WO2025206116A1 - Silane compound polymer, semiconductor insulating material, and semiconductor insulating film-forming agent - Google Patents

Abstract

The present invention provides: a silane compound polymer comprising repeating units [repeating units (1)] represented by formula (a-1) (a-1) HSiO_3/2 <sb />, and repeating units [repeating units (2)] represented by formula (a-2) (a-2) R¹SiO_3/2 [R¹ represents an unsubstituted C6-12 aryl group or a C6-12 aryl group having a substituent]; a semiconductor insulating material comprising the silane compound polymer; and a semiconductor insulating film-forming agent containing the silane compound polymer.

Description

Silane compound polymer, insulating material for semiconductor, and insulating film forming agent for semiconductor

The present invention relates to a silane compound polymer that is suitable for use as an insulating material, an insulating material for semiconductors that comprises this silane compound polymer, and a semiconductor insulating film forming agent that contains the silane compound polymer.

Conventionally, SiO ₂ films have been formed as insulating films for semiconductor devices and the like by vacuum processes such as thermal CVD.
However, since the vacuum process is not suitable for forming an insulating film that fills deep recesses, the SOG (Spin on Glass) method has been attracting attention in recent years.

In the SOG method, an insulating film is usually formed by applying an insulating film-forming solution by spin coating and curing the resulting coating.
For example, Patent Document 1 describes a composition for forming a silicon oxide film, which contains a solvent, a silicon oxide-forming compound dissolved and/or dispersed in the solvent, and silicon particles dispersed in the solvent, and a method for forming a silicon oxide film using this composition.

JP 2015-18952 A

Patent Document 1 describes that a relatively thick silicon oxide film can be formed in a short time by the SOG method, and that by using the composition described in Patent Document 1, a silicon oxide film that is less likely to crack can be formed.
According to the examples in Patent Document 1, silicon particles are considered to be an important component for forming a thick film and preventing cracks. However, when a composition containing silicon particles is used, the silicon particles must be converted into silicon oxide, which requires heat treatment under severe conditions (in the example, at 900°C for 30 minutes).
Therefore, a method for forming an insulating film more efficiently has been desired.

The present invention was made under these circumstances, and aims to provide a silane compound polymer that is suitable for use as an insulating material, an insulating material for semiconductors that comprises this silane compound polymer, and a semiconductor insulating film forming agent that contains the silane compound polymer.

In order to solve the above problems, the present inventors have conducted extensive research on silane compound polymers.
the result,
(1) A silane compound polymer containing a hydrogen atom bonded to a silicon atom has excellent curing properties, and therefore, by using such a silane compound polymer as an insulating material, an insulating film (cured product) can be efficiently formed in a short time.
(2) The cured product obtained by curing a silane compound polymer containing a hydrogen atom bonded to a silicon atom is prone to cracking.
(3) By introducing a repeating unit containing an aryl group into a silane compound polymer containing a hydrogen atom bonded to a silicon atom, the occurrence of cracks in the cured product can be suppressed.
(4) The inventors have found that a silane compound polymer containing a hydrogen atom bonded to a silicon atom and an aryl group exhibits a small weight loss rate even when heated at a temperature exceeding the normal curing temperature, and therefore a higher temperature can be selected as the curing condition for this silane compound polymer, leading to the completion of the present invention.

Thus, according to the present invention, there are provided the following silane compound polymers (1) to (8), insulating materials for semiconductors (9), and insulating film forming agents for semiconductors (10) to (14).
[1] The following formula (a-1)

A repeating unit represented by the formula (1) [repeating unit (1)]
The following formula (a-2)

[ ^R1 represents an unsubstituted aryl group having 6 to 12 carbon atoms or a substituted aryl group having 6 to 12 carbon atoms.]
and a repeating unit represented by the formula (2):
[2] The silane compound polymer according to [1], wherein the amount of the repeating unit (1) is 10 to 45 mol % based on the total amount of the repeating unit (1) and the repeating unit (2).
[3] The silane compound polymer according to [1] or [2], wherein the total amount of the repeating units (1) and (2) is 70 to 100 mol % based on the total amount of repeating units of the silane compound polymer.
[4] The silane compound polymer according to any one of [1] to [3], having a mass average molecular weight (Mw) of 1,500 to 50,000.
[5] The silane compound polymer according to any one of [1] to [4], wherein the silane compound polymer is obtained by hydrolysis and polycondensation of an alkoxysilane compound, and has a residual alkoxy group ratio of 2.0% or less.
[6] The silane compound polymer according to any one of [1] to [5], wherein when a curability evaluation test is carried out under the following conditions, the thickness reduction rate (X _t ) calculated by the following formula (F1) is 20% or less.
[Curability evaluation test]
A1: A 2 μm thick film of a silane compound polymer is formed on a silicon wafer.
A2: The film obtained in A1 above is heated at 250°C for 1 minute to be cured.
A3: The cured film obtained in A2 above is transferred to an environment at 23°C and left there until it cools down to 23°C.
A4: After A3 above, the cured film is immersed in diethylene glycol dimethyl ether at 23°C for 10 minutes, and then dried on a hot plate heated to 150°C for 1 minute.

