pentanol, 16-methyl-1-pentanol, 17-methyl-1-pentanol, 18-methyl-1-pentanol, 19-methyl-1-pentanol, 20-methyl-1-pentanol, 21-methyl-1-pentanol, 22-methyl-1-pentanol, 23-methyl-1-pentanol, 24-methyl-1-pentanol, 25-methyl-1-pentanol, 26-methyl-1-pentanol, 27-methyl-1-pentanol, 28-methyl-1-pentanol, 29-methyl-1-pentanol, 29-methyl-1-pentanol, 21-methyl-1-pentanol, 22-methyl-1-pentanol, 23-methyl-1-pent Examples of the alcohols include 1-hexanol, 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, and 2-ethyl-1-hexanol.

[0025] Examples of the hydrocarbons include n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, n-tetradecane, n-hexadecane, n-octadecane, and n-eicosane, as well as branched hydrocarbons corresponding to the carbon numbers thereof (e.g., isododecane and isocetane), cyclohexane, methylcyclohexane, decalin, benzene, toluene, xylene, (ortho-, meta-, or para-)diethylbenzene, 1,3,5-trimethylbenzene, and naphthalene.

[0026] Examples of the esters include ethyl acetate, n-propyl acetate, i-propyl acetate, n-butyl acetate, i-butyl acetate, n-pentyl acetate, i-pentyl acetate, n-hexyl acetate, n-heptyl acetate, n-octyl acetate, n-pentyl formate, n-butyl propionate, ethyl butyrate, n-propyl butyrate, i-propyl butyrate, n-butyl butyrate, methyl n-octanoate, methyl decanoate, methyl pyruvate, ethyl pyruvate, n-propyl pyruvate, methyl acetoacetate, ethyl acetoacetate, ethyl 2-oxobutanoate, dimethyl adipate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, methyl 3-ethoxypropionate, ethyl 3-ethoxypropionate, ethyl ethoxyacetate, and the like.

[0027] Examples of the ethers include di-n-propyl ether, ethyl-n-butyl ether, di-n-butyl ether, ethyl-n-amyl ether, di-n-amyl ether, ethyl-n-hexyl ether, di-n-hexyl ether, di-n-octyl ether, as well as ethers having a branched hydrocarbon group such as diisopropyl ether and diisoamyl ether corresponding to the carbon numbers of these ethers, dimethyl ether, diethyl ether, methyl ethyl ether, methyl cyclopentyl ether, diphenyl ether, tetrahydrofuran, dioxane, methyl perfluoropropyl ether, methyl perfluorobutyl ether, ethyl perfluorobutyl ether, methyl perfluorohexyl ether, and ethyl perfluorohexyl ether.

[0028] Examples of the ketone include acetone, acetylacetone, methyl ethyl ketone, methyl propyl ketone, methyl butyl ketone, 2-heptanone, 3-heptanone, cyclohexanone, and isophorone.

[0029] Examples of the halogen-containing solvent include perfluorocarbons such as perfluorooctane, perfluorononane, perfluorocyclopentane, perfluorocyclohexane, and hexafluorobenzene; hydrofluorocarbons such as 1,1,1,3,3-pentafluorobutane, octafluorocyclopentane, 2,3-dihydrodecafluoropentane, and Zeorola H (manufactured by Nippon Zeon); methyl perfluoroisobutyl ether, methyl perfluorobutyl ether, ethyl perfluorobutyl ether, ethyl perfluoroisobutyl ether, Asahiklin AE-3000 (manufactured by Asahi Glass Co., Ltd.); and Novec 71 00, Novec7200, Novec7300, Novec7600 (all manufactured by 3M), etc.; chlorocarbons such as tetrachloromethane; hydrochlorocarbons such as chloroform, etc.; chlorofluorocarbons such as dichlorodifluoromethane, hydrochlorofluorocarbons such as 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, etc.; perfluoroethers; and perfluoropolyethers.

