Pattern forming method and article manufacturing method

Abstract

To provide a technique advantageous for controlling the line width of a pattern in an imprint technique.SOLUTION: A pattern forming method includes: a contact step of bringing a mold and a curable composition including a polymerizable compound arranged on a field of a substrate into contact with each other; a curing step of irradiating the curable composition arranged on the field with light to form a cured film including a pattern composed of a cured product of the curable composition; and a separation step of separating the cured film and the mold from each other. The field includes a plurality of areas. The curing step includes, for each of the plurality of areas, irradiating the curable composition with light according to the illuminance and irradiation time determined according to a target line width of the pattern.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a pattern forming method and an article manufacturing method. [Background technology]

[0002] In semiconductor devices, MEMS, and the like, there is an increasing demand for miniaturization, and photo-nanoimprinting technology has attracted attention as a microfabrication technology. In photo-nanoimprinting technology, a mold (die) with a fine concave-convex pattern formed on its surface is pressed against a substrate (wafer) on which a curable composition has been applied, and the curable composition is cured in this state. In this way, the concave-convex pattern of the mold is transferred to a cured film of the curable composition, forming a pattern on the substrate. Photo-nanoimprinting technology makes it possible to form fine structures on the order of several nanometers on the substrate.

[0003] Here, an example of a pattern formation method using photo-nanoimprinting technology will be described. First, a liquid curable composition is discretely dispensed onto a pattern formation region on a substrate. The droplets of the curable composition dispensed onto the pattern formation region spread across the substrate. This phenomenon may be called press spreading. Next, a mold (die) having a pattern is pressed against the curable composition on the substrate. This causes the droplets of the curable composition to spread across the entire gap between the substrate and the mold by capillary action. This phenomenon may be called spreading. The curable composition also fills the recesses that form the mold pattern by capillary action. This filling phenomenon may be called filling. The time required for spreading and filling to be completed may be called filling time. After filling with the curable composition is complete, the curable composition is irradiated with light to harden the curable composition. The mold is then separated from the cured curable composition. By performing these steps, the pattern of the mold is transferred to the curable composition on the substrate, forming a pattern of the curable composition.

[0004] As with conventional projection exposure lithography, it is necessary to establish a linewidth (CD) control technique for photo-nanoimprint (NIL) technology. In conventional projection exposure lithography, the CD of the resist pattern can be adjusted for each field (shot area) by changing the exposure time. On the other hand, with NIL technology, it is impossible to change the mold pattern dimensions for each field, and no CD control technique has been established at present. A feature of NIL technology that provides a hint for CD control is the photoradical polymerization reaction of the resist material. A previous example of using simulations to elucidate the properties of photoradical polymerization reactions is described in Non-Patent Document 1.

[0005] In Non-Patent Document 1, polymerization reactions are calculated using the following procedure to determine the volumetric shrinkage and conversion rates due to polymerization. (1) The monomers and polymerization initiator before polymerization are represented as unit particles and randomly arranged in space. (2) The polymerization initiator is activated by light irradiation, stochastically selecting monomers within the reaction radius to form bonds. (3) The chain-bonded monomers are activated and bond with other monomers within the reaction radius. (4) If there are no monomers within the reaction radius, the bonding range expands to the critical distance. (5) The polymerization reaction terminates if there are no monomers within the critical radius or if activated monomers bond with each other. (6) Finally, a potential function representing intermolecular forces is introduced, and structural relaxation is performed using molecular dynamics to calculate the shape change due to volumetric shrinkage associated with polymerization. The Lenard-Jones potential is used as the intermolecular potential function in this shape change calculation. Furthermore, the volumetric shrinkage due to polymerization is reproduced by introducing an equilibrium interparticle distance corresponding to the number of polymerizations. However, Non-Patent Document 1 does not take into account the individual molecular structure or reactivity; instead, the molecules are spherical and the reactivity is given stochastically. Furthermore, there is no disclosure about CD control in Non-Patent Document 1. Furthermore, although unreacted polymerizable compounds always remain in a polymerization reaction, Non-Patent Document 1 makes no mention of removing the polymerizable compounds.

[0006] In photoradical polymerization reactions, the reaction rate is proportional to the square root of the light illuminance. Patent Document 1 describes a technique for adjusting exposure conditions using this mechanism. In this technique, if the degree of polymerization of the polymerizable compound is not within a predetermined range for the target degree of polymerization, the light irradiation time is adjusted based on the square root of the light illuminance. However, Patent Document 1 also does not disclose anything about CD control or removal of unpolymerized polymerizable compound. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Computational Study on Polymer Filling Process in Nanoimprint Lithography“ Microelectron. Eng.88, 2188 (2011) [Non-patent document 2] BH Besler, KM Merz Jr., and PA Kollman, J. Comp. Chem. 11, 431 (1990) [Non-patent document 3] UC Singh and PA Kollman, J. Comp. Chem. 5, 129 (1984) [Patent documents]

[0008] [Patent Document 1] Patent Publication No. 2019-68085, Canon Inc. Akiko Iimura, Toshiki Ito Summary of the Invention [Problem to be solved by the invention]

[0009] The processing speed during post-processing, such as dry etching, varies to a certain extent within a substrate. This variation in processing speed results in variations in the CD (critical dimension) of the processed layer. Therefore, to ensure uniformity of the CD of the processed layer across the entire substrate after post-processing, it is necessary to vary the CD of the resist before post-processing (after the lithography process) according to the post-processing speed distribution. In the case of NIL, the shape of the liquid film of the resist filled into the mold pattern before exposure faithfully reproduces the line width of the mold pattern, making it impossible to change the line width of the mold pattern for each field. Therefore, the inventors considered some way to control the line width of the hardened resist pattern after exposure.

[0010] The present invention provides an advantageous technique for controlling the line width of a pattern in imprint technology. [Means for solving the problem]

[0011] One aspect of the present invention relates to a pattern formation method, which includes: a contacting step of contacting a mold with a curable composition containing a polymerizable compound that is arranged on a field of a substrate; a curing step of irradiating light onto the curable composition arranged on the field to form a cured film that includes a pattern made of a cured product of the curable composition; and a separation step of separating the cured film from the mold, wherein the field includes a plurality of regions, and in the curing step, the curable composition is irradiated with light according to an illuminance and an irradiation time that are determined according to a target line width of the pattern for each of the plurality of regions. [Effects of the Invention]

[0012] According to the present invention, a technique that is advantageous for controlling the line width of a pattern in imprint technology is provided. [Brief explanation of the drawings]

[0013] [Figure 1] 1A to 1C are schematic cross-sectional views illustrating a pattern forming method according to an embodiment. [Figure 2]Coarse-grained diagram of a molecular assembly of a polymerizable compound. [Figure 3] 1 is a graph showing the dependence of saturated conversion on relative illuminance. [Figure 4] Graph showing the time change of conversion rate corresponding to each relative illuminance. [Figure 5] FIG. 2 is an explanatory diagram of cure shrinkage associated with polymerization. [Figure 6] FIG. 2 is an explanatory diagram of removal shrinkage due to removal of unpolymerized monomers. [Figure 7] A diagram showing the CD shrinkage due to curing shrinkage and removal shrinkage. [Figure 8] 1 is a graph showing the dependence of saturated conversion on relative illuminance. [Figure 9] Graph showing the dependence of CD on relative illuminance. [Figure 10] Graph showing the relationship between time dependence of conversion rate and curing failure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted. [Curable composition] The curable composition (A) according to this embodiment is a composition containing at least a polymerizable compound (component (a)). The curable composition according to this embodiment may further contain a photopolymerization initiator (component (b)), a non-polymerizable compound (c), and a solvent (component (d)).

[0015] In this specification, the term "cured film" refers to a film obtained by polymerizing and curing a curable composition on a substrate. The shape of the cured film is not particularly limited, and the surface may have a patterned shape.

[0016] <Component (a): Polymerizable compound> Component (a) is a polymerizable compound. In this specification, the polymerizable compound refers to a compound that reacts with a polymerization factor (radical, etc.) generated from a photopolymerization initiator (component (b)) to form a film made of a polymer compound through a chain reaction (polymerization reaction).

[0017] Examples of such polymerizable compounds include radically polymerizable compounds. The polymerizable compound as component (a) may be composed of only one type of polymerizable compound, or may be composed of multiple types of polymerizable compounds.

[0018] The radical polymerizable compound is preferably a compound having one or more acryloyl groups or methacryloyl groups, i.e., a (meth)acrylic compound. Therefore, the curable composition according to this embodiment preferably contains a (meth)acrylic compound as component (a), more preferably the main component of component (a) is a (meth)acrylic compound, and most preferably a (meth)acrylic compound. Note that, as described herein, the main component of component (a) is a (meth)acrylic compound means that 90 mass % or more of component (a) is a (meth)acrylic compound.

