JP2010106225A - New fluorinated tetracarboxylic dianhydride, polyimide precursor obtained therefrom, and resulting polyimide and use thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide having a combination of low dielectric constant, low CTE (coefficient of thermal expansion), high Tg (glass transition temperature), sufficient toughness and solution processability, and practically useful as the interlaminar electrical insulation film material for large scale integrated (LSI) circuits, and to provide a method for producing the same. <P>SOLUTION: A tetracarboxylic dianhydride is represented by formula (1). A polyimide precursor is composed of repeat units each represented by formula (2). The resulting polyimide includes repeat units each represented by formula (3). X is an ether group or NH group in the formula (1) to formula (3), and Y in formulae (1) and (2) is a bivalent aromatic or aliphatic group. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polyimide practically useful as an interlayer insulating film material for a large-scale integrated circuit having low dielectric constant, low thermal expansion coefficient, high glass transition temperature, sufficient toughness and solution processability, and use thereof.

In recent years, the importance of polyimide as a heat-resistant insulating material in electronic devices has been increasing. Polyimide has not only excellent heat resistance, but also chemical resistance, radiation resistance, electrical insulation reliability, excellent mechanical properties, etc., so flexible printed wiring substrates, tape automation bonding circuit substrates, Currently, it is widely used in various applications such as chip-on-film circuit substrates, optical waveguide materials, protective films for semiconductor elements, and interlayer insulating films in multilayer circuits.
Polyimide is obtained by polymerizing a solvent-soluble precursor (polyamic acid) by subjecting diamine and tetracarboxylic dianhydride to an equimolar polyaddition reaction without solvent in a solvent such as N-methyl-2-pyrrolidone (NMP). The varnish can be produced relatively easily by solution casting film formation, drying, and heat dehydration cyclization (imidation reaction). In addition, polyimide resin is characterized by extremely high film purity, and is suitable for insulating applications of semiconductor elements that hate metal ions such as residual halogen and sodium ions that cause troubles such as ion migration and corrosion. Further, it is advantageous in that it is easy to improve the physical properties using various available monomers and easily cope with the increasingly demanded characteristics in recent years.

In integrated circuits, polyimide protects the chip from mechanical damage such as tweezers, chemical damage such as chemicals, and electrical damage such as electrostatic breakdown, and also shields alpha rays generated from trace components in the sealant. A passivation film that also has a function to prevent soft errors, a buffer coat film for protecting the inorganic film from stress from the sealant and external impact when using an inorganic passivation film with low mechanical strength such as silicon nitride, Alternatively, it is used as an interlayer insulating film material when a metal wiring and an insulating layer are alternately formed and processed to form a multilayer wiring.
The interlayer insulating film of the integrated circuit includes a planarizing interlayer insulating film and an LSI low dielectric constant interlayer insulating film. Currently, high integration of semiconductor elements is performed by a multilayer circuit technology. At this time, if a chemical vapor deposition (CVD) inorganic film is used to insulate the lower layer from the upper layer wiring, the insulating layer is formed with a uniform thickness on the vapor deposition surface, so that the lower layer wiring portion appears as a step, and the upper layer wiring There is a serious problem that the shoulder of the step is bent and easily disconnected. Therefore, by using a fluid polymer varnish, it is possible to absorb the level difference and flatten it, and to solve the problem of disconnection. The polyimide layer formed by spin-coating, drying, and thermal imidization of the polyimide precursor varnish realizes flattening, has high heat resistance and excellent electrical insulation reliability, and becomes a film without pinholes. Therefore, it has an excellent advantage as an interlayer insulating film.

RC delay based on the product of resistance value R of metal wiring and capacitance between wiring (capacitance of insulating layer) C in multi-layer wiring is solved to cope with higher speed processing and lower power consumption of integrated circuits. It has become an important issue that must be done. In order to reduce the RC delay, an approach to reduce R and C independently is required. By replacing the conventional aluminum wiring with a copper wiring having a lower electric wiring resistance, the wiring resistance value R can be halved. On the other hand, the inter-wiring capacitance C between the wiring layers is reduced by increasing the thickness of the insulating film, and the wiring capacitance within the layer is reduced by increasing the wiring interval, but these are contrary to the direction of high integration. A more realistic measure to reduce C is to lower the dielectric constant of the interlayer insulating material, which is lower than the conventional CVD silicon oxide film (dielectric constant = 4.2) and has a lower capacitance (dielectric constant). Replacement with rate materials is ongoing.
The polyimide interlayer insulating film is advantageous in that it has heat resistance against a high temperature process in a multilayer wiring process and a relatively low dielectric constant (3.0 to 3.5), but further high integration, high speed processing and There is an urgent need to develop a low dielectric constant polyimide material that can support low power consumption.

In addition to the above heat resistance, planarization ability, electrical insulation reliability and low dielectric constant, the required characteristics of the polyimide interlayer insulation film include low dielectric loss, low leakage current, low linear thermal expansion coefficient, chemical and mechanical properties. Examples thereof include mechanical strength that can withstand a polishing (CMP) step, solution processability (film forming property), and fine processability.
As a measure for reducing the dielectric constant of polyimide, it is effective to introduce a fluorine substituent, particularly a trifluoromethyl group, having a low polarizability per unit volume into the polyimide skeleton (for example, see Non-Patent Document 1). As an example, a repeating unit represented by the following formula (7) obtained from 2,2-bis (3,4-carboxyphenyl) hexafluoropropanoic dianhydride and 2,2′-bis (trifluoromethyl) benzidine is used. The fluorinated polyimide film has a very low dielectric constant of 2.65 estimated from the average refractive index (see Non-Patent Document 2, for example).

  In addition, replacing aromatic units with alicyclic units to reduce π electrons is also an effective means for reducing the dielectric constant (see, for example, Non-Patent Document 3). As an example, the all-alicyclic polyimide film represented by the following formula (8) obtained from 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 4,4′-methylenebis (cyclohexylamine) has an average refractive index. It has been reported that the dielectric constant estimated from 1 shows a very low value of 2.6 (for example, see Non-Patent Document 4).

