METHOD FOR MANUFACTURING INDIUM-CONTAINING ORGANIC POLYMER FILM, PATTERNING METHOD, AND METHOD FOR MANUFACTURING SEMICONDUCTOR DEVICE

A method for manufacturing an indium-containing organic polymer film includes forming an organic polymer film on a base body, infiltrating the organic polymer film with an alkylindium having an alkyl group having 2 to 4 carbon atoms, and oxidizing the organic polymer film infiltrated with the alkylindium.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-153437, filed Sep. 21, 2021, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a method for manufacturing an indium-containing organic polymer film, a patterning method, and a method for manufacturing a semiconductor device.

BACKGROUND

The development of a semiconductor device with a three-dimensional structure has proceeded, and a technique for forming a pattern with a high aspect ratio is increasingly desired. Since a mask pattern used in a process for the technique is exposed to an etching gas for an extended period, resistance to the etching gas is required for the mask pattern. For example, when a fluorocarbon gas is used as an etching gas, high etching resistance to a fluoride radical is required. Furthermore, a method for manufacturing a metal-containing organic polymer film used for an etching mask of such a mask pattern is required.

DETAILED DESCRIPTION

Embodiments provide a method for manufacturing an indium-containing organic polymer film used for an etching mask and the like, a patterning method capable of enhancing etching resistance of the etching mask to a fluoride radical, and a method for manufacturing a semiconductor device.

In general, according to at least one embodiment, a method for manufacturing an indium-containing organic polymer film includes forming an organic polymer film on a base body, infiltrating the organic polymer film with an alkylindium having an alkyl group having 2 to 4 carbon atoms, and oxidizing the organic polymer film infiltrated with the alkylindium.

Hereinafter, a method for manufacturing an indium (In)-containing organic polymer film (metal-containing organic polymer film), a patterning method, and a method for manufacturing a semiconductor device of embodiments will be described with reference to the drawings. In each embodiment, substantially the same elements are denoted by the same reference symbols, and description thereof may be partially omitted. The drawings are schematic, and relationships between thicknesses and plane dimensions, ratios of thicknesses of portions, and the like may differ from the actual relationships and ratios.

Method for Manufacturing Indium-Containing Organic Polymer Film and Patterning Method

A method for manufacturing an indium-containing organic polymer film and a patterning method of at least one embodiment will be described with reference toFIGS.1A to1E.FIGS.1A to1Eare cross-sectional views illustrating steps of the patterning method of at least one embodiment. In the patterning method illustrated inFIGS.1A to1E, a film to be processed2formed on a substrate1is prepared, and an etching mask3is formed on the film to be processed2by the method for manufacturing an In-containing organic polymer film of the embodiment, as illustrated inFIG.1A. The etching mask3is a film containing an In oxide manufactured by the method for manufacturing an In-containing organic polymer film of the embodiment. The film to be processed2is not particularly limited, and a various types of function films are used. The film manufactured by the method for manufacturing an In-containing organic polymer film of at least one embodiment is not limited to an organic polymer film containing an In oxide, may be a baked film of an In oxide or the like, and is not limited as long as it is the In oxide-containing film.

Steps of manufacturing the In oxide-containing film as the etching mask3will be described in detail with reference toFIGS.2A to2D. As illustrated inFIG.2A, the substrate1having the film to be processed2is prepared as a base body4. Herein, on the assumption that the metal fluoride-containing organic polymer film is used for a patterning method used in a step of manufacturing a semiconductor device and the like, the substrate1having the film to be processed2is used as the base body4. However, when the In-containing organic polymer film and the In oxide-containing film are used for another application, the base body4is appropriately selected. For example, the substrate1is a semiconductor wafer such as a silicon substrate. As illustrated inFIG.2B, an organic polymer film5is formed on the base body4. The organic polymer film5is used to form an organic polymer film infiltrated with In by exposure to an organometallic compound (organic In compound) that is a precursor of infiltrating In. Herein, the infiltration of the organic polymer film5with the metal (In) by exposure of the organic polymer film5to the organometallic compound is called metallizing.

