WO2016190221A1

WO2016190221A1 - Coating composition and process for producing layered photoresist object

Info

Publication number: WO2016190221A1
Application number: PCT/JP2016/064921
Authority: WO
Inventors: 龍二郎山崎; 伊藤　昌宏; 好彦坂根
Original assignee: 旭硝子株式会社
Priority date: 2015-05-28
Filing date: 2016-05-19
Publication date: 2016-12-01
Also published as: TW201708440A

Abstract

Provided is a coating composition which can form a low-refractive-index antireflection film without requiring the use of fine particles. The coating composition contains at least one fluorine compound selected from among fluorine compounds (A1) and among the following fluorine compounds (A2). Fluorine compounds (A1): polymers which each consist only of one kind of units selected from among the following units (I) and have a number-average molecular weight of 1,000-50,000. Units (I): units each based on a monomer which has only one polymerizable carbon-carbon double bond, composed only of carbon, oxygen, and fluorine atoms, having one or more side chains, at least one of which contains one or more etheric oxygen atoms that constitute no ring, and having -CF₃ at each terminal. Fluorine compounds (A2): compounds each having a number-average molecular weight of 1,000-50,000 and having a perfluoropolyether skeleton in the main chain.

Description

Coating composition and method for producing photoresist laminate

The present invention relates to a coating composition. In particular, the present invention relates to a coating composition useful as a composition for forming an antireflection film in photolithography, and a method for producing a photoresist laminate using the same.

In photolithography technology, a method of providing an antireflection film on the surface of a photoresist layer (TARC method) is known in order to prevent reflection of exposure light in a step of forming a photoresist pattern (resist pattern). Yes.
It is known that the ideal refractive index of the antireflection film for obtaining a good antireflection effect in the TARC method is the square root (√n) of the refractive index n of the photoresist layer (for example, Patent Document 1). Paragraph [0004]).
In photolithography using an ArF excimer laser (193 nm), the refractive index at 193 nm of a commonly used resist is 1.6 to 1.8 (for example, paragraph [0006] of Patent Document 1). The value of the square root of 6 is about 1.265, and the value of the square root of 1.8 is about 1.342. Therefore, the refractive index at 193 nm of the antireflection film is desirably closer to the range of 1.265 to 1.342.

Patent Document 2 describes a method of forming an antireflection film on a photoresist layer using a fluoropolymer having a hydrophilic group that can be dissolved in water, an aqueous solvent or a developer. In Example 4, a coating composition in which a copolymer of a fluorine-containing monomer having a hydroxyl group at the end of the side chain and tetrafluoroethylene was dissolved in a mixed solvent of water and isopropyl alcohol was obtained to form a film. It is described that the refractive index (193 nm) of the film was 1.39.
Patent Document 3 describes a method for realizing an antireflection layer having a low refractive index by a layer mainly composed of fine particles (particle size: 1 to 100 nm). In this method, it is described that the refractive index is lowered by forming voids corresponding to the shape of the fine particles in the antireflection layer, and in Example 8, the refractive index at 193 nm was 1.32.
In Patent Document 4, a polymer having a ring structure in the main chain, obtained by cyclopolymerization of a fluorine-containing monomer having two polymerizable carbon-carbon double bonds, is reflected on the photoresist layer. A method of forming a protective film is described.

Japanese Patent No. 4910829 Japanese Patent No. 4752597 International Publication No. 2008/059918 JP-A-5-74700

As described above, the refractive index of the antireflection film is preferably closer to the range of 1.265 to 1.342 at 193 nm, and the coating composition described in Patent Document 2 is insufficient.
Since the antireflection film of Patent Document 3 contains fine particles, exposure light may be scattered.
When the present inventors measured the refractive index in 193 nm about the antireflection film described in patent document 4 (example 6 mentioned later), it was 1.38 and was inadequate.

The present invention provides a coating composition capable of forming an antireflection film having a low refractive index without using fine particles, and a method for producing a photoresist laminate using the same.

The present invention provides a coating composition having the following constitutions [1] to [12] and a method for producing a photoresist laminate.
[1] A coating composition comprising at least one fluorine-containing compound selected from the following fluorine-containing compound (A1) and the following fluorine-containing compound (A2).
Fluorine-containing compound (A1): A polymer comprising only one unit selected from the following units (I), and having a number average molecular weight of 1,000 to 50,000.
Unit (I): a unit based on a monomer having only one polymerizable carbon-carbon double bond, composed of only carbon, oxygen and fluorine atoms, and having one or more side chains, The unit in which at least one side chain contains one or more etheric oxygen atoms that do not constitute a ring, and the terminal is —CF ₃ .
Fluorine-containing compound (A2): A compound having a perfluoropolyether skeleton in the main chain and a number average molecular weight of 1,000 to 50,000.
[2] The coating composition according to [1], further comprising a solvent.
[3] The coating composition according to [2], wherein the content of the solvent in the coating composition is 70 to 99% by mass.

[4] The coating composition according to any one of [1] to [3], wherein the unit (I) is a unit represented by the following formula (i).
-[CX ¹ X ² -CX ³ X ⁴ ]-(i)
(In the formula, at least one of X ¹ , X ² , X ³ , and X ⁴ independently represents a C 1-12 perfluoro saturated carbon atom containing 1 to 4 etheric oxygen atoms that do not constitute a ring. A hydrogen group (wherein the number of etheric oxygen atoms is less than or equal to the number of carbon atoms), and the other is a perfluoro saturated hydrocarbon group having 1 to 12 carbon atoms not containing an etheric oxygen atom that does not form a ring, or Indicates a fluorine atom.)
[5] At least one of X ¹ , X ² , X ³ , X ⁴ is a —O—Rf ¹ group (the Rf ¹ group is a carbon having 0 to 3 etheric oxygen atoms between carbon-carbon atoms) (4) A coating composition according to [4], which is a perfluoro saturated hydrocarbon group of 1 to 12.
[6] The coating composition according to [5], wherein ^one of X ¹ , X ² , X ³ and X ⁴ is a —O—Rf ¹ group, and the other 3 are fluorine atoms.
[7] The coating composition according to any one of [1] to [6], wherein the fluorine-containing compound (A1) has a refractive index at 193 nm of 1.32 to 1.36.