As a low dielectric constant measure applicable in addition to the control of the molecular structure, there is a method of reducing the density by introducing fine pores in the film. For example, the end of polyimide is sealed with a low heat resistant block such as polypropylene glycol or polyacrylate to form a block copolymer, which is in a microphase separation state. A method has been reported in which this is thermally oxidatively decomposed below the glass transition temperature (Tg) of the polyimide block in the presence of air to remove the low-low heat block and form closed cells with a diameter of several tens of nanometers ( For example, refer nonpatent literature 5).
However, such a porous polyimide film is inferior in mechanical strength to a normal dense polyimide film containing no pores, and may cause a serious trouble in the CMP process.

In recent years, with the progress of multilayer wiring, low linear thermal expansion characteristics are becoming important as required characteristics of interlayer insulating films. When the polyimide precursor film formed on the wiring layer is imidized, the thermal stress generated in the process of cooling from the imidization temperature to room temperature is caused by partial peeling of the metal wiring layer and the film, cracking, degradation of CMP resistance, etc. May cause serious problems in electrical reliability. The greater the number of wiring layers, the more likely they are adversely affected by thermal stress, and the reliability of the device significantly decreases. Design the interlayer insulation film material so that the difference in coefficient of linear thermal expansion between the metal wiring layer and the insulating layer is as low as possible. Therefore, it is necessary to reduce the thermal stress as much as possible.
However, in many polyimide systems, the linear thermal expansion coefficient of the film is in the range of 60 to 80 ppm / K and does not have low thermal expansion characteristics. Although the polyimide represented by the above formula (4) or formula (5) has a low dielectric constant, it does not show a low linear thermal expansion coefficient.

This is because the polyimide main chain contains a bent structure. In order for polyimide to exhibit low thermal expansion characteristics, it is necessary that the polyimide main chain is linear and has no or few internal rotation sites. In such a linear polyimide system, it has been reported that spontaneous orientation of polymer chains in the direction parallel to the film surface is promoted during the process of thermal imidization of the polyimide precursor film. (See Non-Patent Document 6, for example).
As an example, a polyimide represented by the following formula (9) obtained from 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 2,2′-bis (trifluoromethyl) benzidine has an alicyclic structure and trifluoro It has a very low dielectric constant (2.66) because it contains both methyl groups, and it has a rigid main chain skeleton with relatively high linearity, so it has a low coefficient of thermal expansion (21 ppm / K) and a high glass transition temperature (356). (° C.) are simultaneously satisfied (see, for example, Non-Patent Document 2).

However, for example, an alicyclic structure-containing low thermal expansion polyimide represented by the above formula (9) is compared with a wholly aromatic polyimide containing no alicyclic structural unit, such as a plasma treatment process during the production of a semiconductor chip. It has been pointed out that the chemical stability is extremely inferior, and outgas is easily generated.
As a fluorine group-containing polyimide not containing an alicyclic structure, for example, a wholly aromatic polyimide represented by the following formula (10) has a relatively low dielectric constant (2.86) and an extremely low linear thermal expansion coefficient (-4.7 ppm / K). ) Has been reported (see Non-Patent Document 7, for example).

However, since this polyimide has poor solubility in an organic solvent, it is necessary to form a cast film at the stage of a precursor (polyamic acid) soluble in an organic solvent, and heat imidize to form a polyimide film. In that case, the polyamic acid may react with the copper layer and cause migration of copper ions, and if the wiring interval is further narrowed due to high integration, the electrical insulation reliability may be impaired.
From the viewpoint of suppressing ion migration, it is preferable to use polyimide varnish instead of polyimide precursor varnish, and apply and dry it to form an interlayer insulating film, but in order to obtain a stable polyimide varnish at room temperature The polyimide must have high solubility at room temperature in general-purpose volatile organic solvents.

In order to impart solvent solubility to polyimide, it is usually necessary to reduce the intermolecular interaction of polyimide by introducing bending bonds such as ether bonds, sulfonyl bonds, isopropylidene bonds, asymmetric structures, or bulky substituents. However, as a result, the linearity of the polyimide skeleton is greatly reduced, and in-plane orientation cannot be induced by applying and drying the polyimide varnish, and a low linear thermal expansion coefficient (CTE) is exhibited. It becomes difficult. For such a molecular structure, there is no known case where low CTE is expressed using a soluble polyimide varnish.
If a polyimide material with a low dielectric constant, high Tg, and sufficient film toughness can be obtained if the formed film develops low CTE just by applying and drying polyimide varnish on the substrate, Although useful interlayer insulating films can be provided, such materials are not known at present.

“Macromolecules”, 24, 1991, p. 5001-5005 “High Performance Polymers”, Volume 15, 2003, p. 47-64 “Macromolecules”, 32, 1999, p. 4933-4939 “Reactive and Functional Polymers”, Vol. 30, 1996, p. 61-69 “Chemistry of Materials”, Volume 13, 2001, p. 213-221 “Macromolecules”, 29, 1996, p. 7897-7909 “Polymer Journal”, Vol. 39, No. 6, 2007, p. 610-621

  The present invention provides a polyimide which is practically useful as an interlayer insulating film material for a large scale integrated circuit and has a low dielectric constant, low CTE, high Tg, sufficient toughness and solution processability, and a method for producing the same.

  In view of the above problems, as a result of intensive research, the polyimide represented by the following formula (3) exhibits excellent characteristics that satisfy the above required characteristics at the same time. The headline and the present invention were completed.

(In formula (3), X represents an oxygen atom or NH group, and Y represents a divalent aromatic group or aliphatic group.)
The present invention has been found to be a useful material in the industrial field because the polyimide represented by the formula shows excellent characteristics satisfying the required characteristics at the same time, and the present invention has been completed.

That is, the gist of the present invention is as follows.
1. A tetracarboxylic dianhydride represented by the formula (1).

(In the formula (1), X represents an oxygen atom or an NH group.)
2. The polyimide precursor which has a repeating unit represented by Formula (2).