Examples of a monomer constituting an organic polymer for the organic polymer film5to be metallized include methacrylates containing an alkyl ester group having 1 to 12 carbon atoms, such as methyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate, norbornyl methacrylate, isobornyl methacrylate, adamantyl methacrylate, and tricyclo methacrylate, phenyl methacrylate, methacrylates in which a benzyl methacrylate group is ester-bonded to methacrylic acid, naphthyl methacrylate, anthryl methacrylate, naphthyl methylmethacrylate, and methacrylate methylmethacrylate. Methacrylate may be replaced by acrylate. Additional examples include 4-vinyl benzoates containing an alkyl ester group having 1 to 12 carbon atoms, such as styrene, acetoxystyrene, vinyl benzoate, methyl-4-vinyl benzoate, butyl-4-vinyl benzoate, and cyclohexyl-4-vinyl benzoate. The monomer may be an alkyl acrylamide containing an amide group bonded to an alkyl group having 1 to 12 carbon atoms, an amide acrylate such as N-isopropylacrylamide, N-benzylacrylamide, or N-naphthylacrylamide, or the like, or an amide methacrylate thereof. Examples of the organic polymer include a novolac resin such as phenol novolac and cresol novolac, and a resole resin. The monomers may be used alone or be copolymerized. A cross-linking group such as a glycidyl group, a hydroxyl group, or a carboxyl group may be introduced.

Examples of the organic polymer include an organic polymer containing a monomer having at least one selected from an ester group (—C(═O)—OR1), an amido group (—C(═O)—NR1R2), and an imido group (—C(═O)—NR1—C(═O)—R2) in one segment. In the formulae, R1and R2are the same as or different from each other, and are a hydrogen atom (—H), an alkyl group having about 1 to 5 carbon atoms (—CnH2n−1wherein n is an integer of 1 to 5), or the like. At least one group selected from an ester group, an amido group, and an imido group binds to an organic In compound that is an In precursor. As a result, infiltration of the organic polymer with In is promoted. Examples of such an organic polymer include polymethyl methacrylate (PMMA), and poly(N-isopropylacrylamide) (PNIPAM). The organic polymer having at least one group (characteristic group) selected from an ester group, an amido group, and an imido group may have an aromatic ring in addition to the characteristic group. Herein, the aromatic ring is not limited to a benzene ring, and may be a polycyclic aromatic ring such as a naphthalene ring, an anthracene ring and pyrene ring. Examples of such an organic polymer include a polystyrene derivative having an aromatic ring and at least one group selected from an ester group, an amido group, and an imido group on a side chain.

As illustrated inFIG.2C, the organic polymer film5is exposed to an organic In compound6as a precursor of In that is an infiltrating metal, to infiltrate the organic polymer film5with the organic In compound6. Thus, an In-infiltrating organic polymer film5X is manufactured. In the exposure to the organic In compound6, for example, a gas of the organic In compound6is supplied to a chamber.

As a metal used in metallizing, for example, aluminum (Al) is known. Among Al oxides, for example, sapphire (α-Al2O3) has good resistance to a fluorine radical used in reactive ion etching (RIE), or the like, as illustrated in the relationship between the etching time and the etching thickness ofFIG.3. On the contrary, an Al oxide (AlOx) formed by metallizing has resistance to an O radical, but does not have sufficient resistance to a fluorine radical. An In oxide (InOx) formed by metallizing has better resistance to a fluorine radical than such an Al oxide formed by metallizing. Therefore, in the method for manufacturing the metal-containing organic polymer film and the patterning method of the embodiment, indium (In) is used as a metallizing metal.

As the organometallic compound that is a precursor of the metallizing metal, an alkyl metal is well known. In particular, a trimethyl metal (M(CH3)3wherein M is a metal) is generally known as an organic compound of a group 13 metal. However, when In is used as the metal M, trimethyl indium (In(CH3)3) of alkylindiums is difficult to use safely in a step of manufacturing a semiconductor device and the like. This is because trimethyl indium is too highly reactive, and causes an explosion hazard and the like. In the manufacturing step and the patterning step of at least one embodiment, as the organometallic compound that is a precursor of In, an alkylindium having an alkyl group having 2 to 4 carbon atoms, typified by triethylindium (In(C2H5)3) (hereinafter referred to as TEIn) is used. In addition to TEIn, examples of the alkylindium used herein include tripropylindium (In(C3H7)3) and tributylindium (In(C4H9)3). Provided that an alkylindium having5carbon atoms or more is safe, but is not suitable for a metallizing step due too poor reactivity and diffusivity.

