Patent Application
20190284387
The present invention relates to a method of producing a structure containing a phase-separated structure.
Priority is claimed on Japanese Patent Application No. 2018-048196, filed on Mar. 15, 2018, the content of which is incorporated herein by reference.
Recently, as further miniaturization of large scale integrated circuits (LSI) proceeds, a technology for processing a more delicate structure is demanded.
In response to such demand, development has been conducted on a technology in which a fine pattern is formed using a phase-separated structure formed by self-assembly of a block copolymer having mutually incompatible blocks bonded together (see, for example, Patent Document 1).
For using a phase-separation structure of a block copolymer, it is necessary to form a self-organized nano structure by a microphase separation only in specific regions, and arrange the nano structure in a desired direction. For realizing position control and orientational control, processes such as graphoepitaxy to control phase-separated pattern by a guide pattern and chemical epitaxy to control phase-separated pattern by difference in the chemical state of the substrate are proposed (see, for example, Non-Patent Document 1).
A block copolymer forms a regular periodic structure by phase separation.
The “period of a structure” means a period of a phase structure observed when a phase-separated structure is formed, and is the sum of the length of phases which are mutually incompatible. In the case where a phase-separated structure forms a cylinder structure perpendicular to the surface of the substrate, the period (L0) of the structure is the center-to-center distance (pitch) between two adjacent cylinder structures.
It is known that the period (L0) of a block polymer is determined by intrinsic polymerization properties such as the polymerization degree N and the Flory-Huggins interaction parameter χ. Specifically, the repulsive interaction between different block components of the block copolymer becomes larger as the product of χ and N, “χ·N” becomes larger. Therefore, when χ·N>10 (hereafter, referred to as “strong segregation limit”), there is a strong tendency for the phase separation to occur between different blocks in the block copolymer. At the strong segregation limit, the period of the block copolymer is approximately N2/3·°1/6, and a relationship represented by following formula (*1) is satisfied. That is, the period of the structure is in proportion to the polymerization degree N which correlates with the molecular weight and molecular weight ratio between different blocks.
L0∝a·N2/3·χ1/6 (*1)
In the formula, L0 represents the period of the structure; a represents a parameter indicating the size of the monomer; N represents the polymerization degree; and x indicates an interaction parameter. The larger the value of the interaction parameter, the higher the phase-separation performance.
Therefore, by adjusting the composition and the total molecular weight of the block copolymer, the period (L0) of the structure can be adjusted.
It is known that the periodic structure formed by a block copolymer changes to a cylinder, a lamellar or a sphere, depending on the volume ratio or the like of the polymer components. Further, it is known that the period depends on the molecular weight.
Therefore, in order to form a structure having a relatively large period using a phase-separated structure formed by self-assembly of a block copolymer, it is considered that such structure may be formed by increasing the molecular weight of the block copolymer.
[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2008-36491
[Non-Patent Document 1] Proceedings of SPIE (U.S.), vol. 7637, pp. 76370G-1 (2010)
However, currently, in the case of forming a structure using a phase-separated structure formed by directed self-assembly of a widely used block copolymer (e.g., a block copolymer having a styrene block and a methyl methacrylate block), is was difficult to further improve the phase-separation performance.
The present invention takes the above circumstances into consideration, with an object of providing a method of producing a structure containing a phase-separated structure which can further improve the phase-separation performance.
For solving the above-mentioned problems, the present invention employs the following aspects.
Specifically, a first aspect of the present invention is a method of producing a structure containing a phase-separated structure, including: a step (i) of using a resin composition for forming a phase-separated structure including a block copolymer having a period L0 and an ion liquid containing a compound (IL) having a cation moiety and an anion moiety to form a BCP layer containing a block copolymer and having a thickness of d (nm) on a substrate; and a step (ii) of vaporizing at least a part of the compound (IL), and phase-separating the BCP layer to obtain a structure containing a phase-separated structure, wherein, in step (i), the BCP layer is formed such that the period L0 (nm) of the block copolymer and the thickness d (nm) of the BCP layer satisfies the following formula (1):
Thickness d/Period L0=n+a (1)
wherein n represents an integer of 0 or more; and a is a number which satisfies 0<a<1.
According to the present invention, there is provided a method of producing a structure containing a phase-separated structure which can further improve the phase-separation performance.
In the present description and claims, the term “aliphatic” is a relative concept used in relation to the term “aromatic”, and defines a group or compound that has no aromaticity.
The term “alkyl group” includes linear, branched or cyclic, monovalent saturated hydrocarbon, unless otherwise specified. The same applies for the alkyl group within an alkoxy group.
The term “alkylene group” includes linear, branched or cyclic, divalent saturated hydrocarbon, unless otherwise specified.
A “halogenated alkyl group” is a group in which part or all of the hydrogen atoms of an alkyl group is substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.
A “fluorinated alkyl group” or a “fluorinated alkylene group” is a group in which part or all of the hydrogen atoms of an alkyl group or an alkylene group have been substituted with a fluorine atom.
The term “structural unit” refers to a monomer unit that contributes to the formation of a polymeric compound (resin, polymer, copolymer).
The expression “may have a substituent” means that a case where a hydrogen atom (—H) is substituted with a monovalent group, or a case where a methylene (—CH2—) group is substituted with a divalent group.
The term “exposure” is used as a general concept that includes irradiation with any form of radiation.
A “structural unit derived from an acrylate ester” refers to a structural unit that is formed by the cleavage of the ethylenic double bond of an acrylate ester.
An “acrylate ester” refers to a compound in which the terminal hydrogen atom of the carboxy group of acrylic acid (CH2═CH—COOH) has been substituted with an organic group.
The acrylate ester may have the hydrogen atom bonded to the carbon atom on the α-position substituted with a substituent. The substituent (Ra0) that substitutes the hydrogen atom bonded to the carbon atom on the α-position is an atom other than hydrogen or a group, and examples thereof include an alkyl group of 1 to 5 carbon atoms and a halogenated alkyl group of 1 to 5 carbon atoms. Further, an acrylate ester having the hydrogen atom bonded to the carbon atom on the α-position substituted with a substituent (Ra0) in which the substituent has been substituted with a substituent containing an ester bond (e.g., an itaconic acid diester), or an acrylic acid having the hydrogen atom bonded to the carbon atom on the α-position substituted with a substituent (Ra0) in which the substituent has been substituted with a hydroxyalkylgroup or a group in which the hydroxy group within a hydroxyalkyl group has been modified (e.g., α-hydroxyalkyl acrylate ester) can be mentioned as an acrylate ester having the hydrogen atom bonded to the carbon atom on the α-position substituted with a substituent. A carbon atom on the α-position of an acrylate ester refers to the carbon atom bonded to the carbonyl group, unless specified otherwise.
Hereafter, an acrylate ester having the hydrogen atom bonded to the carbon atom on the α-position substituted with a substituent is sometimes referred to as “α-substituted acrylate ester”. Further, acrylate esters and α-substituted acrylate esters are collectively referred to as “(α-substituted) acrylate ester”.
A “structural unit derived from hydroxystyrene” refers to a structural unit that is formed by the cleavage of the ethylenic double bond of hydroxystyrene. A “structural unit derived from a hydroxystyrene derivative” refers to a structural unit that is formed by the cleavage of the ethylenic double bond of a hydroxystyrene derivative.
The term “hydroxystyrene derivative” includes compounds in which the hydrogen atom at the α-position of hydroxystyrene has been substituted with another substituent such as an alkyl group or a halogenated alkyl group; and derivatives thereof. Examples of the derivatives thereof include hydroxystyrene in which the hydrogen atom of the hydroxy group has been substituted with an organic group and may have the hydrogen atom on the α-position substituted with a substituent; and hydroxystyrene which has a substituent other than a hydroxy group bonded to the benzene ring and may have the hydrogen atom on the α-position substituted with a substituent. Here, the α-position (carbon atom on the α-position) refers to the carbon atom having the benzene ring bonded thereto, unless specified otherwise.