[0019] When the radical polymerizable compound is composed of multiple types of compounds each having one or more acryloyl or methacryloyl groups, it preferably contains a monofunctional (meth)acrylic monomer and a polyfunctional (meth)acrylic monomer, because the combination of the monofunctional (meth)acrylic monomer and the polyfunctional (meth)acrylic monomer provides a cured film with high mechanical strength.

[0020] Examples of monofunctional (meth)acrylic compounds having one acryloyl group or one methacryloyl group include phenoxyethyl (meth)acrylate, phenoxy-2-methylethyl (meth)acrylate, phenoxyethoxyethyl (meth)acrylate, 3-phenoxy-2-hydroxypropyl (meth)acrylate, 2-phenylphenoxyethyl (meth)acrylate, 4-phenylphenoxyethyl (meth)acrylate, 3-(2-phenylphenyl)-2-hydroxypropyl (meth)acrylate, (meth)acrylate of EO-modified p-cumylphenol, 2-bromophenoxyethyl (meth)acrylate, 2,4-dibromophenoxyethyl (meth)acrylate, 2,4,6-Tribromophenoxyethyl (meth)acrylate, EO-modified phenoxy (meth)acrylate, PO-modified phenoxy (meth)acrylate, polyoxyethylene nonylphenyl ether (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, 2-ethyl-2-adamantyl (meth)acrylate, bornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate t)acrylate, cyclohexyl (meth)acrylate, 4-butylcyclohexyl (meth)acrylate, acryloylmorpholine, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, amyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pliers (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, benzyl (meth)acrylate, Tetrahydrofurfuryl (meth)acrylate, butoxyethyl (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, methoxyethylene glycol (meth)acrylate, ethoxyethyl (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypolypropylene glycol (meth)acrylate, diacetone (meth)acrylamide, isobutoxymethyl (meth)acrylamide, N,Examples of the acrylate include, but are not limited to, N-dimethyl(meth)acrylamide, t-octyl(meth)acrylamide, dimethylaminoethyl(meth)acrylate, diethylaminoethyl(meth)acrylate, 7-amino-3,7-dimethyloctyl(meth)acrylate, N,N-diethyl(meth)acrylamide, and N,N-dimethylaminopropyl(meth)acrylamide.

[0021] Commercially available products of the monofunctional (meth)acrylic compound include Aronix (registered trademark) M101, M102, M110, M111, M113, M117, M5700, TO-1317, M120, M150, and M156 (all manufactured by Toagosei), MEDOL10, MIBDOL10, CHDOL10, MMDOL30, MEDOL30, MIBDOL30, CHDOL30, LA, IBXA, 2-MTA, HPA, and VISCO. #150, #155, #158, #190, #192, #193, #220, #2000, #2100, #2150 (all manufactured by Osaka Organic Chemical Industry Co., Ltd.), light acrylate BO-A, EC-A, DMP-A, THF-A, HOP-A, HOA-MPE, HOA-MPL, PO-A, P-200A, NP-4EA, NP-8EA, epoxy ester M-600A (all manufactured by Kyoeisha Chemical Industry Co., Ltd.), KAYARAD (registered trademark) Examples of suitable esters include, but are not limited to, TC110S, R-564, and R-128H (all manufactured by Nippon Kayaku), NK Ester AMP-10G and AMP-20G (all manufactured by Shin-Nakamura Chemical Co., Ltd.), FA-511A, 512A, and 513A (all manufactured by Hitachi Chemical), PHE, CEA, PHE-2, PHE-4, BR-31, BR-31M, and BR-32 (all manufactured by Dai-ichi Kogyo Seiyaku), VP (manufactured by BASF), ACMO, DMAA, and DMAPAA (all manufactured by Kohjin).

[0022] Furthermore, examples of polyfunctional (meth)acrylic compounds having two or more acryloyl groups or methacryloyl groups include trimethylolpropane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, EO-modified trimethylolpropane tri(meth)acrylate, PO-modified trimethylolpropane tri(meth)acrylate, EO,PO-modified trimethylolpropane tri(meth)acrylate, dimethyloltricyclodecane di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexane Examples of the diol di(meth)acrylate include, but are not limited to, diol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate, 1,3-adamantanedimethanol di(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, tris(acryloyloxy)isocyanurate, bis(hydroxymethyl)tricyclodecane di(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, EO-modified 2,2-bis(4-((meth)acryloxy)phenyl)propane, PO-modified 2,2-bis(4-((meth)acryloxy)phenyl)propane, and EO,PO-modified 2,2-bis(4-((meth)acryloxy)phenyl)propane.

[0023] Commercially available products of the polyfunctional (meth)acrylic compound include Iupimer (registered trademark) UV SA1002 and SA2007 (all manufactured by Mitsubishi Chemical), Viscoat #195, #230, #215, #260, #335HP, #295, #300, #360, #700, GPT, and 3PA (all manufactured by Osaka Organic Chemical Industry Co., Ltd.), Light Acrylate 4EG-A, 9EG-A, NP-A, DCP-A, BP-4EA, BP-4PA, TMP-A, PE-3A, PE-4A, and DPE-6A (all manufactured by Kyoeisha Chemical), and KAYARAD (registered trademark). Examples of such an adhesive include, but are not limited to, PET-30, TMPTA, R-604, DPHA, DPCA-20, -30, -60, -120, HX-620, D-310, and D-330 (all manufactured by Nippon Kayaku Co., Ltd.), Aronix (registered trademark) M208, M210, M215, M220, M240, M305, M309, M310, M315, M325, and M400 (all manufactured by Toagosei Co., Ltd.), and Lipoxy (registered trademark) VR-77, VR-60, and VR-90 (all manufactured by Showa Polymer Co., Ltd.).

[0024] In the above-mentioned compound group, (meth)acrylate means an acrylate or a methacrylate having an alcohol residue equivalent thereto. A (meth)acryloyl group means an acryloyl group or a methacryloyl group having an alcohol residue equivalent thereto. EO stands for ethylene oxide, and EO-modified compound A refers to a compound in which the (meth)acrylic acid residue and alcohol residue of compound A are bonded via an ethylene oxide group block structure. PO stands for propylene oxide, and PO-modified compound B refers to a compound in which the (meth)acrylic acid residue and alcohol residue of compound B are bonded via a propylene oxide group block structure.

[0025] <Component (b): Photopolymerization initiator> Component (b) is a photopolymerization initiator. In this specification, a photopolymerization initiator is a compound that senses light of a predetermined wavelength and generates the above-mentioned polymerization factor (radical). Specifically, a photopolymerization initiator is a polymerization initiator (radical generator) that generates radicals when exposed to light (radiation such as infrared rays, visible light, ultraviolet rays, far ultraviolet rays, charged particle rays such as X-rays and electron beams). Component (b) may be composed of one type of photopolymerization initiator or multiple types of photopolymerization initiators.

[0026] Examples of the radical generator include 2,4,5-triarylimidazole dimers which may have a substituent, such as 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-di(methoxyphenyl)imidazole dimer, 2-(o-fluorophenyl)-4,5-diphenylimidazole dimer, and 2-(o- or p-methoxyphenyl)-4,5-diphenylimidazole dimer; benzophenone, N,N'-tetramethyl-4,4'-diaminobenzophenone (Michler's ketone), Benzophenone derivatives such as N,N'-tetraethyl-4,4'-diaminobenzophenone, 4-methoxy-4'-dimethylaminobenzophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, and 4,4'-diaminobenzophenone; α-amino aromatic ketone derivatives such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-propan-1-one; 2-ethylanthraquinone, phenanthrenone, and the like. quinones such as anthraquinone, 2-t-butylanthraquinone, octamethylanthraquinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 2-phenylanthraquinone, 2,3-diphenylanthraquinone, 1-chloroanthraquinone, 2-methylanthraquinone, 1,4-naphthoquinone, 9,10-phenanthraraquinone, 2-methyl-1,4-naphthoquinone, and 2,3-dimethylanthraquinone; benzoin ethers such as benzoin methyl ether, benzoin ethyl ether, and benzoin phenyl ether; Derivatives: benzoin derivatives such as benzoin, methylbenzoin, ethylbenzoin, and propylbenzoin; benzil derivatives such as benzil dimethyl ketal; acridine derivatives such as 9-phenylacridine and 1,7-bis(9,9'-acridinyl)heptane; N-phenylglycine derivatives such as N-phenylglycine; acetophenone derivatives such as acetophenone, 3-methylacetophenone, acetophenone benzil ketal, 1-hydroxycyclohexyl phenyl ketone, and 2,2-dimethoxy-2-phenylacetophenone;Thioxanthone, diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, and other thioxanthone derivatives; acylphosphine oxide derivatives such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, and bis-(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide; 1,2-octanedione, 1-[4-(phenylthio)-, 2-(O- Oxime ester derivatives such as benzoyl oxime), ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetyl oxime); xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, etc., but are not limited to these.

[0027] Commercially available products of the radical generator include Irgacure 184, 369, 651, 500, 819, 907, 784, 2959, CGI-1700, -1750, -1850, CG24-61, Darocur 1116, 1173, Lucirin (registered trademark) TPO, LR8893, LR8970 (all manufactured by BASF), and Ubecryl P36 (manufactured by UCB), but are not limited to these.

