JP7639688B2 - Polymer, photosensitive resin composition, resin film, and electronic device - Google Patents

Description

The present invention relates to a polymer, a photosensitive resin composition, a resin film, and an electronic device. More specifically, the present invention relates to a polymer, a photosensitive resin composition containing the polymer, a resin film made of a cured product of the photosensitive resin composition, and an electronic device including the resin film.

In the field of negative photosensitive resin compositions, various techniques have been developed to improve the accuracy of resist patterns associated with finer patterns. For example, the technique described in Patent Document 1 is one such technique. According to this document, a radiation-sensitive resin composition containing a polymer [A] and an acid generator [B] is described. It is also described that the polymer [A] has structural units (I) and (II), and thus has excellent LWR (Line Width Roughness) performance and defect suppression properties, which indicate a small line width jitter (paragraph 0012 of Patent Document 1). Here, it is described that the structural unit (I) is a structural unit derived from N-(t-butyloxycarbonylmethyl)maleimide, N-(1-methyl-1-cyclopentyloxycarbonylmethyl)maleimide, or N-(2-ethyl-2-adamantyloxycarbonylmethyl)maleimide. It is also described that the structural unit (II) is a structural unit derived from 2-norbornene.

JP 2015-184458 A

The present inventors have investigated the durability of negative-type photosensitive resin compositions. As a result, it has been found that the radiation-sensitive resin composition described in Patent Document 1 has room for further improvement in terms of durability and low dielectric properties. The present invention provides a photosensitive resin composition that has an excellent balance between durability and low dielectric properties, and a polymer for use in such a photosensitive resin composition.

The inventors have discovered that by using a polymer having structural units with a specific structure, the cured product of a photosensitive resin composition containing the polymer has improved heat resistance, improved solvent resistance and a low dielectric constant, and have completed the present invention.

After extensive research, the inventors have discovered that the above problems can be solved by using a polymer having a specific fluorine-containing organic group.

According to the present invention, there is provided a polymer comprising structural units represented by the following formulas (1) and (2a):

（式（１）中、
Ｒ_１、Ｒ_２、Ｒ_３およびＲ_４ の少なくとも１つは、炭素数１～３０のパーフルオロアルキル基であり、残りが水素原子であり、ｎは０、１または２であり、
式（２ａ）中、
Ｒ_５は、（メタ）アクリロイル基を有する炭素数１～３０の有機基である。）。

(In formula (1),
At least one of R ₁ , R ₂ , R ₃ and R ₄ is a perfluoroalkyl group having 1 to 30 carbon atoms, and the rest are hydrogen atoms; n is 0, 1 or 2;
In formula (2a),
_R5 is an organic group having 1 to 30 carbon atoms and a (meth)acryloyl group .

Further, according to the present invention,
A polymer comprising structural units represented by the following formulas (1) and (2a):
A cross-linking agent;
A photosensitive resin composition is provided that includes a photosensitizer.

（式（１）中、
Ｒ_１、Ｒ_２、Ｒ_３およびＲ_４ の少なくとも１つは、炭素数１～３０のパーフルオロアルキル基であり、残りが水素原子であり、ｎは０、１または２であり、
式（２ａ）中、
Ｒ_５は、（メタ）アクリロイル基を有する炭素数１～３０の有機基である。）。

(In formula (1),
At least one of R ₁ , R ₂ , R ₃ and R ₄ is a perfluoroalkyl group having 1 to 30 carbon atoms, and the rest are hydrogen atoms; n is 0, 1 or 2;
In formula (2a),
_R5 is an organic group having 1 to 30 carbon atoms and a (meth)acryloyl group .

The present invention also provides a resin film consisting of a cured film of the above-mentioned photosensitive resin composition.

The present invention also provides an electronic device having the above-mentioned resin film.

The present invention provides a polymer that has excellent heat resistance and solvent resistance and can be suitably used to produce low dielectric resin films.

The following describes an embodiment of the present invention.

(Polymer P)
The polymer of this embodiment (hereinafter referred to as "polymer P") contains structural units represented by the following formulas (1) and (2a).

ここで、式（１）中、
Ｒ_１、Ｒ_２、Ｒ_３およびＲ_４はそれぞれ独立して水素または炭素数１～３０の有機基であり、ｎは０、１または２であり、
式（２ａ）中、
Ｒ_５は、炭素数１～３０の有機基であり、
Ｒ_１、Ｒ_２、Ｒ_３、Ｒ_４およびＲ_５の少なくとも１つは、炭素数１～３０の含フッ素有機基である。

Here, in formula (1),
R ₁ , R ₂ , R ₃ and R ₄ each independently represent a hydrogen atom or an organic group having 1 to 30 carbon atoms; n represents 0, 1 or 2;
In formula (2a),
_R5 is an organic group having 1 to 30 carbon atoms;
At least one of R ₁ , R ₂ , R ₃ , R ₄ and R ₅ is a fluorine-containing organic group having 1 to 30 carbon atoms.

Because polymer P contains the structural units described above, the cured product has excellent heat resistance and solvent resistance, as well as low dielectric properties. Therefore, it can be suitably used as a material for producing resin films for electronic devices.

Polymer P has structural units derived from a norbornene-type monomer represented by formula (1) and structural units derived from maleic anhydride represented by formula (2a).

In formula (1), n is 0, 1 or 2, and preferably 0.
R ₁ , R ₂ , R ₃ and R ₄ are each independently hydrogen or an organic group having 1 to 30 carbon atoms.
In formula (2a), R ₅ is an organic group having 1 to 30 carbon atoms.
At least one of R ₁ , R ₂ , R ₃ , R ₄ and R ₅ is a fluorine-containing organic group having 1 to 30 carbon atoms.

The proportion of structural units represented by formula (1) among all structural units of polymer P is preferably 35 mol% or more and 70 mol% or less, more preferably 40 mol% or more and 60 mol% or less.

Examples of the organic group having 1 to 30 carbon atoms which may constitute any of R ₁ , R ₂ , R ₃ and R ₄ , and R ₅ in formula (1) and formula (2a) include an alkyl group, an alkenyl group, an alkynyl group, an alkylidene group, an aryl group, an aralkyl group, an alkaryl group, a cycloalkyl group, and a heterocyclic group.
Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, and decyl groups.
Alkenyl groups include, for example, allyl, pentenyl, and vinyl groups. Alkynyl groups include ethynyl groups.
Alkylidene groups include, for example, methylidene and ethylidene groups.
Aryl groups include, for example, phenyl, naphthyl, and anthracenyl groups. Aralkyl groups include, for example, benzyl and phenethyl groups.
Examples of the alkaryl group include tolyl and xylyl groups. Examples of the cycloalkyl group include adamantyl, cyclopentyl, cyclohexyl, and cyclooctyl groups.
Examples of the heterocyclic group include an epoxy group and an oxetanyl group.

The organic group having 1 to 30 carbon atoms may contain at least one atom selected from O, N, S, P and Si in its structure.

In one embodiment, the organic group having 1 to 30 carbon atoms is preferably an organic group having 1 to 15 carbon atoms, and more preferably an organic group having 1 to 10 carbon atoms. Furthermore, the organic group having 1 to 30 carbon atoms is preferably an alkyl group having 1 to 30 carbon atoms, and more preferably an alkyl group having 1 to 15 carbon atoms, and even more preferably an alkyl group having 1 to 10 carbon atoms.

In the polymer P, at least one of R ₁ , R ₂ , R ₃ , R ₄ and R ₅ is a fluorine-containing organic group having 1 to 30 carbon atoms. Examples of the fluorine-containing organic group having 1 to 30 carbon atoms include a fluoroalkyl group having 1 to 30 carbon atoms and a fluoroalkyl group having 1 to 30 carbon atoms and having an etheric oxygen atom. The fluoroalkyl group having 1 to 30 carbon atoms refers to an organic group in which one or more hydrogen atoms in an alkyl group are substituted with a fluorine atom. Such fluoroalkyl groups include fluorinated alkyl groups and perfluoroalkyl groups.