As the substituent which substitutes the hydrogen atom on the α-position of hydroxystyrene, the same substituents as those described above for the substituent on the α-position of the aforementioned α-substituted acrylate ester can be mentioned.
The term “styrene” is a concept including styrene and compounds in which the hydrogen atom at the α-position of styrene is substituted with other substituent such as an alkyl group and a halogenated alkyl group.
The term “styrene derivative” includes compounds in which the hydrogen atom at the α-position of styrene has been substituted with another substituent such as an alkyl group or a halogenated alkyl group; and derivatives thereof. Examples of the derivatives thereof include styrene which has a substituent other than a hydroxy group bonded to the benzene ring and may have the hydrogen atom on the α-position substituted with a substituent. Here, the α-position (carbon atom on the α-position) refers to the carbon atom having the benzene ring bonded thereto, unless specified otherwise.
A “structural unit derived from styrene” or “structural unit derived from a styrene derivative” refers to a structural unit that is formed by the cleavage of the ethylenic double bond of styrene or a styrene derivative.
As the alkyl group as a substituent on the α-position, a linear or branched alkyl group is preferable, and specific examples include alkyl groups of 1 to 5 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group and a neopentyl group.
Specific examples of the halogenated alkyl group as the substituent on the α-position include groups in which part or all of the hydrogen atoms of the aforementioned “alkyl group as the substituent on the α-position” are substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and a fluorine atom is particularly desirable.
Specific examples of the hydroxyalkyl group as the substituent on the α-position include groups in which part or all of the hydrogen atoms of the aforementioned “alkyl group as the substituent on the α-position” are substituted with a hydroxy group. The number of hydroxy groups within the hydroxyalkyl group is preferably 1 to 5, and most preferably 1.
In the present specification and claims, some structures represented by chemical formulae may have an asymmetric carbon, such that an enantiomer or a diastereomer may be present. In such a case, the one formula represents all isomers. The isomers may be used individually, or in the form of a mixture.
(Method of Producing Structure Containing Phase-Separated Structure)
A method of producing a structure containing a phase-separated structure includes: a step (i) of using a resin composition for forming a phase-separated structure including a block copolymer having a period L0 and an ion liquid containing a compound (IL) having a cation moiety and an anion moiety to form a BCP layer containing a block copolymer and having a thickness of d (nm) on a substrate; and a step (ii) of vaporizing at least a part of the compound (IL), and phase-separating the BCP layer to obtain a structure containing a phase-separated structure.
Hereinafter, one example of the method of producing a structure containing a phase-separated structure will be specifically described with reference to
Firstly, a brush composition is applied to a substrate 1, so as to form a brush layer 2 (
The resin composition for forming a phase-separated structure here includes a block copolymer having a period L0, and an ion liquid containing a compound (IL) having a cation moiety and an anion moiety. In the present embodiment, the BCP layer 3 is formed such that the period of the block copolymer L0 (nm) and the thickness d (nm) of the BCP layer 3 satisfies formula (1) described later.
Next, heating is conducted to perform an annealing treatment, so as to phase-separate the BCP layer 3 into a phase 3a and a phase 3b (
[Step (i)]
In step (i), the resin composition for forming a phase-separated structure is applied to the substrate 1, so as to form a BCP layer 3.
There are no particular limitations on the type of a substrate, provided that the resin composition for forming a phase-separated structure can be coated on the surface of the substrate.
Examples of the substrate include a substrate constituted of an inorganic substance such as a metal (e.g., silicon, copper, chromium, iron or aluminum), glass, titanium oxide, silica or mica; and a substrate constituted of an organic substance such as an acrylic plate, polystyrene, cellulose, cellulose acetate or phenol resin.
The size and the shape of the substrate is not particularly limited. The substrate does not necessarily need to have a smooth surface, and a substrate made of various materials and having various shapes can be appropriately selected for use. For example, a multitude of shapes can be used, such as a substrate having a curved surface, a plate having an uneven surface, and a thin sheet.
On the surface of the substrate, an inorganic and/or organic film may be provided. As the inorganic film, an inorganic antireflection film (inorganic BARC) can be used. As the organic film, an organic antireflection film (organic BARC) can be used.
Before forming a BCP layer 3 on the substrate 1, the surface of the substrate 1 may be cleaned. By cleaning the surface of the substrate, application of the resin composition for forming a phase-separated structure or the brush composition to the substrate 1 may be satisfactorily performed.
As the cleaning treatment, a conventional method may be used, and examples thereof include an oxygen plasma treatment, a hydrogen plasma treatment, an ozone oxidation treatment, an acid alkali treatment, and a chemical modification treatment. For example, the substrate is immersed in an acidic solution such as a sulfuric acid/hydrogen peroxide aqueous solution, followed by washing with water and drying. Thereafter, a BCP layer 3 or a brush layer 2 is formed on the surface of the substrate.
Before forming a BCP layer 3 on the substrate 1, the surface of the substrate 1 may be subjected to a neutralization treatment.
A neutralization treatment is a treatment in which the surface of the substrate is modified so as to have affinity for all polymers constituting the block copolymer. By the neutralization treatment, it becomes possible to prevent only phases of specific polymers to come into contact with the surface of the substrate by phase separation. For example, prior to forming a BCP layer 3, on the surface of the substrate 1, it is preferable to form a brush layer 2 depending on the kind of block copolymer to be used. As a result, by phase-separation of the BCP layer 3, a cylinder structure or lamellar structure oriented in a direction perpendicular to the surface of the substrate 1 can be reliably formed.
Specifically, on the surface of the substrate 1, a brush layer 2 is formed using a brush composition having affinity for all polymers constituting the block copolymer.
The brush composition can be appropriately selected from conventional resin compositions used for forming a thin film, depending on the kind of polymers constituting the block copolymer.
Examples of the brush composition include a composition containing a resin which has all structural units of the polymers constituting the block copolymer, and a composition containing a resin which has all structural units having high affinity for the polymers constituting the block copolymer.
For example, when a block copolymer having a block of a structural unit derived from styrene (PS) and a block of a structural unit derived from methyl methacrylate (PMMA) (PS-PMMA block copolymer) is used, as the brush composition, it is preferable to use a resin composition containing both PS and PMMA, or a compound or a composition containing both a portion having a high affinity for an aromatic ring and a portion having a high affinity for a functional group with high polarity.
Examples of the resin composition containing both PS and PMMA include a random copolymer of PS and PMMA, and an alternating polymer of PS and PMMA (a copolymer in which the respective monomers are alternately copolymerized).
Examples of the composition containing both a portion having a high affinity for PS and a portion having a high affinity for PMMA include a resin composition obtained by polymerizing at least a monomer having an aromatic ring and a monomer having a substituent with high polarity. Examples of the monomer having an aromatic ring include a monomer having a group in which one hydrogen atom has been removed from the ring of an aromatic hydrocarbon, such as a phenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, an anthryl group or a phenanthryl group, or a monomer having a hetero aryl group such as the aforementioned group in which part of the carbon atoms constituting the ring of the group has been substituted with a hetero atom such as an oxygen atom, a sulfur atom or a nitrogen atom. Examples of the monomer having a substituent with high polarity include a monomer having a trimethoxysilyl group, a trichlorosilyl group, a carboxy group, a hydroxy group, a cyano group or a hydroxyalkyl group in which part of the hydrogen atoms of the alkyl group has been substituted with a hydroxy group.
Examples of the compound containing both a portion having a high affinity for PS and a portion having a high affinity for PMMA include a compound having both an aryl group such as a phenethyltrichlorosilane and a substituent with high polarity, and a compound having both an alkyl group and a substituent with high polarity, such as an alkylsilane compound.
Further, as the brush composition, for example, a heat-polymerizable resin composition, or a photosensitive resin composition such as a positive resist composition or a negative resist composition can also be mentioned.
The brush layer 2 may be formed by a conventional method.
The method of applying the brush composition to the substrate 1 to form a brush layer 2 is not particularly limited, and the brush layer 2 can be formed by a conventional method.
For example, the brush composition can be applied to the substrate 1 by a conventional method using a spinner or the like to form a coating film on the substrate 1, followed by drying, thereby forming a brush layer 2.