(In formula (2), X has the same meaning as described in claim 1, Y represents a divalent aromatic group or aliphatic group, R represents a hydrogen atom, a silyl group, or a carbon atom number of 1 to 12. Any one of the straight-chain or branched alkyl groups may be mixed, and these may be mixed.)
3. The polyimide which has a repeating unit represented by Formula (3).

(In formula (3), X and Y are as defined in formula (2).)
4). The polyimide according to 3 above, wherein in the formula (3), the structural unit Y is selected from the following formulas (4) to (6).

5. 5. An interlayer insulating film of an integrated circuit comprising the polyimide described in 3 or 4 above.

  Since the polyimide of the present invention exhibits high solubility in various organic solvents, it can be a varnish that is stable at room temperature. By applying and drying this varnish, a polyimide film can be formed on the conductor layer without requiring any imidization reaction step. Moreover, since the obtained polyimide film has low CTE, low dielectric constant, high Tg, oxygen plasma resistance, and sufficient film toughness at the same time, the present invention provides an interlayer insulating film material for an integrated circuit that is extremely useful and unprecedented. provide.

  Embodiments of the present invention will be described in detail below, but these are examples of the embodiments of the present invention and the present invention is not limited to these contents.

<Method for producing tetracarboxylic dianhydride>
The manufacturing method of the tetracarboxylic dianhydride of this invention represented by following formula (1) is demonstrated.

  In the formula (1), the linking group X is an ether group (O) or an NH group. More preferable embodiments include, for example, the following formulas (11) and (12).

  The manufacturing method of the tetracarboxylic dianhydride of this invention represented by Formula (1) is not specifically limited, A well-known method is applicable. As an example, a method for producing a tetracarboxylic dianhydride represented by the formula (11) will be described below. Specifically, the diol (4,4′-dihydroxy-2,2′-bis (trifluoromethyl) biphenyl, hereinafter referred to as DHTFMB) represented by the formula (13) and trimellitic anhydride as raw materials thereof An esterification reaction is performed using the derivative.

  Applicable methods at this time include, for example, a method in which a hydroxy group of DHTFMB and a carboxyl group of trimellitic anhydride are directly dehydrated at a high temperature, a dehydrating condensation using a dehydrating reagent such as dicyclohexylcarbodiimide, or a diDHTFMB diester. A method of reacting acetate form with trimellitic anhydride at high temperature and deacetating and esterifying (transesterification method), converting the carboxyl group of trimellitic anhydride to acid halide, and removing this and diol. A method of reacting in the presence of an acid agent (base) (acid halide method), a method of activating and carboxylating a carboxyl group in trimellitic anhydride using a tosyl chloride / N, N-dimethylformamide / pyridine mixture Etc. Among the above-mentioned methods, the acid halide method can be preferably applied in terms of economy and reactivity.

  Although the synthesis | combining method by the acid halide method of the tetracarboxylic dianhydride of this invention represented by Formula (11) below is demonstrated concretely, it is not specifically limited. First, trimellitic anhydride chloride (A mol) is dissolved in a solvent and sealed with a septum cap. To this solution, DHTFMB (0.5 × A mol) and an appropriate amount of base (deoxidizer) dissolved in the same solvent are slowly added dropwise with a syringe or a dropping funnel. After the addition is complete, the reaction mixture is stirred for 24 hours. When the solubility of the target compound in the solvent used in the synthesis is high, first the produced hydrochloride is filtered off from the reaction mixture, and the filtrate is evaporated by an evaporator and dried in a vacuum at 100 to 200 ° C. for 24 hours to form a powder. To obtain a crude product. When the solubility of the target product is low, the mixture of the target product and hydrochloride is filtered off and washed with a large amount of water to dissolve and remove only the hydrochloride. Next, the crude product partially hydrolyzed in the partial washing step is vacuum-dried at 100 to 200 ° C. and subjected to ring-closing treatment. The crude product thus obtained is recrystallized with an appropriate solvent, washed, heated and dried in a vacuum, and then subjected to polymerization to obtain a high purity tetracarboxylic dianhydride represented by the formula (11). can get.

  In this reaction, usable solvents are not particularly limited, but tetrahydrofuran, 1,4-dioxane, picoline, pyridine, acetone, chloroform, toluene, xylene, dichloromethane, chloroform, 1,2-dichloroethane, N-methyl. -2-pyrrolidone, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, hexamethylphosphoramide, dimethyl sulfoxide, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone Aprotic solvents such as 1,2-dimethoxyethane-bis (2-methoxyethyl) ether, and phenol, o-cresol, m-cresol, p-cresol, o-chlorophenol, m-chlorophenol, p- Proticity such as chlorophenol A solvent is mentioned. These solvents may be used alone or in combination of two or more. Tetrahydrofuran is preferably used from the viewpoint of solubility of the reaction reagent and easiness of evaporation.

Although the said esterification reaction is performed at -10-50 degreeC, More preferably, it is performed at 0-30 degreeC. If the reaction temperature is higher than 50 ° C., some side reactions occur, which may reduce the yield, which is not preferable.
The esterification reaction is performed in a solute concentration range of 5 to 50% by mass. In consideration of control of side reaction and filtration step of precipitation, it is preferably carried out in the range of 10 to 40% by mass.
Although it does not specifically limit as a deoxidizer used for the said esterification reaction, Inorganic bases, such as organic tertiary amines, such as a pyridine, a triethylamine, N, N- dimethylaniline, potassium carbonate, sodium hydroxide, are used.