[8] The coating composition according to any one of [1] to [3], wherein the fluorine-containing compound (A2) is a compound represented by the following formula (II):
Y—O— (C _n F _2n O) _m —Z (II)
Wherein Y and Z are each independently a monovalent organic group (wherein Y is not an oxygen atom on the side bonded to —O—, and Z is bonded to — (C _n F _2n O) _m —) And n is an integer of 1 to 5, m is an integer of 2 to 200, and when m is 2 or more, a plurality of ( C _n F _2n O) may be the same or different from each other.
[9] The coating composition according to [1], [2], [3] or [8], wherein the fluorine-containing compound (A2) has a refractive index at 193 nm of 1.32 to 1.36.

[10] The coating composition according to any one of [1] to [9], wherein the solvent is a fluorine-containing solvent.
[11] The coating composition according to [10], wherein the fluorine-containing solvent has a fluorine atom content of 65% by mass or more.
[12] A method for producing a photoresist laminate in which an antireflection film is provided on the surface of a photoresist layer, the coating being any one of [1] to [11] on the surface of the photoresist layer A method for producing a photoresist laminate, comprising: applying a composition to form a coating film comprising the coating composition; and if the coating film contains a solvent, the solvent is then removed from the coating film.

According to the coating composition of the present invention, an antireflection film having a low refractive index can be formed without using fine particles.
According to the method for producing a photoresist laminate of the present invention, a photoresist laminate in which an antireflection film having a low refractive index and containing no fine particles is formed on the surface of the photoresist layer can be obtained.

The meanings of the following terms in this specification are as follows.
“Fluorine-containing compound” means a compound having a fluorine atom in the molecule. The fluorine-containing compound includes a fluorine-containing polymer.
The “unit” means a part derived from a monomer that exists in the polymer and constitutes the polymer. In the present specification, the monomer and the unit based thereon are denoted by the same reference numerals. For example, those based on the monomer (I) are referred to as units (I). Further, a unit (I) that is obtained by chemically converting the structure of the unit (I) after forming the polymer is also referred to as the unit (I).
The “perfluoropolyether skeleton” means a molecular chain in which two or more oxyperfluoroalkylene groups are linked.
“Perfluoro” means that all of the hydrogen atoms bonded to the carbon atom are substituted with fluorine atoms.
The term “oxyperfluoroalkylene group” means a group in which an oxygen atom is bonded to one end of the perfluoroalkylene group, and the chemical formula represents the oxygen atom on the right side of the perfluoroalkylene group.
The values of “mass average molecular weight and number average molecular weight of fluorine-containing compound” are polystyrene (PS) equivalent molecular weights determined by gel permeation chromatography (GPC).
“Fluorine atom content of fluorine-containing compound (unit: mass%)” is obtained by fluorine atom content analysis and indicates the ratio of the mass of fluorine atoms to the total mass of all atoms constituting the fluorine-containing compound.
“Fluorine atom content of fluorine-containing solvent (unit: mass%)” is obtained by fluorine atom content analysis and indicates the ratio of the mass of fluorine atoms to the total mass of all atoms constituting the fluorine-containing solvent.
The “molecular weight of the monomer” is a formula weight obtained based on the chemical formula.
“Branched” means having a branched chain, and also having a branched chain and including a ring is also called branched.

[Fluorine-containing compounds]
The coating composition of the present invention contains at least one fluorine-containing compound selected from the fluorine-containing compound (A1) and the fluorine-containing compound (A2). Hereinafter, the fluorine-containing compound (A1) and the fluorine-containing compound (A2) are collectively referred to as “fluorine-containing compound (A)”.
The fluorine-containing compound (A) has a molecular structure that contributes to a decrease in the refractive index, and the refractive index at 193 nm can be adjusted to 1.32 to 1.36. The refractive index can be expressed. That is, the refractive index at 193 nm of the film made of the fluorine-containing compound (A) can be set to 1.32 to 1.36.
When the refractive index of the fluorine-containing compound (A) is not more than the upper limit of the above range, it is preferable because the refractive index is close to the above-described range of 1.265 to 1.342. The refractive index of the fluorine-containing compound (A) is an eigenvalue and is constant regardless of the shape of the film or the like.

(Fluorine-containing compound (A1))
The fluorine-containing compound (A1) is a homopolymer in which the unit present in the polymer is only one selected from the following units (I).
Unit (I): a unit based on a monomer having only one polymerizable carbon-carbon double bond, which is composed of only carbon atoms, oxygen atoms, and fluorine atoms, and has one or more side chains , Wherein at least one side chain includes one or more etheric oxygen atoms that do not constitute a ring, and the terminal is a unit of —CF ₃ .
A carbon chain (—C—C—) generated by cleavage of one double bond is the main chain of the fluorine-containing compound (A1).