The drying method of the coating film is not particularly limited, provided it can volatilize the solvent contained in the brush composition, and a baking method and the like are exemplified. The baking temperature is preferably 80° C. to 300° C., more preferably 180° C. to 270° C., and still more preferably 220° C. to 250° C. The baking time is preferably 30 seconds to 500 seconds, and more preferably 60 seconds to 400 seconds.
The thickness of the brush layer 2 after drying of the coating film is preferably about 10 to 100 nm, and more preferably about 40 to 90 nm.
Subsequently, on the brush layer 2, a BCP layer 3 having a thickness of d is formed using a resin composition for forming a phase-separated structure. The details of the resin composition for forming a phase-separated structure will be described later.
The method of forming the BCP layer 3 on the brush layer 2 is not particularly limited, and examples thereof include a method in which the resin composition for forming a phase-separated structure is applied to the brush layer 2 by a conventional method using spin-coating or a spinner, followed by drying.
The drying method of the coating film of the resin composition for forming a phase-separated structure is not particularly limited, provided it can volatilize the organic solvent component included in the resin composition for forming a phase-separated structure. Examples of the drying method include a shaking method and a baking method.
In the present embodiment, the BCP layer 3 is formed such that the period L0 (nm) and the thickness d (nm) of the BCP layer 3 satisfies the following formula (1). In the present specification and claims, a “block copolymer having a period L0” refers to a block copolymer which forms a phase-separated structure in which the period of the phase structure (sum of the length of phases which are mutually incompatible) is L0.
The “thickness d of the BCP layer 3” refers to the thickness of the layer containing the block copolymer prior to vaporizing at least a part of the compound (IL) in step (ii). For example, the thickness d may refer to the thickness of the BCP layer prior to the anneal treatment described later.
Thickness d/Period L0=n+a (1)
wherein n represents an integer of 0 or more; n is preferably an integer of 0 to 10, more preferably an integer of 0 to 5, still more preferably an integer of 0 to 3, and most preferably 1 or 2.
and a is a number which satisfies 0<a<1. a is preferably 0.1 to 0.9, more preferably 0.25 to 0.75, still more preferably 0.3 to 0.7, and most preferably a=0.5.
The BCP layer 3 may have a thickness d satisfactory for phase-separation to occur. In consideration of the kind of the substrate 1, the structure period size of the phase-separated structure to be formed, and the uniformity of the nanostructure, the thickness is preferably 10 to 200 nm, more preferably 20 to 100 nm and still more preferably 30 to 90 nm.
For example, in the case where the substrate 1 is an Si substrate or an SiO2 substrate, with respect to the thickness of the BCP layer 3, the lower limit is preferably 20 nm or more, more preferably 35 nm or more, and still more preferably 40 nm or more; the upper limit is 100 nm or less, more preferably 85 nm or less, still more preferably 70 nm or less, and most preferably 55 nm or less; and a preferable range may be 20 to 100 nm, or 30 to 90 nm.
For example, in the case where the substrate 1 is a Cu substrate, the thickness of the BCP layer 3 is preferably 10 to 100 nm, and more preferably 30 to 80 nm.
[Step (ii)]
In step (ii), at least a part of the compound (IL) is volatilized, and the BCP layer 3 formed on the substrate 1 is phase-separated.
For example, by heating the substrate 1 after step (i) to conduct the anneal treatment, the block copolymer may be selectively removed, such that a phase-separated structure in which at least part of the surface of the substrate 1 is exposed may formed. That is, on the substrate 1, a structure 3′ containing a phase-separated structure in which phase 3a and phase 3b are phase separated is produced.
The anneal treatment is preferably conducted under temperature condition where at least a part of the compound (IL) may be volatilized, so as to remove the compound (IL) from the BCP layer. As an example of such temperature condition, the anneal treatment may be conducted at a temperature of 210° C. or higher. That is, in step (ii), an anneal treatment is preferably conducted at a temperature of 210° C. or higher, so as to volatilize at least a part of the compound (IL), and remove the compound (IL) from the BCP layer.
In the above operation, the amount of the compound (IL) removed from the BCP layer may be all of the compound (IL) contained in the BCP layer, or a part of the compound (IL) contained in the BCP layer.
The temperature condition in the anneal treatment is preferably 210° C. or higher, more preferably 220° C. or higher, still more preferably 230° C. or higher, and most preferably 240° C. or higher. The upper limit of the temperature condition in the anneal treatment is not particularly limited, but is preferably lower than the heat decomposition temperature of the block copolymer. For example, the temperature condition of the anneal treatment is preferably 400° C. or lower, more preferably 350° C. or lower, and still more preferably 300° C. or lower. The range of the temperature conditions in the anneal treatment may be, for example, 210 to 400° C., 220 to 350° C., 230 to 300° C., or 240 to 300° C.
In the anneal treatment, the heating time is preferably 1 minute or more, more preferably 5 minutes or more, still more preferably 10 minutes or more, and most preferably 15 minutes or more. By extending the heating time, the amount of the compound (IL) remaining in the BCP layer may be reduced. The upper limit of the heating time is not particularly limited. In view of controlling the process time, the heating time is preferably 240 minutes or less, and more preferably 180 minutes or less. The range of the heating time in the anneal treatment may be, for example, 1 to 240 minutes, 5 to 240 minutes, 10 to 240 minutes, 15 to 240 minutes, or 15 to 180 minutes.
Further, the anneal treatment is preferably conducted in a low reactive gas such as nitrogen.
By conducting an anneal treatment, the compound (IL) is volatilized and removed from the BCP layer. As a result, in the BCP layer after the anneal treatment (i.e., structure 3′ in
The ratio (ta/d) of the thickness (ta (nm)) of the BCP layer after the anneal treatment to the thickness (d (nm)) of the BCP layer prior to the anneal treatment is preferably, for example, 0.90 or less. The value of (ta/d) is more preferably 0.85 or less, still more preferably 0.80 or less, and most preferably 0.75 or less. As the value of (ta/d) becomes smaller, the amount of the compound (IL) remaining in the BCP layer reduces. As a result, a structure having a good shape with reduced generation of roughness may be reliably obtained. The lower limit of the value of (ta/d) is not particularly limited, and may be, for example, 0.50 or more.
In the present embodiment, step (ii) may include an operation of volatilizing 40% by weight or more of the compound (IL) from the BCP layer, based on the total amount of the compound (IL) contained in the resin composition for forming a phase-separated structure. In such a case, it is preferable to volatilize 45% by weight or more of the total amount of the compound (IL) contained in the resin composition for forming a phase-separated structure, more preferably 50% by weight or more, still more preferably 60% by weight or more, and most preferably 100% by weight (i.e., the amount of IL remaining is 0% by weight).
In step (ii), the operation of volatilizing 40% by weight or more of the compound (IL) from the BCP layer, based on the total amount of the compound (IL) contained in the resin composition for forming a phase-separated structure, is not particularly limited. For example, as described above, the temperature condition of the anneal treatment for phase-separating the BCP layer may be adjusted, so as to volatilize 40% by weight or more of the compound (IL), based on the total amount of the compound (IL).
In the method of forming a structure containing a phase-separated structure according to the present embodiment described above, in step (i), a BCP layer is formed such that the period L0 (nm) of the block copolymer and the thickness d (nm) of the BCP layer satisfies the following formula: thickness d/period L0=n+a (wherein n represents an integer of 0 or more, and a is a number which satisfies 0<a<). That is, the BCP layer is formed such that thickness d/period L0 is controlled not to be an integer (1, 2, 3 . . . ). Then, after forming the BCP layer, step (ii) is conducted. In this manner, although the reason has not been elucidated yet, the phase-separation performance of the BCP layer may be enhanced.