[In formula (F1), _T1 represents the thickness of the silane compound polymer film before A4, and _T2 represents the thickness of the silane compound polymer film after A4.]
[7] The silane compound polymer according to any one of [1] to [6], which does not crack when subjected to a crack resistance evaluation test under the following conditions:
[Crack resistance evaluation test]
B1: A 1 μm thick film of a silane compound polymer is formed on a silicon wafer.
B2: The film obtained in B1 above is heated at 250° C. for 1 minute to be cured.
B3: The cured film obtained in B2 above is transferred to an environment at 23°C and left there until it cools down to 23°C.
[8] The silane compound polymer according to any one of [1] to [7], wherein when thermogravimetry is carried out under the following conditions, the weight loss rate (X _m ) calculated by the following formula (F2) is 7% or less.
[Thermogravimetric measurement]
C1: The silane compound polymer is heated at 200° C. for 120 minutes.
C2: After C1, the silane compound polymer is heated to 500° C. at a rate of 10° C./min.

(In formula (F2), _M1 represents the weight of the silane compound polymer before C1, and _M2 represents the weight of the silane compound polymer after C2.)
[9] An insulating material for semiconductors comprising the silane compound polymer according to any one of [1] to [8] above.
[10] A semiconductor insulating film forming agent containing the silane compound polymer according to any one of [1] to [8] above and a solvent.
[11] The semiconductor insulating film forming agent according to [10], wherein the solvent has a boiling point of 150° C. or higher.
[12] The semiconductor insulating film forming agent according to [10] or [11], wherein the solvent is a polyether solvent.
[13] The semiconductor insulating film forming agent according to any one of [10] to [12], wherein the total amount of the silane compound polymer according to any one of [1] to [8] and the solvent is 80 mass % or more of the total amount of the semiconductor insulating film forming agent.
[14] The semiconductor insulating film forming agent according to any one of [10] to [13], which is substantially free of reactive compounds other than the silane compound polymer according to any one of [1] to [8].
In the explanations of tests and measurements in this specification, the term "cured product of a silane compound polymer" may be abbreviated to "silane compound polymer."

The present invention provides a silane compound polymer that is suitable for use as an insulating material, an insulating material for semiconductors that comprises this silane compound polymer, and a semiconductor insulating film forming agent that contains the silane compound polymer.

In this specification, for preferred numerical ranges (e.g., ranges of content, etc.), the lower and upper limits described in stages can be independently combined. For example, a description such as "preferably 10 to 90, more preferably 30 to 60" can be combined with the "preferable lower limit (10)" and the "more preferred upper limit (60)" to form "10 to 60."

The present invention will be described in detail below, divided into the following sections: 1) silane compound polymers and insulating materials for semiconductors, and 2) semiconductor insulating film forming agents.

1) Silane Compound Polymer and Semiconductor Insulating Material The silane compound polymer of the present invention is a silane compound polymer having a repeating unit represented by the above formula (a-1) and a repeating unit represented by the above formula (a-2).

[Repeating units constituting silane compound polymer]
The silane compound polymer of the present invention has a repeating unit represented by the following formula (a-1) [repeating unit (1)].

Silane compound polymers containing repeating unit (1) tend to have excellent curing properties. For this reason, the silane compound polymer of the present invention is suitable for use as an insulating material for semiconductors.

The silane compound polymer of the present invention has a repeating unit [repeating unit (2)] represented by the following formula (a-2):

In formula (a-2), R ¹ represents an unsubstituted aryl group having 6 to 12 carbon atoms or a substituted aryl group having 6 to 12 carbon atoms.

When a silane compound polymer contains only the above-mentioned repeating unit (1), cracks tend to occur easily in the cured product of the silane compound polymer. The repeating unit (2) solves this problem, and by introducing the repeating unit (2) into a silane compound polymer containing the repeating unit (1), cracks become less likely to occur in the cured product of the silane compound polymer. For this reason, the silane compound polymer of the present invention is suitable for use as an insulating material for semiconductors.

Examples of the unsubstituted aryl group having 6 to 12 carbon atoms for R ¹ include a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a tolyl group, and a xylyl group.
Examples of the substituted aryl group having 6 to 12 carbon atoms for R ¹ include the above-mentioned unsubstituted aryl group having 6 to 12 carbon atoms in which one or more hydrogen atoms have been substituted with a substituent.
Examples of the substituent include a cyano group, an amino group, an acryloyloxy group, a methacryloyloxy group, an epoxy group, and a halogen atom such as a fluorine atom, a chlorine atom, or a bromine atom.

In the silane compound polymer of the present invention, the amount of the repeating unit (1) is preferably 10 to 45 mol %, more preferably 15 to 35 mol %, and even more preferably 20 to 30 mol %, based on the total amount of the repeating unit (1) and the repeating unit (2).
A silane compound polymer having the repeating unit (1) in an amount within the above range has a good balance between curability and crack resistance, and is suitable for use as an insulating material for semiconductors.