In one embodiment, any one of R ₁ , R ₂ , R ₃ and R ₄ is a fluorine-containing organic group having 1 to 30 carbon atoms, and the remainder is a hydrogen atom. Preferably, any one of R ₁ , R ₂ , R ₃ and R ₄ is a fluoroalkyl group having 1 to 30 carbon atoms, and the remainder is a hydrogen atom. More preferably, any one of R ₁ , R ₂ , R ₃ and R ₄ is a perfluoroalkyl group having 1 to 30 carbon atoms, and the remainder is a hydrogen atom. By any one of R ₁ , R ₂ , R ₃ and R ₄ being a fluorine-containing organic group having 1 to 30 carbon atoms, and the remainder being a hydrogen atom, the film-forming property of the photosensitive resin composition containing this polymer P can be improved, and the obtained cured film can be made low dielectric.

In one embodiment, R ₅ is preferably a fluoroalkyl group having 1 to 30 carbon atoms or a fluoroalkyl group having 1 to 30 carbon atoms and an etheric oxygen atom.

In one embodiment, the organic groups constituting R ₁ , R ₂ , R ₃ and R ₄ are preferably organic groups having no acidic functional group. By not having an acidic organic group, it is possible to easily control the acid value of the polymer P.

The polymer P of this embodiment may further contain at least one of the structural units represented by formulas (B2) to (B6).

In formula (B2), R ₆ and R ₇ each independently represent an organic group having 1 to 30 carbon atoms.
In formula (B6), R ₈ is an organic group having 1 to 30 carbon atoms.
The organic group having 1 to 30 carbon atoms has the same meaning as defined above.
It is preferable that any one of R ₅ , R ₆ and R ₇ has a carbon-carbon double bond that is crosslinked by a photoradical polymerization initiator, for example, a vinyl group, a vinylidene group, an allyl group, an acryloyl group, or a methacryloyl group.

Among these, it is preferable to contain a structural unit derived from maleimide represented by formula (B5) or formula (B6) because the heat resistance of the resulting cured film is improved. It is preferable that none of the organic groups constituting R ₆ to R ₈ has an acidic functional group such as a carboxyl group. This makes it easier to control the acid value of polymer P.

The polymer P of this embodiment can be prepared by addition polymerization of a norbornene type monomer (monomer A) represented by formula (3) and maleic anhydride (monomer B) represented by formula (4). When the polymer P of this embodiment further contains structural units represented by formula (B5) and/or formula (B6), the norbornene type monomer (monomer A) can be addition polymerized with maleic anhydride and maleimide and/or maleimide derivative (monomer B) represented by formula (5) to prepare the desired polymer.

式（３）中、ｎは０、１または２であり、Ｒ_１、Ｒ_２、Ｒ_３およびＲ_４はそれぞれ独立して水素または炭素数１～３０の有機基である。
式（５）中、Ｒ_８は、上記の定義と同様である。

In formula (3), n is 0, 1 or 2, and R ₁ , R ₂ , R ₃ and R ₄ each independently represent a hydrogen atom or an organic group having 1 to 30 carbon atoms.
In formula (5), R ₈ is as defined above.

Examples of norbornene-type monomers that can be used include the following norbornenes:

Examples of maleimide derivatives represented by the above formula (5) include N-methylmaleimide, N-cyclohexylmaleimide, N-phenylmaleimide, N-(4-aminophenyl)maleimide, N-benzylmaleimide, N-tert-butylmaleimide, N-ethylmaleimide, N-(2-hydroxyethyl)maleimide, N-methoxycarbonylmaleimide, 3-maleimidepropionic acid, 4-maleimidebutyric acid, and 6-maleimidehexanoic acid. Of these, it is preferable to use N-cyclohexylmaleimide. This can improve the heat resistance and chemical resistance of the cured product of polymer P.

The polymer P can be synthesized by an addition polymerization reaction between a monomer A and a monomer B.
It should be noted that there is no limitation to using one or more kinds of monomers as the monomer A and the monomer B.
Although there is no limitation on the method of addition polymerization, in this embodiment, the copolymer is synthesized by radical polymerization using a radical polymerization initiator.
By performing addition polymerization using a radical polymerization initiator, a copolymer having a structural unit derived from monomer A and a structural unit derived from monomer B, and having a terminal derived from the radical polymerization initiator, can be synthesized.

The molar ratio of monomer A to monomer B in the copolymer is preferably 1:0.5 to 1:2. The above 1:0.5 to 1:2 includes 1:0.5 and 1:2. Among these, from the viewpoint of improving molecular structure controllability, the molar ratio is preferably 1:1.

Monomer A, monomer B, and a radical polymerization initiator are dissolved in a solvent, and then the mixture is heated for a predetermined period of time to allow addition polymerization to proceed. The heating temperature is, for example, 50°C or higher and 80°C or lower, and the heating time is 3 hours or higher and 20 hours or lower.

In the addition polymerization, additives such as chain transfer agents may be used. It is preferable to add a chain transfer agent to control the terminal structure of the copolymer and introduce a functional group that reacts with the crosslinking agent to the copolymer terminal.

The radical polymerization initiator is not limited as long as it introduces a functional group that reacts with the crosslinking agent to X, which is one of the copolymer terminals, and an azo compound or a peroxide can be used. Among these, it is preferable to use an azo compound.

Specific examples of azo compounds include radical polymerization initiators having a carboxyl group, such as 4,4'-azobis(4-cyanovaleric acid) and 2,2'-azobis[N-(2-carboxyethyl)-2-methyl]; radical polymerization initiators having an amino group, such as 2,2'-azobis(2-methylpropionamidine) and 2,2'-azobis[2-(2-imidazolin-2-yl)propane]; and radical polymerization initiators having a hydroxyl group, such as 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)propionamide]. Among these, it is preferable to use a radical polymerization initiator having a carboxyl group, and it is even more preferable to use 4,4'-azobis(4-cyanovaleric acid). This can improve the heat resistance and chemical resistance of the resulting polymer P.

The amount (molar number) of the radical polymerization initiator added is preferably 1% or more and 10% or less of the total number of moles of monomer A and monomer B. By appropriately setting the amount of the radical polymerization initiator within the above range and appropriately setting the reaction temperature and reaction time, the weight average molecular weight (Mw) of the resulting copolymer can be adjusted.

The copolymer obtained by the addition polymerization reaction of monomer A and monomer B (referred to as the "polymer precursor" or "polymer before ring-opening") becomes polymer P through the ring-opening process. In the ring-opening process, some of the repeating units among the structural units derived from maleic anhydride in the polymer precursor obtained as described above are kept in a ring-closed state, while the remaining repeating units are ring-opened. This makes it possible to adjust the amount of carboxyl groups in the copolymer. In other words, it becomes possible to control the acid value of the copolymer to be produced. And by controlling the acid value, it is possible to adjust the alkali solubility of the photosensitive resin composition containing polymer P.

In this embodiment, for example, 50% or more of the repeating units derived from maleic anhydride in the polymer precursor are not ring-opened, and the cyclic structures (anhydride rings) of the remaining repeating units are ring-opened. That is, the ring-opening rate of the copolymer is, for example, less than 50%. In particular, it is preferable to ring-open 10% or more and 30% or less of the repeating units of the cyclic structure derived from maleic anhydride in the copolymer.

Here, the ring-opening ratio of the repeating unit derived from maleic anhydride can be measured as follows.
The IR absorption intensity (Abs1) of (C═O) in the acid anhydride structure of a polymer (polymer precursor) before ring-opening is measured, and the ring-opening rate is calculated from the IR absorption intensity (Abs2) of (C═O) in the acid anhydride structure after ring-opening according to the following formula.
Ring opening rate (%) = (((Abs1)-(Abs2))/(Abs1))×100
Acetonitrile is used as the internal standard substance.