[0028] Among these, component (b) is preferably an acylphosphine oxide polymerization initiator. Among the above examples, the acylphosphine oxide polymerization initiator is an acylphosphine oxide compound such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, or bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide.

[0029] The blending ratio of component (b) in the curable composition (A) is preferably 0.1 to 50% by mass, more preferably 0.1 to 20% by mass, and even more preferably 1 to 20% by mass, based on the total mass of components (a), (b), and (c) described below, i.e., the total mass of all components excluding solvent component (d). By blending component (b) in a ratio of 0.1% by mass or more, the curing rate of the composition can be increased and the reaction efficiency can be improved, and by blending it in a ratio of 50% by mass or less, the resulting cured film can have a certain degree of mechanical strength.

[0030] <Component (c): Non-polymerizable compound> In addition to the aforementioned components (a) and (b), the curable composition (A) according to this embodiment may further contain a non-polymerizable compound as component (c) depending on various purposes, as long as the effects of this embodiment are not impaired. Examples of such component (c) include compounds that do not have a polymerizable functional group such as a (meth)acryloyl group and that do not have the ability to sense light of a specific wavelength and generate the polymerization factor (radical). Examples of such compounds include sensitizers, hydrogen donors, internal mold release agents, antioxidants, polymer components, and other additives. Component (c) may contain multiple types of the above compounds.

[0031] The sensitizer is a compound that is added as needed for the purpose of accelerating the polymerization reaction and improving the reaction conversion rate. One type of sensitizer may be used alone, or two or more types may be used in combination.

[0032] Examples of sensitizers include sensitizing dyes. Sensitizing dyes are compounds that are excited by absorbing light of a specific wavelength and interact with the photopolymerization initiator (b). The interaction described here refers to energy transfer, electron transfer, or the like from the excited sensitizing dye to the photopolymerization initiator (b). Specific examples of sensitizing dyes include, but are not limited to, anthracene derivatives, anthraquinone derivatives, pyrene derivatives, perylene derivatives, carbazole derivatives, benzophenone derivatives, thioxanthone derivatives, xanthone derivatives, coumarin derivatives, phenothiazine derivatives, camphorquinone derivatives, acridine dyes, thiopyrylium salt dyes, merocyanine dyes, quinoline dyes, styrylquinoline dyes, ketocoumarin dyes, thioxanthene dyes, xanthene dyes, oxonol dyes, cyanine dyes, rhodamine dyes, and pyrylium salt dyes.

[0033] A hydrogen donor is a compound that reacts with the initiating radical generated from the photopolymerization initiator (component (b)) or the radical at the polymer growth terminal to generate a radical with higher reactivity. It is preferably added when the photopolymerization initiator (component (b)) is a photoradical generator.

[0034] Specific examples of such hydrogen donors include, but are not limited to, amine compounds such as n-butylamine, di-n-butylamine, tri-n-butylphosphine, allylthiourea, s-benzylisothiuronium-p-toluenesulfinate, triethylamine, diethylaminoethyl methacrylate, triethylenetetramine, 4,4'-bis(dialkylamino)benzophenone, N,N-dimethylaminobenzoic acid ethyl ester, N,N-dimethylaminobenzoic acid isoamyl ester, pentyl-4-dimethylaminobenzoate, triethanolamine, and N-phenylglycine, and mercapto compounds such as 2-mercapto-N-phenylbenzimidazole and mercaptopropionic acid ester. The hydrogen donors may be used singly or in combination. The hydrogen donors may also function as sensitizers.

[0035] An internal mold release agent can be added to the curable composition to reduce the interfacial bonding strength between the mold and the curable composition, i.e., to reduce the demolding force in the demolding step described below. In this specification, "internal mold release agent" means that the agent is added to the curable composition before the step of placing the curable composition. Examples of internal mold release agents that can be used include surfactants such as silicone surfactants, fluorine-based surfactants, and hydrocarbon surfactants. However, in this embodiment, as described below, there is a limit to the amount of fluorine-based surfactants that can be added. In this embodiment, the internal mold release agent is not polymerizable. One type of internal mold release agent may be used alone, or two or more types may be mixed together.

[0036] Examples of fluorosurfactants include polyalkylene oxide (polyethylene oxide, polypropylene oxide, etc.) adducts of alcohols having perfluoroalkyl groups, and polyalkylene oxide (polyethylene oxide, polypropylene oxide, etc.) adducts of perfluoropolyethers. Note that the fluorosurfactants may have a hydroxyl group, an alkoxy group, an alkyl group, an amino group, a thiol group, etc. in part of their molecular structure (for example, a terminal group). For example, pentadecaethylene glycol mono 1H,1H,2H,2H-perfluorooctyl ether can be mentioned.

[0037] Commercially available fluorine-based surfactants may be used. Examples of commercially available products include Megafac (registered trademark) F-444, TF-2066, TF-2067, TF-2068, and DEO-15 (all manufactured by DIC), Fluorad FC-430 and FC-431 (all manufactured by Sumitomo 3M), Surflon (registered trademark) S-382 (manufactured by AGC), EFTOP EF-122A, 122B, 122C, EF-121, EF-126, EF-127, and MF-100 (all manufactured by Tochem Products), and PF-636, PF-6320, PF-656, and PF-6520 (all manufactured by OMNOVA). Solutions), Unidyne (registered trademark) DS-401, DS-403, DS-451 (all manufactured by Daikin Industries), Ftergent (registered trademark) 250, 251, 222F, 208G (all manufactured by Neos).

[0038] The internal release agent may also be a hydrocarbon surfactant, which includes alkyl alcohol polyalkylene oxide adducts in which alkylene oxides having 2 to 4 carbon atoms are added to alkyl alcohols having 1 to 50 carbon atoms, and polyalkylene oxides.

[0039] Examples of alkyl alcohol polyalkylene oxide adducts include methyl alcohol ethylene oxide adducts, decyl alcohol ethylene oxide adducts, lauryl alcohol ethylene oxide adducts, cetyl alcohol ethylene oxide adducts, stearyl alcohol ethylene oxide adducts, and stearyl alcohol ethylene oxide / propylene oxide adducts. The terminal group of the alkyl alcohol polyalkylene oxide adduct is not limited to a hydroxyl group that can be produced simply by adding a polyalkylene oxide to an alkyl alcohol. The hydroxyl group may be substituted with other substituents, such as polar functional groups such as carboxyl groups, amino groups, pyridyl groups, thiol groups, and silanol groups, or hydrophobic functional groups such as alkyl groups and alkoxy groups.

[0040] Examples of polyalkylene oxides include polyethylene glycol, polypropylene glycol, their mono- or dimethyl ethers, mono- or dioctyl ethers, mono- or dinonyl ethers, mono- or didecyl ethers, monoadipate esters, monooleate esters, monostearate esters, and monosuccinate esters.

[0041] Commercially available alkyl alcohol polyalkylene oxide adducts may be used. Examples of commercially available alkyl alcohol polyalkylene oxide adducts include polyoxyethylene methyl ether (methyl alcohol ethylene oxide adduct) (BLAUNON MP-400, MP-550, MP-1000) manufactured by Aoki Oil & Fat Industries Co., Ltd., polyoxyethylene decyl ether (decyl alcohol ethylene oxide adduct) (FINESURF D-1303, D-1305, D-1307, D-1310) manufactured by Aoki Oil & Fat Industries Co., Ltd., polyoxyethylene lauryl ether (lauryl alcohol ethylene oxide adduct) (BLAUNON EL-1505) manufactured by Aoki Oil & Fat Industries Co., Ltd., polyoxyethylene cetyl ether (cetyl alcohol ethylene oxide adduct) (BLAUNON CH-305, CH-310) manufactured by Aoki Oil & Fat Industries Co., Ltd., and polyoxyethylene stearyl ether (stearyl alcohol ethylene oxide adduct) (BLAUNON Examples of suitable polyoxyethylene alkyl ethers include those manufactured by Aoki Oil Industries Co., Ltd. (SR-705, SR-707, SR-715, SR-720, SR-730, SR-750), randomly polymerized polyoxyethylene polyoxypropylene stearyl ethers (BLAUNON SA-50 / 50 1000R, SA-30 / 70 2000R), polyoxyethylene methyl ethers (Pluriol® A760E) manufactured by BASF, and polyoxyethylene alkyl ethers (Emulgen series) manufactured by Kao. Commercially available polyalkylene oxides may also be used, such as ethylene oxide-propylene oxide copolymers (Pluronic PE6400) manufactured by BASF.