In the silane compound polymer of the present invention, the total amount of the repeating units (1) and (2) is preferably 70 to 100 mol %, more preferably 80 to 100 mol %, and even more preferably 90 to 100 mol %, based on the total amount of repeating units in the silane compound polymer.
A silane compound polymer in which the total amount of repeating units (1) and repeating units (2) is 70 mol % or more based on the total amount of repeating units of the silane compound polymer has a good balance of curability and crack resistance, and is suitable for use as an insulating material for semiconductors.

When the silane compound polymer of the present invention has a repeating unit other than repeating units (1) and (2) [repeating unit (3)], examples of repeating unit (3) include repeating units derived from monofunctional silane compounds such as trimethylmethoxysilane, repeating units derived from difunctional silane compounds such as dimethyldimethoxysilane, repeating units derived from trifunctional silane compounds (excluding repeating units (1) and (2)), and repeating units derived from tetrafunctional silane compounds such as tetramethoxysilane.

[Physical Properties of Silane Compound Polymer]
The mass average molecular weight (Mw) of the silane compound polymer of the present invention is preferably 1,500 to 50,000, more preferably 1,750 to 20,000, still more preferably 2,000 to 10,000, and particularly preferably 3,000 to 9,000.
The molecular weight distribution (Mw/Mn) of the silane compound polymer of the present invention is not particularly limited, but is usually 1.0 to 10.0, preferably 1.1 to 6.0.
The weight average molecular weight (Mw) and number average molecular weight (Mn) can be determined, for example, as a standard polystyrene equivalent value by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

Silane compound polymers with a mass-average molecular weight within the above range tend to have a better balance between curability and crack resistance. Furthermore, when a coating liquid containing a silane compound polymer with a mass-average molecular weight of 1,500 or more is used, thick films can be efficiently formed by spin coating, making such silane compound polymers suitable as insulating materials for semiconductors.

The silane compound polymer of the present invention may be any of a random copolymer, a block copolymer, a graft copolymer, an alternating copolymer, etc., but from the viewpoint of ease of production, etc., a random copolymer is preferred.
The structure of the silane compound polymer of the present invention may be any of a ladder structure, a double-decker structure, a cage structure, a partially cleaved cage structure, a cyclic structure, and a random structure.

As described below, the silane compound polymer of the present invention can be efficiently produced by hydrolytic polycondensation of an alkoxysilane compound. Hereinafter, among the silane compound polymers of the present invention, those obtained by hydrolytic polycondensation of an alkoxysilane compound may be referred to as "silane compound polymer (i)."

The residual alkoxy group ratio of the silane compound polymer (i) is preferably 2.0% or less, more preferably 1.0% or less, and even more preferably 0.5% or less.
The residual alkoxy group ratio of the silane compound polymer (i) indicates the degree to which the alkoxy group contained in the alkoxysilane compound used as a monomer remains in the silane compound polymer (i).
The silane compound polymer (i) having a residual alkoxy group ratio of 2.0% or less is a polymer in which the hydrolysis reaction of the alkoxysilane compound has progressed sufficiently, and contains a large number of Si—O—Si bonds and Si—OH bonds. Such a silane compound polymer (i) is suitable as an insulating material for semiconductors because it has a relatively large molecule and is reactive.

The residual alkoxy group ratio can be calculated by measuring ^1H -NMR of the silane compound polymer (i). For example, when the silane compound polymer (i) is synthesized using triethoxysilane and phenyltriethoxysilane, the residual alkoxy group ratio of the silane compound polymer (i) can be calculated by measuring ^1H -NMR of the silane compound polymer (i) and determining the ratio of the total amount of hydrogen atoms and phenyl groups bonded to silicon atoms to the amount of ethoxy groups based on the peak area ratio.

As described above, the silane compound polymer of the present invention has excellent curability due to the repeating unit (1) containing a hydrogen atom bonded to a silicon atom. Therefore, by heating the silane compound polymer to about 250°C, the curing reaction can be sufficiently promoted, producing a cured product that is difficult to dissolve in solvents.

For example, when a curability evaluation test is carried out under the following conditions, the silane compound polymer of the present invention has a thickness reduction rate (X _t ) calculated by the following formula (F1) of preferably 20% or less, more preferably 10% or less.
[Curability evaluation test]
A1: A 2 μm thick film of a silane compound polymer is formed on a silicon wafer.
A2: The film obtained in A1 above is heated at 250°C for 1 minute to be cured.
A3: The cured film obtained in A2 above is transferred to an environment at 23°C and left there until it cools down to 23°C.
A4: After A3 above, the cured film is immersed in diethylene glycol dimethyl ether at 23°C for 10 minutes, and then dried on a hot plate heated to 150°C for 1 minute.