Further, in the method of forming a structure containing a phase-separated structure according to the present embodiment described above, in step (ii), the compound (IL) is volatilized, and at least a part of the compound (IL) is removed from the BCP layer. The compound (IL) interacts with the block copolymer, and improves the phase-separation performance of the BCP layer. For this reason, conventionally, the anneal treatment was conducted under a temperature condition where the compound (IL) remains in the BCP layer as much as possible. However, in the present embodiment, in step (ii), the amount of the compound (IL) remaining in the BCP layer is reduced, and also the phase-separation of the BCP layer is conducted. Specifically, in the present embodiment, in step (ii), the anneal treatment is preferably conducted under a temperature condition where the amount of the compound (IL) is remaining in the BCP layer is reduced. Alternatively, in the present embodiment, in step (ii), it is preferable to conduct an operation of reducing the amount of the compound (IL) remaining in the BCP layer, and then conducting phase-separation of the BCP layer. By allowing the compound (IL) to interact with the block copolymer, and then removing the compound (IL) from the BCP layer, the phase-separation performance may be improved. Further, a structure having a good shape with reduced generation of roughness may be formed.
Furthermore, a structure produced by the method of forming a structure containing a phase-separated structure according to the present embodiment is unlikely to have generation of defects, and etching property is improved.
Further, in the case where, as in a conventional method, phase-separation of the BCP layer is conducted under conditions where the compound (IL) remains in the BCP layer as much as possible, matching of the polarity between the compound (IL) and the brushing layer 2 had influence on the formation of the phase-separated structure. Therefore, it was necessary to select the brushing composition depending on the kind of the compound (IL) to be used.
In the present embodiment, in step (ii), since the amount of the compound (IL) remaining in the BCP layer is reduced, the influence of the matching of polarity between the compound (IL) and the brushing layer 2 is small. Therefore, by the method of forming a structure containing a phase-separated structure according to the present embodiment, the brush composition may be more freely selected without depending on the kind of the compound (IL) to be used.
[Optional Step]
The method of forming a structure containing a phase-separated structure according to the present invention is not limited to the above embodiment, and may include a step (optional step) other than steps (i) and (ii).
Examples of the optional steps include a step of selectively removing a phase constituted of at least one block of the plurality of blocks constituting the block copolymer contained in the BCP layer 3 (hereafter, referred to as “step (iii)”), and a guide pattern formation step.
Step (iii)
In step (iii), from the BCP layer 3 formed on the brush layer 2, a phase constituted of at least one block of the plurality of blocks constituting the block copolymer (phase 3a and phase 3b) is selectively removed. In this manner, a fine pattern (polymeric nanostructure) can be formed.
Examples of the method of selectively removing a phase constituted of a block include a method in which an oxygen plasma treatment or a hydrogen plasma treatment is conducted on the BCP layer.
Hereafter, among the blocks constituting the block copolymer, a block which is not selectively removed is referred to as “block PA”, and a block to be selectively removed is referred to as “block PB”. For example, after the phase separation of a layer containing a PS-PMMA block copolymer, by subjecting the BCP layer to an oxygen plasma treatment or a hydrogen plasma treatment, the phase of PMMA is selectively removed. In such a case, the PS portion is the block PA, and the PMMA portion is the block PB.
In the embodiment shown in
The substrate 1 having a pattern formed by phase-separation of the BCP layer 3 as described above may be used as it is, or may be further heated to modify the shape of the pattern (polymeric nanostructure) on the substrate 1.
The heat treatment is preferably conducted at a temperature at least as high as the glass transition temperature of the block copolymer used and lower than the heat decomposition temperature. Further, the heating is preferably conducted in a low reactive gas such as nitrogen.
Guide Pattern Forming Step
In the method of forming a structure containing a phase-separated structure according to the present invention, a step of forming a guide pattern on the brush layer (guide pattern forming step) may be included. In this manner, it becomes possible to control the arrangement of the phase-separated structure.
For example, in the case of a block copolymer where a random fingerprint-patterned phase separation structure is formed without using a guide pattern, by providing a trench pattern of a resist film on the surface of the brush layer, a phase separation structure arranged along the trench can be obtained. The guide pattern can be provided on the brush layer 2 in accordance with the above-described principle. Further, when the surface of the guide pattern has affinity for any of the polymers constituting the block copolymer, a phase separation structure having a cylinder structure or lamellar structure arranged in the perpendicular direction of the surface of the substrate can be more reliably formed.
The guide pattern can be formed, for example, using a resist composition.
The resist composition for forming the guide pattern can be appropriately selected from resist compositions or a modified product thereof typically used for forming a resist pattern which have affinity for any of the polymers constituting the block copolymer. The resist composition may be either a positive resist composition capable of forming a positive pattern in which exposed portions of the resist film are dissolved and removed, or a negative resist pattern capable of forming a negative pattern in which unexposed portions of the resist film are dissolved and removed, but a negative resist composition is preferable. As the negative resist composition, for example, a resist composition containing an acid-generator component and a base component which exhibits decreased solubility in an organic solvent-containing developing solution under action of acid, wherein the base component contains a resin component having a structural unit which is decomposed by action of acid to exhibit increased polarity, is preferable.
When the resin composition for forming a phase-separated structure is cast onto the brush layer having the guide pattern formed thereon, an anneal treatment is conducted to cause phase-separation. Therefore, the resist pattern for forming a guide pattern is preferably capable of forming a resist film which exhibits solvent resistance and heat resistance.
<Resin Composition for Forming Phase-Separated Structure>
In the method of forming a structure containing a phase-separated structure according to the present embodiment, the resin composition for forming a phase-separated structure includes a block copolymer and an ion liquid containing a compound (IL) having a cation moiety and an anion moiety. As one embodiment of the resin composition for forming a phase-separated structure, for example, a block copolymer and an ion liquid may be dissolved in an organic solvent component.
«Block Copolymer»
A block copolymer is a polymeric material in which plurality of blocks (partial constitutional components in which the same kind of structural unit is repeatedly bonded) are bonded. As the blocks constituting the block copolymer, 2 kinds of blocks may be used, or 3 or more kinds of blocks may be used.
The plurality of blocks constituting the block copolymer are not particularly limited, as long as they are combinations capable of causing phase separation. However, it is preferable to use a combination of blocks which are mutually incompatible. Further, it is preferable to use a combination in which a phase of at least one block amongst the plurality of blocks constituting the block copolymer can be easily subjected to selective removal as compared to the phases of other blocks.
Further, it is preferable to use a combination in which a phase of at least one block amongst the plurality of blocks constituting the block copolymer can be easily subjected to selective removal as compared to the phases of other blocks. An example of a combination which can be selectively removed reliably include a block copolymer in which one or more blocks having an etching selectivity of more than 1 are bonded.
Examples of the block copolymer include a block copolymer in which a block of a structural unit having an aromatic group is bonded to a block of a structural unit derived from an (α-substituted) acrylate ester; a block copolymer in which a block of a structural unit having an aromatic group is bonded to a block of a structural unit derived from an (α-substituted) acrylic acid; a block copolymer in which a block of a structural unit having an aromatic group is bonded to a block of a structural unit derived from siloxane or a derivative thereof; a block copolymer in which a block of a structural unit derived from an alkyleneoxide is bonded to a block of a structural unit derived from an (α-substituted) acrylate ester; a block copolymer in which a block of a structural unit derived from an alkyleneoxide is bonded to a block of a structural unit derived from an (α-substituted) acrylic acid; a block copolymer in which a block of a structural unit containing a polyhedral oligomeric silsesquioxane structure is bonded to a block of a structural unit derived from an (α-substituted) acrylate ester; a block copolymer in which a block of a structural unit containing a silsesquioxane structure is bonded to a block of a structural unit derived from an (α-substituted) acrylic acid; and a block copolymer in which a block of a structural unit containing a silsesquioxane structure is bonded to a block of a structural unit derived from siloxane or a derivative thereof.
Examples of the structural unit having an aromatic group include structural units having a phenyl group, a naphthyl group or the like. Among these examples, a structural unit derived from styrene or a derivative thereof is preferable.