[0042] Fluorine-based surfactants exhibit an excellent effect of reducing mold release force, making them effective as internal mold release agents. The blending ratio of component (c) excluding the fluorine-based surfactant in the curable composition is preferably 0% by mass or more and 50% by mass or less, based on the total mass of components (a), (b), and (c), i.e., the total mass of all components excluding the solvent. It is more preferably 0.1% by mass or more and 50% by mass or less, and even more preferably 0.1% by mass or more and 20% by mass or less. By setting the blending ratio of component (c) excluding the fluorine-based surfactant to 50% by mass or less, the resulting cured film can have a certain degree of mechanical strength.

[0043] <Component (d): Solvent> The curable composition according to this embodiment may contain a solvent as component (d). Component (d) is not particularly limited as long as it is a solvent that dissolves components (a), (b), and (c). Preferred solvents are those with a boiling point of 80°C or higher and 200°C or lower at normal pressure. More preferred are solvents having at least one of an ester structure, a ketone structure, a hydroxyl group, and an ether structure. Specifically, the solvent may be a single solvent selected from propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, cyclohexanone, 2-heptanone, γ-butyrolactone, and ethyl lactate, or a mixture thereof.

[0044] When spin coating is used as a method for applying the curable composition (A) onto a substrate, the curable composition (A) preferably contains the component (d).

[0045] <Temperature when compounding the curable composition> When preparing the curable composition (A) of this embodiment, at least the components (a) and (b) are mixed and dissolved under predetermined temperature conditions. Specifically, this is carried out in the range of 0° C. to 100° C. The same applies when the components (c) and (d) are also contained.

[0046] <Viscosity of Curable Composition> The curable composition (A) according to the present embodiment is preferably a liquid, because the curable composition (A) can be quickly spread and filled in the mold contact step described below, i.e., the filling time is short.

[0047] When spin coating is used as the application method, the viscosity at 25°C of the mixture of components excluding the solvent (component (d)) of the curable composition (A) according to this embodiment is preferably from 1 mPa·s to 1,000 mPa·s, more preferably from 1 mPa·s to 500 mPa·s, and even more preferably from 1 mPa·s to 100 mPa·s.

[0048] When the inkjet method is used as the coating method, the viscosity is preferably from 1 mPa·s to 100 mPa·s, more preferably from 1 mPa·s to 50 mPa·s, and even more preferably from 1 mPa·s to 12 mPa·s.

[0049] By setting the viscosity of the curable composition (A) to 1000 mPa·s or less, spreading and filling are completed quickly when the curable composition (A) is brought into contact with the mold. In other words, by using the curable composition according to this embodiment, the photo-nanoimprinting method can be performed with high throughput. Furthermore, pattern defects due to insufficient filling are less likely to occur. Furthermore, by setting the viscosity to 1 mPa·s or more, coating unevenness is less likely to occur when the curable composition (A) is applied to a substrate. Furthermore, when the curable composition (A) is brought into contact with the mold, the curable composition (A) is less likely to flow out from the edge of the mold.

[0050] <Surface tension of curable composition> The surface tension of the curable composition (A) according to this embodiment, excluding the solvent (component (d)), at 23°C is preferably 5 mN / m or more and 70 mN / m or less. It is more preferably 7 mN / m or more and 50 mN / m or less, and even more preferably 10 mN / m or more and 40 mN / m or less. The higher the surface tension, for example, 5 mN / m or more, the stronger the capillary force, and therefore, when the curable composition (A) is brought into contact with a mold, the filling (spreading and filling) is completed in a short time. Furthermore, by setting the surface tension to 70 mN / m or less, the cured film obtained by curing the curable composition has a smooth surface.

[0051] <Contact angle of curable composition> The contact angle of the curable composition (A) according to this embodiment, for the composition of components excluding the solvent (component (d)), is preferably 0° or more and 90° or less with respect to both the substrate surface and the mold surface, and particularly preferably 0° or more and 10° or less. If the contact angle is greater than 90°, capillary force acts in the negative direction (a direction that shrinks the contact interface between the mold and the curable composition) inside the mold pattern or in the gap between the substrate and the mold, and filling may not occur. The lower the contact angle, the stronger the capillary force, and the faster the filling speed.

[0052] <Impurities contained in the curable composition> The curable composition (A) according to this embodiment preferably contains as few impurities as possible. The impurities described here refer to components other than the aforementioned components (a), (b), (c), and (d). Therefore, the curable composition according to this embodiment is preferably obtained through a purification process. Such a purification process is preferably filtration using a filter.

[0053] When filtering using a filter, specifically, it is preferable to mix the aforementioned components (a), (b), and (c) and then filter the mixture using a filter with a pore size of 0.001 μm or more and 5.0 μm or less. When filtering using a filter, it is more preferable to perform the filtering in multiple stages or repeatedly multiple times. The filtered liquid may also be filtered again. Filtration may also be performed using multiple filters with different pore sizes. Filters used for filtration may be made of polyethylene resin, polypropylene resin, fluororesin, nylon resin, etc., but are not particularly limited. By undergoing such a purification process, impurities such as particles mixed in the curable composition can be removed. This prevents impurities such as particles from accidentally causing unevenness in the cured film obtained after curing the curable composition, resulting in pattern defects.

[0054] When the curable composition according to this embodiment is used to manufacture a semiconductor integrated circuit, it is preferable to avoid the inclusion of impurities containing metal atoms (metal impurities) in the curable composition as much as possible so as not to impair the operation of the product. In such cases, the concentration of metal impurities contained in the curable composition is preferably 10 ppm or less, and more preferably 100 ppb or less.

[0055] [Substrate (base material)] In this specification, a member on which an underlayer is disposed is referred to as a substrate or base material. A structure including a member on which an underlayer is disposed and the underlayer disposed on the object may also be referred to as a substrate, and in this case, to avoid confusion, the member on which the underlayer is disposed may be understood as a base material.

[0056] The substrate as the base material on which the underlayer is to be disposed is a workpiece substrate, and is typically a silicon wafer. The substrate as the base material may have a workpiece layer on its surface. The substrate may also have another layer formed below the workpiece layer. Furthermore, if a quartz substrate is used as the substrate, a replica (mold replica) of a quartz imprint mold can be produced. However, the substrate is not limited to a silicon wafer or a quartz substrate. The substrate can also be selected from among substrates known as substrates for semiconductor devices, such as aluminum, titanium-tungsten alloy, aluminum-silicon alloy, aluminum-copper-silicon alloy, silicon oxide, and silicon nitride. The surface of the substrate or workpiece layer used may be subjected to surface treatment such as silane coupling treatment, silazane treatment, or formation of an organic thin film to improve adhesion to the curable composition (A).

[0057] [Base layer] The underlayer can be a layer that is easily processed and has resistance to the etching process used to process the substrate (base material) or other layers that underlie the underlayer. The underlayer can be formed on the outermost surface of the substrate on which the nanoimprinting process is performed, and carbon materials such as SOC (spin-on carbon), diamond-like carbon, and graphite can be used as the underlayer material. SOC, which is primarily composed of carbon, can be used as a highly etch-resistant material. Similarly, SOC can be used as a highly etch-resistant material in pattern formation by nanoimprinting. In this embodiment, it is preferable to perform the nanoimprinting process on an SOC layer.

[0058] [Pattern formation method] Next, a pattern formation method according to one embodiment will be described with reference to the schematic cross-sectional view of FIG. 1. According to the pattern formation method of this embodiment, a cured film having a pattern made of a cured product of a curable composition containing a polymerizable compound is formed. The cured film preferably has a pattern of, for example, 1 nm to 10 mm in size, and more preferably 10 nm to 100 μm in size. Generally, a pattern formation technique that uses light to create a film having a nano-sized (1 nm to 100 nm) pattern (relief structure) is called a photo-nanoimprinting method. The pattern formation method according to one embodiment relates to a photo-nanoimprinting method. The pattern formation method according to one embodiment may include, for example, a contacting step of contacting a mold with a curable composition containing a polymerizable compound disposed on a substrate (or a field of the substrate), a curing step of irradiating the curable composition disposed on the substrate (or a field) with light to form a cured film having a pattern made of a cured product of the curable composition, and a separation step of separating the cured film from the mold. In one embodiment, the pattern formation method may include a disposing step of disposing a curable composition on a substrate (or a field of a substrate) before the contacting step. In one embodiment, the pattern formation method may include a forming step of forming a substrate by forming an underlayer on a substrate before the disposing step. In one embodiment, the pattern formation method may include a removing step of removing unpolymerized component (a) after the separating step. The contacting step is performed after the disposing step, the curing step is performed after the contacting step, the separating step is performed after the curing step, and the removing step is performed after the separating step. In this specification, a repeating unit of steps consisting of the contacting step to the separating step or the disposing step to the separating step is referred to as a shot, and an area on a substrate processed in one shot is referred to as a field.