  The precipitate produced by the esterification reaction contains water-soluble pyridine hydrochloride when pyridine is used as a deoxidizing agent. For example, when tetrahydrofuran is used as a solvent, since pyridine hydrochloride is hardly dissolved in the solvent, the hydrochloride can be separated almost completely only by filtering the reaction solution. Usually, when the solubility of the target product is high, the target product is dissolved in the filtrate, so that the target product with high yield and sufficiently high purity can be obtained simply by distilling off the solvent from the filtrate and recrystallization from an appropriate solvent. Although it can be obtained, in order to separate and remove trace amounts of chlorine components, the target product is redissolved in chloroform, ethyl acetate, etc., and the organic layer is washed with water using a separatory funnel, or the precipitate is washed thoroughly with water. It is also possible to use a method. The removal of the hydrochloride can be easily judged by the presence or absence of purification of the white precipitate of silver chloride using a 1% silver nitrate aqueous solution as the washing solution. During the washing operation, the ester group-containing tetracarboxylic dianhydride is partially hydrolyzed to be converted into dicarboxylic acid, but is vacuum-dried at 80 to 250 ° C, preferably 120 to 200 ° C. Even if a dicarboxylic acid is produced by partial hydrolysis, it can be easily dehydrated and closed to return to an acid anhydride. A method of treating with an acid anhydride of an organic acid is also applicable. Examples of the acid anhydride of the organic acid that can be used in this case include acetic anhydride, propionic anhydride, maleic anhydride, and phthalic anhydride, and acetic anhydride is preferably used from the viewpoint of easy removal.

Next, although the manufacturing method of the tetracarboxylic dianhydride represented by Formula (12) is demonstrated, the method is not specifically limited, It can manufacture easily by a well-known method. As an example, a method for producing an amidation reaction from 2,2′-bis (trifluoromethyl) benzidine (hereinafter referred to as TFMB) and trimellitic anhydride chloride will be described.
The amidation reaction is performed as follows. First, trimellitic anhydride chloride is dissolved in a solvent and sealed with a septum cap. To this solution, TFMB and an appropriate amount of a deoxidizing agent dissolved in the same solvent are dropped by a syringe or a dropping funnel. After completion of the dropwise addition, the reaction mixture is stirred for 1 to 24 hours. At this time, the amount of trimellitic anhydride chloride added to TFMB is usually twice as much, but from the viewpoint of ease of separation of trimellitic anhydride chloride after completion of the reaction and trimellitic acid to TFMB. Anhydrous chloride may be added in excess. In this case, the added amount of trimellitic anhydride chloride is 2 to 10 times mol, preferably 2 to 5 times mol.

  In the amidation reaction, usable solvents are not particularly limited, but tetrahydrofuran (THF), 1,4-dioxane, picoline, pyridine, acetone, chloroform, toluene, xylene, dichloromethane, chloroform, 1,2- Dichloroethane, N-methyl-2-pyrrolidone, N, N-dimethylacetamide (hereinafter referred to as DMAc), N, N-diethylacetamide, N, N-dimethylformamide (hereinafter referred to as DMF), hexamethylphosphoramide, dimethyl Aprotic solvents such as sulfoxide, γ-butyrolactone, 1,3-dimethyl-2-imidazolidinone, 1,2-dimethoxyethane-bis (2-methoxyethyl) ether, and phenol, o-cresol, m-cresol , P-cresol, o-chlorofe Examples include protic solvents such as diol, m-chlorophenol, and p-chlorophenol. These solvents may be used alone or in combination of two or more. From the viewpoint of ease of treatment after the reaction and solubility of raw materials, THF is preferably used.

The amidation reaction is performed at −50 to 20 ° C., more preferably −20 to 0 ° C. If the reaction temperature is high, some side reactions occur. That is, the amino group in TFMB reacts with not only the acid chloride group in trimellitic anhydride chloride but also the acid anhydride group, which is not preferable because the yield may be lowered.
The amidation reaction is performed in a solute concentration range of 5 to 50% by mass. In consideration of control of side reaction and filtration step of precipitation, it is preferably carried out in the range of 10 to 40% by mass.
Although it does not specifically limit as a deoxidizer used for reaction, Organic tertiary amines, such as a pyridine, a triethylamine, N, N- dimethylaniline other than a propylene oxide, can be used. Propylene oxide is preferably used as a deoxidizing agent from the viewpoint of suppressing side reactions and ease of purification and separation steps.

Separation / purification of the tetracarboxylic dianhydride obtained by the amidation reaction is performed as follows. After completion of the reaction, the precipitated product is separated by filtration and washed repeatedly with toluene or hexane to dissolve and remove chloropropanol as a by-product or, in some cases, an excessive amount of trimellitic anhydride chloride. Finally, the product is vacuum-dried for 1 to 24 hours under mild temperature conditions in the range of 30 to 150 ° C, preferably 50 to 120 ° C. At this time, if it is vacuum dried at 150 ° C. or higher, some decomposition reaction may occur, which is not preferable.
In this way, the tetracarboxylic dianhydride having a high purity that can be used for the polymerization reaction can be obtained, but it does not react with the tetracarboxylic dianhydride and is recrystallized from a suitable solvent that is easily separated. To further increase the purity.

<Polymerization of polyimide precursor>
The manufacturing method of the polyimide precursor of this invention represented by Formula (2) below is demonstrated. First, diamine is dissolved in a polymerization solvent in a polymerization vessel. Here, the molecular structure of the diamine is one in which two amino groups are bonded to the structural unit Y in the formula (1) (NH ₂ —Y—NH ₂ ). The tetracarboxylic dianhydride powder represented by the formula (1) is gradually added to the diamine solution, and the mechanical stirrer is used in the range of −20 to 100 ° C., preferably 20 to 60 ° C. Stir in the range for 1-72 hours. At this time, the total amount of each of the diamine and the tetracarboxylic dianhydride component is charged in substantially equimolar amounts. The total monomer concentration during the polymerization is 5 to 40% by mass, preferably 10 to 30% by mass. By carrying out polymerization in this monomer concentration range, a polyimide precursor solution having a uniform and high degree of polymerization can be obtained.
When the polymerization is performed at a concentration lower than the above monomer concentration range, the degree of polymerization of the polyimide precursor is not sufficiently high, and the finally obtained polyimide film may be brittle, which is not preferable. In addition, when an aliphatic diamine is used as a diamine monomer, salt formation occurs in the initial stage of polymerization, but if polymerization is performed at a concentration higher than the above monomer concentration, a longer polymerization time is required until the formed salt dissolves and disappears. This is not preferable because it may cause a decrease in productivity.