Examples of the styrene or derivative thereof include α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-t-butylstyrene, 4-n-octylstyrene, 2,4,6-trimethylstyrene, 4-methoxy styrene, 4-t-butoxy styrene, 4-hydroxy styrene, 4-nitrostyrene, 3-nitrostyrene, 4-chlorostyrene, 4-fluorostyrene, 4-acetoxyvinylstyrene, 4-vinylbenzylchloride, 1-vinylnaphthalene, 4-vinylbiphenyl, 1-vinyl-2-pyrolidone, 9-vinylanthracene, and vinylpyridine.
An (α-substituted) acrylic acid refers to either or both acrylic acid and a compound in which the hydrogen atom bonded to the carbon atom on the α-position of acrylic acid has been substituted with a substituent. As an example of such a substituent, an alkyl group of 1 to 5 carbon atoms can be given.
Examples of (α-substituted) acrylic acid include acrylic acid and methacrylic acid.
An (α-substituted) acrylate ester refers to either or both acrylate ester and a compound in which the hydrogen atom bonded to the carbon atom on the α-position of acrylate ester has been substituted with a substituent. As an example of such a substituent, an alkyl group of 1 to 5 carbon atoms can be given.
Specific examples of the (α-substituted) acrylate ester include acrylate esters such as methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, t-butyl acrylate, cyclohexyl acrylate, octyl acrylate, nonyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, benzyl acrylate, anthracene acrylate, glycidyl acrylate, 3,4-epoxycyclohexylmethane acrylate, and propyltrimethoxysilane acrylate; and methacrylate esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, octyl methacrylate, nonyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, benzyl methacrylate, anthracene methacrylate, glycidyl methacrylate, 3,4-epoxycyclohexylmethane methacrylate, and propyltrimethoxysilane methacrylate.
Among these, methyl acrylate, ethyl acrylate, t-butyl acrylate, methyl methacrylate, ethyl methacrylate, and t-butyl methacrylate are preferable.
Examples of siloxane and siloxane derivatives include dimethylsiloxane, diethylsiloxane, diphenylsiloxane, and methylphenylsiloxane.
Examples of the alkylene oxide include ethylene oxide, propylene oxide, isopropylene oxide and butylene oxide.
As the silsesquioxane structure-containing structural unit, polyhedral oligomeric silsesquioxane structure-containing structural unit is preferable. As a monomer which provides a polyhedral oligomeric silsesquioxane structure-containing structural unit, a compound having a polyhedral oligomeric silsesquioxane structure and a polymerizable group can be mentioned.
Among the above examples, as the block copolymer, a block copolymer containing a block of a structural unit having an aromatic group and a block of a structural unit derived from an (α-substituted) acrylic acid or an (α-substituted) acrylate ester is preferable.
In the case of obtaining a cylinder phase-separated structure oriented in a direction perpendicular to the surface of the substrate, the weight ratio of the structural unit having an aromatic group to the structural unit derived from an (α-substituted) acrylic acid or (α-substituted) acrylate ester is preferably in the range of 60:40 to 90:10, and more preferably 60:40 to 80:20.
In the case of obtaining a lamellar phase-separated structure oriented in a direction perpendicular to the surface of the substrate, the weight ratio of the structural unit having an aromatic group to the structural unit derived from an (α-substituted) acrylic acid or (α-substituted) acrylate ester is preferably in the range of 35:65 to 60:40, and more preferably 40:60 to 60:40.
Specific examples of such block copolymers include a block copolymer having a block of a structural unit derived from styrene and a block of a structural unit derived from acrylic acid; a block copolymer having a block of a structural unit derived from styrene and a block of a structural unit derived from methyl acrylate; a block copolymer having a block of a structural unit derived from styrene and a block of a structural unit derived from ethyl acrylate; a block copolymer having a block of a structural unit derived from styrene and a block of a structural unit derived from t-butyl acrylate; a block copolymer having a block of a structural unit derived from styrene and a block of a structural unit derived from methacrylic acid; a block copolymer having a block of a structural unit derived from styrene and a block of a structural unit derived from methyl methacrylate; a block copolymer having a block of a structural unit derived from styrene and a block of a structural unit derived from ethyl methacrylate; a block copolymer having a block of a structural unit derived from styrene and a block of a structural unit derived from t-butyl methacrylate; a block copolymer having a block of a structural unit containing a polyhedral oligomeric silsesquioxane (POSS) structure and a block of a structural unit derived from acrylic acid; and a block copolymer having a block of a structural unit containing a polyhedral oligomeric silsesquioxane (POSS) structure and a block of a structural unit derived from methyl acrylate.
In the present embodiment, the use of a block copolymer having a block of a structural unit derived from styrene (PS) and a block of a structural unit derived from methyl methacrylate (PMMA) is particularly preferable.
The period L0 (nm) of the block copolymer is preferably 20 to 50 nm, more preferably 25 to 45 nm, and still more preferably 30 to 40 nm.
When the period L0 of the block copolymer is no more than the upper limit of the above preferable range, the compound (IL) may be more reliably volatilized, and the phase-separation performance may be more reliably enhanced. On the other hand, when the period L0 of the block copolymer is at least as large as the lower limit of the above preferable range, a nano structure having a good shape may be more stably obtained.
The number average molecular weight (Mn) (the polystyrene equivalent value determined by gel permeation chromatography (GPC)) of the block copolymer is preferably 20,000 to 200,000, more preferably 30,000 to 150,000, and still more preferably 50,000 to 90,000.
According to method of producing a structure containing a phase-separated structure of the present embodiment, when a block copolymer having a number average molecular weight capable of causing phase-separation without addition of compound (IL) containing the compound (IL) to the resin composition for forming a phase-separated structure is used (e.g., Mn>80000), by addition of the ion liquid, roughness may be reduced without changing the period (L0) of the structure, so as to form a structure having a satisfactory shape.
The dispersity (Mw/Mn) of the block copolymer is preferably 1.0 to 3.0, more preferably 1.0 to 1.5, and still more preferably 1.0 to 1.3.
Here, Mw is the weight average molecular weight.
In the resin composition for forming a phase-separated structure, 1 kind of block copolymer may be used, or 2 or more kinds of block copolymers may be used in combination.
In the resin composition for forming a phase-separated structure, the amount of the block copolymer may be adjusted depending on the thickness of the layer containing the block copolymer to be formed.
«Ion Liquid»
In the resin composition for forming a phase-separated structure, the ion liquid contains a compound (IL) having a specific cation moiety and anion moiety.
An ion liquid refers to a salt which is present in the form of a liquid. An ion liquid is constituted of a cation moiety and an anion moiety. The electrostatic interaction between the cation moiety and the anion moiety is week, and the salt is unlikely to be crystallized. The ion liquid has a boiling point of 100° C. or lower, and has the following characteristics 1) to 5).
Characteristic 1) The vapor pressure is extremely low. Characteristic 2) Non-flammable over a wide temperature range. Characteristic 3) Maintains a liquid state over a wide temperature range Characteristic 4) The density can be largely changed. Characteristic 5) The polarity can be controlled.
In the present embodiment, the ion liquid may be non-polymeric.
The weight average molecular weight (Mw) of the ion liquid is preferably 1,000 or less, more preferably 750 or less, and still more preferably 500 or less.
Compound (IL) Having Cation Moiety and Anion Moiety
The compound (IL) is a compound having a cation moiety and an anion moiety.
Cation Moiety of Compound (IL)
The cation moiety of the compound (IL) is not particularly limited. However, in terms of improvement in the phase-separation performance, the cation moiety preferably has a dipole moment of 3 debye or more, more preferably 3.2 to 15 debye, and still more preferably 3.4 to 12 debye.
The “dipole moment of the cation moiety” is a parameter quantitatively indicating the polarity (deviation of charge) of the cation moiety. 1 debye is defined as 1×10−18esu·cm. In the present specification, the dipole moment of the cation moiety refers to a simulation value by CAChe. For example, the dipole moment of the cation moiety can be determined by optimization of the structure by CAChe Work System Pro Version 6.1.12.33, using MM geometry (MM2) and PM3 geometry.
Preferable examples of cation moiety having a dipole moment of 3 debye or more include an imidazolium ion, a pyrrolidinium ion, a piperidinium ion and an ammonium ion.