[0030] Examples of the sulfoxide include dimethyl sulfoxide, etc. Examples of the lactone include β-propiolactone, γ-butyrolactone, γ-valerolactone, γ-hexanolactone, γ-heptanolactone, γ-octanolactone, γ-nonanolactone, γ-decanolactone, γ-undecanolactone, γ-dodecanolactone, δ-valerolactone, δ-hexanolactone, δ-octanolactone, δ-nonanolactone, δ-decanolactone, δ-undecanolactone, δ-dodecanolactone, ε-hexanolactone, etc.

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

[0032] Examples of the polyhydric alcohol 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 monobutyl ether, Propyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monobutyl ether, tetrapropylene glycol monomethyl ether, butylene glycol 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 acetate, 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, butylene glycol dimethyl ether, butylene glycol monomethyl ether acetate, butylene glycol diacetate, glycerin triacetate, etc.,

[0033] Examples of the nitrogen-containing solvent include formamide, N,N-dimethylformamide, 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, and pyridine.

[0034] Examples of the silicone include hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, and dodecamethylpentasiloxane.

[0035] From the viewpoint of the stability of the etching solution, the organic solvent is preferably a hydrocarbon, an ester, an ether, a halogen-containing solvent, a carbonate, or a polyhydric alcohol derivative that does not have an OH group. Among these, from the viewpoint of cost and environmental load, an ester, an ether, or a polyhydric alcohol derivative that does not have an OH group is preferred, and propylene glycol monoalkyl ether acetate is more preferred, with propylene glycol monomethyl ether acetate being particularly preferred.

[0036] In addition, since β-diketones tend to precipitate as solids when they form hydrates, the water content of the etching solution is Mass % It is preferably 20% by mass or less, more preferably 10% by mass or less, and particularly preferably 1% by mass or less.

[0037] In addition, the concentration of β-diketone in the etching solution is 0.5 to 15 MassThe β-diketone content is preferably 1 to 12% by mass, more preferably 1 to 12% by mass, and even more preferably 2 to 10% by mass. If the β-diketone content is too high, the etching solution will be too expensive because β-diketones are generally more expensive than organic solvents. Furthermore, if the β-diketone content is greater than 10% by mass, the roughness tends to worsen. On the other hand, if the β-diketone content is less than 1% by mass, etching tends to slow down.

[0038] The etching solution may also contain additives such as citric acid, formic acid, acetic acid, and trifluoroacetic acid for the purposes of improving the etching rate or increasing the etching selectivity, as long as they do not adversely affect the object to be treated.

[0039] The amount of the additive added is adjusted within a range that does not adversely affect the object to be treated, and may be added, for example, in a range of 0.01 to 20 mass %, 0.1 to 15 mass %, or even 0.5 to 10 mass % relative to the etching solution. The etching solution may essentially consist of a β-diketone having a trifluoromethyl group and a carbonyl group bonded thereto, and an organic solvent.

[0040] The wet etching method of the present disclosure includes a first step of contacting the metal-containing film with the surface-modifying liquid and a second step of contacting the metal-containing film modified by the surface-modifying liquid with the etching liquid, thereby enabling etching without increasing the roughness of the metal-containing film. The wet etching method may include placing the surface-modifying liquid and / or the etching liquid in an apparatus such as an etching apparatus on which a processing object having a metal-containing film on a substrate is placed, and bringing the surface-modifying liquid and / or the etching liquid into contact with the metal-containing film on the processing object, thereby wet-etching the metal-containing film.

[0041] The apparatus and method for applying the wet etching solution of the present disclosure are not particularly limited, as long as an apparatus capable of retaining the surface modification liquid and / or the etching solution on the surface of the object to be treated is used. Examples include a single-wafer method using a spinning device that holds and rotates the substrates approximately horizontally while supplying liquid near the center of rotation to process the substrates one by one, and a batch method using an apparatus that immerses and processes multiple substrates together in a tank. When supplying the liquid etching solution to the surface of the object to be treated, the form of the etching solution is not particularly limited as long as it becomes liquid when retained by the object to be treated, and may be, for example, a liquid or a vapor.