[0059] <Formation process [1]> In the formation step, as shown schematically in [1] of FIG. 1, an underlayer 102 is formed on the surface of a substrate (base material) 101 (or on the surface of the layer to be processed if the substrate 101 has a layer to be processed). Here, a structure including the substrate (base material) 101 and the underlayer 102 disposed on the substrate 101 can also be referred to as a substrate. The underlayer 102 can be formed, for example, by depositing or applying a material for the underlayer 102 on the substrate 101 and then baking the substrate 101 to which the material has been applied. Examples of methods for forming the underlayer 102 include inkjet printing, dip coating, air knife coating, curtain coating, wire bar coating, gravure coating, extrusion coating, spin coating, and slit scanning. Among these methods, spin coating is particularly preferred. When forming the underlayer 102 using spin coating, a baking step may be performed as necessary to volatilize the solvent component. The baking conditions may be, for example, about 200°C to about 350°C for about 30 seconds to about 90 seconds. The baking conditions are adjusted appropriately depending on the type of composition used. The average film thickness of the underlayer 102 may be determined depending on the application, but is, for example, 0.1 nm to 10,000 nm, preferably 1 nm to 350 nm, and particularly preferably 1 nm to 250 nm.

[0060] <Placement process [2]> In the disposing step, as shown schematically in [2] of FIG. 1, a curable composition may be disposed on an underlayer 102 on a substrate (base material) 101. In the disposing step, as shown schematically in [2] of FIG. 1, droplets of a curable composition (A) 103 may be disposed. Examples of disposing methods that can be used include inkjet coating, dip coating, air knife coating, curtain coating, wire bar coating, gravure coating, extrusion coating, spin coating, and slit scanning. Among these methods, spin coating and inkjet coating are particularly preferred. The droplets of the curable composition (A) 103 are preferably disposed densely on regions of the substrate 101 facing regions where the recesses constituting the pattern of the mold 104 are densely present, and sparsely on regions of the substrate 101 facing regions where the recesses are sparsely present. This allows the residual film 107 (described later) to be controlled to a uniform thickness regardless of the density of the pattern of the mold 104.

[0061] <Contact process [3]> In the contacting step, as shown schematically in [3] of FIG. 1, the curable composition is brought into contact with a mold 104. The contacting step includes a step of changing the state in which the curable composition and the mold 104 are not in contact with each other to a state in which they are in contact with each other, and a step of maintaining the state in which they are in contact with each other. In one example, the mold 104 having the pattern to be transferred can be brought into contact with the curable composition (A). This causes the curable composition (A) to fill the recesses of the fine pattern on the surface of the mold 104, and the liquid becomes a liquid film that fills the fine pattern of the mold.

[0062] When the subsequent curing step includes a light irradiation step, a mold made of a light-transmitting material can be used as the mold 104 in consideration of this. Specific examples of materials for the mold 104 include glass, quartz, light-transmitting resins such as PMMA and polycarbonate resin, transparent metal vapor deposition films, flexible films such as polydimethylsiloxane, light-cured films, metal films, and the like. However, when a light-transmitting resin is used as the material for the mold 104, a resin that is insoluble in the components contained in the curable composition can be selected. Quartz is particularly preferred as the material for the mold 104 because it has a small thermal expansion coefficient and results in little pattern distortion.

[0063] The fine pattern on the surface of the mold 104 may have a height of, for example, 4 nm or more and 200 nm or less. The lower the pattern height, the lower the force required to peel the mold 104 from the cured film of the curable composition in the separation step, i.e., the demolding force, and the fewer demolding defects remaining on the mold 104 when the curable composition pattern is torn off during the separation step. The impact of peeling the mold can cause elastic deformation of the curable composition pattern, which can lead to contact between adjacent pattern elements, resulting in adhesion or breakage. However, to avoid these problems, it is advantageous for the height of the pattern elements to be approximately twice or less the width of the pattern elements (aspect ratio of 2 or less). On the other hand, if the height of the pattern elements is too low, the processing accuracy of the substrate 101 can be reduced.

[0064] The mold 104 may be surface-treated before the contact step to improve the releasability of the surface of the mold 104 from the curable composition (A). Examples of surface treatment methods include applying a release agent to the surface of the mold 104 to form a release agent layer. Examples of release agents that can be applied to the surface of the mold 104 include silicone-based release agents, fluorine-based release agents, hydrocarbon-based release agents, polyethylene-based release agents, polypropylene-based release agents, paraffin-based release agents, montan-based release agents, and carnauba-based release agents. For example, commercially available coating-type release agents such as Optool (registered trademark) DSX manufactured by Daikin Industries, Ltd. can also be suitably used. The release agents may be used alone or in combination of two or more. Among these, fluorine-based and hydrocarbon-based release agents are particularly preferred.

[0065] In the contacting step, when the mold 104 is brought into contact with the curable composition (A), the pressure applied to the curable composition (A) is not particularly limited. The pressure may be, for example, from 0 MPa to 100 MPa. The pressure is preferably from 0 MPa to 50 MPa, more preferably from 0 MPa to 30 MPa, and even more preferably from 0 MPa to 20 MPa.

[0066] The contacting step can be carried out under any of the conditions of air, reduced pressure, and inert gas atmosphere, but a reduced pressure or inert gas atmosphere is preferred because it can prevent the influence of oxygen and moisture on the curing reaction. Specific examples of the inert gas used when the contacting step is carried out under an inert gas atmosphere include nitrogen, carbon dioxide, helium, argon, various chlorofluorocarbon gases, and mixtures of these. When the contacting step is carried out under a specific gas atmosphere, including air, the preferred pressure is 0.0001 atmospheres or more and 10 atmospheres or less.

[0067] <Curing process [4]> In the curing step, as shown in [4] of FIG. 1, the curable composition is irradiated with light as curing energy to cure the curable composition, thereby forming a cured film having a pattern made of a cured product of the curable composition. In the curing step, for example, light may be irradiated through a mold 104 onto a layer formed by disposing the curable composition (A). More specifically, light may be irradiated through the mold 104 onto the curable composition (A) filled into the fine pattern of the mold 104. As a result, the curable composition (A) filled into the fine pattern of the mold 104 is cured to form a cured film 106 having a pattern.

[0068] The light 105 to be irradiated can be selected depending on the wavelength to which the curable composition (A) is sensitive. Specifically, the light 105 can be appropriately selected from ultraviolet light having a wavelength of 150 nm or more and 400 nm or less, X-rays, electron beams, etc. Among these, ultraviolet light is particularly preferred. This is because many commercially available curing aids (photopolymerization initiators) are compounds sensitive to ultraviolet light. Examples of light sources that emit ultraviolet light include high-pressure mercury lamps, ultra-high-pressure mercury lamps, low-pressure mercury lamps, deep-UV lamps, carbon arc lamps, chemical lamps, metal halide lamps, xenon lamps, KrF excimer lasers, ArF excimer lasers, and F2 excimer lasers, with ultra-high-pressure mercury lamps being particularly preferred. The number of light sources used may be one or more. The light irradiation may be performed on the entire area of ​​the curable composition (A) filled into the fine pattern of the mold, or may be limited to only a partial area.

[0069] In the curing process, the illuminance and irradiation time of the light for curing the curable composition are adjusted for each of multiple regions in each field of the substrate, thereby adjusting the CD distribution (pattern line width distribution) within each field. Alternatively, in the curing process, the illuminance and irradiation time of the light for curing the curable composition are adjusted for each of multiple fields (shot areas) of the substrate, thereby adjusting the CD distribution (pattern line width distribution) within the substrate. Alternatively, in the curing process, the illuminance and irradiation time of the light for curing the curable composition can be adjusted according to the CD distribution (target line width distribution) of the cured film on the substrate.

[0070] The illuminance and exposure time within a field can be adjusted or controlled using a light modulation element such as a digital mirror device (DMD). Each of the multiple regions that make up each field can correspond to, for example, one mirror or a predetermined number of mirrors in the DMD. <Separation Process [5]> In the separation step, as shown schematically in [5] of FIG. 1, the patterned cured film 106 and the mold 104 are separated. By separating the patterned cured film 106 and the mold 104, a free-standing cured film 106 having a pattern that is an inverse of the fine pattern of the mold 104 is obtained. Here, the cured film remains in the recesses of the patterned cured film 106. This film may be called a residual film 107.

[0071] The method for separating the patterned cured film 106 and the mold 104 is not particularly limited, and various conditions may be used as long as no part of the patterned cured film 106 is physically damaged during the separation. For example, the substrate 101 may be fixed and the mold 104 may be moved away from the substrate 101. Alternatively, the mold 104 may be fixed and the substrate 101 may be moved away from the mold 104. Alternatively, both of these may be pulled in opposite directions to separate them.

[0072] <Removal process [6]> As shown schematically in [6] of Figure 1, the removal step can be carried out to remove the unpolymerized polymerizable compound (a) after the separation step. The curable composition not only undergoes cure shrinkage in the curing step, but also shrinks in line width as the unpolymerized polymerizable compound is removed in the removal step. This shrinkage is controlled by the irradiance and irradiation time in the curing step, thereby obtaining a pattern with the desired line width (CD). Details will be described later.