In formula (F1), _T1 represents the thickness of the silane compound polymer film before A4, and _T2 represents the thickness of the silane compound polymer film after A4. Note that _T1 and _T2 can be measured using, for example, a stylus-type surface profiler (Dektak 150, manufactured by ULVAC).

As described above, the silane compound polymer of the present invention has the repeating unit (2) containing an aryl group, and therefore cracks are unlikely to occur in the cured product, and therefore cracks are unlikely to occur in the cured product when the silane compound polymer is heated and cured and then allowed to cool to room temperature.
For example, when a crack resistance evaluation test is carried out under the following conditions, the silane compound polymer of the present invention preferably does not cause cracks in a film having a thickness of 1 μm, and more preferably does not cause cracks in both a film having a thickness of 1 μm and a film having a thickness of 2 μm.

[Crack resistance evaluation test]
D1: A film of a silane compound polymer having a thickness of 1 μm or 2 μm is formed on a silicon wafer.
D2: The film obtained in D1 above is heated at 250° C. for 1 minute to be cured.
D3: The cured film obtained in D2 above is transferred to an environment at 23°C and left there until it cools down to 23°C.

Furthermore, since the silane compound polymer of the present invention contains a hydrogen atom and an aryl group bonded to a silicon atom, weight loss and volume shrinkage are unlikely to occur even when baked at a temperature higher than the usual curing temperature, and cracks are unlikely to occur.
For example, when thermogravimetry is carried out under the following conditions, the silane compound polymer of the present invention preferably has a weight loss rate (X _m ) calculated by the following formula (F2) of 7% or less, more preferably 5% or less.

[Thermogravimetric measurement]
C1: The silane compound polymer is heated at 200° C. for 120 minutes.
C2: After C1, the silane compound polymer is heated to 500° C. at a rate of 10° C./min.

In formula (F2), _M1 represents the weight of the silane compound polymer before C1, and _M2 represents the weight of the silane compound polymer after C2.

As described above, the silane compound polymer of the present invention has excellent curing properties and is less likely to crack when cured. Furthermore, it can be baked at higher temperatures depending on the purpose. Therefore, the silane compound polymer of the present invention is suitable for use as an insulating material for semiconductors.

[Method for producing silane compound polymer]
The method for producing the silane compound polymer of the present invention is not particularly limited.
For example, the silane compound polymer of the present invention can be produced by carrying out a step (step PO) of hydrolyzing and polycondensing a trifunctional alkoxysilane compound corresponding to a desired repeating unit in the presence of water and an acid catalyst.

Step PO is a step in which a trifunctional alkoxysilane compound corresponding to the desired repeating unit is subjected to hydrolytic polycondensation in the presence of water and an acid catalyst.

In step PO, for example, a compound represented by the following formula (a-3) and a compound represented by the following formula (a-4) are used as trifunctional alkoxysilane compounds.

In formula (a-4), ^R1 has the same meaning as defined above. OR represents an alkoxy group. OR may be the same or different.

The alkoxy group represented by OR preferably has 1 to 6 carbon atoms, and more preferably 1 to 3 carbon atoms.
Examples of the alkoxy group represented by OR include a methoxy group, an ethoxy group, and a propoxy group.

Specific examples of the trifunctional alkoxysilane compound represented by formula (a-3) include trimethoxysilane, triethoxysilane, and tripropoxysilane.
These trifunctional alkoxysilane compounds can be used either individually or in combination of two or more.

Specific examples of the trifunctional alkoxysilane compound represented by formula (a-4) include phenyltrimethoxysilane, phenyltriethoxysilane, phenyltrippropoxysilane, pentafluorophenyltrimethoxysilane, pentafluorophenyltriethoxysilane, and pentafluorophenyltrippropoxysilane.
These trifunctional alkoxysilane compounds can be used either individually or in combination of two or more.

In the method for producing a silane compound polymer of the present invention, the molar ratio of the compound represented by formula (a-3) to the compound represented by formula (a-4) [compound represented by formula (a-3) : compound represented by formula (a-4)] is preferably 10:90 to 45:55, more preferably 15:85 to 35:65, and even more preferably 20:80 to 30:70.

In step PO, in addition to the trifunctional alkoxysilane compounds described above, monofunctional alkoxysilane compounds such as trimethylmethoxysilane, difunctional alkoxysilane compounds such as dimethyldimethoxysilane, trifunctional alkoxysilane compounds other than those represented by formula (a-3) and formula (a-4), and tetrafunctional alkoxysilane compounds such as tetramethoxysilane may also be used as monomers.

In the method for producing a silane compound polymer of the present invention, the total amount of the compound represented by formula (a-3) and the compound represented by formula (a-4) is preferably 70 to 100 mol %, more preferably 80 to 100 mol %, and even more preferably 90 to 100 mol %, based on the total amount of monomers.

In step PO, it is preferable to add water to the reaction system in an amount sufficient to sufficiently hydrolyze the hydrolyzable groups contained in the monomer (e.g., "OR" in formula (a-3) and formula (a-4)).