[0042] The first step and the second step do not have to be consecutive. It is preferable to provide a cleaning step between the first step and the second step to rinse the metal-containing film surface to which the surface modification liquid has adhered. By providing the cleaning step, the content of the oxidizing substance contained in the etching solution can be reduced, and further, it is possible to avoid contact with the metal-containing film.

[0043] An example of the cleaning step is to bring water, an organic solvent, or the like into contact with the metal-containing film to remove the oxidizing substance from the metal-containing film. The organic solvent used in the cleaning step is not particularly limited, and any conventionally known organic solvent can be used as long as it can dissolve the etching solution and / or the oxidizing substance. For example, the organic solvents exemplified as those used in etching solutions can be used. Furthermore, from the viewpoint of the solubility of the surface modification solution, water, alcohol, and polyhydric alcohol derivatives are preferred. It is also preferable to use the solvent of the surface modification solution. Furthermore, in the cleaning step, rinsing may be performed multiple times using water or an organic solvent. For example, a method of rinsing with the solvent of the surface modification solution and then rinsing with the solvent of the etching solution is possible. This rinsing method is preferred when the solvent of the surface modification solution reacts with the β-diketone contained in the etching solution.

[0044] If the solvent of the surface modification liquid and the solvent of the etching liquid are not compatible, it is preferable to rinse with a solvent that dissolves in both. For example, as shown in the examples described later, one preferred embodiment is to rinse with ultrapure water, 2-propanol, or propylene glycol-1-monomethyl ether-2-acetate after contact with the surface modification liquid, and then contact with the etching liquid.

[0045] The first step and the second step may be repeated, which allows the etching amount to be increased without worsening the surface roughness.

[0046] Furthermore, when the first step and the second step are repeatedly performed, one preferred embodiment is to rinse the substrate taken out after contact with the etching solution with ultra-propylene glycol-1-monomethyl ether-2-acetate, 2-propanol, ultra-pure water, or the like, and then contact the substrate with the surface modifying liquid.

[0047] The oxidizing substance contained in the etching solution in this disclosure is % It is preferable that the amount of the oxidizing substance is 0.01% by mass or less, and more preferably 0.005% by mass or less, relative to the total amount of the oxidizing substance. Within this range, it is not necessarily necessary to provide a cleaning step between the first step and the second step and rinse the metal-containing film surface to which the surface modification liquid has adhered, but by performing rinsing and adjusting the amount of the oxidizing substance to 0.001% by mass or less, it is possible to minimize the roughness of the metal surface after etching.

[0048] In the second step, in order to prevent the oxidizing substance contained in the etching solution from coming into contact with the metal-containing film, it is desirable to repeatedly rinse until the content of the oxidizing substance reaches 0 mass %. However, in order to efficiently perform the cleaning step, the detection limit may be set as the lower limit for the content of the oxidizing substance. Alternatively, the lower limit may be set to 0.0001 mass %, and rinsing may be repeated until the content reaches 0.0001 mass % or more and 0.001 mass % or less. In addition, when the oxidizing substance in the etching solution reaches 0.0001 mass % or less when the oxidizing substance reaches 100 mass % of the etching solution, the detection limit may be set as the lower limit. %If the amount of dissolved metal exceeds 0.01 mass % with respect to the total mass, it becomes difficult to reduce the difference in roughness of the metal-containing film surface before and after etching.

[0049] Before the first step, a step of contacting the metal-containing film with an etching solution capable of etching the metal-containing film may be carried out. The outermost surface of the metal-containing film may be naturally oxidized due to a step prior to the treatment with the surface modification liquid or exposure to air. The step of contacting the metal-containing film with the etching solution first is preferable because it allows the natural oxide on the outermost surface to be removed. The etching solution used in the second step may be used as the etching solution here.

[0050] In the wet etching method of the present disclosure, the temperature of the surface modification liquid is not particularly limited as long as it is a temperature at which the surface modification liquid can be maintained in a liquid state, but can be appropriately set to about -10 to 60°C, taking into consideration the length of time the surface modification liquid is in contact and the roughness of the metal-containing film after etching. The temperature of the etching solution is not particularly limited as long as it is a temperature at which the etching solution can be kept in a liquid state, but can be appropriately set to about −10 to 100° C., taking into consideration the length of time the etching solution is in contact with the metal-containing film and the roughness of the metal-containing film after etching.

