JP2024089895A - Compound including silsesquioxane with cage structure, polymer including constitutional unit derived from the compound, and resist composition including the polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compound including silsesquioxane with a cage structure, featuring superior developer solubility.

SOLUTION: The present invention provides a compound including silsesquioxane with a cage structure, represented by the following Formula 1. (RmSiO_1.5)_n (Formula 1). (In Formula 1, n is an integer of 3-30, Rm includes Ra and Rb, Ra is a structure represented by the following Formula 2, and Rb is a radical-polymerizable functional group). (In the Formula 2, L is a C1-6 hydrocarbon chain, Y is a hetero bond, Z¹ is a linear or branched alkyl group or the like, Z² and Z³ independently represent one of a hydrogen atom, a linear or branched alkyl group, a cycloalkyl group and the like, at least one selected from Z² and Z³ is not a hydrogen atom, j is an integer of 1-6, and k is an integer of 0-2).

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a compound containing a silsesquioxane having a cage structure, a polymer having structural units derived from the compound, and a resist composition containing the polymer.

Silsesquioxanes with a cage structure have a rigid polysiloxane skeleton and a molecular size at the sub-nano level, which gives them high transparency, heat resistance, surface hardness, scratch resistance, mechanical strength, etc., and they are being investigated for use as hard coat materials, heat-resistant materials, resist materials, etc.
For example, Patent Document 1 listed below describes a resist composition for lithography that contains silsesquioxane having a cage structure.

International Publication No. 2017/056928

However, the resist composition described in Patent Document 1 has insufficient solubility in a developer due to the silsesquioxane having a hydrocarbon side chain such as an ethyl group or an isobutyl group, and there are cases in which a problem remains with respect to resolution in fine patterns.
Therefore, an object of the present invention is to solve these problems and to provide a compound containing a silsesquioxane having a cage structure, which has good solubility in a developer, a polymer having a structural unit derived from the compound, a resist composition containing the polymer, and a pattern formation method using the resist composition.

The present invention has the following aspects:

[1] A compound containing a silsesquioxane having a cage structure represented by the following formula 1:
( _RmSiO1.5 ) _n (Formula 1)
(In formula 1, n is an integer of 3 to 30, Rm includes Ra and Rb, Ra is a structure represented by formula 2 below, and Rb is a radical polymerizable functional group.)

（上記式２中、Ｌは炭素数１～６の炭化水素鎖、Ｙはエーテル結合、エステル結合、チオエーテル結合、チオエステル結合から選ばれる少なくとも１種のヘテロ結合であり、Ｚ^１は直鎖または分岐アルキル基、シクロアルキル基、アリール基、アラルキル基であり、Ｚ^２、Ｚ^３はそれぞれ独立に、水素原子、直鎖状もしくは分岐状のアルキル基、シクロアルキル基、アリール基またはアラルキル基、アルコキシル基、アリールオキシ基、アルキルオキシカルボニル基、アリールオキシカルボニル基、アルキルカルボニル基、アリールカルボニル基、置換基としてアルコキシル基、アリールオキシ基、アルキルオキシカルボニル基、アリールオキシカルボニル基、アルキルカルボニル基、アリールカルボニル基から選ばれる少なくとも１種を有する直鎖状もしくは分岐状のアルキル基のいずれかであり、Ｚ^２、Ｚ^３から選ばれる少なくとも１つは水素原子以外であり、ｊは１～６の整数であり、ｋは０～２の整数である。）

(In the above formula 2, L is a hydrocarbon chain having 1 to 6 carbon atoms; Y is at least one hetero bond selected from an ether bond, an ester bond, a thioether bond, and a thioester bond; Z ¹ is a linear or branched alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group; Z ² and Z ³ are each independently any one of a hydrogen atom, a linear or branched alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkoxyl group, an aryloxy group, an alkyloxycarbonyl group, an aryloxycarbonyl group, an alkylcarbonyl group, an arylcarbonyl group, and a linear or branched alkyl group having at least one substituent selected from an alkoxyl group, an aryloxy group, an alkyloxycarbonyl group, an aryloxycarbonyl group, an alkylcarbonyl group, and an arylcarbonyl group; at least one selected from Z ² and Z ³ is other than a hydrogen atom; j is an integer of 1 to 6; and k is an integer of 0 to 2.)

[2]. A polymer having a structural unit derived from the compound described in [1].

[3]. The polymer according to [2], further comprising a structural unit derived from a monomer containing an acid-dissociable group.

[4]. The polymer according to [2] or [3], further comprising a structural unit derived from a monomer containing a phenolic hydroxyl group.

[5]. The polymer according to any one of [2] to [4], further comprising a structural unit derived from a monomer containing a lactone skeleton.

[6]. A resist composition containing the polymer described in any one of [2] to [5].

[7]. A method for forming a resist pattern using the resist composition described in [6].

The present invention was made by discovering that, by having the structure represented by the above formula 2, a cage-type silsesquioxane can be easily obtained, and in addition, the acid diffusion caused by exposure can be appropriately suppressed by the polar group such as an ester group or a thioether group, and further improvement in resolution can be achieved, in combination with the effect of good solubility in a developer.
According to the present invention, it is possible to provide a polymer made of silsesquioxane having a cage structure that has good solubility in a developer and excellent pattern resolution, a resist composition containing the polymer, and a pattern forming method using the resist composition.

The present invention will be described based on one embodiment. However, the present invention is not limited to this embodiment.

[Compound containing silsesquioxane having a cage structure]
A compound containing silsesquioxane having a cage structure according to one embodiment of the present invention (hereinafter also referred to as the present compound) is represented by the following formula 1.
( _RmSiO1.5 ) _n (Formula 1)

In formula 1, n is an integer from 3 to 30, Rm includes Ra and Rb, Ra is a structure represented by formula 2 below, and Rb is a radical polymerizable functional group.