The amount of water added is preferably such that the molar ratio M of water to alkoxy groups calculated by the following formula (F3) is 1.0 or more, more preferably 1.0 to 5.0, and even more preferably 1.0 to 3.0.

In formula (F3), M _H2O is the amount of water (number of moles) added to the reaction system, and M _OR is the total number of alkoxy groups (total number of moles) in the monomer.
For example, when 6.0 moles of water are added to 1.0 mole of a trifunctional alkoxysilane compound, the molar ratio M is 6.0/3.0 (=2.0).

By ensuring that the molar ratio M is 1.0 or greater, the hydrolysis reaction of the monomers can proceed sufficiently, making it easier to obtain a silane compound polymer with excellent curing properties.

The acid catalyst used in step (PO) includes inorganic acids such as phosphoric acid, hydrochloric acid, boric acid, sulfuric acid, and nitric acid; and organic acids such as formic acid, citric acid, acetic acid, methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid, and p-toluenesulfonic acid. Among these, at least one selected from phosphoric acid, hydrochloric acid, boric acid, sulfuric acid, formic acid, citric acid, acetic acid, and methanesulfonic acid is preferred.

The amount of the acid catalyst used is usually 0.05 to 10 mol %, preferably 0.1 to 5 mol %, based on the total amount of the monomers.
By adjusting the amount of the acid catalyst used, the polycondensation reaction can be allowed to proceed appropriately, and a silane compound polymer having the desired molecular weight can be obtained.

Step PO can be carried out, for example, by placing a trifunctional alkoxysilane compound, water, and an acid catalyst in a reaction vessel and stirring the resulting mixture. In addition to these components, an organic solvent may also be present in the reaction vessel. The presence of an organic solvent in the reaction vessel allows the polymerization reaction to continue even if a solid silane compound polymer is produced during the polymerization reaction.

The organic solvent used in the step PO is not particularly limited as long as it dissolves the trifunctional alkoxysilane compound used as a raw material.
However, a high boiling point solvent (for example, a solvent having a boiling point of 150° C. or higher) is preferred as the organic solvent, since the organic solvent is less likely to volatilize during the step PO and the step PO can be carried out stably.

Examples of high-boiling point solvents include polyether solvents such as dipropylene glycol dimethyl ether (boiling point 171°C), diethylene glycol dimethyl ether (boiling point 162°C), and diethylene glycol ethyl methyl ether (boiling point 176°C); ester solvents such as γ-butyrolactone (boiling point 204°C), ethyl lactate (boiling point 154°C), 3-methoxybutyl acetate (boiling point 171°C), and ethylene glycol monoethyl ether acetate (boiling point 156°C); ketone solvents such as cyclohexanone (boiling point 156°C); amide solvents such as N,N-dimethylformamide (boiling point 153°C), N,N-dimethylacetamide (boiling point 165°C), and N-methylpyrrolidone (boiling point 202°C); and sulfoxide solvents such as dimethyl sulfoxide (boiling point 189°C).
Among these, polyether solvents are preferred because they are less likely to react even at high temperatures.

When an organic solvent is used in step PO, the organic solvent is preferably used in an amount of 0.05 to 3 times, more preferably 0.1 to 1.5 times, by volume, the amount of the trifunctional alkoxysilane compound.
When the reaction solution obtained in step PO is used as it is as an insulating film forming agent, it is preferable to adjust the amount of the organic solvent used in consideration of the concentration of the silane compound polymer in the insulating film forming agent.

The reaction conditions for step PO are not particularly limited.
The reaction temperature in step PO is usually 0 to 180°C, preferably 10 to 170°C.
The reaction time in step PO is usually from 30 minutes to 50 hours, preferably from 1 to 24 hours.

Process PO may be carried out under constant conditions from start to finish (i.e., it may have one step), or it may have multiple steps with different reaction conditions.

After step PO, the reaction liquid may be used as it is as an insulating film forming agent, or a step (step PU) of purifying the silane compound polymer produced in step PO may be carried out.
By carrying out the step PU, a high-purity silane compound polymer can be obtained.

The step PU may be a purification step using a solvent extraction method.
An example of a purification process using the solvent extraction method includes the following steps:
(Step PU-I) If necessary, the solvent is evaporated from the reaction solution, and then a water-immiscible organic solvent or water is added, followed by stirring and leaving to stand to separate into an organic phase and an aqueous phase. (Step PU-II) The organic phase produced in Step PU-I is separated, and if necessary, the organic phase is washed with water. (Step PU-III) The organic phase separated in Step PU-II is concentrated and dried.

The amount of solvent and type of organic solvent added in step PU-I are not particularly limited, as long as they ultimately separate into an organic phase and an aqueous phase.

The silane compound polymer is usually contained in the organic phase. Therefore, in step PU-II, the organic phase produced in step PU-I is separated and collected. The organic phase may then be washed with water using standard methods.

Step PU-III can be carried out according to conventional methods, such as concentration using an evaporator and vacuum drying.