The atoms constituting the unit (I) are only carbon atoms, oxygen atoms and fluorine atoms. By not containing other atoms such as hydrogen atoms, the fluorine atom content is increased, which contributes to a decrease in refractive index.
Unit (I) has one or more side chains. The number of side chains is 1 to 4, preferably 1 to 3, and particularly preferably 1 to 2. When two or more side chains are present, the structures of the plurality of side chains may be the same or different.
At least one of the side chains of the unit (I) contains one or more etheric oxygen atoms that do not form a ring, and the terminal is —CF ₃ .
The etheric oxygen atom that does not constitute a ring increases the mobility of the molecule and contributes to a decrease in crystallinity of the fluorine-containing compound (A1). As a result, it is thought that it contributes to the fall of the refractive index of a fluorine-containing compound (A1).
Note that etheric oxygen atoms present in the ring structure have a small effect of lowering the refractive index. This is probably because there is no molecular end in the ring structure, so even if an etheric oxygen atom is present, the contribution to the mobility of the molecule is small.
The upper limit of the number of etheric oxygen atoms that do not constitute a ring present in one side chain is not particularly limited, but is preferably 4 or less, more preferably 3 or less, and particularly preferably 2 or less, from the viewpoint of ease of production. preferable.
The molecular weight of the unit (I) is preferably 60 or more. When the molecular weight of the unit is not less than the lower limit of the above range, the fluorine atom content increases and the refractive index tends to be low. The upper limit of the molecular weight of the unit (I) is preferably 800 or less, particularly preferably 500 or less, from the viewpoint of ease of production and easy recovery of unreacted monomers.

The unit (I) is preferably a unit (i) represented by the following formula (i).
-[CX ¹ X ² -CX ³ X ⁴ ]-(i)
(In the formula, at least one of X ¹ , X ² , X ³ , and X ⁴ independently represents a C 1-12 perfluoro saturated carbon atom containing 1 to 4 etheric oxygen atoms that do not constitute a ring. A hydrogen group (hereinafter also referred to as “side chain 1”) (wherein the number of etheric oxygen atoms is not more than the number of carbon atoms) and the terminal is —CF ₃ ; A perfluoro saturated hydrocarbon group having 1 to 12 carbon atoms not containing an etheric oxygen atom that does not constitute a ring (hereinafter also referred to as “side chain 2”) or a fluorine atom.)

The side chain 1 is preferably an —O—Rf ¹ group (the Rf ¹ group is a C 1-12 perfluoro saturated hydrocarbon group containing 0 to 3 etheric oxygen atoms between carbon-carbon atoms). . When the number of carbon atoms is 3 or more, the Rf ¹ group may be linear or branched, and is preferably branched from the viewpoint that the refractive index tends to be lower. If there is a branched structure, the fluorine-containing compound (A1) becomes bulky and the density decreases, so the refractive index is considered to be low. The Rf ¹ group may contain a ring. When a ring is included, the ring may or may not have an etheric oxygen atom.
The Rf ¹ group preferably has 3 to 12 carbon atoms. If it is less than or equal to the upper limit, the boiling point does not become too high, and the recovery of unreacted monomers is facilitated. Rf present in ¹ group, the upper limit of the number of rings does not constitute etheric oxygen atoms is less than or equal to the number of carbon atoms in the Rf ¹ group. From the viewpoint of ease of production, it is preferably 4 or less, more preferably 3 or less, and particularly preferably 2 or less.
Specific examples of the side chain 1 include the following.
—OCF ₃ , —OCF ₂ CF ₂ CF ₃ , —OCF ₂ CF ₂ CF ₂ CF ₃ , —OCF ₂ CF ₂ OCF ₃ , —OCF ₂ CF ₂ CF ₂ OCF ₃ , —OCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ CF ₃ , —OCF ₂ CF (CF ₃ ) OCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ CF ₃ .
From the viewpoint of ease of production, —OCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ CF ₃ is preferable.

The side chain 2 is preferably a perfluoro saturated hydrocarbon group having 1 to 12 carbon atoms (hereinafter also referred to as “Rf ² group”). When the number of carbon atoms is 3 or more, the Rf ² group may be linear or branched, and is preferably branched from the viewpoint of further reducing the manufacturability and refractive index.
The Rf ² group has 1 to 12 carbon atoms, preferably 1 to 6, more preferably 1 to 4, and particularly preferably 1 to 3. To become the Rf ² group is present when there at least the lower limit within the above range, the refractive index of the polymer becomes lower, it becomes easy recovery of unreacted monomers to be less than the upper limit value.
Specific examples of the Rf ² group include —CF ₃ and —CF (CF ₃ ) CF ₃ .

As X ¹ , X ² , X ³ , X ⁴ in the unit (i), one of them is preferably a side chain 1 and the other 3 are fluorine atoms or other 3 It is preferable that one of them is a side chain 2 and the other two are fluorine atoms. As the unit (i), ^{one in which one} of X ¹ , X ² , X ³ and X ⁴ is an —O—Rf ¹ group and the other three are fluorine atoms is particularly preferable.
Preferable specific examples of the unit (i) include the following.
A unit in which X ¹ is F, X ² is F, X ³ is F, and X ⁴ is —OCF (CF ₃ ) CF ₂ OCF ₂ CF ₂ CF ₃ .
A unit in which X ¹ is F, X ² is —CF (CF ₃ ) CF ₃ , X ³ is F, and X ⁴ is —OCF (CF ₃ ) CF ₂ OCF ₂ CF ₂ CF ₃ .

The structure of both ends of the main chain of the fluorine-containing compound (A1) is not particularly limited. For example, a residue derived from the polymerization initiator or chain transfer agent used in the production of the fluorine-containing compound (A1) may be present. Both end groups may be the same as or different from each other.
Specific examples of the terminal group of the main chain include the following.
F-, CF _3- , CF ₃ CF ₂ CF ₂ O-, CF ₃ CH ₂ OCF ₂ CF _2- , HCF ₂ CF ₂ OCH (CF ₃ )-, CF ₃ CF ₂ CCl _2- , ClCF ₂ CF ₂ CFCl _{_{_{_{-, CF 3 CF 2 CF 2}}}} CFHCF 2 OCH 2 CF 2 O-, HOCH 2 CF 2 O -, (CH 3) 2 CHOCOO-.