  The aromatic diamine that can be used is not particularly limited, but p-phenylenediamine, 2-methyl-1,4-phenylenediamine, 2-trifluoromethyl-1,4-phenylenediamine, 2-methoxy-1, 4-phenylenediamine, 2,5-dimethyl-1,4-phenylenediamine, 2,5-bis (trifluoromethyl) -1,4-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2, 5-diaminotoluene, 2,4-diaminoxylene, 2,4-diaminodurene, 4,4′-diaminodiphenylmethane, 4,4′-methylenebis (2-methylaniline), 4,4′-methylenebis (2-ethyl) Aniline), 4,4′-methylenebis (2,6-dimethylaniline), 4,4′-methylenebis (2,6- Ethyl aniline), 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 2,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,3'- Diaminodiphenyl sulfone, 4,4′-diaminobenzophenone, 3,3′-diaminobenzophenone, 4,4′-diaminobenzanilide, benzidine, 3,3′-dihydroxybenzidine, 3,3′-dimethoxybenzidine, 3,3 '-Dichlorobenzidine, o-tolidine, m-tolidine, 2,2'-bis (trifluoromethyl) benzidine, 3,3'-bis (trifluoromethyl) benzidine, octafluorobenzidine, 3,3', 5 5′-tetramethylbenzidine, 2,2 ′, 5 '-Tetrachlorobenzidine, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4'- Bis (4-aminophenoxy) biphenyl, bis (4- (3-aminophenoxy) phenyl) sulfone, bis (4- (4-aminophenoxy) phenyl) sulfone, 2,2-bis (4- (4-aminophenoxy) ) Phenyl) propane, 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoropropane, p-terphenylenediamine and the like. Two or more of these may be used in combination.

  Of the aromatic diamines, it is preferable to use a diamine having a rigid and linear molecular structure from the viewpoint of low thermal expansion characteristics. For example, p-phenylenediamine, 2-methyl-1,4-phenylenediamine, 2-trifluoromethyl-1,4-phenylenediamine, 2-methoxy-1,4-phenylenediamine, 2,5-dimethyl-1,4 -Phenylenediamine, 2,5-bis (trifluoromethyl) -1,4-phenylenediamine, 4,4'-diaminobenzanilide, 4-aminophenyl-4'-aminobenzoate, benzidine, 3,3'-dihydroxy Benzidine, 3,3′-dimethoxybenzidine, 3,3′-dichlorobenzidine, o-tolidine, m-tolidine, 2,2′-bis (trifluoromethyl) benzidine, 3,3′-bis (trifluoromethyl) Benzidine, octafluorobenzidine, 3,3 ′, 5,5′-tetramethylbenzidine, 2,2 ′, , 5'-tetrachloro-benzidine, etc. are suitably used.

  From the viewpoint of solution processability (solvent solubility), it is desirable to use an aromatic diamine containing a sulfonyl group or a trifluoromethyl group, for example, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenyl. Sulfone, bis (4- (3-aminophenoxy) phenyl) sulfone, bis (4- (4-aminophenoxy) phenyl) sulfone, 2-trifluoromethyl-1,4-phenylenediamine, 2,5-bis (tri Fluoromethyl) -1,4-phenylenediamine, 2,2′-bis (trifluoromethyl) benzidine, 3,3′-bis (trifluoromethyl) benzidine, 2,2-bis (4- (4-aminophenoxy) ) Phenyl) hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoropropane, etc. are preferably used. It is.

Although it does not specifically limit as aliphatic diamine which can be used when superposing | polymerizing the polyimide precursor of this invention, 4,4'-methylenebis (cyclohexylamine), 4,4'-methylenebis (3-methylcyclohexylamine), isophorone Diamine, trans-1,4-cyclohexanediamine, cis-1,4-cyclohexanediamine, 1,4-cyclohexanebis (methylamine), 2,5-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,6-bis (aminomethyl) bicyclo [2.2.1] heptane, 3,8-bis (aminomethyl) tricyclo [5.2.1.0] decane, 1,3-diaminoadamantane, 2,2 -Bis (4-aminocyclohexyl) propane, 2,2-bis (4-aminocyclohexyl) hexafluoropropane, , 3-propanediamine, 1,4-tetramethylenediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9- Nonamethylenediamine and the like can be mentioned. Two or more of these may be used in combination.
Among the above aliphatic diamines, it is preferable to use a diamine having a rigid and linear molecular structure from the viewpoint of expression of low thermal expansion characteristics. For example, trans-1,4-cyclohexanediamine is preferably used.

  When the above aliphatic diamine is used, a salt is formed at the initial stage of polymerization of the polyimide precursor. By continuing stirring at room temperature for a long time, the salt gradually dissolves and becomes a uniform and viscous polyimide precursor varnish. Can be obtained without problems. However, in some cases, a very strong salt is formed and does not dissolve at all, and the polymerization reaction may not proceed at all. In such a case, prior to the polymerization reaction, the aliphatic diamine is completely or partially converted into a silyl form using a silylating agent, and this is converted to the tetra- amide of the present invention represented by the formula (1). By reacting with carboxylic dianhydride, salt formation is avoided or suppressed, and finally a uniform and viscous polyimide precursor (polyamide acid silyl ester or partially silyl esterified polyamide acid) A varnish can be obtained. Moreover, even if it is a case where aromatic diamine is used, a silylated polyamic acid can be obtained in the same procedure.

  The silylating agent that can be used in the silylation of diamine is not particularly limited, but N, O-bis (trimethylsilyl) acetamide, N, O-bis (trimethylsilyl) trifluoroacetamide (hereinafter referred to as BSTFA), etc. Examples thereof include chlorine-containing silylating agents, and chlorine-containing silylating agents such as trimethylsilyl chloride (TMSC) and tributylsilyl chloride. BSTFA is suitably used because it does not contain chlorine and does not require a separation / purification step of the disilyl compound after the silylation reaction. When BSTFA is used, the diamine can be easily converted into a disilyl form by adding a silylating agent to a diamine dissolved in a well-dehydrated polymerization solvent and stirring for several hours at room temperature. At this time, since the silylating agent reacts quantitatively with the amino group of the diamine, it is possible to easily control the average silylation rate by simply adjusting the addition amount of the silylating agent. The applicable silylation rate is not particularly limited as long as the polymerization reaction proceeds. When TMSC is used as the silylating agent, the aliphatic diamine can be easily silylated by the presence of an acid acceptor such as triethylamine or pyridine. In this case, the hydrochloride as a by-product and the target disilyl compound can be separated by a method such as distillation under reduced pressure.