2) Semiconductor Insulating Film Forming Agent The semiconductor insulating film forming agent of the present invention contains the silane compound polymer of the present invention (hereinafter referred to as "silane compound polymer (A)") and a solvent.

[Silane Compound Polymer (A)]
The agent for forming a semiconductor insulating film of the present invention contains a silane compound polymer (A).
As described above, the silane compound polymer (A) has excellent curability and is less likely to crack when cured. Therefore, by using the semiconductor insulating film forming agent of the present invention, a semiconductor insulating film can be efficiently formed.

〔solvent〕
The solvent constituting the semiconductor insulating film forming agent of the present invention is not particularly limited as long as it dissolves the silane compound polymer (A).
Therefore, when the silane compound polymer (A) is synthesized in the presence of an organic solvent and a homogeneous reaction solution is obtained, the same solvent as that used during synthesis can be used as the solvent constituting the semiconductor insulating film forming agent of the present invention.

Solvents that make up the semiconductor insulating film forming agent of the present invention include solvents with a boiling point of 150°C or higher, such as polyether solvents such as dipropylene glycol dimethyl ether (boiling point 171°C), diethylene glycol dimethyl ether (boiling point 162°C), and diethylene glycol ethyl methyl ether (boiling point 176°C); ester solvents such as gamma-butyrolactone (boiling point 204°C), ethyl lactate (boiling point 154°C), 3-methoxybutyl acetate (boiling point 171°C), and ethylene glycol monoethyl ether acetate (boiling point 156°C); ketone solvents such as cyclohexanone (boiling point 156°C); amide solvents such as N,N-dimethylformamide (boiling point 153°C), N,N-dimethylacetamide (boiling point 165°C), and N-methylpyrrolidone (boiling point 202°C); and sulfoxide solvents such as dimethyl sulfoxide (boiling point 189°C).

Using a solvent with a boiling point of 150°C or higher can prevent the solvent from evaporating during application of the semiconductor insulating film forming agent using spin coating, allowing for the formation of a film with a more uniform thickness.

Among these, polyether solvents are preferred, since polyether solvents easily form azeotropes with water, and by using a polyether solvent, the coating film can be dried efficiently in the drying step.
In this specification, the term "polyether solvent" refers to a compound having an ether group at the end or inside of the hydrocarbon chain. Such a compound is stable even at high temperatures and is suitable as a component of a semiconductor insulating film forming agent.

[Semiconductor insulating film forming agent]
The amount of the silane compound polymer (A) contained in the semiconductor insulating film forming agent of the present invention is preferably 10 to 70 mass %, more preferably 15 to 65 mass %, and even more preferably 20 to 60 mass %, based on the total amount of the silane compound polymer (A) and the solvent.
When the amount of the silane compound polymer (A) is 10% by mass or more relative to the total amount of the silane compound polymer (A) and the solvent, a thick semiconductor insulating film can be efficiently formed. When the amount of the silane compound polymer (A) is 70% by mass or less relative to the total amount of the silane compound polymer (A) and the solvent, a film of uniform thickness can be formed by spin coating.

The agent for forming a semiconductor insulating film of the present invention may contain components other than the silane compound polymer (A) and the solvent (hereinafter referred to as "other components").
Other components include a curing catalyst and a surfactant.

The total amount of silane compound polymer (A) and solvent contained in the semiconductor insulating film forming agent of the present invention is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, of the total amount of the semiconductor insulating film forming agent.

The semiconductor insulating film forming agent of the present invention preferably does not substantially contain any reactive compounds other than the silane compound polymer (A).
In this specification, the term "reactive compound other than the silane compound polymer (A)" refers to a compound other than the silane compound polymer (A) that is reactive at 250° C. or less. Examples of such compounds include silane coupling agents, isocyanate-based curing agents, and epoxy-based curing agents.
Moreover, the phrase "substantially free of" means that no reactive compounds other than the silane compound polymer (A) are intentionally added to the semiconductor insulating film forming agent.

By using a semiconductor insulating film forming agent that contains substantially no reactive compounds other than the silane compound polymer (A), it is possible to efficiently form a crack-free semiconductor insulating film.

The semiconductor insulating film forming agent of the present invention can be prepared, for example, by mixing the silane compound polymer (A), a solvent, and other components in a predetermined ratio.
When the silane compound polymer (A) is synthesized in a solvent, the reaction mixture may be used as the semiconductor insulating film forming agent of the present invention.

When a semiconductor insulating film is formed using the semiconductor insulating film forming agent of the present invention, the semiconductor insulating film forming agent is usually applied, the resulting coating film is dried, and then the dried coating film is cured.
When applying the semiconductor insulating film forming agent, a spin coating method is preferably used.
Conditions for drying the coating film of the semiconductor insulating film-forming agent include, for example, a drying temperature of usually 100 to 200°C, preferably 120 to 180°C, and a drying time of usually 10 to 300 seconds, preferably 40 to 120 seconds.
The conditions for curing the dried coating film include, for example, a curing temperature of usually 200 to 350°C, preferably 230 to 300°C, and a curing time of usually 30 to 600 seconds, preferably 60 to 300 seconds.