The number average molecular weight of the fluorine-containing compound (A1) is 1,000 to 50,000, preferably 3,000 to 30,000, particularly preferably 3,000 to 10,000. When it is at least the lower limit of the above range, the influence of the terminal group on the refractive index of the fluorine-containing compound (A1) is small, and it is easy to control the refractive index. Moreover, it is excellent in film forming property, and it is excellent in the uniformity of the film thickness in a flat part. If it is less than the upper limit value, it is excellent in followability to a step during coating, and when the surface of the resist layer has irregularities, the amount of coating necessary to cover the entire surface of the convex and concave portions can be reduced.
The fluorine-containing compound (A1) can be produced by a known production method. For example, the manufacturing method described in Japanese Patent No. 4962559 can be used.

(Fluorine-containing compound (A2))
The fluorine-containing compound (A2) is a compound having a perfluoropolyether skeleton in the main chain.
In the fluorine-containing compound (A2), an etheric oxygen atom that does not constitute a ring is present in the main chain. For this reason, compared to the case where such etheric oxygen atoms are present only in the side chain, the mobility of the whole molecule is easily improved. Therefore, it is considered that the crystallinity of the fluorine-containing compound (A2) is further reduced and the refractive index of the fluorine-containing compound (A2) is further reduced.

The oxyperfluoroalkylene group constituting the perfluoropolyether skeleton has 1 to 5 carbon atoms, preferably 1 to 3, and particularly preferably 1 to 2.
The oxyperfluoroalkylene group may be linear or branched when it has 3 or more carbon atoms. A branched shape is preferable in that the refractive index of the fluorine-containing compound (A2) tends to be lower. If the branched structure is present, the fluorine-containing compound (A2) becomes bulky and the density decreases, so that the refractive index is considered to be lower.
The oxyperfluoroalkylene group may be one type or two or more types. When two or more kinds of oxyperfluoroalkylene groups are linked, the bonding order thereof is not particularly limited. Any of random, block, and alternate may be used, or a combination thereof.

As the fluorine-containing compound (A2), a compound represented by the following formula (II) is preferable.
Y—O— (C _n F _2n O) _m —Z (II)
Wherein Y and Z are each independently a monovalent organic group (wherein Y is not an oxygen atom on the side bonded to —O—, and Z is bonded to — (C _n F _2n O) _m —) And n is an integer of 1 to 5, m is an integer of 2 to 200, and when m is 2 or more, a plurality of ( C _n F _2n O) may be the same or different from each other.

Preferable examples of (C _n F _2n O) include the following.
A combination of (CF ₂ O) and (CF ₂ CF ₂ O), a combination of (CF ₂ CF ₂ O) and (CF ₂ CF ₂ CF ₂ CF ₂ O), (CF ₂ CF ₂ CF ₂ O) and (CF ₂ CF ₂ CF ₂ CF ₂ O), (CF (CF ₃ ) CF ₂ O) alone.
M in the formula (II) is preferably 10 to 100, more preferably 10 to 30, further preferably 15 to 25, and particularly preferably 20 to 25.

Y and Z are preferably groups having a fluorine atom. Specific examples include —CF ₂ CH ₂ OH, —CF ₂ H, —CF ₂ CF ₂ CF ₃ , —CF ₂ CH ₂ OCF ₂ CHFOCF ₂ CF ₂ CF ₃ .

The fluorine-containing compound (A2) can be produced by a known production method. For example, the production method described in International Publication No. 2009/008380 can be used. In addition, as the fluorine-containing compound (A2), a commercially available product may be used. For example, FLUOROLINK D4000 or FLUOROLINK D10 / H (all are product names) manufactured by Solvay Solexis, DENNUM SA (product name) manufactured by Daikin Is mentioned.
Moreover, the fluorine-containing compound (A2) from which Y and Z differ from a commercially available thing can also be manufactured from a commercially available fluorine-containing compound (A2). For example, from a commercially available fluorine-containing compound (A2) in which both Y and Z are —CF ₂ CH ₂ OH (for example, the above FLUOROLINK D4000), a fluorine-containing compound in which both ends of Y and Z are perfluoroalkyl groups ( A2) can be produced. Specifically, for example, perfluoro (alkyl vinyl ether) can be added to the hydroxyl group of —CF ₂ CH ₂ OH to convert the perfluoro (alkyl vinyl ether) to Y or Z having a perfluoroalkyl moiety at the terminal.

The number average molecular weight of the fluorine-containing compound (A2) is 1,000 to 50,000, preferably 3,000 to 30,000, particularly preferably 3,000 to 10,000. When it is at least the lower limit of the above range, the influence of the terminal group on the refractive index of the fluorine-containing compound (A2) is small, and it is easy to control the refractive index. Moreover, it is excellent in film forming property, and it is excellent in the uniformity of the film thickness in a flat part. If it is less than the upper limit value, it is excellent in the ability to follow a step during coating, and if the surface of the resist layer is uneven, the amount of coating required to cover the entire surface of the convex and concave portions can be reduced.

[Coating composition]
The coating composition of this invention contains a solvent as needed. As long as the effects of the present invention are not impaired, the polymer other than the fluorine-containing compound (A), or other components inevitable in production (unreacted raw materials, by-products, additives used in the production of the polymer) ) May be included.
For the purpose of further reducing the refractive index of the film formed using the coating composition of the present invention, fine particles may be contained. When fine particles are included, care must be taken so that scattering by the fine particles is not excessive.
Examples of the polymer other than the fluorine-containing compound (A) include a homopolymer of CH ₂ = CFCF ₂ OCF (CF ₃ ) CF ₂ OCF (CF ₃ ) C (CF ₃ ) (CF ₃ ) OH.