  In the present invention, it is particularly preferable that Y in the formula (2) is selected from the following formulas (4) to (6) because the effects of the present invention can be expressed more efficiently when polyimide is used.

  Moreover, when polymerizing the polyimide precursor of this invention, you may use a part of other alicyclic tetracarboxylic dianhydrides with the tetracarboxylic dianhydride of this invention. In that case, the alicyclic tetracarboxylic dianhydride that can be used as a copolymerization component is not particularly limited, but bicyclo [2.2.2] octane-2,3,5,6-tetracarboxylic dianhydride, Bicyclo [2.2.2] oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 5- (dioxotetrahydrofuryl-3-methyl-3-cyclohexene-1,2-dicarboxylic acid Acid anhydride, 4- (2,5-dioxotetrahydrofuran-3-yl) -tetralin-1,2-dicarboxylic anhydride, tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride, bicyclo- 3,3 ′, 4,4′-tetracarboxylic dianhydride, cis, cis, cis, cis-1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclo Pentanetetracar Examples thereof include boronic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, etc. In the case of copolymerization, the content of the tetracarboxylic dianhydride of the present invention represented by the formula (1) is not particularly limited as long as the required properties are not impaired, It is preferably in the range of 50 to 100 mol% with respect to the amount of carboxylic dianhydride used.

  Aromatic tetracarboxylic dianhydride may also be partially used as a copolymerization component. The aromatic tetracarboxylic dianhydride that can be used is not particularly limited, but pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4, 4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyl ether tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenylsulfone tetracarboxylic dianhydride, 2 , 2'-bis (3,4-dicarboxyphenyl) hexafluoropropanoic acid dianhydride, 2,2'-bis (3,4-dicarboxyphenyl) propanoic acid dianhydride, hydroquinone bis (trimellitic amine Hydride), 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride and the like. These may be used alone or in combination of two or more as copolymerization components. At this time, the content of the tetracarboxylic dianhydride of the present invention represented by the formula (1) is not particularly limited as long as the required characteristics are not impaired, but it is 80 to The range is preferably 100 mol%.

  The polymerization solvent is not particularly limited, but N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, dimethylsulfoxide, γ- Butyrolactone, 1,3-dimethyl-2-imidazolidinone, 1,2-dimethoxyethane-bis (2-methoxyethyl) ether, terahydrofuran, 1,4-dioxane, picoline, pyridine, acetone, chloroform, toluene, Aprotic solvents such as xylene and protic solvents such as phenol, o-cresol, m-cresol, p-cresol, o-chlorophenol, m-chlorophenol, and p-chlorophenol can be used. These solvents may be used alone or in combination of two or more.

<Production method of polyimide>
The polyimide of the present invention represented by the formula (3) can be produced by a dehydration cyclization reaction (imidization reaction) of the polyimide precursor obtained by the above method. Applicable polyimide forms include films, substrate / polyimide film laminates, powders, molded bodies, and solutions (varnishes). A well-known method can be used for imidation reaction, It does not specifically limit.
First, a method for producing a polyimide film will be specifically described. A polymerization solution of the polyimide precursor is cast on a substrate of glass, copper, aluminum, stainless steel, silicon or the like, and dried at 40 to 180 ° C., preferably 50 to 150 ° C. in an air oven. A polyimide film is obtained by heating the obtained polyimide precursor film on a substrate in vacuum, in an inert gas such as nitrogen, or in air at 200 to 400 ° C., preferably 250 to 350 ° C. The heating temperature at this time is preferably 200 ° C. or higher from the viewpoint of sufficiently carrying out the imidization ring-closing reaction, and 400 ° C. or lower from the viewpoint of the thermal stability of the produced polyimide film. The imidization is preferably performed under reduced pressure, in a vacuum or in an inert gas, but if the imidization temperature is not too high, it may be performed in air.

Imidization can be carried out by heat treatment, or by using a dehydrating cyclization agent (chemical imidization agent) comprising an acid anhydride of an organic acid and an organic tertiary amine. For example, by using the polyimide precursor varnish as it is or after appropriately diluting with a solvent, a dehydration cyclization reagent is added thereto and stirred at 0 to 100 ° C., preferably 20 to 60 ° C. for 0.5 to 48 hours. It can be easily imidized.
The acid anhydride of the organic acid used in that case is not particularly limited, and acetic anhydride, propionic anhydride, maleic anhydride, phthalic anhydride, etc. can be used, but the cost and ease of post-treatment are not limited. In view of the above, acetic anhydride is preferably used. The organic tertiary amine is not particularly limited, and pyridine, triethylamine, N, N-dimethylaniline and the like can be used, but pyridine is preferably used from the viewpoint of safety.
In the chemical imidation reaction, the amount of acid anhydride used in the dehydration cyclization reagent is preferably in the range of 1 to 10 times the theoretical dehydration amount of the polyimide precursor, and the basicity in the dehydration cyclization reagent is The amount of catalyst used is preferably in the range of 0.1 to 2 moles relative to the acid anhydride. If the chemical imidization is carried out outside these ranges, the imidation reaction may not be completed, or imidation may not be completed in the reaction solution, resulting in insufficient imidization.

After completion of chemical imidization, the reaction solution is dropped into a large amount of poor solvent to deposit and wash the polyimide to remove the reaction solvent and excess chemical imidizing agent, followed by drying under reduced pressure to obtain polyimide powder. it can. The poor solvent that can be used is not particularly limited as long as it does not dissolve polyimide, but water, methanol, ethanol, n, from the viewpoint of affinity with the reaction solvent and chemical imidizing agent and ease of removal by drying. -Propanol, isopropanol and the like are preferably used.
The obtained polyimide powder can be redissolved in the above-mentioned solvent that can be used for polymerization to obtain a polyimide varnish.
The polyimide varnish is coated on a substrate by a method such as a bar coating method, a spin coating method, a spray coating method, an ink jet method, a dipping method, or a spray coating method, and is dried at 40 to 300 ° C., preferably 80 to 250 ° C. A polyimide film can also be formed.