By using the semiconductor insulating film forming agent of the present invention, a relatively thick semiconductor insulating film can be efficiently formed.
The thickness of the semiconductor insulating film is, for example, 0.1 to 5.0 μm, preferably 0.5 to 4.0 μm, and more preferably 1.0 to 3.0 μm.

The present invention will be explained in more detail below using examples. However, the present invention is not limited to the following examples in any way.

Example 1
250 mmol (30.6 g) of trimethoxysilane and 750 mmol (148.7 g) of phenyltrimethoxysilane were weighed into a flask, and diethylene glycol dimethyl ether was added to adjust the monomer concentration to 30% by mass. Next, an aqueous formic acid solution (10 mmol (0.460 g) of formic acid diluted with 4500 mmol (81.0 g) of water) was added dropwise to the flask at 30° C. over 30 minutes.
The temperature of the content of the flask was raised to 50°C and stirred for 2 hours. Thereafter, while distilling off volatiles from the content of the flask, the temperature of the content of the flask was raised to 110°C and stirred for 2 hours, and then to 160°C and stirred for 1 hour, to obtain a solution of a silane compound polymer.

[Examples 2 to 3, Comparative Examples 1 to 3]
A solution of a silane compound polymer was obtained in the same manner as in Example 1, except that the amounts of silane compounds shown in Table 1 were used as monomers in the ratios shown in Table 1 (however, the total amount of the silane compounds was 1,000 mmol).

The following measurements were performed on the silane compound polymers obtained in Examples 1 to 3 and Comparative Examples 1 to 3. The results are shown in Table 1.

[Average molecular weight measurement]
The mass average molecular weight (Mw) of the silane compound polymer was measured using the following apparatus and conditions.
Device name: Tosoh Corporation HLC-8220GPC
Column: "TSK guard column Super H-H", "TSK gel Super HM-H", "TSK gel Super HM-H", and "TSK gel Super H2000" connected in sequence. Solvent: tetrahydrofuran. Standard material: polystyrene. Injection volume: 20 μl.
Measurement temperature: 40℃
Flow rate: 0.6 ml/min Detector: differential refractometer

[ ^1H -NMR measurement]
Device name: Bruker Biospin AV-500
¹ H-NMR resonance frequency: 500MHz
Probe: 5 mmφ solution probe Measurement temperature: room temperature (25°C)
Repeat time: 1 s
Number of times accumulated: 16

< ^1H -NMR sample preparation method>
Silane compound polymer concentration: 3%
Measurement solvent: acetone-d6
Internal standard: TMS

[Alkoxy group residual ratio]
Based on the results of ¹ H-NMR measurement, the ratio of alkoxy groups to methyl groups and phenyl groups was determined, and the residual alkoxy group ratio of the silane compound polymer was calculated.

[Curability evaluation test]
A curability evaluation test was carried out under the following conditions.
A solution of a silane compound polymer was spin-coated onto a silicon wafer, and the wafer was heated on a hot plate heated to 150°C for 1 minute to volatilize the solvent and form a 2 μm-thick film of a silane compound polymer. The wafer was then heated on a hot plate heated to 250°C for 1 minute to harden the film of the silane compound polymer. The obtained cured film was transferred to a 23°C environment and allowed to stand until it cooled to 23°C.
Next, the thickness (T ₁ ) of the cured film was measured, and then the cured film was immersed in diethylene glycol dimethyl ether at 23° C. for 10 minutes and dried for 1 minute on a hot plate heated to 150° C. Thereafter, the thickness (T ₂ ) of the cured film was measured, and the thickness reduction rate (X _t ) was calculated according to the following formula (F1), and the curability of the silane compound polymer was evaluated according to the following criteria.
The thicknesses (T ₁ ) and (T ₂ ) of the cured film were measured using a stylus surface profiler (Dektak 150, manufactured by ULVAC).

A: The thickness reduction rate (X _t ) is 20% or less.
F: The thickness reduction rate (X _t ) is more than 20%.

[Crack resistance evaluation test]
A crack resistance evaluation test was carried out under the following conditions.
A solution of a silane compound polymer was spin-coated onto a silicon wafer, and the wafer was heated on a hot plate heated to 150°C for 1 minute to volatilize the solvent, forming a 2 μm-thick film of a silane compound polymer. The wafer was then heated on a hot plate heated to 250°C for 1 minute to harden the film of the silane compound polymer. The resulting cured film was transferred to a 23°C environment and allowed to cool to 23°C, after which the presence or absence of cracks was examined.
In addition, the same experiment as above was conducted except that a silane compound polymer film having a thickness of 1 μm was formed instead of the silane compound polymer film having a thickness of 2 μm, and the crack resistance was evaluated according to the following criteria.
A: No cracks occur in both the 2 μm thick film and the 1 μm thick film.
B: Cracks occur only in the film having a thickness of 2 μm.
F: Cracks occur in both the 2 μm thick film and the 1 μm thick film.