When the coating composition contains a solvent, the fluorine-containing compound (A) is preferably dissolved in the solvent.
The solvent for the coating composition is preferably a fluorine-containing solvent.
The fluorine atom content of the fluorinated solvent is preferably 65% by mass or more, and particularly preferably 70% by mass or more, from the viewpoint that good solubility of the fluorinated compound (A) is easily obtained. Moreover, since the solubility of a fluorine-containing compound (A) will become low easily when the polarity of a fluorine-containing solvent is high, it is preferable that a fluorine-containing solvent does not contain polar groups, such as a hydroxyl group and a carboxy group.
As will be described later, when the film is formed by spin coating, a solvent having a high boiling point is preferable because the film thickness can be easily increased even at the same polymer concentration. A preferable boiling point is, for example, 95 ° C. or more, and 110 to 150 ° C. is particularly preferable.
Moreover, it is preferable that the solvent of a coating composition does not melt | dissolve a photoresist layer, even if it contacts a photoresist layer. A fluorine-containing solvent is also preferable in this respect.

The following are mentioned as an example of a preferable fluorine-containing solvent.
CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ CH ₂ CH ₃ (boiling point 114 ° C.),
CF ₃ CF (CF ₃ ) CF (OCH ₃ ) CF ₂ CF ₃ (boiling point 98 ° C.).
The temperature for dissolving the fluorine-containing compound (A) in these fluorine-containing solvents is sufficient at room temperature, and for example, stirring may be performed for about 3 hours.

When the coating composition contains a solvent, the concentration of the total amount of the fluorine-containing compound (A) and the other polymer in the coating composition is preferably 1 to 30% by mass.
The ratio of the fluorine-containing compound (A) to the total amount of the fluorine-containing compound (A) and the other polymers in the coating composition is preferably 50% by mass or more, more preferably 70% by mass or more, and 100 Mass% is particularly preferred.
When the coating composition contains a solvent, the content of the solvent in the coating composition is preferably 70 to 99% by mass. When the coating composition contains a fluorine-containing solvent, the content of the fluorine-containing solvent in the coating composition is preferably 70 to 99% by mass.

[Method for producing photoresist laminate]
The method for producing a photoresist laminate of the present invention is a method for producing a photoresist laminate in which an antireflection film is provided on the surface of a photoresist layer, the coating of the present invention on the surface of the photoresist layer. The coating composition is applied to form a coating film comprising the coating composition, and when the coating film contains a solvent, the solvent is then removed from the coating film.

As a method for forming a coating film by applying the coating composition of the present invention on the surface of the photoresist layer, a known method can be used. The spin coating method is preferable from the viewpoint of the uniformity and simplicity of the antireflection film.
When the coating film contains a solvent, an antireflection film can be obtained by removing the solvent from the coating film after the coating film is formed. As a method for removing the solvent, it is preferable to perform heat drying using, for example, a hot plate or an oven. As drying conditions, for example, in the case of a hot plate, conditions of 80 to 150 ° C. and 30 to 200 seconds are preferable.
The film thickness of the antireflection film may be set in accordance with a known antireflection theory. The film thickness is set to an odd multiple of “(exposure wavelength) / (4 × (refractive index of antireflection film))”. Since prevention performance becomes high, it is preferable.

The antireflection film formed on the surface of the photoresist layer using the coating composition of the present invention needs to be removed using a top antireflection film removing solvent after exposing the photoresist laminate. . Then, after removing the antireflection film, the photoresist is developed using an alkaline aqueous solution.
The solvent for removing the top antireflection film is preferably one having high solubility of the fluorine-containing compound (A), and is the same as the fluorine-containing solvent used in the coating composition including specific examples.
The solvent for removing the top antireflection film may be mixed with a non-fluorine solvent in the fluorinated solvent as long as the resist is not dissolved and the top antireflection film can be removed. Examples of the non-fluorine solvent include ketone compounds such as 2-butanone; ether compounds such as diethyl ether, dimethyl ether, tetrahydrofuran, dibutyl ether, and diisoamyl ether, and ether compounds are preferred. The ether compound has an etheric oxygen atom in the same manner as the fluorine-containing compound (A) to be dissolved. Compared with non-fluorine solvents other than the ether compound, the ether compound contains a fluorine-containing solvent mixed with a fluorine-containing solvent ( Since the decrease in the solubility of A) can be further suppressed, a larger amount can be mixed with the fluorinated solvent.
When the non-fluorine solvent is mixed with the fluorine-containing solvent, the ratio of the non-fluorine solvent is preferably fluorine-containing solvent: non-fluorine solvent = 99: 1 to 30:70 (mass ratio).

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. Of Examples 1 to 9, Examples 1 to 5 and 9 are Examples, and Examples 6 to 8 are Comparative Examples. The measurement method and evaluation method used the following methods.

[Measuring method]
(Film thickness and refractive index)
On a hot plate that was prepared by diluting the fluorine-containing compound solution obtained in each example, and applying 3 mL of a fluorine-containing compound solution having a concentration of 2% by mass on a silicon wafer by spin coating, and adjusting the temperature to 150 ° C. And dried for 90 seconds to form a film made of a fluorine-containing compound (antireflection film). The film thickness and refractive index at a wavelength of 193 nm were simultaneously measured with an ellipsometer.

(Storage stability of coating composition)
The fluorine-containing compound solution obtained in each example (fluorine-containing compound concentration of 20% by mass) was left (stored) at 5 ° C. for 2 weeks after production, and then coated on a silicon wafer by spin coating. Was applied to a thickness of about 500 nm. The surface state of the formed coating film was visually observed.
When aggregates of fluorine-containing compounds are generated during storage, even if the aggregates are so small that they are not visible, the surface of the coating film does not become uniform when a thin film is formed by spin coating. To do. For example, film thickness unevenness called repelling occurs.
The case where the surface of the coating film was uniform and completely free of abnormalities was judged as being ◯ (good), and when even one abnormality occurred, it was judged as x (bad).