The polymer precursor is treated with either (i) a metal alkoxide as a base, (ii) an alcohol and an alkali metal hydroxide as a base, or (iii) an alcohol and an organic base such as a tertiary amine, to form a polymer P in which the maleic anhydride structural unit is ring-opened. Specifically, in the polymerization step, the above-mentioned reagent (i) or reagent (ii) is added to the reaction solution in which the monomers A and B are polymerized, and an organic solvent such as methyl ethyl ketone (MEK) is further added, and the mixture is stirred at 40°C to 50°C for 1 hour to 5 hours to obtain a reaction solution L1. In the reaction solution L1, some of the anhydride rings of the repeating units derived from maleic anhydride in the copolymer are ring-opened, and some of the ends formed by the ring-opening are esterified. The remaining ends are not esterified and become metal salt structures.

In this embodiment, the number of moles of the metal alkoxide or alkali metal hydroxide is preferably 50% or less of the number of moles of maleic anhydride used in the polymerization process. In particular, the number of moles of the metal alkoxide or alkali metal hydroxide is preferably 40% or less, 10% or more, and more preferably 30% or less of the number of moles of maleic anhydride used in the polymerization process. In this way, the amount of the metal alkoxide or alkali metal hydroxide can be reduced, and the alkali metal concentration in the finally obtained polymer P can be reduced. By reducing the alkali metal concentration in the polymer P, migration of metal ions in a device using a resin composition using this polymer P can be suppressed.

The metal alkoxide is preferably one represented by M( _OR5 ) (wherein M is a monovalent metal and _R5 is an organic group having 1 to 30 carbon atoms). The metal M may be an alkali metal, and sodium is preferred from the viewpoint of ease of handling. Examples of _R5 include the same as _R5 in the above formula (2a).
Two or more different metal alkoxides may be used, however, from the viewpoint of production stability, it is preferable to use one type of metal alkoxide.

On the other hand, as mentioned above, the maleic anhydride-derived structure of the polymer precursor may be (ii) ring-opened in the presence of an alcohol and an alkali metal hydroxide as a base.
As the alkali metal hydroxide, sodium hydroxide is preferred from the viewpoint of ease of handling.
The alcohol is preferably a monohydric alcohol (R ₅ OH). The organic group R ₅ can be any of those described above. R ₅ preferably has 1 to 30 carbon atoms.

Examples of the monohydric alcohol (R ₅ OH) preferably used in this embodiment include allyl alcohol, methallyl alcohol, 3-buten-1-ol, 3-methyl-3-buten-1-ol, 4-penten-1-ol, 5-hexen-1-ol, 6-hepten-1-ol, 7-octen-1-ol, 8-nonen-1-ol, 9-decen-1-ol, 10-undecen-1-ol, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, 1,4-cyclohexanedimethanol monoacrylate, and 1,4-cyclohexanedimethanol monomethacrylate, 1H,1H-trifluoroethenol, 1H,1H-pentafluoropropanol, 6-(perfluoroethyl)hexanol, 1H,1H-heptafluorobutanol, and the like. perfluorobutyl)ethanol, 2-perfluoropropoxy-2,2,3,3-tetrafluoropropanol, 2-perfluorohexyl)ethanol, 3-perfluorohexyl)propanol, 6-perfluorohexyl)hexanol, 1H,1H-2,5-di(trifluoromethyl)-3,6-dioxaundecafluorononanol, 6-(perfluoro-1-methylethyl)hexanol, 1H,1H,3H-tetrafluoropropanol, 1H,1H,5H-octafluoropentanol, 1H,1H,7H-dodecafluoroheptanol, 2H-hexafluoro-2-propanol, 1H,1H,3H-hexafluorobutanol, 2,2-bis(trifluoromethyl)propanol, and the like, but are not limited thereto. These alcohols may be used alone or in combination of two or more.

The repeating unit derived from maleic anhydride that is opened in this ring-opening process has the structure shown in formula (5a) below, which has a salt portion of the carboxyl group.

（式（５ａ）中、Ｒ_５は炭素数１以上３０以下の有機基である。）

(In formula (5a), _R5 is an organic group having 1 to 30 carbon atoms.)

When the copolymer is ring-opened with (i) a metal alkoxide as a base, or (ii) an alcohol and an alkali metal hydroxide as a base, structures shown in the following general formula (B2) or (5b) may be formed, although only slightly. In the following general formula (B2), R ₆ and R ₇ may be the same as R ₅ .

（式（Ｂ２）中、Ｒ_６、およびＲ_７は、それぞれ独立して炭素数１以上３０以下の有機基である。）

(In formula (B2), R ₆ and R ₇ are each independently an organic group having 1 to 30 carbon atoms.)

After the ring-opening reaction, a monomer having an epoxy group and a double bond group can be further reacted to obtain a polymer P having a crosslinkable double bond-containing group. In this embodiment, it is preferable to use glycidyl acrylate, glycidyl methacrylate, or 3,4-epoxycyclohexylmethyl methacrylate as a monomer having an epoxy group and a double bond group, in view of availability. It is also possible to introduce a fluorine functional group by reacting a monomer having an epoxy group and a fluorine functional group in a similar manner. For example, 3-perfluorobutyl-1,2-epoxypropane, 3-perfluorohexyl-1,2-epoxypropane, 3-perfluorooctyl-1,2-epoxypropane, etc. can be used. By providing the polymer P with a group having a double bond, it is possible to improve the crosslinkability by a photoradical polymerization initiator, and as a result, it is possible to improve the sensitivity of the polymer P.

Next, an acidic aqueous solution such as hydrochloric acid or formic acid is added to the reaction liquid L1 to acidify the copolymer, thereby replacing the metal ions (Na ⁺ ) with protons (H ⁺ ).
The structural unit represented by the above formula (6) becomes the structural units represented by the following formulas (2a) and (B4) by proton substitution, respectively.

（式（２ａ）中、Ｒ_５は炭素数１以上３０以下の有機基である。）

(In formula (2a), _R5 is an organic group having 1 to 30 carbon atoms.)

In this ring-opening step (S3), it is preferable not to open 50% or more of the repeating units derived from maleic anhydride in the polymer precursor. As described above, in the polymer P, a metal such as Na is bonded to one end formed by ring-opening of the maleic anhydride ring. By not opening 50% or more of the repeating units, the amount of metal contained in the product polymer P can be reduced. This makes it possible to reduce the amount of alkali metal in the polymer P finally obtained in this embodiment, and to exhibit the desired properties in the photosensitive resin composition containing this polymer P.

After the ring-opening step, the solution containing the obtained polymer P may be washed with a mixture of water and an organic solvent (e.g., methyl ethyl ketone) to remove residual metal components. It is preferable to perform the washing step so that the alkali metal concentration in the polymer P is 10 ppm or less, preferably 5 ppm or less.

The weight average molecular weight (Mw) of the polymer P of this embodiment is preferably in the range of 1000 to 20000, more preferably 1500 to 15000, and even more preferably 2000 to 10000 from the viewpoint of forming an appropriate crosslinked structure. The number average molecular weight (Mn) of the polymer P of this embodiment is preferably 500 to 10000, and more preferably 1000 to 8000 from the viewpoint of forming an appropriate crosslinked structure. Furthermore, from the viewpoint of making the physical properties of each molecular chain of the polymer P uniform and improving the shape of the resin film obtained by curing, the molecular weight distribution (Mw/Mn) of the polymer P is preferably 1.0 to 2.5, and more preferably 1.2 to 2.0. The molecular weight of the polymer P can be controlled by adjusting the type and amount of the monomer used in the preparation of the polymer P, the preparation conditions, and the like.

The double bond equivalent of the polymer P of this embodiment is preferably 500 g/mol or more and 2500 g/mol or less, and more preferably 500 g/mol or more and 2000 g/mol or less. Since the double bond equivalent is within the above range, the polymer P is suitably used in a photosensitive resin composition that is subjected to exposure and development processing.

The fluorine content of the polymer P of this embodiment is preferably 25 wt% or more and 45 wt% or less, and more preferably 30 wt% or more and 40 wt% or less. When the fluorine content is in the above range, the cured product of the polymer P has excellent heat resistance and solvent resistance. The fluorine content of the polymer P can be controlled by adjusting the type and the amount of the above-mentioned monomer used in the preparation of the polymer P.