[Thermogravimetric measurement]
Thermogravimetry was carried out under the following conditions.
The silane compound polymer solution was spin-coated to obtain a test sample, which was then subjected to thermogravimetric measurement under the following conditions using a thermal analyzer (Shimadzu Corporation: DTG-60).
The test sample was heated at 150°C for 90 minutes to volatilize the solvent, and the weight _M1 of the test sample after the solvent volatilization was measured. The temperature was then increased to 200°C and maintained at that temperature for 120 minutes to cure the silane compound polymer. Thereafter, the test sample was heated to 500°C at a temperature increase rate of 10°C/min, and the weight _M2 of the test sample at that time was measured, and the weight loss rate ( _Xm ) was calculated using the following formula (F2).

The following can be seen from the above examples and comparative examples.
The silane compound polymers of Examples 1 to 3 have excellent curability and good crack resistance, and further have a low weight loss rate.
On the other hand, the silane compound polymer of Comparative Example 1 has only methyl groups as side chains, which results in poor crack resistance and a high weight loss rate.
The silane compound polymer of Comparative Example 2 has only phenyl groups as side chains, and therefore the silane compound polymer of Comparative Example 2 is inferior in curability.
The silane compound polymer of Comparative Example 3 has a methyl group instead of a phenyl group, and therefore the silane compound polymer of Comparative Example 3 is inferior in crack resistance.

Claims (14)

The following formula (a-1)
A repeating unit represented by the formula (1) [repeating unit (1)]
The following formula (a-2)
[R ¹ represents an unsubstituted aryl group having 6 to 12 carbon atoms or a substituted aryl group having 6 to 12 carbon atoms.]
and a repeating unit represented by the formula (2): The silane compound polymer according to claim 1, wherein the amount of repeating unit (1) is 10 to 45 mol % based on the total amount of repeating unit (1) and repeating unit (2). The silane compound polymer according to claim 1, wherein the total amount of repeating units (1) and repeating units (2) is 70 to 100 mol % based on the total amount of repeating units in the silane compound polymer. The silane compound polymer according to claim 1, having a mass average molecular weight (Mw) of 1,500 to 50,000. The silane compound polymer according to claim 1, wherein the silane compound polymer is a silane compound polymer obtained by hydrolysis and polycondensation of an alkoxysilane compound, and has a residual alkoxy group ratio of 2.0% or less. The silane compound polymer according to claim 1, wherein when a curability evaluation test is carried out under the following conditions, the thickness reduction rate (X _t ) calculated by the following formula (F1) is 20% or less.
[Curability evaluation test]
A1: A 2 μm thick film of a silane compound polymer is formed on a silicon wafer.
A2: The film obtained in A1 above is heated at 250°C for 1 minute to be cured.
A3: The cured film obtained in A2 above is transferred to an environment at 23°C and left there until it cools down to 23°C.
A4: After A3 above, the cured film is immersed in diethylene glycol dimethyl ether at 23°C for 10 minutes, and then dried on a hot plate heated to 150°C for 1 minute.
[In formula (F1), _T1 represents the thickness of the silane compound polymer film before A4, and _T2 represents the thickness of the silane compound polymer film after A4.] 2. The silane compound polymer according to claim 1, which does not crack when subjected to a crack resistance evaluation test under the following conditions:
[Crack resistance evaluation test]
B1: A 1 μm thick film of a silane compound polymer is formed on a silicon wafer.
B2: The film obtained in B1 above is heated at 250° C. for 1 minute to be cured.
B3: The cured film obtained in B2 above is transferred to an environment at 23°C and left there until it cools down to 23°C. The silane compound polymer according to claim 1, wherein when thermogravimetry is carried out under the following conditions, the weight loss rate (X _m ) calculated by the following formula (F2) is 7% or less.
[Thermogravimetric measurement]
C1: The silane compound polymer is heated at 200° C. for 120 minutes.
C2: After C1, the silane compound polymer is heated to 500° C. at a rate of 10° C./min.
(In formula (F2), _M1 represents the weight of the silane compound polymer before C1, and _M2 represents the weight of the silane compound polymer after C2.) An insulating material for semiconductors comprising the silane compound polymer described in claim 1. A semiconductor insulating film forming agent containing the silane compound polymer of claim 1 and a solvent. The semiconductor insulating film forming agent according to claim 10, wherein the solvent has a boiling point of 150°C or higher. The semiconductor insulating film forming agent according to claim 10, wherein the solvent is a polyether-based solvent. The semiconductor insulating film forming agent according to claim 10, wherein the total amount of the silane compound polymer according to claim 1 and the solvent is 80 mass % or more of the total amount of the semiconductor insulating film forming agent. The semiconductor insulating film forming agent according to claim 10, which is substantially free of reactive compounds other than the silane compound polymer according to claim 1.