(Resist solubility of coating composition)
A commercially available resist composition (product name: Sumiresist PAR-855S75 (J), manufactured by Sumitomo Chemical Co., Ltd.) was applied to a silicon wafer by spin coating so that the film thickness was about 120 nm, and the temperature was 150 ° C. The resist film was formed by drying for 90 seconds on the adjusted hot plate. Thereafter, several drops of the fluorine-containing compound solution obtained in each example (fluorine-containing compound concentration of 20% by mass) were dropped and allowed to stand for 30 minutes. After 30 minutes, the fluorine-containing compound was removed by flowing a solvent for removing the top antireflection film of the type shown in the table over the substrate, and the resist surface was observed. If there was no change, it was judged as ◯ (good), and if unevenness or the like occurred, it was judged as x (defect).

[Used compounds]
(Monomer)
(A): CF ₂ = CFOCF ₂ CF ₂ CF ₃ (molecular weight 266)
(B): CF ₂ = CFOCF ₂ CF ₂ CF ₂ OCF ₃ (molecular weight 332)
(C): CF ₂ ═CF—O—CF ₂ CF (CF ₃ ) —O—CF ₂ CF ₂ CF ₃ (molecular weight 432)
_{_{(D): CF 2 = CFOCF}} 2 CF 2 CF = CF 2 ( molecular weight 278)
_{(E): CH 2 = CFOCF} 2 CF 2 CF 3 ( molecular weight 230)
(F): CF ₂ ═CF—O—CF ₂ CF (CF ₃ ) —O—CF ₂ CF ₂ CF ₂ COOCH ₃ (molecular weight 472)
(Polymerization initiator)
Polymerization initiator solution (1): diisopropyl peroxydicarbonate solution (concentration 50% by mass, solvent: CF ₃ CH ₂ OCF ₂ CF ₂ H)

(Commercially available fluorine-containing compounds)
(A2-1): HOCH ₂ CF ₂ —O— (CF ₂ O) _a (CF ₂ CF ₂ O) _b —CF ₂ CH ₂ OH (product name: FLUOROLINK D4000, manufactured by Solvay Solexis, a is about 20 , B is about 20.)

(Solvent for coating composition)
(1): CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ CH ₂ CH ₃
(2): Water (3): Mixed solution having a mass ratio of water / isopropyl alcohol (hereinafter also referred to as “IPA”) of 7/3

(Solvent for removing the top antireflection film)
(1): CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ CH ₂ CH ₃
(2): Water (3): Mixed solvent in which CF ₃ CF ₂ CF ₂ CF ₂ CF ₂ CF ₂ CH ₂ CH ₃ and tetrahydrofuran are mixed at 1: 1 (mass ratio).

[Example 1: Synthesis and evaluation of fluorine-containing compound (A1-1)]
After charging 50 g of the monomer (a) and 0.68 g of the polymerization initiator solution (1) into a 50 mL pressure-resistant glass container, the system was replaced with nitrogen.
Subsequently, it stirred while heating so that internal temperature might be 40 degreeC, and the polymerization reaction was performed for 72 hours. After completion of the polymerization reaction, the unreacted raw material was distilled off by vacuum drying at 80 ° C. to obtain 17.4 g of a fluorine-containing compound (A1-1).
In a separable flask, the fluorine-containing polymer (A1-1) and the solvent (1) are stirred at room temperature for 3 hours to obtain a fluorine-containing compound solution (coating composition) having a concentration of the fluorine-containing compound of 20% by mass. )
The mass average molecular weight, number average molecular weight, and fluorine atom content of the fluorine-containing compound (A1-1) are shown in Table 1 (hereinafter the same).
With respect to the obtained fluorine-containing compound (A1-1), the film thickness, the refractive index of the film, the storage stability, and the resist solubility were evaluated by the above methods.
Table 1 also describes the main manufacturing conditions. Moreover, the value which converted the usage-amount of the polymerization initiator into the ratio (unit: mol%) with respect to the sum total of the number-of-moles of the monomer used for a polymerization reaction is described (hereinafter, the same).

[Examples 2 and 3: Synthesis and evaluation of fluorine-containing compounds (A1-2) and (A1-3)]
A fluorine-containing compound solution (coating composition) having a fluorine-containing compound content (concentration) of 20% by mass was obtained in the same manner as in Example 1 except that the polymerization process conditions were changed as shown in Table 1. Evaluation was performed in the same manner as in Example 1.

[Example 4: Evaluation of fluorine-containing compound (A2-1)]
The fluorine-containing compound (A2-1) was dissolved in the solvent (1) so that the concentration of the fluorine-containing compound was 20% by mass to obtain a fluorine-containing compound solution (coating composition). Evaluation was performed in the same manner as in Example 1.

[Example 5: Synthesis and evaluation of fluorine-containing compound (A2-2)]
The fluorine-containing polymer (A2-1) and the monomer (a) were reacted to replace the hydrogen atoms at both ends of the fluorine-containing compound (A2-1) with —CF ₂ CFHCF ₂ CF ₂ CF ₃ . A fluorine-containing compound (A2-2) was obtained.
That is, in a three-necked flask, 1.45 g of a 20 wt% KOH aqueous solution, 16.5 g of tert-butyl alcohol, 55 g of 1,3-bis (trifluoromethyl) benzene, a fluorine-containing compound (A2-1) ) Was added and 14.6 g of monomer (a) was added. The mixture was stirred at 40 ° C. for 20 hours under a nitrogen atmosphere. By washing once with a dilute hydrochloric acid solution, the organic phase is recovered, and concentrated by an evaporator to obtain a fluorine-containing compound (A2-2): CF ₃ CF ₂ CF ₂ CFHCF ₂ OCH ₂ CF ₂ —O— (CF ₂ O) 115 g of _a (CF ₂ CF ₂ O) _b —CF ₂ CH ₂ OCF ₂ CFHCF ₂ CF ₂ CF ₃ was obtained. 10 g was collected from this and dissolved in the solvent (1) in the same manner as in Example 4 to obtain a fluorine-containing compound solution (coating composition). Evaluation was performed in the same manner as in Example 1.