[0051] The length of time for contact with the surface modifying liquid is not particularly limited, 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. The length of time for contact with the etching liquid is not particularly limited, but considering the efficiency of the semiconductor device manufacturing process, it is preferably within 60 minutes, more preferably within 10 minutes, and particularly preferably within 2 minutes. Here, the length of time for contact with the surface modification liquid or etching liquid refers to, for example, the time for which the liquid is discharged onto the substrate to be processed, the time for which the substrate is immersed, or the time from when the etching liquid is introduced into the process chamber in which the substrate is placed until the etching liquid is subsequently discharged from the process chamber to complete the etching process.

[0052] By using the wet etching method of the present disclosure, it is possible to etch a metal-containing film to be etched without etching a substrate that is not the target of etching and that does not contain a metal element that forms a complex with β-diketone, or a film of a silicon-based semiconductor material. Furthermore, by using the wet etching method of the present disclosure, it is possible to improve the roughness after etching of a metal-containing film using a wet etching apparatus that is less expensive than a dry etching apparatus, thereby improving the quality of semiconductor devices.

[0053] (device) The wet etching method according to the present disclosure enables the fabrication of high-performance devices. The devices according to the present disclosure can be fabricated inexpensively by using a metal-containing film etched by the wet etching method according to the present disclosure. Examples of such devices include solar cells, hard disk drives, clock ICs, microprocessors, dynamic random access memories, phase-change memories, ferroelectric memories, magnetoresistive memories, resistive memories, and MEMS. [Example]

[0054] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0055] The evaluation method, solution preparation, etching treatment, and evaluation results are described below.

[0056] [Evaluation method] (Measurement of etching amount) The amount of etching was calculated from the change in the mass of the substrate before and after immersion in the etching solution. The specific gravity of Cu used as the metal-containing film was 8.94 g / cm. 3 The etching rate is calculated by etching amount [nm] / immersion time [sec]. (surface roughness measurement) The surface of the metal-containing film before etching (initial state) and after etching were each measured using an AFM (SHIMADZU SPM-9700: scanning range 1.00 μm, scanning speed 1.0 Hz) to determine the center line average surface roughness Ra (nm), and the difference in Ra (ΔRa) before and after etching was calculated. Note that Ra is the center line average roughness defined in JIS B 0601 expanded three-dimensionally by applying it to the measurement surface, and was calculated using the following formula as "the average of the absolute values ​​of the deviation from the reference surface to the specified surface." [ka] where X L , X R , Y B , Y T indicate the measurement range of the X and Y coordinates, respectively. S0 is the area when the measurement surface is assumed to be ideally flat, and (X R -X L )×(Y B -Y T ) value. F(X, Y) represents the height at the measurement point (X, Y), and Z0 represents the average height within the measurement surface. (Observation of surface shape) The surface morphology was observed using an SEM (Hitachi SU8010: accelerating voltage 10.0 KV, emission 20 μA).

[0057] [Example 1] (Solution preparation) A surface modification liquid was prepared by mixing hydrogen peroxide and ultrapure water (HO) to a hydrogen peroxide concentration of 1% by mass. An etching solution was prepared by mixing hexafluoroacetylacetone (HFAc) and propylene glycol-1-monomethyl ether-2-acetate (PGMEA) as a solvent to a HFAc concentration of 5% by mass. The water content in the etching solution was 1% by mass or less. (wet etching process) The silicon substrate to be treated had a Cu film (thickness: 1 μm, centerline average surface roughness: Ra = 6 nm) formed by plating as a metal-containing film. This substrate was immersed in the surface modification solution obtained above for 20 seconds at 24°C as a pretreatment step, forming an oxide film on the outermost surface of the Cu. The surface modification solution adhering to the substrate surface was then rinsed off. The substrate was immersed in ultrapure water, 2-propanol (IPA), and PGMEA for 20 seconds at 24°C, respectively. Next, the substrate was immersed in the etching solution obtained above for 20 seconds at 24°C, performing an etching step. The etching solution adhering to the substrate surface was then rinsed off. The substrate was immersed in PGMEA, IPA, and ultrapure water for 20 seconds at 24°C, respectively. Finally, the surface was dried for 10 seconds using a gas blower.