  Instead of using the above-mentioned chemical imidizing agent, the imidization reaction uses the polyimide precursor polymerization solution as it is or after appropriately diluting with a solvent, and then heating the varnish to 150 to 230 ° C. to use the polyimide itself. When dissolved in a solvent, a polyimide varnish can be easily produced. When insoluble in the solvent, the polyimide powder can be obtained as a precipitate. At this time, toluene, xylene or the like may be added in order to azeotropically distill off water or the like which is a by-product of imidization. Further, a base such as γ-picoline can be added as a catalyst. The obtained varnish can be dropped and deposited in a large amount of poor solvent such as water or methanol, and this can be filtered to isolate the polyimide as a powder. Further, when the polyimide powder is soluble in a solvent, it can be redissolved in the polymerization solvent to obtain a polyimide varnish.

  The polyimide of the present invention is obtained by reacting the tetracarboxylic dianhydride of the present invention represented by the formula (1) with a diamine in a solvent at a high temperature (one-pot polymerization) without isolating the polyimide precursor. It can also be manufactured in stages. At this time, the reaction temperature may be maintained in the range of 130 to 250 ° C., preferably 150 to 230 ° C., from the viewpoint of promoting the reaction. When the polyimide is insoluble in the solvent used, the polyimide is obtained as a precipitate, and when it is soluble, it is obtained as a polyimide varnish. Solvents that can be used for one-pot polymerization are not particularly limited, but examples include aprotic solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone (NMP), and dimethyl sulfoxide. More preferably, phenol solvents such as m-cresol and amide solvents such as NMP are used. In order to azeotropically distill off water, which is a by-product of the imidization reaction, to these solvents, toluene, xylene, or the like can be added. A base such as γ-picoline can be added as an imidization catalyst. The resulting varnish can be dropped and filtered into a large amount of poor solvent such as water or methanol to isolate the polyimide as a powder. When the polyimide is soluble in a solvent, the powder can be redissolved in the solvent to obtain a polyimide varnish.

The polyimide varnish is coated on a substrate by a method such as a bar coating method, a spin coating method, a spray coating method, an ink jet method, a dipping method, or a spray coating method, and is dried at 40 to 300 ° C., preferably 80 to 250 ° C. A polyimide film can also be formed.
A polyimide molded body can also be produced by heat-compressing the polyimide powder obtained as described above at 200 to 450 ° C., preferably 250 to 430 ° C.
It is an isomer of polyimide by adding and stirring a dehydrating reagent such as N, N-dicyclohexylcarbodiimide or trifluoroacetic anhydride in the polyimide precursor solution and reacting at 0 to 100 ° C., preferably 0 to 60 ° C. Polyisoimide is formed. The isoimidization reaction can also be performed by immersing the polyimide precursor film in a solution containing the dehydrating reagent. After polyisoimide varnish is formed in the same procedure as above, it can be easily converted to polyimide by heat treatment at 250 to 450 ° C., preferably 270 to 400 ° C.
In the polyimide of the present invention and its precursor, an oxidation stabilizer, a filler, an adhesion promoter, a silane coupling agent, a photosensitizer, a dye, a pigment, a photopolymerization initiator, a sensitizer, and an end-capping agent as necessary. Additives such as cross-linking agents can be added.

<Examples of required characteristics of polyimide as an interlayer insulating film>
The higher the glass transition temperature Tg of polyimide is, the better, but if it is 230 ° C. or higher, there is no practical problem, and if it is 250 ° C. or higher, it is more preferable.
The lower the CTE of polyimide, the better. However, if it is 40 ppm / K or less, there is no practical problem, and if it is 30 ppm / K or less, it is more preferable.
The lower the dielectric constant of polyimide, the better. However, if it is 2.8 or less, there is no practical problem, and if it is 2.75 or less, it is more preferable.
The polyimide film needs to exhibit sufficient film toughness. As an index, it is necessary that the film does not break by a 180 ° bending test.
Even if polyimide is not soluble in the solvent of the polyimide itself, if the polyimide precursor is soluble in the volatile organic solvent, there is no problem in forming the interlayer insulating film, but the polyimide is highly soluble in the organic solvent at room temperature. It is more desirable from the viewpoint of process simplification to be a stable varnish.
Polyimides are also required to have sufficiently high thermal oxidation stability. As an index, if the 5% weight loss temperature measured in an air atmosphere is 400 ° C. or higher, there is no practical problem, and 420 ° C. or higher is more preferable.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, it is not limited to these Examples. The physical property values in the following examples were measured by the following methods.

<Infrared absorption spectrum>
The infrared absorption spectrum of the tetracarboxylic dianhydride of the present invention was measured by the KBr method using a Fourier transform infrared spectrophotometer (FT-IR5300 manufactured by JASCO Corporation). Further, an infrared absorption spectrum of the polyimide thin film (5 μm thickness) of the present invention was measured by a transmission method.

^<1 H-NMR spectrum>
A ¹ H-NMR spectrum of the tetracarboxylic dianhydride of the present invention was measured in deuterated dimethyl sulfoxide using a JEOL NMR spectrophotometer (ECP400).
<Differential scanning calorimetry (melting point and melting curve)>
The melting point and melting curve of the tetracarboxylic dianhydride of the present invention were measured at a temperature rising rate of 5 ° C./min in a nitrogen atmosphere using a differential scanning calorimeter (DSC3100) manufactured by Bruker Ax. The higher the melting point and the sharper the melting peak, the higher the purity.

<Intrinsic viscosity>
A 0.5 mass% solution of the polyimide precursor of the present invention was measured at 30 ° C. using an Ostwald viscometer.