The polymer P of this embodiment has excellent alkali solubility, and therefore has excellent processability in exposure and development treatment using an alkaline aqueous solution as a developer. The alkaline dissolution rate of the polymer P can be, for example, 10 Å/sec to 2500 Å/sec, more preferably 50 Å/sec to 2000 Å/sec. Here, the alkaline dissolution rate is calculated by applying a propylene glycol monomethyl ether acetate solution (solid content 35% by mass) of the polymer P to a silicon wafer by spin coating and soft baking at 100°C for 120 seconds to obtain a polymer film, which is then immersed in a 2.38% aqueous tetramethylammonium hydroxide solution at 23°C, and visually measuring the time it takes for the polymer film to disappear.

The polymer P of this embodiment has, for example, a refractive index of 1.38 or more and 1.48 or less, and more preferably a refractive index of 1.40 or more and 1.46 or less. The polymer P having a refractive index within the above range has excellent processability by exposure and development, and the cured product has the desired properties as a permanent film for an electronic device.

(Photosensitive resin composition)
The polymer P of this embodiment is used in a photosensitive resin composition for forming a resin film of an electronic device.
The photosensitive resin composition of the present embodiment is
The polymer P,
A cross-linking agent;
and a photosensitizer.

The photosensitive resin composition of this embodiment contains the above-mentioned polymer P, so that the cured product has excellent heat resistance and solvent resistance as well as low dielectric properties. Therefore, the photosensitive resin composition of this embodiment can be suitably used as a material for producing a permanent film for electronic devices.

Each component used in the photosensitive resin composition will be described in detail below. The polymer P is as described above.
(Crosslinking Agent)
The photosensitive resin composition of the present embodiment includes a crosslinking agent. The crosslinking agent is not limited as long as it is a compound containing a functional group capable of reacting with the active hydrogen of the polymer P. Examples of such crosslinking agents include compounds having at least one functional group selected from a glycidyl group, an oxetanyl group, and a blocked isocyanate group. As the crosslinking agent, a compound having a glycidyl group or an oxetanyl group is more preferable, and a compound having a glycidyl group is even more preferable. By using such a crosslinking agent, a suitable crosslinked structure can be formed. In addition, as the crosslinking agent, one or more types selected from a compound having a blocked isocyanate group, an epoxy compound, and an oxetane compound can be used in combination.

Examples of compounds having a glycidyl group that can be used as a crosslinking agent include glycidyl ethers such as allyl glycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, glycerol polyglycidyl ether, sorbitol polyglycidyl ether, and glycidyl ether of bisphenol A (or F), glycidyl esters such as diglycidyl ester of adipic acid and diglycidyl ester of o-phthalic acid, 3,4-epoxycyclohexylmethyl (3,4-epoxycyclohexane) carboxylate, 3,4-epoxy-6-methylcyclohexylmethyl (3,4-epoxy-6 -methylcyclohexane)carboxylate, bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate, dicyclopentanediene oxide, bis(2,3-epoxycyclopentyl)ether, alicyclic epoxies such as CELLOXIDE 2021, CELLOXIDE 2081, CELLOXIDE 2083, CELLOXIDE 2085, CELLOXIDE 8000, and Epolead GT401 manufactured by Daicel Corporation, 2,2'-(((((1-(4-(2-(4-(oxiran-2-ylmethoxy)phenyl)propan-2-yl)phenyl)ethane-1,1-diyl)bis(4,1-phenylene))bis(oxy))bis(methylene))bis(oxirane) (for example, Techmore Examples of epoxy resins that can be used include aliphatic glycidyl ethers such as VG3101L (manufactured by Printec Co., Ltd.), Epolite 100MF (manufactured by Kyoeisha Chemical Co., Ltd.), Epiol TMP (manufactured by NOF Corp.), and 1,4-cyclohexanedimethanol diglycidyl ether (manufactured by New Japan Chemical Co., Ltd., Showa Denko K.K., etc.); aromatic glycidyl ethers such as 3,3',5,5'-tetramethyl-4,4'-bis(glycidyloxy)-1,1'-biphenyl; and 1,1,3,3,5,5-hexamethyl-1,5-bis(3-(oxiran-2-yl methoxy)propyl)trisiloxane (for example, DMS-E09 (manufactured by Gelest Co., Ltd.)).

In addition, for example, bisphenol A type epoxy resins such as LX-01 (manufactured by Daiso Co., Ltd.), jER1001, jER1002, jER1003, jER1004, jER1007, jER1009, jER1010, jER828, and jER825 (trade name; manufactured by Mitsubishi Chemical Corporation), bisphenol F type epoxy resins such as jER807 (trade name; manufactured by Mitsubishi Chemical Corporation), phenol novolac type epoxy resins such as jER152 and jER154 (trade name; manufactured by Mitsubishi Chemical Corporation), EPPN201, and EPPN202 (trade name; manufactured by Nippon Kayaku Co., Ltd.), EOCN102, EOCN103S, EOCN104S, EOCN1020, EOCN1025, and EOCN1027 (trade name; manufactured by Nippon Kayaku Co., Ltd.), and bisphenol F type epoxy resins such as jER807 (trade name; manufactured by Mitsubishi Chemical Corporation) cresol novolak type epoxy resins such as Araldite CY179, CY184 (trade name; manufactured by Huntsman Advanced Materials), ERL-4206, 4221, 4234, 4299 (trade name; manufactured by Dow Chemical Company), Epiclon 200, 400 (trade name; manufactured by DIC Corporation), jER871, 872 (trade name; manufactured by Mitsubishi Chemical Corporation), and other cyclic aliphatic epoxy resins; poly[(2-oxiranyl)-1,2-cyclohexanediol]2-ethyl-2-(hydroxymethyl)-1,3-propanediol ether (3:1) and other polyfunctional alicyclic epoxy resins; and EHPE-3150 (manufactured by Daicel Corporation) can also be used.

Examples of compounds having an oxetanyl group that can be used as a crosslinking agent include 1,4-bis{[(3-ethyl-3-oxetanyl)methoxy]methyl}benzene, bis[1-ethyl(3-oxetanyl)]methyl ether, 4,4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl, 4,4'-bis(3-ethyl-3-oxetanylmethoxy)biphenyl, ethylene glycol bis(3-ethyl-3-oxetanylmethyl)ether, and diethylene glycol bis(3-ethyl-3-oxetanylmethyl). ether, bis(3-ethyl-3-oxetanylmethyl)diphenoate, trimethylolpropane tris(3-ethyl-3-oxetanylmethyl)ether, pentaerythritol tetrakis(3-ethyl-3-oxetanylmethyl)ether, poly[[3-[(3-ethyl-3-oxetanyl)methoxy]propyl]silasesquioxane] derivatives, oxetanyl silicate, phenol novolac-type oxetane, 1,3-bis[(3-ethyloxetan-3-yl)methoxy]benzene and other oxetane compounds.

Compounds having blocked isocyanate groups that can be used as cross-linking agents include, but are not limited to, compounds in which the isocyanate groups of polyfunctional isocyanates are protected by a blocking agent.

The polyfunctional isocyanate is an organic compound having multiple isocyanate groups in one molecule. Examples of the polyfunctional isocyanate include 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, lysine diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), 1,3-bis(isocyanatomethyl)-cyclohexane, 4,4'- Examples of the diisocyanate compound include dicyclohexylmethane diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, tolidine diisocyanate, xylylene diisocyanate, and the like; and derivatives of the above diisocyanate compounds, such as isocyanurate-modified polyfunctional isocyanate, biuret-modified polyfunctional isocyanate, and urethane-modified polyfunctional isocyanate.

Examples of the blocking agent include one or more selected from alcohol-based compounds, phenol-based compounds, active methylene-based compounds, mercaptan-based compounds, acid amide-based compounds, acid imide-based compounds, imidazole-based compounds, urea-based compounds, oxime-based compounds, amine-based compounds, imine-based compounds, bisulfites, pyridine-based compounds, etc.