That is, preferable examples of the compound (IL) include an imidazolium salt, a pyrrolidinium salt, a piperidinium salt and an ammonium salt. Among these salts, in terms of improving the phase-separation performance, the cation moiety preferably has a substituent. Among these, a cation containing an alkyl group of 2 or more carbon atoms optionally having a substituent, or a cation containing a polar group. The alkyl group of 2 or more carbon atoms contained in the cation preferably has 2 to 12 carbon atoms, more preferably 2 to 6 carbon atoms. The alkyl group may be a linear alkyl group or a branched alkyl group, but is preferably a linear alkyl group. Examples of the substituent for the alkyl group of 2 or more carbon atoms include a hydroxy group, a vinyl group and an allyl group.
The alkyl group of 2 or more carbon atoms preferably has no substituent. Examples of the polar group contained in the cation include a carboxy group, a hydroxy group, an amino group and a sulfo group.
More preferable examples of the cation moiety of the compound (IL) include a pyrrolidinium ion. Among pyrrolidinium ions, a pyrrolidinium ion containing an alkyl group of 2 or more carbon atoms which may have a substituent is preferable.
Anion Moiety of Compound (IL)
The anion moiety of the compound (IL) is not particularly limited, and examples thereof include anions represented by any one of general formulae (a1) to (a5) shown below.
In formula (a1), R represents an aromatic hydrocarbon group which may have a substituent, an aliphatic cyclic group which may have a substituent, or a chain hydrocarbon group which may have a substituent. In formula (a2), R′ represents an alkyl group of 1 to 5 carbon atoms optionally substituted with a fluorine atom. k represents an integer of 1 to 4, and 1 represents an integer of 0 to 3, provided that k+l=4. in formula (a3), R″ represents an alkyl group of 1 to 5 carbon atoms optionally substituted with a fluorine atom; m represents an integer of 1 to 6, and n represents an integer of 0 to 5, provided that m+n=6.
In formula (a4), X″ represents an alkylene group of 2 to 6 carbon atoms in which at least one hydrogen atom has been substituted with a fluorine atom; in formula (a5), Y″ and Z″ each independently represents an alkyl group of 1 to 10 carbon atoms in which at least one hydrogen atom has been substituted with a fluorine atom;
In general formula (a1), R represents an aromatic hydrocarbon group which may have a substituent, an aliphatic cyclic group which may have a substituent, or a chain hydrocarbon group which may have a substituent.
In general formula (a1), in the case where R is an aromatic hydrocarbon group which may have a substituent, examples of the aromatic ring contained in the aromatic hydrocarbon group include aromatic hydrocarbon rings, such as benzene, biphenyl, fluorene, naphthalene, anthracene and phenanthrene; and aromatic hetero rings in which part of the carbon atoms constituting the aforementioned aromatic hydrocarbon rings has been substituted with a hetero atom. Examples of the hetero atom within the aromatic hetero rings include an oxygen atom, a sulfur atom and a nitrogen atom.
Specific examples of the aromatic hydrocarbon group include a group in which 1 hydrogen atom has been removed from the aforementioned aromatic hydrocarbon ring (aryl group); and a group in which 1 hydrogen atom of the aforementioned aryl group has been substituted with an alkylene group (an arylalkyl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group or a 2-naphthylethyl group). The alkylene group (alkyl chain within the arylalkyl group) preferably has 1 to 4 carbon atom, more preferably 1 or 2, and most preferably 1.
As the aromatic hydrocarbon group for R, a phenyl group or a naphthyl group is preferable, and a phenyl group is more preferable.
In general formula (a1), in the case where R represents an aliphatic cyclic group which may have a substituent, the cyclic group may be polycyclic or monocyclic. As the monocyclic aliphatic hydrocarbon group, a group in which one hydrogen atoms have been removed from a monocycloalkane is preferable. The monocycloalkane preferably has 3 to 8 carbon atoms, and specific examples thereof include cyclopentane, cyclohexane and cyclooctane. As the polycyclic aliphatic cyclic group, a group in which one hydrogen atoms have been removed from a polycycloalkane is preferable, and the polycyclic group preferably has 7 to 12 carbon atoms. Examples of the polycycloalkane include adamantane, norbornane, isobornane, tricyclodecane and tetracyclododecane.
Among these examples, as the aliphatic cyclic group, a polycyclic group is preferable, and a group in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane or tetracyclododecane is more preferable.
In general formula (a1), as the chain hydrocarbon group for R, a chain alkyl group is preferable. The chain-like alkyl group preferably has 1 to 10 carbon atoms, and specific examples thereof include a linear alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl or a decyl group, and a branched alkyl group such as a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group or a 4-methylpentyl group. The chain-like alkyl group preferably has 1 to 6 carbon atoms, and more preferably 1 to 3 carbon atoms. Further, a linear alkyl group is preferable.
In general formula (a1), examples of the substituent for the aromatic hydrocarbon group, the aliphatic cyclic group or the chain hydrocarbon group for R include a hydroxy group, an alkyl group, a fluorine atom or a fluorinated alkyl group.
In general formula (a1), as R, a methyl group, a trifluoromethyl group or a p-tolyl group is preferable.
In general formula (a2), R′ represents an alkyl group of 1 to 5 carbon atoms optionally substituted with a fluorine atom.
k represents an integer of 1 to 4, preferably an integer of 3 to 4, and most preferably 4.
l represents an integer of 0 to 3, preferably 0 to 2, most preferably 0. When 1 is 2 or more, the plurality of R′ may be the same or different from each other, but are preferably the same.
In general formula (a3), R″ represents an alkyl group of 1 to 5 carbon atoms optionally substituted with a fluorine atom;
m represents an integer of 1 to 6, preferably an integer of 3 to 6, and most preferably 6.
n represents an integer of 0 to 5, preferably 0 to 3, most preferably 0. When n is 2 or more, the plurality of R″ may be the same or different from each other, but are preferably the same.
In formula (a4), X″ represents an alkylene group of 2 to 6 carbon atoms in which at least one hydrogen atom has been substituted with a fluorine atom. The alkylene group may be linear or branched, and has 2 to 6 carbon atoms, preferably 3 to 5 carbon atoms, and most preferably 3 carbon atoms.
In formula (a5), Y″ and Z″ each independently represents an alkyl group of 1 to 10 carbon atoms in which at least one hydrogen atom has been substituted with a fluorine atom. The alkyl group may be linear or branched, and has 1 to 10 carbon atoms, preferably 1 to 7 carbon atoms, and most preferably 1 to 3 carbon atoms.
The smaller the number of carbon atoms of the alkylene group for X″ or those of the alkyl group for Y″ and Z″ within the above-mentioned range of the number of carbon atoms, the more the solubility in an organic solvent component is improved.
In the alkylene group for X″ and the alkyl group for Y″ and Z″, it is preferable that the number of hydrogen atoms substituted with fluorine atoms is as large as possible because the acid strength increases. The amount of fluorine atoms within the alkylene group or alkyl group, i.e., fluorination ratio, is preferably from 70 to 100%, more preferably from 90 to 100%, and it is particularly desirable that the alkylene group or alkyl group be a perfluoroalkylene or perfluoroalkyl group in which all hydrogen atoms are substituted with fluorine atoms.
As the anion moiety of the compound (IL), among the anion moieties represented by the aforementioned general formulae (a1) to (a5), an anion moiety represented by general formula (a1), (a3) or (a5) is preferable, and an anion moiety represented by general formula (a1) or (a5) is more preferable.
Preferable combinations of the anion moiety and the cation moiety of the compound (IL) include a combination of a cation moiety consisting of a pyrrolidinium ion and an anion moiety represented by the aforementioned general formula (a1) or (a5).
Specific examples of the compound (IL) are shown below, but the compound (IL) is by no means limited by these examples.
In the resin composition for forming a phase-separated structure, as the compound (IL), 1 kind of compound may be used, or 2 or more kinds of compounds may be used in combination.
In the resin composition for forming a phase-separated structure, the amount of the compound (IL) relative to 100 parts by weight of the block copolymer is preferably 1.0 parts by weight or more, and more preferably 3.0 parts by weight or more.