[0058] [Examples 2 to 4] A surface modification liquid and an etching liquid were prepared in the same manner as in Example 1. The same silicon substrate as in Example 1 was used as the treatment object, and a wet etching treatment was performed in the same manner as in Example 1, except that the series of operations of pretreatment step → rinsing → etching step → rinsing was repeated 2, 5, and 10 times, and finally the surface was dried for 10 seconds with a gas blower.

[0059] [Example 5] A surface modification liquid and an etching liquid were prepared in the same manner as in Example 1. Before immersion in the surface modification liquid, the same silicon substrate as in Example 1 was immersed in the etching liquid at 24°C for 20 seconds, and then the etching liquid adhering to the substrate surface was rinsed. To rinse, the substrate was immersed in PGMEA, IPA, and ultrapure water at 24°C for 20 seconds each. Thereafter, a wet etching treatment was performed in the same manner as in Example 1.

[0060] [Example 6] A surface modification liquid was prepared in the same manner as in Example 1. An etching solution was also prepared in the same manner as in Example 1, except that propylene glycol monomethyl ether (PGME) was used as the solvent. In the wet etching process, the same silicon substrate as in Example 1 was immersed in the surface modification liquid at 24°C for 20 seconds. Then, without rinsing the surface modification liquid adhering to the substrate surface, the substrate was immersed in the etching liquid at 24°C for 20 seconds with the surface modification liquid still attached. This operation was repeated 10 times, and then the etching liquid adhering to the substrate surface was rinsed. The substrate was immersed in PGME, IPA, and ultrapure water for 20 seconds at 24°C for rinsing. Finally, the surface was dried for 10 seconds with a gas blower. That is, in this example, the surface modification liquid was slightly dissolved in the etching liquid, and 0.003 mass% of hydrogen peroxide was dissolved in the total amount of the etching liquid and the dissolved surface modification liquid.

[0061] [Comparative Example 1] An etching solution was prepared in the same manner as in Example 1. The same silicon substrate as in Example 1 was immersed in the etching solution at 24°C for 20 seconds, then immersed in PGMEA and 2-propanol (IPA) for 20 seconds each at 24°C, and finally the surface was dried for 10 seconds with a gas blower, except that a wet etching treatment was performed in the same manner as in Example 1. That is, in this comparative example, the treatment was performed using a method that omitted the pretreatment step of immersion in a surface modification liquid.

[0062] Comparative Example 2 In the etching step, wet etching was performed in the same manner as in Comparative Example 1, except that the substrate was immersed in the etching solution at 24° C. for 40 seconds.

[0063] Comparative Example 3 In the etching step, wet etching was performed in the same manner as in Comparative Example 1, except that the substrate was immersed in the etching solution at 24° C. for 80 seconds.

[0064] Comparative Example 4 Wet etching was carried out in the same manner as in Example 1, except that an etching solution prepared by mixing 98% sulfuric acid and IPA so that the sulfuric acid concentration was 5 mass % was used.

[0065] Comparative Example 5 Wet etching was carried out in the same manner as in Example 1, except that an etching solution was prepared by mixing 25% aqueous ammonia and IPA so that NH3 was 2% by mass.

[0066] Comparative Example 6 In the etching step, wet etching was performed in the same manner as in Comparative Example 5, except that the substrate was immersed in the etching solution at 24° C. for 40 seconds.

[0067] Comparative Example 7 In the etching step, wet etching was performed in the same manner as in Comparative Example 5, except that the substrate was immersed in the etching solution at 24° C. for 80 seconds.