Specific blocking agents include alcohol compounds such as methanol, ethanol, propanol, butanol, 2-ethylhexanol, methyl cellosolve, butyl cellosolve, methyl carbitol, benzyl alcohol, and cyclohexanol; phenol compounds such as phenol, cresol, ethylphenol, butylphenol, nonylphenol, dinonylphenol, styrenated phenol, and hydroxybenzoic acid esters; active methylene compounds such as dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, and acetylacetone; mercaptan compounds such as butyl mercaptan and dodecyl mercaptan; acetanilide, acetic acid amide, Examples of the compound include acid amide compounds such as ε-caprolactam, δ-valerolactam, and γ-butyrolactam; acid imide compounds such as succinimide and maleimide; imidazole compounds such as imidazole and 2-methylimidazole; urea compounds such as urea, thiourea, and ethyleneurea; oxime compounds such as formaldoxime, acetaldoxime, acetoxime, methyl ethyl ketoxime, and cyclohexanone oxime; amine compounds such as diphenylamine, aniline, and carbazole; imine compounds such as ethyleneimine and polyethyleneimine; bisulfites such as sodium bisulfite; and pyridine compounds such as 2-hydroxypyridine and 2-hydroxyquinoline.

Specific examples of compounds having blocked isocyanate groups that can be used as crosslinking agents include Burnock D-500 (blocked with tolylene diisocyanate), Burnock D-550 (blocked with 1,6-hexamethylene diisocyanate), and Burnock D-980K (blocked with 1,6-hexamethylene diisocyanate) manufactured by Dainippon Ink and Chemicals, Inc.; Takenate B-830 (blocked with tolylene diisocyanate), Takenate B-815N (blocked with 4,4'-methylenebis(cyclohexylisocyanate)), Takenate B-842N (blocked with 1,3-bis(isocyanatomethyl)cyclohexane), and Takenate B-846N (blocked with 1,3-bis(isocyanatomethyl)cyclohexane) manufactured by Mitsui Takeda Chemicals, Inc. Examples of the blocked polyisocyanate include Takenate B-874N (isophorone diisocyanate blocked product), Takenate B-882N (1,6-hexamethylene diisocyanate blocked product), Takenate B-890 (xylylene diisocyanate blocked product); Takenate B-820NP (1,3-bis(isocyanate methyl)cyclohexane blocked product), Takenate B-885N (1,6-hexamethylene diisocyanate blocked product); and Asahi Kasei Corporation's Duranate MF-B60X (1,6-hexamethylene diisocyanate blocked product) and Duranate MF-K60X (1,6-hexamethylene diisocyanate blocked product).

(Photosensitizer)
When the photosensitive resin composition is a positive type, a photoactive compound such as a diazoquinone compound can be used as the photosensitizer.
For example, any one or more of the following compounds may be used:

（ｎ２は、１以上、５以下の整数である。）

(n2 is an integer of 1 or more and 5 or less.)

In each of the above compounds, Q is any of the structures shown below or a hydrogen atom, with the proviso that at least one of Q in each compound is any of the structures shown below.
Among these, from the viewpoints of the transparency and dielectric constant of the photosensitive resin composition, o-naphthoquinone diazide sulfonic acid derivatives in which Q is (a) or (b) are preferred.

In addition to the above-mentioned photoactive compound, the positive-type photosensitive resin composition may contain an acid generator that generates an acid by light or heat. By containing such an acid generator, the crosslinking reaction of the crosslinking agent can be promoted by irradiating the photosensitive resin composition with light or heating after exposure and development.
In this case, the amount of the acid generator is preferably 3 parts by mass or less per 100 parts by mass of the crosslinking agent.
As the photoacid generator that generates an acid by exposure to light, those described below can be used.
As the thermal acid generator which generates an acid by heat, aromatic sulfonium salts such as SI-45L, SI-60L, SI-80L, SI-100L, SI-110L, and SI-150L (manufactured by Sanshin Chemical Industry Co., Ltd.) can be used.
The content of the thermal acid generator is preferably, for example, 0.1% by mass or more and 5% by mass or less when the total solid content of the photosensitive resin composition is taken as 100% by mass.
In this embodiment, the total solid content of the photosensitive resin composition refers to the components excluding the solvent.

In addition, when the photosensitive resin composition is a negative type, a photoacid generator can be used as the photosensitizer. The photoacid generator may be any that absorbs the energy of light to generate a Bronsted acid or a Lewis acid, and examples of such photoacid generators include sulfonium salts such as triphenylsulfonium trifluoromethanesulfonate and tris(4-t-butylphenyl)sulfonium-trifluoromethanesulfonate; diazonium salts such as p-nitrophenyldiazonium hexafluorophosphate; ammonium salts; phosphonium salts; diphenyliodonium trifluoromethanesulfonate and (tricumyl)iodonium-tetrakis(pentafluorophenyl)borate. Examples of the photoacid generator include iodonium salts such as quinone diazides and diazomethanes such as bis(phenylsulfonyl)diazomethane, sulfonic acid esters such as 1-phenyl-1-(4-methylphenyl)sulfonyloxy-1-benzoylmethane and N-hydroxynaphthalimide-trifluoromethanesulfonate, disulfones such as diphenyl disulfone, and triazines such as tris(2,4,6-trichloromethyl)-s-triazine and 2-(3,4-methylenedioxyphenyl)-4,6-bis(trichloromethyl)-s-triazine. These photoacid generators can be used alone or in combination.

In addition, when the photosensitive resin composition is a negative type, the composition may contain a second crosslinking agent that crosslinks the copolymer by the action of an acid. This second crosslinking agent crosslinks the copolymer by using the acid generated by the photoacid generator as a catalyst, and is different from the compound used for the crosslinking agent.
For example, melamine-based crosslinking agents and urea-based crosslinking agents can be used.
Examples of the melamine-based crosslinking agent include hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, and hexabutoxybutylmelamine, with hexamethoxymethylmelamine being preferred.
Examples of the urea-based crosslinking agent include methylated urea resin, bismethoxymethylurea, bisethoxymethylurea, bispropoxymethylurea, bisbutoxymethylurea, and the like, and among these, methylated urea resin is preferred.
Commercially available methylated urea resins include, for example, MX-270, MX-280, and MX-290 (manufactured by Sanwa Chemical Co., Ltd.).

The proportion of the second crosslinking agent in the negative photosensitive resin composition is preferably 5% by mass or more and 40% by mass or less, when the total solid content of the resin composition is 100% by mass, and from the viewpoint of resolution, is more preferably 5% by mass or more and 30% by mass or less, and even more preferably 10 to 25% by mass.

In the above photosensitive resin composition, when the photosensitive resin composition is a positive type, the ratio of each component is, for example, as follows.
When the total solid content of the photosensitive resin composition is taken as 100 mass%, the photosensitive resin composition preferably contains the above-mentioned copolymer in an amount of, for example, 30 mass% or more and 70 mass% or less, and more preferably 40 mass% or more and 60 mass% or less.
In addition, when the total solid content of the photosensitive resin composition is taken as 100 mass%, the crosslinking agent is preferably contained in an amount of, for example, 15 mass% or more and 50 mass% or less, and more preferably 20 mass% or more and 50 mass% or less.
Furthermore, when the total solid content of the photosensitive resin composition is taken as 100 mass%, the photosensitive resin composition preferably contains a photoactive compound as a photosensitizer in an amount of, for example, 5 mass% or more and 40 mass% or less, and more preferably 10 mass% or more and 30 mass% or less.

When the photosensitive resin composition is a negative type, the ratio of each component is, for example, as follows:
When the total solid content of the photosensitive resin composition is taken as 100 mass%, the photosensitive resin composition preferably contains the above-mentioned copolymer in an amount of, for example, 30 mass% or more and 70 mass% or less, and more preferably 40 mass% or more and 60 mass% or less.
In addition, when the total solid content of the photosensitive resin composition is taken as 100 mass%, the crosslinking agent (excluding the second crosslinking agent) is preferably contained in an amount of, for example, 15 mass% or more and 50 mass% or less, and more preferably 20 mass% or more and 50 mass% or less.
Furthermore, when the total solid content of the photosensitive resin composition is taken as 100 mass%, the amount of the photoacid generator is, for example, 0.1 mass% or more and 40 mass% or less, and from the viewpoint of being able to form a pattern film with high resolution, it is more preferably 1 mass% or more and 30 mass% or less.