[0073] The removal step may include, for example, a waiting step in which the substrate that has undergone the separation step is left in a room temperature and normal pressure environment for a predetermined time (e.g., 1 second or more and 1 hour or less). Alternatively, the removal step may include a depressurization step in which the substrate that has undergone the separation step is placed in a reduced pressure environment for a predetermined time. The reduced pressure environment is, for example, an environment of 0.0001 atmospheres or more and 0.9 atmospheres or less. The predetermined time is, for example, 1 second or more and 1 hour or less. Alternatively, the removal step may include a baking step in which the substrate is heated. The baking step may be, for example, a step in which the substrate is heated at a temperature of 50 to 250°C for 1 second to 10 minutes. Alternatively, the removal step may include a rinsing step in which the cured film 106 is exposed to an organic solvent. As the removal step, a baking step or a rinsing step is preferably performed, and a rinsing step is particularly preferred. Examples of the solvent used in the rinsing step include solvents in which the polymerizable compound (a) dissolves, such as alcohol solvents, ketone solvents, ether solvents, ester solvents, nitrogen-containing solvents, etc. Specifically, a single solvent selected from propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, cyclohexanone, 2-heptanone, γ-butyrolactone, and ethyl lactate, or a mixture thereof, is preferred, but the solvent is not limited to these.

[0074] By performing the above steps [1] to [6] in this order (manufacturing process), a cured film having the desired concave-convex pattern shape (a pattern shape derived from the concave-convex shape of the mold 104) at the desired position can be obtained.

[0075] In one example, in the pattern formation method, the formation step [1] is performed over the entire surface of the substrate, and a repeating unit (shot) consisting of the placement step [2] to separation step [5] is repeatedly performed on the same substrate, and the removal step [6] can be performed over the entire surface of the substrate. Alternatively, the formation step [1] and the placement step [2] can be performed over the entire surface of the substrate, and a repeating unit (shot) consisting of the contact step [3] to separation step [5] is repeatedly performed on the same substrate, and the removal step [6] can be performed over the entire substrate. In this way, a cured film 106 having multiple desired patterns at desired positions on the substrate can be obtained.

[0076] <Post-processing process> A post-processing step may be carried out in which the substrate 101 (or the processable layer, if the substrate 101 has a processable layer) is processed using the cured film 106 having the pattern obtained through the formation step to the removal step as a mask. The post-processing step may include an etching step in which the substrate 101 (or the processable layer, if the substrate 101 has a processable layer) is etched, or a film-forming step in which a film is formed on the cured film 106. The etching step transfers the pattern of the cured film 106 to the substrate 101 (or the processable layer, if the substrate 101 has a processable layer), forming a second pattern on the substrate 101 (or the processable layer, if the substrate 101 has a processable layer). The film-forming step forms a film on the pattern of the cured film 106, forming a second pattern. In post-processing steps such as the etching step and film-forming step, non-uniformity in the processing speed within the surface of the substrate may exist. Therefore, the line width of the second pattern formed through the post-processing step may be non-uniform.

[0077] <Decision process> The pattern line width of the patterned cured film 106 may be adjusted so that the line width of the second pattern formed in the post-processing step is uniform. To this end, the line width of the second pattern formed in the post-processing step is measured, and first correlation information indicating the correlation between the line width of the pattern of the cured film 106 and the line width of the second pattern formed in the post-processing step can be calculated for each field and / or each region within each field. Second correlation information indicating the correlation between the illuminance and irradiation time and the line width of the pattern of the cured film 106 can be calculated for each field and / or each region within each field. Then, based on the first correlation information and the second interlayer information, the illuminance and irradiation time in the curing step can be determined so as to obtain a target line width distribution. Furthermore, to control the line width distribution of the pattern of the cured film 106 to the target line width distribution, the illuminance and irradiation time in the curing step can be determined based on the second correlation information.

[0078] [Manufacturing methods for circuit boards, electronic components, and optical devices] The substrate 101 (or the processable layer if the substrate 101 has one) can be processed according to the above-described embodiment. Alternatively, a processable layer may be formed on the patterned cured film 106, and then the pattern may be transferred using a processing method such as etching. In this manner, a microstructure such as a circuit structure can be formed on the substrate 101 (or the processable layer if the substrate 101 has one). This allows devices such as semiconductor devices to be manufactured. Furthermore, it is also possible to form electronic devices including such devices, such as displays, cameras, and medical devices. Examples of devices include LSI, system LSI, DRAM, SDRAM, RDRAM, D-RDRAM, and NAND flash.

[0079] It is also possible to obtain an optical component that utilizes the patterned cured film 106 formed according to the embodiment of the present invention as an optical element (including when used as a part of an optical element) such as a diffraction grating or a polarizing plate. In such a case, the optical component can have at least a substrate 101 and a patterned cured film 106 on the substrate 101. [Example]

[0080] <Calculation of molecular aggregates of curable compositions> The structure of a molecular assembly consisting of the curable composition (A) can be determined, for example, by using molecular dynamics. The curable composition (A) may contain a photopolymerization initiator (b) in addition to the polymerizable compound (a). The polymerizable compound (a) may contain a reactive monomer (hereinafter referred to as "monomer"). A monomer is a molecule containing a reactive functional group, such as an acrylic group, a methacrylic group, or a vinyl group. Here, we will discuss polymers of so-called monofunctional monomers containing one acrylic group in the molecule and so-called bifunctional monomers containing two acrylic groups in the molecule.

[0081] In molecular dynamics, the target molecules are placed within a unit cell to which periodic boundary conditions are imposed, the forces acting between the atoms in each molecule are calculated at each time point, and the trajectories of all atoms over time are calculated.

[0082] To perform molecular dynamics calculations, force field parameters, which define the interactions between atoms, must be set in advance; the setting method is described below. A molecular dynamics calculation consists of four stages: compression, relaxation, equilibration, and the main calculation. The compression stage is performed to form appropriate molecular aggregates, the equilibration stage is performed to bring the calculation system to a thermodynamic equilibrium state, and the main calculation involves sampling the equilibrium state. The calculation conditions used for the compression stage can be, for example, a simulation time of 40 ps, ​​a temperature of 700 K, a compression ratio setting of 0.000045, and a pressure setting of 10,000 atm, and can be a constant-temperature, constant-pressure simulation using the Berendsen method. The calculation conditions used for the equilibration stage can be, for example, a simulation time of 5 ns, a temperature of 300 K, a compression ratio setting of 0.000045, and a pressure setting of 1 atm, and can be a constant-temperature, constant-pressure simulation using the Berendsen method. The calculation conditions used in this study are, for example, a simulation time of 20 ns, a temperature of 300 K, a compression ratio of 0.000045, and a pressure of 1 atm. This simulation can be performed at constant temperature and pressure using the Berendsen method. The force field parameters can be composed of two types: electrostatic and non-electrostatic. The electrostatic force field parameters can be assigned to each atom by charge fitting using points based on the MERZ-Singh-Killmans scheme to the electrostatic potential calculated using the Kohn-Sham method (exchange-correlation functional B3LYP) and basis set 6-31g*, a quantum chemical calculation method.In addition to the specific design, the Gaussian design Gaussian09(Gaussian09,RevisionC.01,MJFrisch,GWTrucks,HBSchlegel,GEScuser). ia, MARobb, JRCheeseman, G. Scalmani, V. Barone, B. Mennucci, G. Petersson, H. Nakatsuji, M. Caricato, X. Li, HPHra tchian, AFIzmaylov, J. Bloino, G. Zheng, JLSonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishi da,T.Nakajima,Y.Honda,O.Kitao,H.Nakai,T.Vreven,JAMontgomery,Jr.,JEPeralta,F.Ogliaro,M.Bearpark,JJHe yd, E. Brothers, KNKudin, VNS Taroverov, T. Keith, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, JCBurant ,SSIyengar,J.Tomasi,M.Cossi,N.Rega,JMMillam,M.Klene,JEKnox,JBCross,V.Bakken,C.Adamo,J.Jaramillo,R.G omperts,REStratmann,O.Yazyev,AJAustin,R.Cammi,C.Pomelli,JWOchterski,RLMartin,K.Morokuma,VGZakrzews ki,GAVoth,P.Salvador,JJDannenberg,S.Dapprich,ADDaniels,O.Farkas,JBForesman,JVOrtiz,JCioslowski,and DJFox,Gaussian,Inc.,Wallingford CT,2010.) Merz-Singh-Ki In the llmans range, it offers a range of options 2 and 3 options.As the non-electrostatic force field parameters, the general Amber force field (GAFF), which is generally used for organic molecules, can be used.

[0083] <Photopolymerization simulation> After generating the structure of a molecular assembly consisting of curable composition (A) using molecular dynamics, a photopolymerization simulation was performed using the resulting molecular assembly structure. First, the center of gravity of the polymerization initiator and monomer was calculated, and the monomer was coarse-grained as a point mass with mass concentrated at the center of gravity (Figure 2). As shown in Figure 2, the polymerization initiator and monomer are randomly arranged. Next, a photopolymerization reaction simulation was performed using the coarse-grained structure. The reaction algorithm is as follows:

[0084] (1) The polymerization initiator is activated by light irradiation and stochastically selects monomers within the reaction radius to form bonds.