The reactivity of the alkylindium having an alkyl group having 2 to 4 carbon atoms, typified by TEIn, is lower than that of trimethylindium, and therefore the alkylindium can be safely used in the step of manufacturing a semiconductor device and the like. Further, the diffusion rate of the alkylindium such as TEIn in the polymer is high, and therefore the organic polymer can be infiltrated with the alkylindium.FIG.4illustrates the metallizing temperature dependency of the ratio of increased film thickness of PMMA and PNIPAM after exposure as the organic polymer to TEIn. As illustrated inFIG.4, it is shown that even when any of PMMA and PNIPAM is used, metallizing with TEIn is infiltrated more at a lower temperature. Therefore, it is preferable that metallizing with the alkylindium such as TEIn be performed at a relatively low temperature, for example, a temperature range of 60° C. to 120° C.

As illustrated inFIG.2D, the organic polymer film5X infiltrated with the alkylindium such as TEIn is then annealed, to oxidize In in the organic polymer film5X. The annealing (oxidation) process of the In-infiltrating organic polymer film5X is performed, for example, in water vapor (H2O), oxygen (O2), ozone (O3), oxygen radicals, oxygen plasma, or the like. For example, when the organic polymer film5X infiltrated with the alkylindium such as TEIn is annealed in air, In is oxidized to obtain an indium oxide (InOx, and the like), but the organic polymer film5itself is maintained as it is. When the In-infiltrating organic polymer film5X is annealed in oxygen, ozone, oxygen radicals, oxygen plasma, or the like, the organic polymer may be burned down. Therefore, a film5Y after annealing (annealed film) may be a baked film of the In oxide. The annealed film5Y of the In-infiltrating organic polymer film5X is not limited as long as it is a film containing an In oxide. For example, the annealed film5Y is not limited to an organic polymer film containing an In oxide, and may be a baked film of the In oxide. When the annealed film5Y is an organic polymer film containing an In oxide, it is preferable that the content of the In oxide be 5% by mass or more.

FIGS.5and6illustrate relationships between the amount of increased film thickness by metallizing and the amount of increased film thickness after annealing.FIG.5illustrates results when PMMA and PNIPAM are used as the organic polymer.FIG.6illustrates results when a styrene-based resin is used as the organic polymer. A structural formula of the styrene-based resin (Chemical Formulae 1 and 2) used inFIG.6is illustrated inFIG.7. The reactivity of metallizing with TEIn varies depending on the type of the organic polymer. For example, when PMMA is metallized with TEIn, the film thickness after annealing (film thickness of the indium oxide) increases with an increase in film thickness after metallizing. When PNIPAM is used, the amount of increased film thickness after annealing is smaller than the amount of increased film thickness after metallizing. This also applies to a case where the styrene-based resin is used. Thus, the reactivity of metallizing with TEIn varies depending on the type of the organic polymer. Therefore, it is preferable that an annealing condition after metallizing, the film thickness after annealing, and the like be set in consideration of the type of the organic polymer.

Next, the etching resistance of the organic polymer film metallized with TEIn will be described with reference toFIGS.8,9, and10.FIG.8illustrates a relationship between the etching time and the film thickness when a PMMA film and the PMMA film that is metallized with TEIn are etched using a CF4gas.FIG.9illustrates a relationship between the etching time and the etching depth when films of the styrene-based resins (Chemical Formulae 1 and 2), the films the styrene-based resins that are metallized with TEIn alone, and the films the styrene-based resins that are metallized with TEIn and trimethylaluminum (TMA:Al(CH3)3) are etched using a CF4gas. It is seen that the CF4resistance is improved when the PMMA film and the films of styrene-based resins (Chemical Formulae 1 and 2) are metallized with TEIn, as illustrated inFIGS.8and9. A comparison between the film metallized with TEIn alone and the film metallized with TEIn and TMA shows that the film metallized with TEIn alone has better resistance.