[0068] <Etching amount [nm] and ΔRa [nm]> As shown in Tables 1 and 2 for Examples 1 to 6 and Comparative Examples 1 to 3, the etching method of the present invention was able to improve the etching rate and suppress an increase in ΔRa when etching a metal-containing film containing a predetermined metal element. Furthermore, the etching amount could be increased depending on the number of times the etching process was repeated, and even if the etching amount increased, an increase in ΔRa could be suppressed. In Comparative Examples 4 to 7, in which an acid or a base was used instead of a β-diketone in the etching solution, ΔRa increased significantly. FIG. 1 is an SEM image of the Cu surface after the etching treatment of Example 3 was carried out five times. The Cu surface after etching was smooth and no significant roughness was observed.

[0069] In Examples 1 to 5, the surface roughness after etching did not change significantly compared to the Cu film surface before the surface modification liquid was brought into contact with the metal-containing film and the Cu oxide film surface before the etching process. However, Examples 1 to 5, in which the surface modification liquid was removed by rinsing, had a smaller surface roughness after etching than Example 6, in which the surface modification liquid was not removed by rinsing.

[0070] [Table 1] [Table 2] [Explanation of symbols]

[0071] 1: PCB 2: Metal-containing film 3: Surface of metal-containing film (= roughness surface) 4: Cross section of metal-containing film

Claims

1. A wet etching method in which a metal-containing film on a substrate is pretreated with a surface modification liquid and then etched using an etching liquid, comprising: the etching solution is a solution containing a β-diketone having a trifluoromethyl group and a carbonyl group bonded thereto and an organic solvent, the metal-containing film contains a metal element capable of forming a complex with the β-diketone, the surface modification liquid contains an oxidizing substance for the metal element, a first step of contacting the surface modifying liquid with the metal-containing film to form an oxide film of the metal element on the surface of the metal-containing film; a second step of contacting the metal-containing film having the oxide film with the etching solution; a step of cleaning the surface of the substrate between the first step and the second step, a content of an oxidizing substance contained in the etching solution when brought into contact with the metal-containing film in the second step is 0 to 0.001 mass % relative to 100 mass % of the etching solution.

2. The wet etching method according to claim 1 , wherein in the second step, the oxidizing substance is not brought into contact with the metal-containing film.

3. A wet etching method as described in claim 1 or 2, wherein a second step is performed after the cleaning step without drying.

4. 4. The wet etching method according to claim 1, wherein the time for which the metal-containing film is brought into contact with the surface modification liquid is 2 minutes or less, and the time for which the etching liquid is brought into contact with the metal-containing film having the oxide film is 2 minutes or less.

5. 5. The wet etching method according to claim 1, wherein the concentration of the β-diketone in the etching solution is 0.5 to 15 mass %.

6. The wet etching method according to any one of claims 1 to 5, wherein, prior to the first step, a step of contacting the metal-containing film with an etching solution containing a β-diketone having a trifluoromethyl group and a carbonyl group bonded thereto and an organic solvent is carried out.

7. 7. The wet etching method according to claim 1, wherein the oxidizing substance is at least one selected from the group consisting of oxygen, ozone, peroxide, an oxidizing acid or a salt thereof, persulfonic acid or a salt thereof, percarbonate or a salt thereof, persulfuric acid or a salt thereof, perchloric acid or a salt thereof, and periodic acid or a salt thereof.

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

9. 9. The wet etching method according to claim 1, wherein the surface modifying liquid contains 0.01% by mass to 20% by mass of an oxidizing substance relative to 100% by mass of the surface modifying liquid.

10. 10. The wet etching method according to claim 1, wherein the material of the substrate is a silicon-based semiconductor material or a silicate glass material.

11. A wet etching method described in any one of claims 1 to 10, characterized in that the center line average surface roughness Ra of the metal-containing film after etching the metal-containing film by 6 nm or more in the second step is 6 nm or less.

12. A wet etching method described in any one of claims 1 to 11, characterized in that when the metal-containing film is etched by 6 nm or more in the second step, the difference (ΔRa) in center line average surface roughness Ra of the metal-containing film before and after etching is -1 nm to 0 nm.

13. A wet etching method described in any one of claims 1 to 12, characterized in that the surface modification liquid further contains a solvent, and 50 mass% or more of the 100 mass% solvent is water.

14. A wet etching method according to claim 1, wherein the cleaning step is carried out using an organic solvent.

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