In the above formula 1, in order to form a fine pattern, it is preferable that n has a small molecular size and weak entanglement of molecular chains, and from that viewpoint, n is preferably 30 or less, and more preferably 20 or less. Also, from the viewpoint of structural stability, n is preferably 3 or more, and more preferably 6 or more.

In the above formula 2, L is a hydrocarbon chain having 1 to 6 carbon atoms; Y is at least one hetero bond selected from an ether bond, an ester bond, a thioether bond, and a thioester bond; ^Z1 is a linear or branched alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group; ^Z2 and ^Z3 are each independently any of a hydrogen atom, a linear or branched alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkoxyl group, an aryloxy group, an alkyloxycarbonyl group, an aryloxycarbonyl group, an alkylcarbonyl group, an arylcarbonyl group, and a linear or branched alkyl group having at least one substituent selected from an alkoxyl group, an aryloxy group, an alkyloxycarbonyl group, an aryloxycarbonyl group, an alkylcarbonyl group, and an arylcarbonyl group; at least one selected from ^Z2 and ^Z3 is other than a hydrogen atom; j is an integer of 1 to 6; and k is an integer of 0 to 2.

The mass average molecular weight (Mw)/number average molecular weight (Mn) (polystyrene equivalent by gel permeation chromatography) of the present compound is preferably 1.0 to 2.0, more preferably 1.0 to 1.8, in view of the ability to form fine patterns.
The mass average molecular weight (Mw) is not particularly limited, but is preferably from 800 to 10,000, and more preferably from 1,300 to 6,000.
The number average molecular weight (Mn) is not particularly limited, but is preferably from 800 to 10,000, and more preferably from 1,300 to 6,000.

The silsesquioxane having a cage structure of the present compound is a cage structure having n vertices expressed as (SiO _1.5 ) _n . The cage structure may be a complete cage silsesquioxane structure or an incomplete cage silsesquioxane structure. For example, the following compound may be an example of a complete cage silsesquioxane structure.

Here, each vertex is a silicon atom containing one substituent, and each edge represents a Si-O-Si bond.

The compound contains an organosilicon compound with a rigid chemical structure, which gives it, for example, excellent resistance to dry etching.

In this compound, Rm of the silsesquioxane includes Ra and Rb, and Ra includes a structure represented by the following formula 2.

In the above formula 2, L is a hydrocarbon chain having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms, and particularly preferably 1 to 3 carbon atoms.

Y is at least one hetero bond selected from an ether bond, an ester bond, a thioether bond, and a thioester bond, of which an ester bond is preferred.

Z ¹ is a linear or branched alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group, and Z ² and Z ³ are each independently a hydrogen atom, a linear or branched alkyl group, a cycloalkyl group, an aryl group or an aralkyl group, an alkoxyl group, an aryloxy group, an alkyloxycarbonyl group, an aryloxycarbonyl group, an alkylcarbonyl group, an arylcarbonyl group, or a linear or branched alkyl group having at least one selected from an alkoxyl group, an aryloxy group, an alkyloxycarbonyl group, an aryloxycarbonyl group, an alkylcarbonyl group, or an arylcarbonyl group as a substituent, and at least one selected from Z ² and Z ³ is other than a hydrogen atom. Among these, Z ² is preferably a hydrogen atom, a linear or branched alkyl group, an alkyloxycarbonyl group, or a linear or branched alkyl group having an alkyloxycarbonyl group as a substituent, and Z ³ is preferably a hydrogen atom, a linear or branched alkyl group, or a linear or branched alkyl group having an alkyloxycarbonyl group as a substituent.

j is an integer from 1 to 6, preferably 2 to 4. k is an integer from 0 to 2, preferably 0 to 1.

Rb represents a radically polymerizable functional group, and examples of the radically polymerizable functional group include a (meth)acryloyl group, an allyl group, a styryl group, an α-methylstyryl group, a vinyl group, etc. Among these, a (meth)acryloyl group and a styryl group are preferred, and a (meth)acryloyl group is particularly preferred.
In the present invention, the term "(meth)acryloyl group" refers to an acryloyl group or a methacryloyl group, the term "(meth)acrylic acid" refers to an acrylic acid or a methacrylic acid, and the term "(meth)acrylate" refers to an acrylate or a methacrylate.

In this compound, the ratio of Ra and Rb introduced is usually a molar ratio of 4:1 to 14:1, preferably 5:1 to 12:1, and particularly preferably 6:1 to 10:1, since this can reduce the molecular weight distribution of the silsesquioxane-containing compound and its polymer.

[Polymer]
A polymer according to one embodiment of the present invention (hereinafter also referred to as the present polymer) has a constitutional unit derived from the present compound.
The present polymer may be a polymer obtained by polymerizing the present compound, but is preferably a copolymer having two or more kinds of constitutional units. In other words, the present polymer preferably contains one or more kinds of constitutional units other than the constitutional unit containing the silsesquioxane skeleton shown as the present compound, and more preferably contains 1 to 5 kinds of other constitutional units.
As the other structural unit, any structural unit known in the art for use in chemically amplified resist compositions can be used, such as a structural unit containing an acid dissociable group, a structural unit containing a phenolic hydroxyl group, or a structural unit containing a lactone skeleton.

The present polymer may contain one or more types of structural units containing a silsesquioxane skeleton. From the viewpoint of the balance with structural units other than the structural units containing a silsesquioxane skeleton, the structural units containing a silsesquioxane skeleton are preferably three or less types.
The content of the structural unit containing a silsesquioxane skeleton relative to all structural units of the present polymer is preferably from 1 to 50 mol %, more preferably from 1 to 40 mol %, and even more preferably from 1 to 30 mol %.
The mass average molecular weight of the present polymer is preferably from 1,000 to 100,000, more preferably from 3,000 to 50,000, and even more preferably from 5,000 to 30,000.