FIG.10is a scanning electron microscope (SEM) image in a state where a film in which the film of the styrene-based resin (Chemical Formula 2) is metallized under each of various types of conditions is etched using a C4F6gas. InFIG.10, a row (A) illustrates a SEM image after etching of the film metallized with TMA, a row (B) illustrates a SEM image after etching of the film metallized with TMA and TEIn, a row (C) illustrates a SEM image after etching of the film metallized with TEIn, and a row (D) illustrates a SEM image after etching of a styrene-based resin film not metallized. InFIG.10, a column (a) illustrates a SEM image of an organic polymer film in which holes with a diameter of 148 nm are formed at an interval of 500 nm, a column (b) illustrates a SEM image of a film in which holes with a diameter of 148 nm are formed at an interval of 700 nm, and a column (c) illustrates a SEM image of a film in which holes with a diameter of 148 nm are formed at an interval of 900 nm. It is shown that the retreat amount from a y line (etching amount) of the films metallized with TEIn of the row (C) is the smallest, and the films have excellent etching resistance by a C4F6, as illustrated inFIG.10.

In the steps of the patterning method illustrated inFIGS.1A to1E, the aforementioned organic polymer film is formed on the film to be processed2as the etching mask3, as illustrated inFIG.1A. Subsequently, a resist pattern7is formed on the etching mask3, as illustrated inFIG.1B. The resist pattern7is formed by forming a resist film on the etching mask3, and patterning the resist film by optical lithography, electron beam lithography, imprint lithography or the like. In the imprint lithography, a resist is dropped on the etching mask3, a template having a fine pattern is pressed on the resist film, and the resist film is irradiated with ultraviolet light, resulting in curing, to form the resist pattern7. The formed resist pattern7is subjected to metallizing described above.

Subsequently, the etching mask3is etched by dry etching such as reactive ion etching (RIE) or ion beam etching (IBE) using the resist pattern7as a mask, resulting in patterning, as illustrated inFIG.1C.FIG.1Cillustrates the patterned etching mask3. When the difference in etching rates by an etching gas between the resist film and the etching mask3is small, a SiOxfilm and the like may be interposed between the resist film and the etching mask3, and the etching mask3may be patterned by using the resist film and the SiOxfilm as masks. As illustrated inFIG.1D, the resist pattern7is removed, and a step of infiltrating the organic In compound and a step of annealing the organic polymer film infiltrated with In are performed. A structure (patterned body)8having the etching mask3of the organic polymer film infiltrated with In on the film to be processed2is obtained.

As illustrated inFIG.1E, the patterned body8is used in patterning of the film to be processed2. Specifically, the film to be processed2is exposed to an etching gas via the patterned etching mask3, to achieve dry etching. Thus, the patterned film to be processed2is obtained. For the dry etching, for example, RIE, IBE, and the like are applied. As the etching gas, a gas containing a fluorine atom (F) is used. It is preferable that the etching gas contain fluorine (F) in a form of fluorocarbon having 1 to 6 carbon atoms (CnF2n+2, CnF2n, or CnF2n−2wherein n is a number of 1 to 6). It is preferable that the etching gas further contain oxygen (O2). In an etching gas containing a fluorine atom (F) and an oxygen atom (O), it is preferable that the amount of F be larger than the amount of O, rather than the ratio by atom of F to O of 1:1. Argon (Ar) and nitrogen (N2) may be added, if necessary. In this case, Ar and N2are not involved in the ratio of a fluorine atom to an oxygen atom.

When the patterned film to be processed2using such an etching gas containing a fluorine atom (F) is formed, an enhancement in etching resistance to a F radical and the like of the etching mask3is desired. The In-infiltrating organic polymer film5X formed by the method for manufacturing an In-containing organic polymer film of the embodiment and the annealed film5Y thereof in response to the demand have excellent etching resistance to a F radical and the like. Therefore, the In-infiltrating organic polymer film5X and the annealed film5Y are suitable for a mask of dry etching such as RIE. Accordingly, the precision of the steps of the patterning method illustrated inFIGS.1A to1Eand the subsequent etching step can be improved.