[0085] (2) The chain-linked monomer becomes activated and combines with another monomer within the reaction radius.

[0086] (3) If there are no monomers within the reaction radius, the binding range is extended up to a critical distance.

[0087] (4) The polymerization reaction stops when there are no monomers within the critical radius or when activated monomers bond with each other.

[0088] In this example, the reaction radius was set to 12 Å and the critical distance to 15 Å, but these values ​​are not limited to these. The reaction rate between monomers was calculated using quantum chemical calculations, but experimental or other estimated values ​​may also be used, and the method is not limited to these. The monomers within the reaction radius with which the activated monomer reacts are determined using the Monte Carlo method based on the reaction rate values. The above process is described by the following mathematical formula:

[0089] The photoradical polymerization process proceeds as follows: First, the polymerization initiator (Init.) is cleaved by light to form a radical (R · ) is generated.

[0090]

number

[0091] The generated radical (R · ) reacts with the monomer (M), and the radicalization of the monomer proceeds.

[0092]

number

[0093] The radicalized monomer (M · The reaction between the hydroxyl group and the monomer (M) proceeds, resulting in the growth of a polymer.

[0094]

number

[0095] If radicals collide with each other during the polymer growth, the reaction will stop.

[0096]

number

[0097] The conversion rate of the monomer to polymer in this way is expressed by the following formula:

[0098]

number

[0099] where √I represents the monomer concentration, and [M0] is the initial monomer concentration. I is the light intensity, and t is the light exposure time. In other words, the conversion rate is determined by √I)·t. The conversion rate reaches saturation when the reaction stops, which is called the saturated conversion rate. As shown in Figure 3, the saturated conversion rate is determined by the light intensity, and increases with increasing light intensity. Figure 4 shows the time evolution of the conversion rate at relative light intensities I = 0.5, 1.0, 3.0, 4.0, and 5.0. Time is an arbitrary unit. The relative light intensity I is determined by the photoinitiator concentration, and calculations were performed under the assumption that the photoinitiator is fully activated in the early stages of the reaction. As can be seen from Figure 4, as the relative light intensity I increases, the reaction stop time t decreases and the conversion rate increases. When the polymerization reaches saturation, the conversion rate remains constant at the relative light intensity. For example, when the relative illuminance is 5, the reaction stop time is relative time=100 (au), as shown in FIG.

[0100] <Quantification of curing shrinkage and removal shrinkage> Pattern shrinkage during pattern formation includes (1) curing shrinkage associated with the formation of bonds between monomers through photopolymerization (Figure 5) and (2) shrinkage associated with the removal of unpolymerized monomers (hereafter referred to as removal shrinkage) (Figure 6). Regarding curing shrinkage, the intermolecular distance before the reaction can be estimated using the van der Waals distance, and after the reaction, the intermolecular distance can be estimated using the covalent bond distance. Furthermore, removal shrinkage can be calculated by counting the molecular volume removed by unreacted monomers. Furthermore, the following model was developed to quantify the curing shrinkage and removal shrinkage relative to the CD. Figure 7 shows the pattern formed on the substrate. The line depth direction is assumed to be infinite, meaning there is no shrinkage. Shrinkage is evaluated in two dimensions: the height and width directions. Here, we assume that the portion bonded to the residual film is constrained by the residual film and does not shrink. Under this assumption, only the portion not bonded to the residual film shrinks, resulting in a trapezoidal shape due to shrinkage. The trapezoidal volume of the pattern is expressed by the following equation.

[0101]

number

[0102] Therefore, the line width shrinkage rate is

[0103] [Number] and becomes

[0104] [Number] and becomes. Thus, CD can be calculated.

[0105] <Calculation of CD> Calculate the saturation conversion rate by photopolymerization simulation. Calculate the curing shrinkage and removal shrinkage based on the saturation conversion rate, and calculate CD by the method of "Quantification of Curing Shrinkage and Removal Shrinkage" above. Table 1 shows the results of examining the case of a line pattern with a reference CD of 20 nm and relative illuminances I of 0.5, 2, 3, and 5.

[0106] [Table 1]

[0107] The calculation procedure is as follows.

[0108] (Curing shrinkage) The saturation conversion rate was obtained from the results of the photopolymerization simulation. The line width shrinkage rate at a relative illuminance of 5 was the experimental value of 15.0 as shown in Table 1. Using this value, the volume shrinkage rate at a relative illuminance of 5 can be obtained by Equation 7 (15.0). Based on this volume shrinkage rate at a relative illuminance of 5, the volume shrinkage rates for relative intensities of 0.5, 2, and 3 are calculated from the ratio of the saturation conversion rates. Furthermore, the obtained volume shrinkage rates are converted to line width shrinkage rates by Equation 7. Using these line width shrinkage rates, CD is calculated by Equation 8.

[0109] (Removal shrinkage) The unpolymerized monomer ratio was calculated from the results of the photopolymerization simulation. From this unpolymerized monomer ratio, the molecular volume of the unpolymerized monomer was calculated, and the volume shrinkage rate when these monomers were removed was calculated.

[0110] (Curing shrinkage + removal shrinkage) The total volumetric shrinkage is calculated by adding up the volumetric shrinkage rates for the above-mentioned curing shrinkage and removal shrinkage. This is used to calculate the total line width shrinkage rate, and the CD is obtained.

[0111] From these results, the dependency of saturated conversion on relative illuminance is shown in Figure 8. It can be seen that the higher the illuminance, the higher the saturated conversion. Based on this saturated conversion, the CD value due to curing shrinkage and the CD value due to curing shrinkage + removal shrinkage can be calculated, as shown in Figure 9. The following became clear from these figures. (1) In the case of only cure shrinkage (black circles in Figure 9), the higher the illuminance, the greater the shrinkage and the smaller the CD value. This is because the higher the illuminance, the more the polymerization of the monomers progresses, resulting in a shrinkage of the distance between the monomers. (2) In the case of removal shrinkage, the lower the irradiance, the larger the shrinkage value (the smaller the CD value). This is because the number of unpolymerized monomers increases with decreasing irradiance, and the number of removed monomers increases. (3) In the case of both curing shrinkage and removal shrinkage (white circles in Figure 9), the lower the illuminance, the greater the shrinkage (smaller the CD value). This means that the effect of removal shrinkage is greater than that of curing shrinkage. In other words, if a removal process is performed to remove unpolymerized monomer, the higher the illuminance, the larger the CD value (thicker the line width).

[0112] Based on these results, we investigated the possibility of CD control by controlling illuminance and exposure time and by applying a removal process. When the reference CD width is 20 nm, the CD range from the data marked with a circle in Figure 9 is a minimum of 14.3, a maximum of 15.9, and a median of 15.1. In this case, the CD is 15.1 ± 0.8, and ± 0.8 corresponds to ± 5.3% of 15.1. This indicates the possibility of CD control of ± 5.3%.

[0113] Example 1 The processing speed in dry etching, a post-processing step, varies within the substrate. Therefore, in order to make the CD of the second pattern of the processed layer after the post-processing step uniform across the entire surface of the substrate, multiple fields within the substrate were classified into three groups (fast, medium, slow) based on processing speed, and CD control was performed by adjusting the illuminance and irradiation time for each group. In this case, with the "medium" group as the standard, the processing speed in the "fast" group was about 5% faster, and in the "slow" group it was about 5% slower. In addition, the photopolymerization monomer used had an illuminance of 10,000 W / m 2 The curable composition (A-1) exhibited saturated polymerization at an irradiation time of 0.1 s, resulting in a saturated cure shrinkage of 15%. This curable composition was subjected to an imprinting process using a mold with a line pattern having a line width of 20 nm. The illuminance and exposure time were adjusted to increase the line width in the fast processing speed group and decrease the line width in the slow processing speed group. As a result, the line widths (CD) for the three groups were as shown in Table 2 below. The fast processing speed group had a CD of 16.4 nm, which was 5% larger than the medium processing speed group. The slow processing speed group had a CD of 14.8 nm, which was 5% smaller than the medium processing speed group. This corresponds to the ratio of the processing speeds, and after the processing process, the CDs were uniform across the three groups (in other words, uniform across the entire surface of the substrate).

[0114] [Table 2]

[0115] Example 2 The same experiment as in Example 1 was carried out at an illuminance of 10,000 W / m 2This experiment was performed using curable composition (A-2), which exhibits saturated polymerization at an irradiation time of 0.0316 seconds and a saturated cure shrinkage of 15%. The CD control results are shown in Table 3. Again, the line width (CD) for the "fast" processing speed group was 16.4 nm, 5% thicker than the "medium" processing speed group. The line width (CD) for the "slow" processing speed group was 14.8 nm, 5% thinner than the "medium" processing speed group. This corresponds to the ratio of the processing speeds, and after the processing process, the line width was uniform across the three groups.