<Structural Unit Containing Acid-Labeling Group>
As described above, the present polymer preferably has one or more structural units derived from a monomer containing an acid-dissociable group. The acid-dissociable group refers to a group whose alkali solubility is improved by the action of an acid.
The monomer containing an acid dissociable group is preferably a (meth)acrylic acid ester compound. Specific examples of the monomer containing an acid dissociable group include t-butyl (meth)acrylate, t-amyl (meth)acrylate, 1,1-diethylpropyl (meth)acrylate, 1-methylcyclopentyl (meth)acrylate, 1-ethylcyclopentyl (meth)acrylate, 1-isopropylcyclopentyl (meth)acrylate, 1-t-butylcyclopentyl (meth)acrylate, 1-methylcyclohexyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, 2-ethyl-2-adamantyl (meth)acrylate, and 2-isopropyl-2-adamantyl (meth)acrylate.

The monomer containing an acid-dissociable group may be used alone or in combination of two or more. The content of the structural units containing an acid-dissociable group relative to the total structural units of the polymer is preferably 5 to 80 mol%, more preferably 10 to 70 mol%, and even more preferably 20 to 65 mol%.

<Structural Unit Containing a Phenolic Hydroxyl Group>
The present polymer preferably has one or more structural units derived from a monomer containing a phenolic hydroxyl group.
The monomer containing a phenolic hydroxyl group is preferably a styrene compound or a (meth)acrylic acid ester compound. Specific examples of the monomer containing a phenolic hydroxyl group include 4-hydroxystyrene, 2-hydroxystyrene, 3-hydroxystyrene, 2,3-dihydroxystyrene, 3,4-dihydroxystyrene, 3,5-dihydroxystyrene, 4-isopropenylphenol, 2-hydroxy-6-vinylnaphthalene, 4-hydroxy-6-vinylnaphthalene, 5-hydroxy-6-vinylnaphthalene, and 4-hydroxyphenyl (meth)acrylate.

The monomer containing a phenolic hydroxyl group may be used alone or in combination of two or more. The content of the structural units containing a phenolic hydroxyl group relative to the total structural units of the polymer is preferably 5 to 90 mol%, more preferably 10 to 80 mol%, and even more preferably 20 to 70 mol%.

<Structural Units Containing Lactone Skeleton>
The present polymer may have one or more constituent units of a monomer containing a lactone skeleton. The lactone skeleton means a monocyclic or polycyclic atomic group containing a ring having -O-C(=O)-. The ring having -O-C(=O)- may be a ring having -C(=O)-O-C(=O)-.
The lactone skeleton is preferably a 4- to 20-membered ring, more preferably a 5- to 10-membered ring.
The lactone skeleton may be a monocyclic lactone ring, or an aromatic or non-aromatic hydrocarbon ring or heterocyclic ring may be condensed with the lactone ring.
As the monomer containing a lactone skeleton, a (meth)acrylic acid ester compound is preferred. In particular, from the viewpoint of excellent adhesion to a substrate, etc., at least one selected from the group consisting of a (meth)acrylic acid ester having a substituted or unsubstituted δ-valerolactone ring and a (meth)acrylic acid ester having a substituted or unsubstituted γ-butyrolactone ring is preferred, and a monomer having an unsubstituted γ-butyrolactone ring is particularly preferred.
Specific examples of monomers having a lactone skeleton include β-(meth)acryloyloxy-β-methyl-δ-valerolactone, 4,4-dimethyl-2-methylene-γ-butyrolactone, β-(meth)acryloyloxy-γ-butyrolactone, β-(meth)acryloyloxy-β-methyl-γ-butyrolactone, α-(meth)acryloyloxy-γ-butyrolactone, 2-(1-(meth)acryloyloxy)ethyl-4-butanolide, (meth)acrylic acid pantoyl lactone, 5-(meth)acryloyloxy-2,6-norbornane carbolactone, 8-methacryloxy-4-oxatricyclo[5.2.1.02,6]decan-3-one, and 9-methacryloxy-4-oxatricyclo[5.2.1.02,6]decan-3-one.

The monomer containing a lactone skeleton may be used alone or in combination of two or more kinds.
When the present polymer has a monomer unit containing a lactone skeleton, the content thereof is preferably from 1 to 70 mol %, more preferably from 5 to 60 mol %, and even more preferably from 10 to 50 mol %, based on all constitutional units.

[Resist Composition]
A resist composition according to one embodiment of the present invention (hereinafter also referred to as the present resist composition) preferably contains the present polymer, a resist solvent, and a compound that generates an acid upon irradiation with actinic rays or radiation. The present polymer may be one type, or two or more types may be used in combination. The resist composition may be for alkaline development or for organic solvent development.
The content of the present polymer in the resist composition (excluding the solvent) is not particularly limited, but is preferably from 70 to 99.9% by mass.

Examples of the resist solvent include cyclopentanone, cyclohexanone, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME), etc. The resist solvent may be used alone or in combination of two or more kinds.
The amount of the resist solvent used depends on the thickness of the resist film to be formed, but is preferably in the range of 100 to 10,000 parts by mass per 100 parts by mass of the present polymer.

The compound that generates an acid upon irradiation with actinic rays or radiation can be arbitrarily selected from those usable as a photoacid generator for a chemically amplified resist composition. The photoacid generator may be used alone or in combination of two or more kinds.
Examples of the photoacid generator include an onium salt compound, a sulfonimide compound, a sulfone compound, a sulfonate compound, a quinone diazide compound, and a diazomethane compound.
The amount of the photoacid generator used is preferably 0.1 to 20 parts by mass, and more preferably 0.5 to 10 parts by mass, based on 100 parts by mass of the present polymer.