Further, in the resin composition for forming a phase-separated structure, the amount of the compound (IL) relative to the total amount (100% by weight) of the resin composition for forming a phase-separated structure is preferably 0.030% by weight or more, more preferably 0.065% by weight or more, and still more preferably 0.070% by weight or more.
In the resin composition for forming a phase-separated structure, the upper limit of the amount of the compound (IL) relative to 100 parts by weight of the block copolymer is not particularly limited, but is preferably 40 parts by weight or less, more preferably 30 parts by weight or less, and still more preferably 20 parts by weight or less. The range of the amount of the compound (IL) relative to 100 parts by weight of the block copolymer may be 1.0 to 40 parts by weight, 3.0 to 30 parts by weight, 5.0 to 30 parts by weight, or 8.5 to 20 parts by weight.
Further, in the resin composition for forming a phase-separated structure, the amount of the compound (IL) relative to the total amount (100% by weight) of the resin composition for forming a phase-separated structure is preferably 3.0% by weight or less, more preferably 1.0% by weight or less, and still more preferably 0.5% by weight or less. The range of the amount of the compound (IL) relative to 100% by weight of the resin composition for forming a phase-separated structure may be 0.030 to 3.0% by weight, 0.065 to 1.0% by weight, or 0.070 to 0.5% by weight.
In the method of forming a structure containing a phase-separated structure according to the present embodiment, by conducting the anneal treatment at a high temperature, the compound (IL) is vaporized and removed from the BCP layer. Therefore, in the resin composition for forming a phase-separated structure, the amount of the compound (IL) may be increased, as compared to a conventional method. By increasing the amount of the compound (IL) in the resin composition for forming a phase-separated structure, the interaction between the block copolymer and the compound (IL) is promoted, and the phase-separation performance is improved. In general, when the BCP layer contains a compound (IL), the period (L0) of the structure becomes large. However, as described above, since the compound (IL) is removed from the BCP layer by the anneal treatment, the phase-separation performance may be improved while maintaining the period (L0) of the structure. Therefore, in the case where a block copolymer having a low polymerization degree is used, a structure having a smaller period, i.e., a pattern having a finer structure may be more reliably formed.
In the resin composition for forming a phase-separated structure according to the present embodiment, the ion liquid may contain a compound other than the compound (IL) which has a cation moiety and an anion moiety.
In the ion liquid the amount of the compound (IL) based on the total weight of the ion liquid is preferably 50% by weight or more, more preferably 70% by weight or more, still more preferably 90% by weight or more, and may be even 100% by weight.
When the amount of the compound (IL) within the ion liquid is at least as large as the lower limit of the above preferable range, the phase-separation performance may be further improved.
«Organic Solvent»
The resin composition for forming a phase-separated structure may be prepared by dissolving the block copolymer and the ion liquid in an organic solvent component.
The organic solvent component may be any organic solvent which can dissolve the respective components to give a uniform solution, and one or more kinds of any organic solvent can be appropriately selected from those which have been conventionally known as solvents for a film composition containing a resin as a main component.
Examples of the organic solvent component include lactones such as γ-butyrolactone; ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl-n-pentyl ketone, methyl isopentyl ketone, and 2-heptanone; polyhydric alcohols, such as ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol; compounds having an ester bond, such as ethylene glycol monoacetate, diethylene glycol monoacetate, propylene glycol monoacetate, and dipropylene glycol monoacetate; polyhydric alcohol derivatives including compounds having an ether bond, such as a monoalkylether (e.g., monomethylether, monoethylether, monopropylether or monobutylether) or monophenylether of any of these polyhydric alcohols or compounds having an ester bond (among these, propylene glycol monomethyl ether acetate (PGMEA) and propylene glycol monomethyl ether (PGME) are preferable); cyclic ethers such as dioxane; esters such as methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, and ethyl ethoxypropionate; and aromatic organic solvents such as anisole, ethylbenzylether, cresylmethylether, diphenylether, dibenzylether, phenetole, butylphenylether, ethylbenzene, diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymene and mesitylene.
As the organic solvent component, 1 kind of solvent may be used, or 2 or more kinds of solvents may be used in combination.
Among these examples, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME), cyclohexanone and ethyl lactate (EL) are preferable.
Further, among the mixed solvents, a mixed solvent obtained by mixing PGMEA with a polar solvent is preferable. The mixing ratio (weight ratio) of the mixed solvent can be appropriately determined, taking into consideration the compatibility of the PGMEA with the polar solvent, but is preferably in the range of 1:9 to 9:1, more preferably from 2:8 to 8:2.
For example, when EL is mixed as the polar solvent, the PGMEA:EL weight ratio is preferably from 1:9 to 9:1, and more preferably from 2:8 to 8:2. Alternatively, when PGME is mixed as the polar solvent, the PGMEA:PGME weight ratio is preferably from 1:9 to 9:1, more preferably from 2:8 to 8:2, and still more preferably 3:7 to 7:3. Alternatively, when PGME and cyclohexanone is mixed as the polar solvent, the PGMEA:(PGME+cyclohexanone) weight ratio is preferably from 1:9 to 9:1, more preferably from 2:8 to 8:2, and still more preferably 3:7 to 7:3.
Further, as the organic solvent component for the resin composition for forming a phase-separated structure, a mixed solvent of γ-butyrolactone with PGMEA, EL or the aforementioned mixed solvent of PGMEA with a polar solvent, is also preferable. The mixing ratio (former:latter) of such a mixed solvent is preferably from 70:30 to 95:5. The amount of the organic solvent component in the resin composition for forming a phase-separated structure is not particularly limited, and is adjusted appropriately to a concentration that enables application of a coating solution depending on the thickness of the coating film. In general, the organic solvent component is used in an amount that yields a solid content within a range from 0.2 to 70% by weight, and preferably from 0.2 to 50% by weight.
<Optional Components>
If desired, in addition to the block copolymer, the ion liquid and the organic solvent component, other miscible additives can also be added to the resin composition for forming a phase-separated structure. Examples of such miscible additives include additive resins for improving the performance of the layer of the brush layer, surfactants for improving the applicability, dissolution inhibitors, plasticizers, stabilizers, colorants, halation prevention agents, dyes, sensitizers, base amplifiers and basic compounds.
As follows is a description of examples of the present invention, although the scope of the present invention is by no way limited by these examples.
(Preparation of Resin Composition for Forming Phase-Separated Structure)
The components shown in Table 1 were mixed together and dissolved to obtain resin composition (P1) and resin composition (P2), each having a solid content of 1.2% by weight.
In Table 1, the reference characters indicate the following. The values in brackets [ ] indicate the amount (in terms of parts by weight) of the component added.
BCP-1: a block copolymer of polystyrene (PS block) and poly(methyl methacrylate) (PMMA block); period L0 36 nm; number average molecular weight (Mn) of PS block was 41,000, number average molecular weight (Mn) of PMMA block was 41,000, and the total number average molecular weight (Mn) was 82,000; PS/PMMA compositional ratio (weight ratio) 50/50; dispersity (Mw/Mn) 1.02.
BCP-2: a block copolymer of polystyrene (PS block) and poly(methyl methacrylate) (PMMA block); period L0 30 nm; number average molecular weight (Mn) of PS block was 30,000, number average molecular weight (Mn) of PMMA block was 30,000, and the total number average molecular weight (Mn) was 61,000; PS/PMMA compositional ratio (weight ratio) 50/50; dispersity (Mw/Mn) 1.02.
(IL)-1: Compound represented by following chemical formula (IL-3)
(S)-1: propyleneglycol monomethyletheracetate
(Production of Structure Containing Phase-Separated Structure)
Using resin composition (P1) and resin composition (P2), the production method of the following test examples was performed.
[Step (i)]
The following brush composition was applied to a silicon (Si) wafer having a diameter of 300 mm by spin-coating (number of rotation: 1,500 rpm, 60 seconds), followed by drying by baking in air at 250° C. for 60 seconds, so as to form a brush layer having a film thickness of 60 nm.