Method for Manufacturing Semiconductor Device

Next, a method for manufacturing a semiconductor device of the embodiment will be described with reference toFIGS.11A to11E.FIGS.11A to11Eare cross-sectional views illustrating steps of the method for manufacturing a semiconductor device of at least one embodiment. In the method for manufacturing a semiconductor device illustrated inFIGS.11A to11E, a film12to be processed is formed on a semiconductor substrate11as illustrated inFIG.11A. For example, the film12to be processed is a stacked film including a silicon nitride film13and a silicon oxide film14alternately stacked. For example, the stacked film12is used in manufacture of a three-dimensional nonvolatile memory device having a memory cell with a vertical transistor structure. On the film12to be processed that is such a stacked film, the etching mask3is formed by the steps of the pattering method of at least one embodiment. The etching mask3is the same as the etching mask used in the patterning method of at least one embodiment. That is, after an organic polymer film is formed on the stacked film12, and patterned, metallizing, that is, infiltration with the alkylindium and oxidation of the etching mask3infiltrated with the alkylindium are performed. The film12to be processed is not limited to the stacked film including the silicon nitride film13and the silicon oxide film14, and may be a single film of a silicon oxide film or a silicon nitride film.

As illustrated inFIG.11B, the resist pattern7is then formed on the etching mask3. The resist pattern7is formed by patterning the resist film formed on the etching mask3by lithography, an imprint technique, or the like, in the same manner as in the patterning method of the embodiment. As illustrated inFIG.11C, the etching mask3is then etched by dry etching using the resist pattern7as a mask, resulting in patterning. As illustrated inFIG.11D, the resist pattern7is removed, and the film12to be processed is exposed to an etching gas via the patterned etching mask3, to achieve dry etching. By such dry etching, the patterned film12to be processed is obtained as illustrated inFIG.11E.

For the dry etching, RIE, IBE, and the like are applied. As the etching gas, a gas containing a fluorine atom (F) is used. It is preferable that the etching gas contain a fluorine atom (F) in a form of fluorocarbon having 1 to 6 carbon atoms (CnF2n+2n, CnF2, or CnF2n−2wherein n is a number of 1 to 6). It is preferable that the etching gas further contain oxygen gas (O2). In an etching gas containing a fluorine atom (F) and an oxygen atom (O), it is preferable that the amount of F be larger than the amount of O, rather than the ratio by atom of F to O of 1:1. By using such an etching gas containing fluorocarbon and the like, the film12to be processed such as the aforementioned stacked film can be effectively etched.

When as described in the patterning method of the embodiment, the etching mask3formed in the particular steps from the particular materials is used, high etching resistance can be achieved even in dry etching of the film12to be processed using the etching gas containing fluorocarbon and the like. Even when a pattern having a hole with a high aspect ratio is formed like the film12to be processed as illustrated inFIGS.11A to11E, the patterning precision of the film12to be processed can be enhanced. Thus, the precision of formation of a semiconductor device, the yield of manufacture of a semiconductor device, and the like can be improved. In the method for manufacturing a semiconductor device of the embodiment, the film12to be processed is not limited to the aforementioned stacked film, and a various types of films can be used.

For example, the film12to be processed that is patterned as illustrated inFIG.11Eis used in manufacture of a memory cell array by a known method. For example, a hole pattern (memory hole) is formed in the stacked film by the aforementioned processing. In such a memory hole, a block insulating layer, a charge storage layer, a tunnel insulating layer, a channel layer, and a core layer are formed in order. Further, only a nitride film in the stacked film is removed via a slit formed separately from the memory hole, and a formed space is filled with a conductive film. As a result, a stacked film in which the insulating film (oxide film) and the conductive film are alternately stacked is obtained. Thus, a memory cell structure with a vertical transistor structure can be formed. The conductive film in the stacked film can function as a word line.