The resist composition may contain various additives, such as nitrogen-containing compounds, acid compounds (organic carboxylic acids, phosphorus oxoacids or derivatives thereof), surfactants, other quenchers, sensitizers, antihalation agents, storage stabilizers, and defoamers, as necessary. Additives that are known in the art can be used.

[Method of producing the present compound]
Next, an example of a method for producing the present compound will be described.
The silsesquioxane compound having the cage structure of this compound can be obtained by hydrolysis and co-condensation of a silane compound having Rm including Ra and/or Rb by a known method. In the present invention, the hydrolysis and co-condensation refers to a series of reactions in which two or more kinds of silane compounds are mixed with a predetermined amount of water and a catalyst, and the desired silsesquioxane compound is produced by hydrolysis of the alkoxysilyl group and the subsequent condensation reaction of the silanol group.

Suitable catalysts for the hydrolysis and co-condensation of the silane compound having Rm include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and hydrofluoric acid, and quaternary ammonium salts such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, benzyltriethylammonium hydroxide, ammonium fluoride, tetrabutylammonium fluoride, benzyltrimethylammonium chloride, and benzyltriethylammonium chloride.
Among these, hydrofluoric acid and ammonium fluoride are particularly preferred since they specifically form a cage structure.

The amount of catalyst is preferably 0.001 to 1 times the theoretical total number of moles of hydrolyzable alkoxy groups of the silane compound having Rm, and more preferably 0.005 to 0.5 times. At 0.001 times or more, sufficient catalytic activity can be obtained. At 1 time or less, gelation can be suppressed.

The amount of water used for hydrolysis of the silane compound having Rm is preferably 0.1 to 10 times, more preferably 1 to 3 times, the theoretical total amount of the number of moles of hydrolyzable alkoxy groups.
The reaction temperature for hydrolysis and co-condensation is preferably 0 to 100° C., more preferably 20 to 50° C. If the reaction temperature is 0° C. or higher, the reaction proceeds sufficiently. If the reaction temperature is 100° C. or lower, there is little possibility of side reactions being induced or gelation being formed.

During hydrolysis and co-condensation, it is preferable to use an organic solvent. There are no particular limitations on the organic solvent as long as it can dissolve the silane compound having Rm, but examples include methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, 1-methoxy-2-propanol, and acetonitrile. These organic solvents may be used alone or in combination of two or more.

The silane compound having Ra has a structure represented by the following formula 2, and can be produced, for example, by a Michael addition reaction between a silane compound containing a thiol group and an α,β-unsaturated ester compound.

Examples of silane compounds containing thiol groups include 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane.

The α,β-unsaturated ester compound is any one of a divalent chain hydrocarbon group having 1 to 6 carbon atoms (L), at least one hetero bond (Y) selected from an ether bond, an ester bond, a thioether bond, and a thioester bond, a linear or branched alkyl group, a cycloalkyl group, an aryl group, and an aralkyl group (Z ¹ ), a hydrogen atom, a linear or branched alkyl group, a cycloalkyl group, an aryl group or an aralkyl group, an alkoxyl group, an aryloxy group, an alkyloxycarbonyl group, an aryloxycarbonyl group, an alkylcarbonyl group, an arylcarbonyl group, and a linear or branched alkyl group having at least one substituent selected from an alkoxyl group, an aryloxy group, an alkyloxycarbonyl group, an aryloxycarbonyl group, an alkylcarbonyl group, and an arylcarbonyl group (Z ² and Z ³ ).
However, at least one of the groups selected from ^Z2 and ^Z3 is other than a hydrogen atom, k is 0 to 2, and an unsaturated bond is present between the carbon to which ^Z2 is bonded and the carbon to which ^Z3 is bonded.