[0116] [Table 3]

[0117] (Comparative Example 1) Illuminance=10,000W / m 2 In the case of the curable composition (A-1) in which polymerization is saturated at an irradiation time of 0.1 s, the irradiance is 10,000 W / m 2 If the exposure time is shortened to less than 0.1 seconds, the conversion rate is low and the polymerization chain length is short, as shown in Figure 10. This causes pattern collapse in the separation process, resulting in a low manufacturing yield.

[0118] [Embodiment] To summarize the above, the present specification provides the following embodiments: In the following description, the description in ( ) indicates a variable, and the description in [ ] indicates a unit. (First embodiment) The pattern forming method of the first embodiment includes: a contacting step of contacting the mold with a curable composition comprising a polymerizable compound disposed on the field of the substrate; a curing step of irradiating the curable composition disposed on the field with light to form a cured film including a pattern made of a cured product of the curable composition; and a separation step of separating the cured film from the mold.

[0119] The field includes a plurality of regions. In the curing step, the curable composition is irradiated with light in accordance with an illuminance and an irradiation time determined according to a target line width of the pattern for each of the plurality of regions.

[0120] Here, each of the plurality of regions is referred to as an m-th region (m is an integer between 1 and M, and M is the number of the plurality of regions), and the illuminance of light irradiated onto the m-th region is I(m) [W / m 2 ], and the irradiation time of the light to the m-th region is t(m) [s].

[0121] In the curing step, it is desirable that √I(m)×t(m) is 3.16 [(√W)·s / m] or more for all of the plurality of regions.

[0122] In addition, for all of the plurality of regions, the illuminance I [m] is 100 or more and 100,000 [W / m 2 ] or less is desirable.

[0123] The pattern formation method of the first embodiment may further include a determination step of determining a target line width for determining illuminance and irradiation time in accordance with a target line width distribution after a post-processing step for the pattern formed through the curing step.

[0124] The pattern formation method of the first embodiment may further include a removal step of removing unpolymerized polymerizable compound after the separation step. The removal step may include a rinsing step of exposing the cured film after the separation step to an organic solvent. Alternatively, the removal step may include a baking step of heating the substrate after the separation step. Alternatively, the removal step may include a depressurization step of placing the substrate in a depressurized environment for a predetermined time. The depressurized environment may be, for example, an environment of 0.0001 atmospheres or more and 0.9 atmospheres or less. The predetermined time may be, for example, 1 second or more and 1 hour or less. (Second embodiment) The pattern forming method of the second embodiment includes: a contacting step of bringing a curable composition containing a polymerizable compound disposed on a substrate into contact with a mold; a curing step of irradiating the curable composition disposed on the substrate with light to form a cured film including a pattern made of a cured product of the curable composition; and a separation step of separating the cured film from the mold.

[0125] The substrate includes a plurality of fields, and in the curing step, the curable composition is irradiated with light in accordance with an illuminance and an irradiation time determined according to a target line width of the pattern for each of the plurality of fields.

[0126] Here, each of the plurality of fields is designated as an nth field (n is an integer between 1 and N, and N is the number of the plurality of fields), and the illuminance of light irradiated to the nth field is designated as I(n) [W / m 2 ], and the irradiation time of light for the nth field is t(m) [s].

[0127] In the curing step, the nth field has a uniform illuminance I(n) [W / m 2 ], and it is desirable that for all of the plurality of fields, √I(n)×t(n) is 3.16[(√W)·s / m] or more.

[0128] In addition, for all of the plurality of fields, the illuminance I(n) is 100 or more and 100,000 [W / m 2 ] or less is desirable.

[0129] The pattern formation method of the second embodiment may further include a removal step of removing unpolymerized polymerizable compound after the separation step. The removal step may include a rinsing step of exposing the cured film after the separation step to an organic solvent. Alternatively, the removal step may include a baking step of heating the substrate after the separation step. Alternatively, the removal step may include a depressurization step of placing the substrate in a depressurized environment for a predetermined time. The depressurized environment may be, for example, an environment of 0.0001 atmospheres or more and 0.9 atmospheres or less. The predetermined time may be, for example, 1 second or more and 1 hour or less. (Third embodiment) The pattern forming method of the third embodiment includes: a contacting step of bringing a curable composition containing a polymerizable compound disposed on a substrate into contact with a mold; a curing step of irradiating the curable composition disposed on the substrate with light to form a cured film including a pattern made of a cured product of the curable composition; and a separation step of separating the cured film from the mold.

[0130] In the curing step, the curable composition is irradiated with light in accordance with a distribution of illuminance and irradiation time determined according to a target line width distribution in the cured film.

[0131] The pattern formation method of the third embodiment may further include a removal step of removing unpolymerized polymerizable compound after the separation step. The removal step may include a rinsing step of exposing the cured film after the separation step to an organic solvent. Alternatively, the removal step may include a baking step of heating the substrate after the separation step. Alternatively, the removal step may include a depressurization step of placing the substrate in a depressurized environment for a predetermined time. The depressurized environment may be, for example, an environment of 0.0001 atmospheres or more and 0.9 atmospheres or less. The predetermined time may be, for example, 1 second or more and 1 hour or less.

Claims

1. a contacting step of contacting the mold with a curable composition comprising a polymerizable compound disposed on the field of the substrate; a curing step of irradiating the curable composition disposed on the field with light to form a cured film including a pattern made of a cured product of the curable composition; a separation step of separating the cured film from the mold, The field includes a plurality of regions; In the curing step, the curable composition is irradiated with light in accordance with an illuminance and an irradiation time determined according to a target line width of the pattern for each of the plurality of regions. A pattern forming method comprising:

2. Each of the plurality of regions is designated as the mth region (m is an integer of 1 or more and M or less, and M is the number of the plurality of regions), and the illuminance of the light irradiated onto the mth region is designated as I(m) [W / m ２ ], the irradiation time of the light to the m-th region is t (m) [s], In the curing step, for all of the plurality of regions, √I(m) × t(m) is 3.16 [(√W) s / m] or more, 2. The pattern forming method according to claim 1.

3. For all of the plurality of regions, the illuminance I [m] is 100 or more and 100,000 [W / m ２ ]or less, 3. The pattern forming method according to claim 2.

4. a contacting step of bringing a curable composition containing a polymerizable compound disposed on a substrate into contact with a mold; a curing step of irradiating the curable composition disposed on the substrate with light to form a cured film including a pattern made of a cured product of the curable composition; a separation step of separating the cured film from the mold, the substrate includes a plurality of fields; In the curing step, the curable composition is irradiated with light in accordance with an illuminance and an irradiation time determined according to a target line width of the pattern for each of the plurality of fields. A pattern forming method comprising:

5. Each of the plurality of fields is designated as the nth field (n is an integer of 1 or more and N or less, and N is the number of the plurality of fields), and the illuminance of the light irradiated to the nth field is designated as I(n) [W / m ２ ], the irradiation time of light for the nth field is t (m) [s], In the curing step, the nth field has a uniform illuminance I(n) [W / m ２ ], and for all of the plurality of fields, √I(n)×t(n) is 3.16 [(√W)·s / m] or more.

5. The pattern forming method according to claim 4.

6. For all of the plurality of fields, the illuminance I(n) is 100 or more and 100,000 [W / m ２ ]or less, 6. The pattern forming method according to claim 5.

7. a contacting step of bringing a curable composition containing a polymerizable compound disposed on a substrate into contact with a mold; a curing step of irradiating the curable composition disposed on the substrate with light to form a cured film including a pattern made of a cured product of the curable composition; a separation step of separating the cured film from the mold, In the curing step, the curable composition is irradiated with light in accordance with a distribution of illuminance and irradiation time determined according to a target line width distribution in the cured film. A pattern forming method comprising:

8. The method further includes a determining step of determining a target line width for determining irradiance and irradiation time according to a target line width distribution after a post-processing step for the pattern formed through the curing step.

8. The pattern forming method according to claim 1, wherein the pattern forming method is a method for forming a pattern on a substrate.

9. Further comprising a removal step of removing unpolymerized polymerizable compounds after the separation step.

9. The pattern forming method according to claim 1, wherein the step of:

10. The removing step includes a rinsing step of exposing the cured film after the separating step to an organic solvent.

10. The pattern forming method according to claim 9.

11. the removing step includes a baking step of heating the substrate after the separating step; 10. The pattern forming method according to claim 9.

12. The removing step includes a decompression step of placing the substrate in a decompressed environment for a predetermined time.

10. The pattern forming method according to claim 9.

13. The reduced pressure environment is an environment of 0.0001 atmospheres or more and 0.9 atmospheres or less.

13. The pattern forming method according to claim 12.

14. The predetermined time is equal to or greater than 1 second and equal to or less than 1 hour.

14. The pattern forming method according to claim 12 or 13.

15. forming a pattern on a substrate by the pattern forming method according to any one of claims 1 to 14; processing the patterned substrate to obtain an article; A method for manufacturing an article, comprising:

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