The photosensitive resin composition may further contain additives such as solvents, antioxidants, surfactants, adhesion aids, dissolution promoters, fillers, sensitizers, and polyphenols.

(Resin film)
The resin film according to this embodiment is made of a cured product of the above-mentioned photosensitive resin composition. This resin film has excellent heat resistance and is therefore used as a resist or permanent film in electronic devices.

When the resin film of this embodiment is used as a resist, the resist is prepared by applying the photosensitive resin composition of this embodiment by a method such as spin coating, roll coating, flow coating, dip coating, spray coating, doctor coating, etc. to obtain a coating film, and then removing the solvent.

When the resin film of this embodiment is used as a permanent film, the coating film of the photosensitive resin composition obtained as described above is exposed to light and developed, patterned into a desired shape, and then cured by heat treatment or the like. The permanent film can be used, for example, as a protective film or interlayer film for electronic devices.

The electronic device of this embodiment has the above-mentioned resin film.

The electronic device of the present embodiment includes the above-described resin film.
For example, when the electronic device is a semiconductor chip, a passivation film and an insulating layer constituting the semiconductor chip are formed from a cured product of the photosensitive resin composition of this embodiment.

The above describes embodiments of the present invention, but these are merely examples of the present invention and various configurations other than those described above can also be adopted.

The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these.

(Synthesis Example 1: Synthesis of Precursor Polymer A)
In a suitable reaction vessel, 5-nonafluorobutylbicyclo[2.2.1]hept-2-ene (NBC4F9, 22.9 g, 72.8 mmol), maleic anhydride (MAN, 7.1 g, 72.8 mmol), 2,2'-azobis(2-methylpropionate)dimethyl (Wako Pure Chemical Industries, Ltd., trade name: V-601, 3.4 g, 14.6 mmol) as an initiator, and 9.5 g of methyl ethyl ketone (MEK) were added and stirred to dissolve. Then, the dissolved oxygen in the system was removed by nitrogen bubbling, and the mixture was heated and reacted at an internal temperature of 60°C for 16 hours. The reaction mixture was then cooled to room temperature, and 32.1 g of MEK was added to dilute the mixture. The diluted solution was poured into a large amount of methanol to precipitate a polymer. The polymer was then collected by filtration, washed with methanol, and vacuum dried at 120°C for 16 hours. The polymer yield was 25.0 g, and the yield was 83%. The polymer had a weight average molecular weight Mw of 2,400 and a dispersity (weight average molecular weight Mw/number average molecular weight Mn) of 1.69.

(Synthesis Example 2: Synthesis of Precursor Polymer B)
In a suitable reaction vessel, NBC4F9 (22.9 g, 72.8 mmol), MAN (7.1 g, 72.8 mmol), V-601 (1.7 g, 7.3 mmol) and MEK11.2 g were added and stirred to dissolve. Then, dissolved oxygen in the system was removed by nitrogen bubbling, and the mixture was heated and reacted at an internal temperature of 60° C. for 5 hours. Then, the internal temperature was raised to 80° C., and the mixture was reacted for another 3 hours. The reaction mixture was cooled to room temperature and poured into a large amount of methanol to precipitate a polymer. The polymer was then filtered, washed with methanol, and vacuum dried at 120° C. for 16 hours. The yield of the polymer was 14.9 g, and the yield was 50%. The polymer also had an Mw of 4,000 and an Mw/Mn of 1.50.

(Synthesis Example 3: Synthesis of Precursor Polymer C)
Maleic anhydride (Nippon Shokubai Co., Ltd., 24.3 g, 247.8 mmol), bicyclo[2.2.1]hept-5-ene-2-carboxylate-3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl (NBCOOCH4F13, 120.0 g, 247.8 mmol) and dimethyl 2,2'-azobis(2-methylpropionate) (V-601, Fujifilm Wako Pure Chemical Industries, Ltd., 7.61 g, 30.6 mmol) were weighed and dissolved in methyl ethyl ketone (MEK, 28.5 g) in a suitable size reaction vessel equipped with a stirrer and a cooling tube. Nitrogen was bubbled through the solution for 10 minutes to remove oxygen, and the solution was heated to 60°C with stirring and maintained for 2 hours. The temperature was then raised to 80°C and maintained at that temperature for 3 hours, after which V-601 (3.81 g, 15.3 mmol) was added and reacted for another 3 hours. This reaction mixture was diluted with MEK and then dropped into a large amount of methanol to precipitate a polymer. After filtration using a Nutsche funnel, the solid was further washed with methanol and dried in vacuum. The weight average molecular weight (Mw) of the obtained polymer was 5,400 and the dispersity (Mw/Mn) was 1.72.

(Synthesis Example 4: Synthesis of Precursor Polymer D)
Maleic anhydride (4.76 g, 48.5 mmol), 5-tridecafluorohexyl-2-norbornene (NBC6F13, 20.0 g, 48.5 mmol) and V-601 (1.5 g, 6.0 mmol) were weighed and dissolved in MEK (4.7 g) in a suitable size reaction vessel equipped with a stirrer and a cooling tube. Nitrogen was bubbled through this solution for 10 minutes to remove oxygen, and the solution was heated to 60° C. with stirring and maintained for 2 hours. The solution was then heated to 80° C. and maintained for 3 hours, after which V-601 (0.74 g, 3.0 mmol) was added and reacted for another 3 hours. The reaction mixture was diluted with MEK and then dropped into a large amount of methanol to precipitate a polymer. After filtration using a Nutsche funnel, the solid was further washed with methanol and vacuum dried. The weight average molecular weight (Mw) of the resulting polymer was 3,700 and the dispersity (Mw/Mn) was 1.64.

The amounts of the components used in Synthesis Examples 1 to 4, as well as the weight average molecular weight and dispersity of the obtained precursor polymers, are shown in Table 1.

(Synthesis Example 5: Synthesis of fluorine-containing polymer A-1)
15.0 g of the precursor polymer A synthesized in Synthesis Example 1 was dissolved in 27.9 g of MEK. 3.0 g of 2-hydroxyethyl methacrylate (HEMA) and 1.5 g of triethylamine (TEA) were further added, and the mixture was heated to 70° C. and reacted for 6 hours. Then, 1.6 g of glycidyl methacrylate (GMA) was added, and the mixture was reacted for another 4 hours. The reaction mixture was cooled to room temperature and neutralized with formic acid. The solution was poured into a large amount of pure water to precipitate the polymer. The obtained polymer was filtered and washed with pure water, and then dissolved in propylene glycol monomethyl ether acetate (PGMEA). The remaining water was removed and concentrated under reduced pressure to obtain a polymer solution with a solid content of about 35%.
The weight average molecular weight (Mw) of the polymer thus obtained was 2,100, the molecular weight distribution was 1.55, the double bond equivalent was 1,700 g/mol, and the fluorine content in the polymer solids was 30 wt%.

(Synthesis Example 6: Synthesis of fluorine-containing polymer B-1)
5.0 g of the precursor polymer B synthesized in Synthesis Example 2 was dissolved in 27.9 g of MEK. 1.0 g of 2-hydroxyethyl methacrylate (HEMA) and 0.75 g of triethylamine (TEA) were further added, and the mixture was heated to 70°C and reacted for 6 hours. Next, 0.5 g of glycidyl methacrylate (GMA) and 1.0 g of 3-perfluorobutyl-1,2-epoxypropane (PFBEp) were added, and the mixture was further reacted at 70°C for 4 hours. The reaction mixture was cooled to room temperature and neutralized with formic acid. The solution was poured into a large amount of pure water to precipitate the polymer. The obtained polymer was filtered and washed with pure water, and then dissolved in PGMEA. The remaining water was removed and concentrated under reduced pressure to obtain a polymer solution with a solid content of about 35%.
The weight average molecular weight (Mw) of the polymer thus obtained was 4,000, the molecular weight distribution was 1.50, the double bond equivalent was 1,100 g/mol, and the fluorine content in the polymer solids was 33 wt%.