Examples of the α,β-unsaturated ester compound include methyl crotonate, ethyl crotonate, propyl crotonate, isopropyl crotonate, butyl crotonate, s-butyl crotonate, pentyl crotonate, 2-ethylhexyl crotonate, n-hexyl crotonate, t-butyl crotonate, cyclopentyl crotonate, cyclohexyl crotonate, isobornyl crotonate, dicyclopentanyl crotonate, phenyl crotonate, 4-methylphenyl crotonate, dimethylphenyl crotonate, benzyl crotonate, phenethyl crotonate, methyl isocrotonic acid, ethyl isocrotonic acid, propyl isocrotonic acid, isopropyl isocrotonic acid, butyl isocrotonic acid, s-butyl isocrotonic acid, pentyl isocrotonic acid, 2-ethylhexyl isocrotonic acid, n-hexyl isocrotonic acid, t-butyl isocrotonic acid, cyclopentyl isocrotonic acid, cycloisocrotonic ... cyclohexyl, isobornyl isocrotonic acid, dicyclopentanyl isocrotonic acid, phenyl isocrotonic acid, 4-methylphenyl isocrotonic acid, dimethylphenyl isocrotonic acid, benzyl isocrotonic acid, phenethyl isocrotonic acid, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, butyl methacrylate, s-butyl methacrylate, pentyl methacrylate, 2-ethylhexyl methacrylate, n-hexyl methacrylate, t-butyl methacrylate, cyclopentyl methacrylate, cyclohexyl methacrylate, isobornyl methacrylate, dicyclopentanyl methacrylate, phenyl methacrylate, 4-methylphenyl methacrylate, dimethylphenyl methacrylate, benzyl methacrylate, phenethyl methacrylate, methyl angelic acid, ethyl angelic acid, propyl angelic acid, isopropyl angelic acid, angelic acid Butyl angelate, s-butyl angelate, pentyl angelate, 2-ethylhexyl angelate, n-hexyl angelate, t-butyl angelate, cyclopentyl angelate, cyclohexyl angelate, isobornyl angelate, dicyclopentanyl angelate, phenyl angelate, 4-methylphenyl angelate, dimethylphenyl angelate, benzyl angelate, phenethyl angelate, tigline methyl tiglate, ethyl tiglate, propyl tiglate, isopropyl tiglate, butyl tiglate, s-butyl tiglate, pentyl tiglate, 2-ethylhexyl tiglate, n-hexyl tiglate, t-butyl tiglate, cyclopentyl tiglate, cyclohexyl tiglate, isobornyl tiglate, dicyclopentanyl tiglate, phenyl tiglate, 4-methylphenyl tiglate, dimethylphenyl tiglate, Benzyl phosphate, phenethyl tiglate, methyl 2-ethyl-2-butenoate, ethyl 2-ethyl-2-butenoate, propyl 2-ethyl-2-butenoate, isopropyl 2-ethyl-2-butenoate, butyl 2-ethyl-2-butenoate, sec-butyl 2-ethyl-2-butenoate, pentyl 2-ethyl-2-butenoate, 2-ethylhexyl 2-ethyl-2-butenoate, n-hexyl 2-ethyl-2-butenoate, t-butyl 2-ethyl-2-butenoate, 2 2-ethyl-2-butenoic acid cyclopentyl, 2-ethyl-2-butenoic acid cyclohexyl, 2-ethyl-2-butenoic acid isobornyl, 2-ethyl-2-butenoic acid dicyclopentanyl, 2-ethyl-2-butenoic acid phenyl, 2-ethyl-2-butenoic acid 4-methylphenyl, 2-ethyl-2-butenoic acid dimethylphenyl, 2-ethyl-2-butenoic acid benzyl, 2-ethyl-2-butenoic acid phenethyl, dimethyl maleate, diethyl maleate, maleic acid dipropyl maleate, diisopropyl maleate, dibutyl maleate, di-s-butyl maleate, dipentyl maleate, di-2-ethylhexyl maleate, di-n-hexyl maleate, di-t-butyl maleate, dicyclopentyl maleate, dicyclohexyl maleate, diisobornyl maleate, bisdicyclopentanyl maleate, diphenyl maleate, di-4-methylphenyl maleate, bisdimethylphenyl maleate, Dibenzyl fumarate, diphenethyl maleate, dimethyl fumarate, diethyl fumarate, dipropyl fumarate, diisopropyl fumarate, dibutyl fumarate, di-s-butyl fumarate, dipentyl fumarate, di-2-ethylhexyl fumarate, di-n-hexyl fumarate, di-t-butyl fumarate, dicyclopentyl fumarate, dicyclohexyl fumarate, diisobornyl fumarate, bisdicyclopentanyl fumarate, diphenyl fumarate, fumaric acid Di-4-methylphenyl, bisdimethylphenyl fumarate, dibenzyl fumarate, diphenethyl fumarate, dimethyl citraconic acid, diethyl citraconic acid, dipropyl citraconic acid, diisopropyl citraconic acid, dibutyl citraconic acid, di-s-butyl citraconic acid, dipentyl citraconic acid, di-2-ethylhexyl citraconic acid, di-n-hexyl citraconic acid, di-t-butyl citraconic acid, dicyclopentyl citraconic acid, di Cyclohexyl, diisobornyl citraconic acid, bisdicyclopentanyl citraconic acid, diphenyl citraconic acid, di-4-methylphenyl citraconic acid, bisdimethylphenyl citraconic acid, dibenzyl citraconic acid, diphenethyl citraconic acid, dimethyl mesaconic acid, diethyl mesaconic acid, dipropyl mesaconic acid, diisopropyl mesaconic acid, dibutyl mesaconic acid, di-s-butyl mesaconic acid, dipentyl mesaconic acid, di-2-ethyl mesaconic acid n-Hexyl mesaconic acid, di-n-hexyl mesaconic acid, di-t-butyl mesaconic acid, dicyclopentyl mesaconic acid, dicyclohexyl mesaconic acid, diisobornyl mesaconic acid, bisdicyclopentanyl mesaconic acid, diphenyl mesaconic acid, di-4-methylphenyl mesaconic acid, bisdimethylphenyl mesaconic acid, dibenzyl mesaconic acid, diphenethyl mesaconic acid, dimethyl glutaconate, diethyl glutaconate, dipropyl glutaconate, diisobornyl glutaconate ... isopropyl, dibutyl glutaconate, di-s-butyl glutaconate, dipentyl glutaconate, di-2-ethylhexyl glutaconate, di-n-hexyl glutaconate, di-t-butyl glutaconate, dicyclopentyl glutaconate, dicyclohexyl glutaconate, diisobornyl glutaconate, bisdicyclopentanyl glutaconate, diphenyl glutaconate, di-4-methylphenyl glutaconate, bisdimethylphenyl glutaconate, dibenzyl itaconate, diphenethyl glutaconate, dimethyl itaconate, diethyl itaconate, dipropyl itaconate, diisopropyl itaconate, dibutyl itaconate, di-s-butyl itaconate, dipentyl itaconate, di-2-ethylhexyl itaconate, di-n-hexyl itaconate, di-t-butyl itaconate, dicyclopentyl itaconate, dicyclohexyl itaconate, diisobornyl itaconate, bisdicyclopentanyl itaconate, Examples of the methyl 2-(4-methoxybenzylidene)malonate include diphenyl itaconate, di-4-methylphenyl itaconate, bisdimethylphenyl itaconate, dibenzyl itaconate, diphenethyl itaconate, dimethyl isopropylidenemalonate, diethyl isopropylidenemalonate, dimethyl isopropylidene succinate, diethyl ethoxymethylenemalonate, diethyl benzylidenemalonate, diethyl 2-(4-methoxybenzylidene)malonate, and diethyl isopropylidene succinate.
Among these, diester structures such as maleic acid ester, fumaric acid ester, citraconic acid ester, mesaconic acid ester, glutaconic acid ester, itaconic acid ester, methylenemalonic acid ester, and methylenesuccinic acid ester are preferred because of their excellent solubility in the developer of the silsesquioxane compound, and among these, maleic acid ester, fumaric acid ester, and itaconic acid ester are particularly preferred from the viewpoint of easy availability.