[Example 6: Synthesis and evaluation of fluorine-containing compound (D)]
A fluorine-containing compound solution (coating composition) having a fluorine-containing compound content (concentration) of 20% by mass was obtained in the same manner as in Example 1 except that the polymerization process conditions were changed as shown in Table 1. Evaluation was performed in the same manner as in Example 1. In this example, a chain transfer agent (methanol) was also added when the monomer and the polymerization initiator solution (1) were charged.
The monomer (d) is a fluorine-containing monomer having a polymerizable carbon-carbon double bond at both ends. The monomer (d) is a unit (d-1) represented by the following formula (d-1) by cyclopolymerization: )

[Example 7: Synthesis and evaluation of fluorine-containing compound (E)]
A fluorine-containing compound solution (coating composition) having a fluorine-containing compound content (concentration) of 20% by mass was obtained in the same manner as in Example 1 except that the polymerization process conditions were changed as shown in Table 1. Evaluation was performed in the same manner as in Example 1. In this example, a chain transfer agent (methanol) was also added when the monomer and the polymerization initiator solution (1) were charged.

[Example 8: Synthesis and evaluation of fluorine-containing compound (F-1)]
After charging 50 g of the monomer (f) and 0.60 g of the polymerization initiator solution (1) into a 50 mL pressure-resistant glass container, the system was replaced with nitrogen.
Subsequently, it stirred while heating so that internal temperature might be 40 degreeC, and the polymerization reaction was performed for 72 hours. After completion of the polymerization reaction, unreacted raw materials were distilled off by vacuum drying at 80 ° C. to obtain 19 g of a fluorine-containing compound (F).
Fluorine-containing compound (F) and water are charged into a separable flask and hydrolyzed by stirring for 72 hours while maintaining at 80 ° C. to obtain an aqueous solution of fluorine-containing compound (F-1) having a concentration of 5% by mass. It was. The fluorine-containing compound (F-1) is a fluorine-containing polymer in which —COOCH _{3 at} the terminal of the fluorine-containing compound (F) is hydrolyzed and converted to —COOH. The obtained aqueous solution was dried to remove the solvent to obtain a fluorine-containing compound (F-1).
In a separable flask, the fluorine-containing compound (F-1) and the solvent (3) are stirred at room temperature for 3 hours to obtain a fluorine-containing compound solution having a concentration of 20% by mass of the fluorine-containing compound (coating composition). Got.
The mass average molecular weight and number average molecular weight of the fluorine-containing compound (F-1) can be regarded as the same as the mass average molecular weight and number average molecular weight of the fluorine-containing compound (F). These are shown in Table 1.
The obtained fluorine-containing compound (F-1) was evaluated in the same manner as in Example 1.

[Example 9]
In the same manner as in Example 3, a fluorine-containing compound solution (coating composition) having a fluorine-containing compound content (concentration) of 20% by mass was obtained and evaluated. In this example, the solvent for removing the top antireflection film used for the resist solubility evaluation of the coating composition was changed as shown in Table 1.

As shown in the results of Table 1, according to the coating compositions of Examples 1 to 5 and 9 using the fluorine-containing compound (A1) or (A2) according to the present invention, the refractive index is 1.36 or less. A membrane could be obtained.
Monomer (a) and monomer (e) are composed of only C, O, and F, whereas monomer (e) has a hydrogen atom bonded to a carbon atom. It differs in that it is. Example 1 using a fluorine-containing compound (A1-1) which is a homopolymer of monomer (a) and Example 7 using a fluorine-containing compound (E) which is a homopolymer of monomer (e) In comparison, Example 7 has a slightly higher refractive index of the film. This shows that the refractive index of the film increases when hydrogen atoms are present in the units of the fluoropolymer.

The monomer (c) and the monomer (f) differ in the side chain end groups. The terminal group of the side chain of the monomer (c) is —CF ₃ , and the terminal group of the side chain of the unit based on the monomer (f) in the fluorine-containing compound (F-1) is a carboxy group-containing group. .
Comparing Example 3 using the fluorinated polymer (A1-3), which is a homopolymer of the monomer (c), and Example 8 using the fluorinated compound (F-1), Example 8 was more The refractive index of the film is much higher. As this factor, it is considered that the carboxy group present in the fluorine-containing compound (F-1) has a property of absorbing light at 193 nm.

Monomer (a) has only one polymerizable carbon-carbon double bond, whereas monomer (d) has a polymerizable carbon-carbon double bond at both ends, The fluoropolymer (D) has a unit (d-1) represented by the above formula (d-1). The unit based on the monomer (a) has an etheric oxygen atom that does not form a ring, but the unit (d-1) has an etheric oxygen atom only in the ring structure.
Comparing Example 1 using the fluorine-containing compound (A1-1), which is a homopolymer of the monomer (a), with Example 6 using the fluorine-containing compound (D), the film of Example 6 is more refracted. The rate is slightly high. This shows that even if it has an etheric oxygen atom, if it exists in the ring structure, the refractive index reducing effect is small.

From the above, in the fluorine-containing compound (A1), the unit in the polymer is composed only of C, O, and F, has an etheric oxygen atom that does not constitute a ring, and the terminal is —CF ₃ . It can be seen that having side chains is important for achieving a low refractive index. It can also be seen that it is preferable in reducing the refractive index that the fluorine-containing polymer does not have a highly polar functional group such as a hydroxyl group or a carboxy group that absorbs light near 193 nm.