(Synthesis Example 7: Synthesis of fluorine-containing polymer C-1)
The precursor polymer C (10.0 g) synthesized in Synthesis Example 3 was weighed and dissolved in MEK (10 g) in a reaction vessel of appropriate size equipped with a stirrer and a cooling tube. Further, 4-hydroxybutyl acrylate (4HBA, manufactured by Mitsubishi Chemical Corporation, 2.48 g, 17.2 mmol) and triethylamine (2.0 g) were added, and the mixture was heated at 70° C. for 6 hours. After acid treatment with formic acid, the reaction solution was dropped into a large amount of pure water to precipitate a polymer. PGMEA was added to the solid collected by filtration and concentrated to obtain a PGMEA solution of the polymer. The Mw was 4,900, the Mw/Mn was 1.81, and the double bond equivalent was 1,600 g/mol. The fluorine content in the polymer was 34 wt %.

(Synthesis Example 8: Synthesis of fluorine-containing polymer D-1)
In a reaction vessel of suitable size equipped with a stirrer and a cooling tube, the precursor polymer D (10.0 g) synthesized in Synthesis Example 4 was weighed and dissolved in MEK (10 g). 4HBA (2.83 g, 17.2 mmol) and triethylamine (2.0 g) were further added and heated at 70° C. for 6 hours. After acid treatment with formic acid, the reaction solution was dropped into a large amount of pure water to precipitate the polymer. PGMEA was added to the solid collected by filtration and concentrated to obtain a PGMEA solution of the polymer. Mw was 3,900, Mw/Mn was 1.60, and double bond equivalent was 1,400 g/mol. The fluorine content in the polymer was 39 wt%.

(Synthesis Example 9: Synthesis of Polymer 1)
2-Norbornene (75 wt% toluene solution, Maruzen Petrochemicals, 125.5 g, 1.00 mol) and dimethyl 2,2'-azobis(2-methylpropionate) (V-601, Wako Pure Chemical Industries, 9.2 g, 40 mmol) were weighed and dissolved in methyl ethyl ketone (MEK, 196.1 g) in a suitable size reaction vessel equipped with a stirrer and a cooling tube. Nitrogen was passed through the solution for 10 minutes to remove oxygen, and the solution was heated to 80°C while stirring. While the solution was kept at 80°C, a solution of maleic anhydride (Nippon Shokubai, 98.1 g, 1.00 mol) prepared in advance and dissolved in 119.9 g of MEK was added dropwise over 1.5 hours, and the reaction was continued at that temperature for another 8 hours. The reaction mixture was added dropwise to a large amount of methanol to precipitate a polymer. After filtration using a Nutsche funnel, the solid was further washed with methanol and dried in vacuum at 70°C. The weight average molecular weight (Mw) of the resulting polymer was 6,900 and the dispersity (Mw/Mn) was 1.76.

The above-mentioned precursor polymer (50.0 g) was weighed and dissolved in MEK (90 g) in a suitable-sized reaction vessel equipped with a stirrer and a cooling tube. 2-Hydroxyethyl methacrylate (HEMA, Nippon Shokubai Co., Ltd., 21.2 g, 163 mmol) and triethylamine (5.0 g) were then added and heated at 70°C for 6 hours. Glycidyl methacrylate (GMA, 11.1 g, 78 mmol) was added to this reaction solution and further stirred at 70°C for 4 hours. After acid treatment with formic acid, the reaction solution was dropped into a large amount of pure water to precipitate the polymer. The filtered solid was dried in a vacuum dryer at 40°C for 16 hours to obtain a polymer. The Mw was 7,800 and the Mw/Mn was 1.70. The double bond equivalent was 540 g/mol.

(Weight average molecular weight/molecular weight distribution)
In this specification, the weight average molecular weight (Mw), number average molecular weight (Mn), and molecular weight distribution (Mw/Mn) are polystyrene equivalent values obtained from a calibration curve of standard polystyrene (PS) obtained by GPC measurement. The measurement conditions are as follows.
Tosoh gel permeation chromatography device HLC-8320GPC
Column: TSK-GEL Supermultipore HZ-M manufactured by Tosoh Corporation
Detector: RI detector for liquid chromatography Measurement temperature: 40°C
Solvent: THF
Sample concentration: 2.0 mg/ml

(Double bond equivalent)
The double bond equivalent of the fluorine-containing polymers A-1 to D-1 was measured by the following method. First, about 50 mg of the polymer from which the solvent had been removed by drying under reduced pressure and about 5 mg of dimethyl terephthalate as an internal standard substance were weighed and dissolved in DMSO-d6. This solution was subjected to 1H-NMR measurement using a nuclear magnetic resonance spectrometer JNM-AL300 (manufactured by JEOL). The polymer weight per mole of double bonds (g/mol, double bond equivalent) was calculated from the integral ratio of the signal (5-7 ppm) derived from the (meth)acrylic group in the obtained spectrum chart to the signal (4H, 8.1 ppm) of the phenyl group of the internal standard substance.

(Measurement of fluorine content)
The fluorine content of the fluorine-containing polymers A-1 to D-1 was measured by the following method. First, about 10 mg of the polymer from which the solvent had been removed by drying under reduced pressure was completely combusted in a sealed flask in which the oxygen had been replaced. The generated gas was collected in an alkali hydrogen peroxide absorption solution to which had been added beforehand, and the resulting solution was adjusted to a constant volume of 50 mL to serve as a test solution. The test solution and the standard solution were introduced into an ion chromatography analyzer (ICS-3000 chromatograph manufactured by Dionex Corporation), and the concentration of fluoride ions was determined by the calibration curve method, and the amount of fluorine contained in the sample was calculated.

(Measurement of refractive index)
The refractive index of fluorine-containing polymers A-1 to D-1 was measured by the following method. The polymer was dissolved in PGMEA at a concentration of 35% by weight. The obtained polymer solution was spin-coated on a 3-inch silicon wafer and heat-treated at 100°C for 120 seconds to obtain a thin film having a thickness of 1.0 to 1.5 μm. The refractive index at a wavelength of 632.8 nm was measured using a prism coupler (Model 2010M manufactured by Metricon).

(Alkaline dissolution rate)
The alkaline dissolution rate of the fluorine-containing polymers A-1 to D-1 was measured as follows. The polymer was dissolved in PGMEA to prepare a solution with a solid concentration of 35%. This polymer solution was applied by spin coating onto a silicon wafer, which was soft-baked at 100° C. for 120 seconds to form a polymer film with a thickness H of about 2.0 μm. The silicon wafer on which this polymer film was formed was immersed in a 2.38% aqueous solution of tetramethylammonium hydroxide at 23° C., and the time T until the polymer film was visually erased was measured. The alkaline dissolution rate was calculated from H and T according to the following formula.
(Alkaline dissolution rate) [Å/sec] = (film thickness H) / (time until polymer film is erased T)

The amounts of the components used in Synthesis Examples 5 to 8, as well as the weight average molecular weight distribution, double bond equivalent, fluorine content, refractive index, and alkaline dissolution rate of the obtained fluorine-containing polymers are shown in Table 2.

(Preparation of Photosensitive Resin Composition)
For each Example and Comparative Example, the polymers prepared in Synthesis Examples 5 to 9, photosensitizers, crosslinking agents, adhesion improvers, and surfactants were dissolved in PGMEA and cyclohexanone in the amounts shown in Table 3, and then stirred. After stirring, the mixture was filtered through a 0.2 μm filter to prepare negative photosensitive resin compositions.