The addition reaction may be carried out without a solvent, or a solvent may be used. Specific examples of solvents include methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol, 1-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, benzyl alcohol, 2-methoxyethyl alcohol, 2-ethoxyethyl alcohol, 2-(methoxymethoxy)ethanol, 2-butoxyethanol, furfuryl alcohol, tetrahydrofurfuryl alcohol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol, and the like. monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether, diacetone alcohol, acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, 2-hexanone, methyl isobutyl ketone, 2-heptanone, 4-heptanone, diisobutyl ketone, cyclohexanone, methylcyclohexanone, acetophenone, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dihexyl ether, anisole, phenetole, tetrahydrofuran, tetrahydropyran, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol di Examples of the solvent include ethyl ether, diethylene glycol dibutyl ether, glycerin ether, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, sec-butyl acetate, pentyl acetate, isopentyl acetate, 3-methoxybutyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, methyl propionate, ethyl propionate, butyl propionate, γ-butyrolactone, 2-methoxyethyl acetate, 2-ethoxyethyl acetate, 2-butoxyethyl acetate, 2-phenoxyethyl acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, benzene, toluene, and xylene. These solvents can be used alone or in combination of two or more. The amount of each solvent used can be determined appropriately.

The reaction molar ratio of the silane compound containing a thiol group to the α,β-unsaturated ester compound is preferably 0.5 to 5 moles, more preferably 0.8 to 3 moles, of the α,β-unsaturated ester compound per mole of the silane compound containing a thiol group, since this reduces unreacted materials.

The temperature of the addition reaction is preferably −40 to 100° C., more preferably −20 to 80° C. If the temperature is −40° C. or higher, the addition reaction can proceed sufficiently. If the temperature is 100° C. or lower, the polymerization of the α,β-unsaturated ester compound can be suppressed.
The time for the addition reaction is preferably 1 to 60 hours, more preferably 2 to 48 hours. If it is 1 hour or more, the addition reaction can proceed sufficiently. If it is within 60 hours, the polymerization of the α,β-unsaturated ester compound can be suppressed.

The addition reaction can be carried out in the presence of a catalyst.
The catalyst may be any known catalyst used in Michael addition reactions, such as amines, alkali metal alkoxides, metal hydrides, metal carbonates, alkyl metal compounds, and phosphines. Examples of the catalyst include amines such as triethylamine, diisopropylamine, diisopropylethylamine, dibutylamine, hexylamine, piperidine, pyridine, 4-dimethylaminopyridine, 1,4-diazabicyclo[2,2,2]octane, and 1,8-diazabicyclo[5,4,0]undecene-7; alkali metal alkoxides such as sodium methoxide, sodium ethoxide, and potassium tert-butoxide; metal hydrides such as sodium hydride; metal carbonates such as potassium carbonate; alkyl metal compounds such as n-butyllithium and s-butyllithium; and phosphines such as triphenylphosphine and tributylphosphine.

In order to suppress the polymerization of the α,β-unsaturated ester compound, a polymerization inhibitor may be added to the reaction system. The type of the polymerization inhibitor is not particularly limited. One type of polymerization inhibitor may be used, or two or more types may be used in combination.
Examples of the polymerization inhibitor include phenolic compounds such as hydroquinone, p-methoxyphenol, 2,4-dimethyl-6-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, 4-tert-butylcatechol, 2,6-di-tert-butyl-4-methylphenol, pentaerythritol tetrakis (3,5-di-tert-butyl-4-hydroxyhydrocinnamate), and 2-sec-butyl-4,6-dinitrophenol; N,N-diisopropylparaphenylenediamine, N,N-di-2-naphthylparaphenylenediamine, N-phenylene-N amine compounds such as N-(1,3-dimethylbutyl)paraphenylenediamine, N,N'-bis(1,4-dimethylphenyl)-paraphenylenediamine, and N-(1,4-dimethylphenyl)-N'-phenyl-paraphenylenediamine; N-oxyl compounds such as 4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine-N-oxyl, and bis(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)sebacate; and metal compounds such as copper, copper(II) chloride, and iron(III) chloride.

The amount of the polymerization inhibitor used can be appropriately set. For example, it is preferably 20 ppm or more relative to the α,β-unsaturated ester compound, and more preferably 50 ppm or more in order to obtain a sufficient polymerization inhibitory effect. On the other hand, from the viewpoint of cost, the amount of the polymerization inhibitor used is preferably 10,000 ppm or less, more preferably 5,000 ppm or less.
Regarding the purification method after the completion of this addition reaction, known purification methods such as separation, washing with water, distillation, crystallization, filtration, etc. can be appropriately combined, taking into consideration the physical properties of the product, the raw materials, the presence or absence of a solvent, etc.

Examples of silane compounds having Rb include vinyltriethoxysilane, vinyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloyloxypropyltrimethoxysilane, p-styryltriethoxysilane, p-styryltrimethoxysilane, allyltriethoxysilane, allyltrimethoxysilane, triethoxy(7-octen-1-yl)silane, trimethoxy(7-octen-1-yl)silane, etc. Among these, 3-(meth)acryloyloxypropyltriethoxysilane and 3-(meth)acryloyloxypropyltrimethoxysilane are preferred.

[Production method of the present polymer]
The present polymer can be produced, for example, by a solution polymerization method in which the present compound is used alone or the present compound is mixed with a monomer having other structural units in an appropriate ratio, and radically polymerized using a polymerization initiator in the presence of a polymerization solvent.