The fluorine-containing compounds (A2-1) and (A2-2) in Examples 4 and 5 are both compounds having a perfluoropolyether skeleton in the main chain.
In both Example 4 using the fluorine-containing compound (A2-1) whose main chain terminal is a hydroxyl group and Example 5 using the fluorine-containing compound (A2-2) whose main chain terminal is a perfluoroalkyl group, refraction A film having a sufficiently low rate of 1.34 was obtained.
From these results, it is understood that the fluorine-containing compound having a perfluoropolyether skeleton in the main chain has a low refractive index, and the influence of the main chain end group on the refractive index of the film is small.

Paying attention to the film thickness results in Table 1, Examples 1 to 7 and 9 using the solvent (1) which is a fluorine-containing solvent are compared with Example 8 using a solvent (3) which is a mixture of water and IPA. The film thickness increased despite the polymer concentration in the coating composition being the same.
This is presumably because the boiling point of the solvent (1) is higher than either water or IPA, and the surface tension of the solvent (1) is lower than either water or IPA. In other words, when the solvent (1) is used as the solvent for the spin coating solution, the spin coating solution tends to spread on the silicon wafer and the spin coating solution spread on the silicon wafer is difficult to evaporate. It is considered that the time that the wafer is covered becomes longer, and as a result, the film thickness increases.

Paying attention to the storage stability results in Table 1, in Examples 1 to 7 and 9 using the solvent (1) which is a fluorine-containing solvent, good storage stability was obtained.
On the other hand, Example 8 using the solvent (3) which is a mixture of water and IPA was inferior in storage stability. It can be seen that the fluorine-containing compound (F-1) used in Example 8 has a carboxy group which is a hydrophilic functional group but is not sufficiently soluble in an aqueous solvent (3).

Paying attention to the results of resist solubility in Table 1, no change was observed on the resist film surface even when the fluorine-containing compound solutions (coating compositions) of Examples 1 to 7 and 9 were brought into contact with the resist film.
On the other hand, when the fluorine-containing compound solution (coating composition) of Example 8 using the solvent (3) which is a mixture of water and IPA was similarly brought into contact with the resist film, the resist film surface was roughened (unevenness, etc.). Occurred.

The coating composition of the present invention is useful as a composition for forming an antireflection film in photolithography. In particular, an antireflection film having a refractive index suitable for photolithography using an ArF excimer laser (193 nm) can be formed.
It should be noted that the description, claims, abstract and drawings of Japanese Patent Application No. 2015-108897 filed on May 28, 2015 and Japanese Patent Application No. 2015-157194 filed on August 7, 2015. Is hereby incorporated by reference as a disclosure of the specification of the present invention.

Claims

A coating composition comprising at least one fluorine-containing compound selected from the following fluorine-containing compound (A1) and the following fluorine-containing compound (A2).
Fluorine-containing compound (A1): A polymer comprising only one unit selected from the following units (I), and having a number average molecular weight of 1,000 to 50,000.
Unit (I): a unit based on a monomer having only one polymerizable carbon-carbon double bond, composed of only carbon, oxygen and fluorine atoms, and having one or more side chains, The unit in which at least one side chain contains one or more etheric oxygen atoms that do not constitute a ring, and the terminal is —CF 3 .
Fluorine-containing compound (A2): A compound having a perfluoropolyether skeleton in the main chain and a number average molecular weight of 1,000 to 50,000.
The coating composition according to claim 1, further comprising a solvent.
The coating composition according to claim 2, wherein the content of the solvent in the coating composition is 70 to 99% by mass.
The coating composition according to any one of claims 1 to 3, wherein the unit (I) is a unit represented by the following formula (i).
-[CX 1 X 2 -CX 3 X 4 ]-(i)
(In the formula, at least one of X 1 , X 2 , X 3 , and X 4 independently represents a C 1-12 perfluoro saturated carbon atom containing 1 to 4 etheric oxygen atoms that do not constitute a ring. A hydrogen group (wherein the number of etheric oxygen atoms is less than or equal to the number of carbon atoms), and the other is a perfluoro saturated hydrocarbon group having 1 to 12 carbon atoms not containing an etheric oxygen atom that does not form a ring, or Indicates a fluorine atom.)
At least one of X 1 , X 2 , X 3 and X 4 is a —O—Rf 1 group (the Rf 1 group is a group having 1 to 3 carbon atoms containing 0 to 3 etheric oxygen atoms between carbon-carbon atoms). The coating composition according to claim 4, which is 12 perfluoro saturated hydrocarbon groups.
6. The coating composition according to claim 5, wherein one of X 1 , X 2 , X 3 and X 4 is a —O—Rf 1 group, and the other 3 are fluorine atoms.
The coating composition according to any one of claims 1 to 6, wherein the fluorine-containing compound (A1) has a refractive index at 193 nm of 1.32 to 1.36.
The coating composition according to any one of claims 1 to 3, wherein the fluorine-containing compound (A2) is a compound represented by the following formula (II).
Y—O— (C n F 2n O) m —Z (II)
Wherein Y and Z are each independently a monovalent organic group (wherein Y is not an oxygen atom on the side bonded to —O—, and Z is bonded to — (C n F 2n O) m —) And n is an integer of 1 to 5, m is an integer of 2 to 200, and when m is 2 or more, a plurality of ( C n F 2n O) may be the same or different from each other.
The coating composition according to claim 1, 2, 3, or 8, wherein the fluorine-containing compound (A2) has a refractive index of 1.32 to 1.36 at 193 nm.
The coating composition according to any one of claims 1 to 9, wherein the solvent is a fluorine-containing solvent.
The coating composition according to claim 10, wherein the fluorine atom content of the fluorine-containing solvent is 65% by mass or more.
A method for producing a photoresist laminate in which an antireflection film is provided on the surface of a photoresist layer, the composition for coating according to any one of claims 1 to 11 on the surface of the photoresist layer. A method for producing a photoresist laminate, comprising: forming a coating film comprising the coating composition by coating an object, and then removing the solvent from the coating film when the coating film contains a solvent.