The following components were used as shown in Table 3.
(Fluorine-containing polymer)
Polymer A-1: Fluorine-containing polymer A-1 prepared in Synthesis Example 5
Polymer B-1: Fluorine-containing polymer B-1 prepared in Synthesis Example 6
Polymer C-1: Fluorine-containing polymer C-1 prepared in Synthesis Example 7
Polymer D-1: Fluorine-containing polymer D-1 prepared in Synthesis Example 8
(Other polymers)
Polymer 1: Polymer 1 prepared in Synthesis Example 9
(Crosslinking Agent)
Crosslinking agent 1: an acrylic crosslinking agent represented by the following formula (12) (DPHA, manufactured by Daicel Cytec Co., Ltd.).

(Photosensitizer)
Photosensitizer 1: A photoradical polymerization initiator represented by the following formula (11) (Irgacure OXE02, manufactured by BASF) was used.

(Adhesion aid)
Adhesion aid 1: 3-glycidoxypropyltrimethoxysilane (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.)

(Surfactant)
Surfactant 1: Megafac F-556 (manufactured by DIC Corporation)

(solvent)
Solvent 1: Propylene glycol monomethyl ether acetate (PGMEA)
Solvent 2: Cyclohexanone

The negative photosensitive resin composition obtained as described above was evaluated for the following items.

(Sensitivity Evaluation)
The negative photosensitive resin compositions thus prepared were each applied onto a 3-inch silicon wafer using a spin coater. After application, the wafer was prebaked on a hot plate at 100° C. for 2 minutes to obtain a coating film (thin film A) having a thickness of about 3.0 μm.
This thin film was exposed to g+h+i rays at an exposure dose of 100 mJ/cm ² using a Canon g+h+i ray mask aligner (PLA-501F) through a photomask having a gradation of transmittance of 1 to 100%.
After exposure, the unexposed areas were dissolved and removed by developing at 23° C. for 60 seconds using 2.38% tetramethylammonium hydroxide as a developer, to obtain thin films (thin film B) exposed to exposure amounts of 1 to 100 mJ/cm ² .

From the film thicknesses of Thin Film A and Thin Film B obtained by the above method, the remaining film rate was calculated according to the following formula.
Residual film rate after development (%)={(film thickness (μm) of thin film B at each exposure dose)/(film thickness (μm) of thin film A)}×100
The minimum exposure amount at which the post-development residual film ratio obtained by the above formula was 95% or more was taken as the sensitivity of the resist.

(Measurement of dielectric constant)
After applying the photosensitive resin composition to a low resistance silicon wafer (Ω<), the solvent was removed by performing a heat treatment under the conditions of 100 ° C. and 120 seconds. Next, the entire surface was exposed to g + h + i lines at an exposure dose of 100 mJ / cm ² using a Canon g + h + i line mask aligner (PLA-501F). The obtained film was subjected to a heat treatment in an oven at 230 ° C. in the atmosphere for 60 minutes to cure the photosensitive resin composition. In this way, a cured film was obtained for each of the examples and comparative examples. A gold electrode was formed on this thin film, and the dielectric constant was calculated from the capacitance obtained using a Hewlett Packard LCR meter (4282A) at room temperature and 100 kHz.

(Evaluation of chemical resistance)
After applying the photosensitive resin composition to a 3-inch silicon wafer, the solvent was removed by heat treatment at 100°C for 120 seconds. Next, the entire surface was exposed to g+h+i lines at an exposure dose of 100 mJ/ ^cm2 using a Canon g+h+i line mask aligner (PLA-501F). The obtained film was heat-treated in an oven at 230°C for 60 minutes in the atmosphere to cure the photosensitive resin composition. In this way, a cured film was obtained for each of the examples and comparative examples. The obtained silicon wafer with the cured film was immersed in TOK106 (manufactured by Tokyo Ohka Kogyo Co., Ltd.) at room temperature for 5 minutes, and then rinsed with pure water for 30 seconds. At this time, the film thickness change rate defined by the following calculation formula was obtained and used as an index of chemical resistance. A smaller film thickness change rate indicates better chemical resistance.
Film thickness change rate (%)=[(film thickness after immersion in chemical solution)−(film thickness before immersion in chemical solution)/(film thickness before immersion in chemical solution)]×100

(Evaluation of Light Transmittance)
After applying the photosensitive resin composition to a Corning 1737 glass substrate having a length of 100 mm and a width of 100 mm, the solvent was removed by performing a heat treatment under conditions of 100 ° C. and 120 seconds. Next, the entire surface was exposed to g + h + i rays at an exposure dose of 100 mJ / cm ² using a Canon g + h + i ray mask aligner (PLA-501F). The obtained film was subjected to a heat treatment in an oven at 230 ° C. in the atmosphere for 60 minutes to cure the photosensitive resin composition. In this way, a cured film was obtained for each of the examples and comparative examples. The transmittance (%) of this cured film at a wavelength of 400 nm was measured using an ultraviolet-visible light spectrophotometer, and the value converted to a film thickness of 3 μm was taken as the transmittance.

(Evaluation of heat resistance)
For each example, the weight loss rate of the cured film was evaluated using the obtained photosensitive resin composition as follows.
First, the photosensitive resin composition was applied to a 3-inch wafer, and then heat-treated at 100°C for 120 seconds to remove the solvent. Next, the entire surface was exposed to g+h+i-line at an exposure dose of 100 mJ/ ^cm2 using a Canon g+h+i-line mask aligner (PLA-501F). The resulting film was heat-treated in an oven at 230°C in the atmosphere for 60 minutes to cure the photosensitive resin composition. In this manner, a cured film was obtained for each of the Examples and Comparative Examples.
Next, the weight loss rate of the above sample was measured. The measurement was performed by weighing 5 mg of the cured film, and heating the sample to 250°C using a thermogravimetry/differential thermal analyzer (TG/DTA) under the conditions of a starting temperature of 30°C, a heating rate of 10°C/min, and a _N2 flow rate of 200 mL/min, and then holding the sample at 250°C for 60 minutes. The weight loss rate was determined as the weight change rate from the weight at the time of reaching 250°C until 60 minutes had elapsed.
The evaluation results for the above items are shown in Table 3.

The cured product of the photosensitive resin composition of the embodiment had a low dielectric constant and excellent heat resistance and chemical resistance.

This application claims priority based on Japanese Patent Application No. 2019-175111, filed on September 26, 2019, the disclosure of which is incorporated herein in its entirety.

Claims (8)

A polymer comprising structural units represented by the following formulas (1) and (2a):

(In formula (1),
At least one of R ₁ , R ₂ , R ₃ and R ₄ is a perfluoroalkyl group having 1 to 30 carbon atoms, and the rest are hydrogen atoms; n is 0, 1 or 2;
In formula (2a),
_R5 is an organic group having 1 to 30 carbon atoms and a (meth)acryloyl group . The polymer of claim 1 , further comprising at least one of the structural units represented by formulas (B2) to (B6).

(In formula (B2), R ₆ and R ₇ are each independently an organic group having 1 to 30 carbon atoms.)

(In formula (B6), R ₈ is an organic group having 1 to 30 carbon atoms). The polymer according to claim 1 or 2 , having a weight average molecular weight of 1,500 or more and 30,000 or less. A polymer comprising structural units represented by the following formulas (1) and (2a):
A cross-linking agent;
A photosensitive resin composition comprising:

(In formula (1),
At least one of R ₁ , R ₂ , R ₃ and R ₄ is a perfluoroalkyl group having 1 to 30 carbon atoms, and the rest are hydrogen atoms; n is 0, 1 or 2;
In formula (2a),
_R5 is an organic group having 1 to 30 carbon atoms and a (meth)acryloyl group . The photosensitive resin composition according to claim 4 , wherein the polymer further comprises at least one of the structural units represented by formulae (B2) to (B6).

(In formula (B2), R ₆ and R ₇ are each independently an organic group having 1 to 30 carbon atoms.)

(In formula (B6), R ₈ is an organic group having 1 to 30 carbon atoms). The photosensitive resin composition according to claim 4 or 5 , wherein the weight average molecular weight of the polymer is 1,500 or more and 30,000 or less. A resin film comprising a cured film of the photosensitive resin composition according to any one of claims 4 to 6 . An electronic device comprising the resin film according to claim 7 .