[Uses of this polymer]
The present polymer can be contained in the present resist composition, and can be used to form, for example, a resist pattern on a semiconductor substrate.
An example of a method for manufacturing a substrate having a pattern formed thereon will now be described.
First, the resist composition is applied to the surface of a substrate to be processed, such as a silicon wafer, by spin coating, etc. Then, the substrate to be processed to which the resist composition has been applied is dried by baking treatment (pre-bake), etc., to form a resist film on the substrate.
Next, the resist film is irradiated with light having a wavelength of 250 nm or less through a photomask to form a latent image (exposure). The irradiated light is preferably a KrF excimer laser, an ArF excimer laser, an F2 excimer laser, an EUV excimer laser, or an electron beam, and more preferably an EUV excimer laser or an electron beam.
After exposure, the resist film is appropriately heat-treated (post-exposure bake, PEB) and then brought into contact with a developer to dissolve a part of the resist film. The developer may be appropriately selected, but it is preferable to use an alkaline developer or an organic developer.
In a positive development process, the exposed areas are dissolved and removed using an alkaline developer, while in a negative development process, the unexposed areas are dissolved and removed using an organic developer.

An alkaline aqueous solution is used as the alkaline developer. Examples include aqueous solutions of inorganic alkalis such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium silicate, sodium metasilicate, and aqueous ammonia; primary amines such as ethylamine and n-propylamine; secondary amines such as diethylamine and di-n-butylamine; tertiary amines such as triethylamine and methyldiethylamine; alcohol amines such as dimethylethanolamine and triethanolamine; quaternary ammonium salts such as tetramethylammonium hydroxide and tetraethylammonium hydroxide; and cyclic amines such as pyrrole and piheridine.

As organic developers, polar solvents such as ketone solvents, ester solvents, alcohol solvents, amide solvents, and ether solvents, as well as hydrocarbon solvents, can be used.

Examples of ketone solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, 2-heptanone, 4-heptanone, 1-hexanone, 2-hexanone, 1-octanone, 2-octanone, 1-nonanone, 2-nonanone, diisobutyl ketone, cyclohexanone, and methylcyclohexanone.

Examples of ester solvents include methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, sec-butyl acetate, pentyl acetate, isopentyl acetate, propylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, ethyl-3-ethoxypropionate, 3-methoxybutyl acetate, 3-methyl-3-methoxybutyl acetate, methyl propionate, ethyl propionate, butyl propionate, and the like.

Examples of alcohol-based solvents include methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol, 1-butyl alcohol, 2-butyl alcohol, isobutyl alcohol, tert-butyl alcohol, benzyl alcohol, 2-methoxyethyl alcohol, 2-ethoxyethyl alcohol, 2-(methoxymethoxy)ethanol, 2-butoxyethanol, furfuryl alcohol, tetrahydrofurfuryl alcohol, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, and tripropylene glycol monomethyl ether.

Examples of ether solvents include dioxane and tetrahydrofuran.

Examples of amide solvents include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, hexamethylphosphoric triamide, and 1,3-dimethyl-2-imidazolidinone.

Examples of hydrocarbon solvents include toluene, xylene, hexane, heptane, octane, and decane.

Among these, a developer containing at least one solvent selected from ketone-based solvents, ester-based solvents, alcohol-based solvents, amide-based solvents, and ether-based solvents is preferred. These solvents can be used alone or in combination of two or more.

Development may be carried out by a known method, such as immersing the substrate in a tank filled with a developer for a fixed period of time, piling up the developer on the substrate surface by surface tension and leaving it there for a fixed period of time, spraying the developer onto the substrate surface, or discharging the developer by scanning a nozzle at a fixed speed over a substrate rotating at a fixed speed.
After development, the substrate is appropriately rinsed with pure water, an organic solvent, etc. In this manner, a resist pattern is formed on the substrate to be processed.

The substrate on which the resist pattern has been formed is appropriately heat-treated (post-baked) to strengthen the resist, and the portions without resist are selectively dry-etched.
After the dry etching, the resist is removed with a stripping agent to obtain a substrate on which a fine pattern is formed.

An example of the present invention will be described below. The present invention is not limited to the following example as long as it does not deviate from the gist of the invention. In the example, "parts" and "%" are based on mass unless otherwise specified.
The number average molecular weight (Mn) and molecular weight distribution (Mw/Mn) of the silsesquioxane compound were determined by gel permeation chromatography in terms of polystyrene.

<Synthesis of Compound (SQ1) Containing Silsesquioxane Skeleton>
In a flask equipped with a stirrer and a thermometer, 1.00 g (2.8 mmol) of silane compound (A1) shown in the following formula 3, synthesized by the method described in Japanese Patent No. 4909081, 0.10 g (0.40 mmol) of 3-methacryloyloxypropyltriethoxysilane, and 5.3 ml of tetrahydrofuran were added and dissolved, and 0.47 g of a 3.2% aqueous ammonium fluoride solution was added dropwise. The mixture was stirred at room temperature for 3 hours and then concentrated.
10 mL of ethyl acetate was added, and the mixture was washed twice with 10 mL of water and then with 5 mL of water. The resulting organic layer was concentrated and dried under reduced pressure to obtain 0.82 g of a polymerizable monomer (SQ1) having a silsesquioxane skeleton represented by the following formula 4 as a colorless viscous liquid in a yield of 93%.

The Mn was 2,150 and the Mw/Mn was 1.05, and in the following chemical formula, m is presumed to be 8. From the integral ratio of ¹ H-NMR, the molar ratio of the side chain (Ra) derived from the silane compound (A1) to the side chain (Rb) derived from 3-methacryloyloxypropyltriethoxysilane was 7.0:1.0. ^1H -NMR (400MHz, _CDCl3 ): δ 6.10 ppm (s, 1H), 5.55 ppm (s, 1H), 4.11 ppm (brt, 2H), 3.71 ppm (s, 21H), 3.67 ppm (s, 21H), 3.05 ppm (m, 7H), 2.90-2.50 ppm (m, 42H), 1.94 ppm (s, 3H), 1.64 ppm (m, 16H), 0.71 ppm (brt, 16H).