As the brush composition, a PGMEA solution of a random copolymer having a styrene (St) unit, a methyl methacrylate (MMA) unit and a 2-hydroxyethyl methacrylate (HEMA) unit (St/MMA/HEMA=82/12/6 (molar ratio)) (copolymer content: 2.0% by weight).
Subsequently, the brush layer was rinsed with OK73 thinner (product name; manufactured by Tokyo Ohka Kogyo Co., Ltd.) for 15 seconds, so as to remove the uncrosslinked portions and the like of the random copolymer. Then, baking was conducted at 100° C. for 60 seconds. After the baking, the brush layer formed on the Si wafer had a film thickness of 7 nm.
Thereafter, resin composition (P1) was spin-coated (number of rotation: 1,500 rpm, 60 seconds) to cover the brush layer formed on the Si wafer while adjusting the “thickness d/period L0” as indicated in Table 2, followed by drying by shaking, so as to form a PS-PMMA block copolymer layer having a predetermined thickness (27 to 108 nm).
[Step (ii)]
Next, in a nitrogen atmosphere, an anneal treatment was conducted at 270° C. for 60 minutes, so as to phase-separate the PS-PMMA block copolymer layer into a phase constituted of PS and a phase constituted of PMMA, so as to obtain a structure containing a phase-separated structure.
[Step (iii)]
An oxygen plasma treatment was conducted on the silicon (Si) wafer having the phase-separated structure formed thereon, so as to selectively remove the phase constituted of PMMA, and obtain a pattern of PS phases separated apart (polymeric nanostructure).
Steps (i), (ii) and (iii) were conducted in the same manner as in Test Example 1-1, except that the “thickness d/period L0” was adjusted as indicated in Table 3 using resin composition (P1) to form a PS-PMMA block copolymer layer having a predetermined thickness (27 to 108 nm), and the anneal treatment was conducted at 270° C. for 1 minute, so as to obtain a pattern (polymeric nanostructure).
Steps (i), (ii) and (iii) were conducted in the same manner as in Test Example 2-1, except that resin composition (P1) was changed to resin composition (P2) in step (i), and the “thickness d/period L0” was adjusted as indicated in Table 4 to form a PS-PMMA block copolymer layer having a thickness d of 22.5 to 90 nm, so as to obtain a pattern (polymeric nanostructure).
Steps (i), (ii) and (iii) were conducted in the same manner as in Test Example 1-1, except that the “thickness d/period L0” was adjusted as indicated in Table 5 using resin composition (P1) to form a PS-PMMA block copolymer layer having a predetermined thickness (27 to 108 nm), and the anneal treatment was conducted at 250° C. for 60 minutes, so as to obtain a pattern (polymeric nanostructure).
Steps (i), (ii) and (iii) were conducted in the same manner as in Test Example 1-1, except that the “thickness d/period L0” was adjusted as indicated in Table 6 using resin composition (P1) to form a PS-PMMA block copolymer layer having a predetermined thickness (27 to 108 nm), and the anneal treatment was conducted at 250° C. for 1 minute, so as to obtain a pattern (polymeric nanostructure).
Steps (i), (ii) and (iii) were conducted in the same manner as in Test Example 4-1, except that resin composition (P1) was changed to resin composition (P2) in step (i), and the “thickness d/period L0” was adjusted as indicated in Table 7 to form a PS-PMMA block copolymer layer having a thickness d of 22.5 to 90 nm, so as to obtain a pattern (polymeric nanostructure).
<Evaluation of Residual Ratio of Ion Liquid>
A part of the structure containing a phase-separated structure formed following step (ii) in each example where the anneal treatment was conducted for 60 minutes was cut out, and the residual ratio (weight %) of the ion liquid within the structure containing a phase-separated structure was measured by high performance liquid chromatography (HPLC). The results are indicated “IL residual ratio (%)” in Tables 2 and 5.
<Evaluation of Phase-Separation Performance>
In the production method of each test example, the surface of the Si wafer having a structure containing a phase-separated structure thereon (phase-separation state) was observed by a scanning electron microscope (CG6300; manufactured by Hitachi High-Technologies Corporation), and the phase-separation performance was evaluated in accordance with the following criteria. The results are shown in Tables 2 to 7.
Criteria:
A: Formation of a perpendicular phase-separated structure was clearly observed over the entire Si wafer.
B: Although formation of a perpendicular phase-separated structure was observed, defect was observed on part of the Si wafer.
C: No perpendicular phase-separated structure was observed.
A “perpendicular phase-separated structure” herein means a lamellar phase-separated structure oriented in a perpendicular direction of the substrate surface, like structure 3′ shown in
In Table 2, Test Examples 1-1, 1-3, 1-4, 1-5 and 1-7 apply the present invention. Test Examples 1-2, 1-6 and 1-8 are outside the scope of the present invention (comparative examples).
As seen from the results shown in Table 2, the production methods of examples which applied the present invention were capable of achieving a high phase-separation performance, as compared to the production methods of comparative examples (the case where thickness d/period L0 was an integer).
In Table 3, Test Examples 2-1, 2-3, 2-4, 2-5, 2-7, 2-8 and 2-9apply the present invention. Test Examples 2-2, 2-6 and 2-10 are outside the scope of the present invention (comparative examples).
As seen from the results shown in Table 2, the production methods of examples which applied the present invention were capable of achieving a high phase-separation performance, as compared to the production methods of comparative examples (the case where thickness d/period L0 was an integer). Further, among the production methods of examples, it was confirmed that higher phase-separation performance could be achieved in Test Examples 2-4 and 2-8.
In Table 4, Test Examples 2-11, 2-13, 2-14, 2-15, 2-17, 2-18 and 2-19 apply the present invention. Test Examples 2-12, 2-16 and 2-20 are outside the scope of the present invention (comparative examples).
As seen from the results shown in Table 4, the production methods of examples which applied the present invention were capable of achieving a high phase-separation performance, as compared to the production methods of comparative examples (the case where thickness d/period L0 was an integer).
In Table 5, Test Examples 3-1, 3-3, 3-4, 3-5 and 3-7 apply the present invention. Test Examples 3-2, 3-6 and 3-8 are outside the scope of the present invention (comparative examples).
As seen from the results shown in Table 5, the production methods of examples which applied the present invention were capable of achieving a high phase-separation performance, as compared to the production methods of comparative examples (the case where thickness d/period L0 was an integer).
In Table 6, Test Examples 4-1, 4-3, 4-4, 4-5, 4-7, 4-8 and 4-9 apply the present invention. Test Examples 4-2, 4-6 and 4-10 are outside the scope of the present invention (comparative examples).
As seen from the results shown in Table 6, the production methods of examples which applied the present invention were capable of achieving a high phase-separation performance, as compared to the production methods of comparative examples (the case where thickness d/period L0 was an integer). Further, among the production methods of examples, it was confirmed that higher phase-separation performance could be achieved in Test Examples 4-4 and 4-8.
In Table 7, Test Examples 4-11, 4-13, 4-14, 4-15, 4-17, 4-18 and 4-19 apply the present invention. Test Examples 4-12, 4-16 and 4-20 are outside the scope of the present invention (comparative examples).
As seen from the results shown in Table 7, the production methods of examples which applied the present invention were capable of achieving a high phase-separation performance, as compared to the production methods of comparative examples (the case where thickness d/period L0 was an integer).
From the results shown in Tables 2 to 7, it was confirmed that, by forming a BCP layer such that the period L0 (nm) of the block copolymer and the thickness d (nm) of the block copolymer layer (BCP layer) satisfies the following formula: thickness d/period L0=n+a (wherein n represents an integer of 0 or more; and a is a number which satisfies 0<a<1), the phase-separation performance can be improved.
Further, it can be seen that, in the above formula: thickness d/period L0=n+a, when a is 0.5, or a is a value close to 0.5, phase-separation performance can be more reliably enhanced.
1: Substrate 2: Brush layer 3: BCP layer 3′: Structure 3a: Phase 3b: Phase
| Number | Date | Country | Kind |
|---|---|---|---|
| 2018-048196 | Mar 2018 | JP | national |