<Synthesis of silane compound (A2)>
In a flask equipped with a stirrer and a thermometer, 11.36 g of potassium carbonate, 204 mL of acetone, and 37.92 g (5.1 mmol) of diethyl itaconate were added, and then 40.00 g (5.1 mmol) of 3-mercaptopropyltrimethoxysilane was added dropwise and reacted at room temperature for 8 hours. After the reaction was completed, the mixture was filtered, concentrated, and dried under reduced pressure to obtain 74.61 g of silane compound (A2) represented by the following formula 5 as a colorless liquid in a yield of 95.8%. ^1H -NMR (270MHz, _CDCl3 ): δ 4.17ppm (q, 2H), 4.15ppm (q, 2H), 3.57ppm (s, 9H), 3.03ppm (m, 1H), 2.88ppm (dd, 1H), 2.68ppm (m, 3H), 2.55ppm (t, 2H), 1.70ppm (m, 2H), 1.27ppm (t, 3H), 1.26ppm (t, 3H), 0.75ppm (m, 2H).

<Synthesis of Compound (SQ2) Containing Silsesquioxane Skeleton>
A polymerizable monomer (SQ2) having a silsesquioxane skeleton represented by the following formula 6 was obtained as a colorless viscous liquid in a yield of 99.0% in the same manner as in SQ1, except that the silane compound (A2) was used instead of the silane compound (A1).

From the integral ratio of ¹ H-NMR, the molar ratio of the side chain (Ra) derived from the silane compound (A2) to the side chain (Rb) derived from 3-methacryloyloxypropyltriethoxysilane was 7.0:1.0. ^1H -NMR (270MHz, _CDCl3 ): δ 6.12 ppm (s, 1H), 5.56 ppm (s, 1H), 4.21-4.10 ppm (m, 30H), 3.03 ppm (m, 7H), 2.91-2.63 ppm (m, 28H), 2.55 ppm (brt, 14H), 1.95 ppm (s, 3H), 1.66 ppm (m, 16H), 1.27 ppm (t, 21H), 1.26 ppm (t, 21H), 0.73 ppm (brt, 16H).

Example 1
The obtained SQ1 was dissolved at a predetermined concentration in propylene glycol monomethyl ether acetate (PGMEA) as a resist solvent at room temperature to evaluate the solubility.

Example 2
The solubility was evaluated in the same manner as in Example 1, except that the PGMEA in Example 1 was replaced with butyl acetate as an ester-based organic developer.

<Examples 3 and 4>
The solubility was evaluated in the same manner as in Examples 1 and 2, except that SQ1 in Examples 1 and 2 was replaced with SQ2.

<Comparative Examples 1 and 2>
The solubility was evaluated in the same manner as in Example 1, except that in Examples 1 and 2, SQ1 was replaced with methacryloyloxypropylheptaisobutyl-T8-silsesquioxane and the concentrations were as shown in Table 1.

(Evaluation of Solubility)
The solubility of Examples 1 to 4 and Comparative Examples 1 and 2 was evaluated.
The solubility was evaluated by placing silsesquioxane and a solvent in a container at a desired concentration and shaking gently at room temperature. The resulting solution was visually observed and evaluated as dissolved if it was completely dissolved and became a homogeneous solution, and as insoluble if there was any residual dissolution. The results are shown in Table 1 below.

As shown in Table 1, Examples 1 to 4 are compounds containing a silsesquioxane skeleton having a structure containing Ra represented by Formula 2 above, and it was confirmed that they were soluble in resist solvents and developing solutions even at a concentration of 50 wt %, and therefore pose no practical problems.
On the other hand, Comparative Examples 1 and 2 have a structure that does not contain Ra represented by the above formula 2, and are insoluble in a resist solvent and a developer at a concentration of 2.2 wt %. It was confirmed that the solubility is inferior to that of each Example, and there is room for improvement in practicality.

Claims (7)

A compound containing a silsesquioxane having a cage structure represented by the following formula 1:
( _RmSiO1.5 ) _n (Formula 1)
(In formula 1, n is an integer of 3 to 30, Rm includes Ra and Rb, Ra is a structure represented by formula 2 below, and Rb is a radical polymerizable functional group.)

(In the above formula 2, L is a hydrocarbon chain having 1 to 6 carbon atoms; Y is at least one hetero bond selected from an ether bond, an ester bond, a thioether bond, and a thioester bond; Z ¹ is a linear or branched alkyl group, a cycloalkyl group, an aryl group, or an aralkyl group; Z ² and Z ³ are each independently any one of a hydrogen atom, a linear or branched alkyl group, a cycloalkyl group, an aryl group, an aralkyl group, an alkoxyl group, an aryloxy group, an alkyloxycarbonyl group, an aryloxycarbonyl group, an alkylcarbonyl group, an arylcarbonyl group, and a linear or branched alkyl group having at least one substituent selected from an alkoxyl group, an aryloxy group, an alkyloxycarbonyl group, an aryloxycarbonyl group, an alkylcarbonyl group, and an arylcarbonyl group; at least one selected from Z ² and Z ³ is other than a hydrogen atom; j is an integer of 1 to 6; and k is an integer of 0 to 2.) A polymer having a structural unit derived from the compound described in claim 1. The polymer according to claim 2, further comprising a structural unit derived from a monomer containing an acid-dissociable group. The polymer according to claim 2, further comprising a structural unit derived from a monomer containing a phenolic hydroxyl group. The polymer according to claim 2, further comprising a structural unit derived from a monomer containing a lactone skeleton. A resist composition comprising the polymer according to any one of claims 2 to 5. A method for forming a resist pattern using the resist composition according to claim 6.