<Glass transition temperature: Tg>
Tests using a thermomechanical analyzer (TMA4000) manufactured by Bruker Ax Co., Ltd. with a static load of 0.5 g / film thickness of 1 μm (static load of 10 g when the film thickness is 20 μm) and a heating rate of 5 ° C./min. The elongation of the piece was measured, tangent lines were drawn on the curves before and after the temperature at which the test piece suddenly stretched, and the glass transition temperature (Tg) was determined from the intersection of these tangent lines.

<Linear thermal expansion (coefficient): CTE>
Using a thermal mechanical analysis apparatus (TMA4000) manufactured by Bruker Ax, a test at a load of 0.5 g / film thickness of 1 μm (static load of 10 g when the film thickness is 20 μm) and a temperature rising rate of 5 ° C./min. From the elongation of the piece, the linear thermal expansion coefficient of the polyimide film (20 μm thickness) of the present invention was determined as an average value in the range of 100 to 150 ° C. which is not higher than the glass transition temperature.

<5% weight loss temperature: T _d ⁵ >
Using a thermogravimetric analyzer (TG-DTA2000) manufactured by Bruker Ax, the initial weight of the polyimide film (20 μm thickness) is 5% in the temperature rising process at a heating rate of 10 ° C./min in nitrogen or air. The temperature at the time of decrease was measured. Higher values indicate higher thermal stability.

<Dielectric constant: ε _cal >
Based on the average refractive index [n _av = (2n _in + n _out ) / 3] of the polyimide film using an Abbe refractometer (Abbe 4T) manufactured by Atago Co., the following formula: ε _cal = 1.1 × n _av ² The dielectric constant (ε _cal ) of the polyimide film corresponding to a frequency of 1 MHz was calculated.

[Example 1]
<Synthesis of ester group-containing tetracarboxylic dianhydride>
The tetracarboxylic dianhydride of the present invention represented by the formula (11) (hereinafter also referred to as TATFBP) was synthesized from a diol (DHTFMB) represented by the formula (13) and trimellitic anhydride chloride. First, DHTFMB was synthesized as follows. 2.20 g (10 mmol) of 2,2′-bis (trifluoromethyl) benzidine (TFMB) was placed in a 500 mL eggplant-shaped flask, and 100 mL of water was added and stirred to suspend. To this, 24 mL (100 mmol) of concentrated hydrochloric acid was added and stirred to give A solution. A 50 mL eggplant-shaped flask was charged with 1.38 g (30 mmol) of sodium nitrite, and 8 mL of water was added to dissolve it to prepare a solution B. The solution B was quickly added to the solution A cooled in an ice bath with a syringe while stirring. After stirring for 2 hours, 0.1 g of urea was added to decompose unreacted sodium nitrite, and the mixture was further stirred for 30 minutes to obtain solution C. Next, 7 mL of phosphoric acid and 600 mL of water were placed in a 1 L three-necked flask, and a reflux tube was attached and heated to 120 ° C. in a nitrogen atmosphere. The solution C was slowly added to this aqueous solution, and hydrolyzed by refluxing at 120 ° C. for 1 hour. After cooling to room temperature, the product was extracted with diethyl ether, and the solvent was distilled off with an evaporator to obtain an orange oily product. Water and activated carbon were added thereto for decolorization, followed by hot filtration, and water was removed by an evaporator to obtain a pale yellow solid. Finally, recrystallization and vacuum drying were performed with cyclohexane to obtain white crystals with a yield of 43%. It was confirmed that the product obtained from the FT-IR spectrum and the ¹ H-NMR spectrum was the target diol represented by the formula (13). The analysis results are shown below.
FT-IR: 3316 cm ⁻¹ (phenolic OH group), 1593 cm ⁻¹ (biphenylene group)
¹ H-NMR: δ 10.2 ppm (OH, 2H), δ 7.0 to 7.1 ppm (C _arom H on biphenylene group, 6H)
DSC: melting point 149.9 ° C.

Next, the tetracarboxylic dianhydride (TATFBP) of the present invention represented by the formula (11) was synthesized from trimellitic anhydride chloride and DHTFMB obtained as described above as follows. First, 4.21 g (20 mmol) of trimellitic chloride was placed in an eggplant-shaped flask, and 18.9 mL of dehydrated tetrahydrofuran (THF) was added and dissolved, followed by septum sealing to prepare Solution A. Further, in another flask, 3.22 g (10 mmol) of DHTFMB was dissolved in 14.5 mL of THF, 2.42 mL (30 mmol) of pyridine was added thereto and dissolved, and a septum was sealed to prepare Solution B.
Solution B was added dropwise with stirring to solution A cooled in an ice bath, and the mixture was stirred for 3 hours, and then stirred at room temperature for 12 hours. Precipitated white pyridine hydrochloride was filtered off, the solvent was distilled off from the filtrate with an evaporator, and the precipitate was washed repeatedly with water to remove pyridine. The product was vacuum-dried at 80 ° C. for 12 hours, an appropriate amount of acetic anhydride was further added, and the mixture was heated at 120 ° C. for 3 hours to completely close the partially opened acid anhydride group. Toluene was added thereto to remove acetic anhydride azeotropically, and the resulting white solid was vacuum dried at 120 ° C. for 24 hours to obtain a crude product in a yield of 42%. Finally, it was recrystallized with toluene (recrystallization yield: 92%) and dried in vacuo at 120 ° C. for 24 hours to obtain white crystals. The product obtained from the FT-IR spectrum (FIG. 1) and the ¹ H-NMR spectrum (FIG. 2) is the target tetracarboxylic dianhydride represented by the formula (11), and the product of melting by differential thermal analysis is The endothermic peak (FIG. 3) was very sharp, confirming that the product was highly pure. The analysis results are shown below.
FT-IR: 1856 cm ⁻¹ , 1784 cm ⁻¹ (acid anhydride group C═O stretching vibration), 1750 cm ⁻¹ (ester group C═O stretching vibration)
DSC: melting point 245.3 ° C.

[Example 2]
<Polymerization of polyimide precursor, imidization and evaluation of polyimide film characteristics>
In a well-dried sealed reaction vessel with a stirrer, 3 mmol of 2,2′-bis (trifluoromethyl) benzidine (hereinafter referred to as TFMB) was placed, and N, N-dimethylacetamide (DMAc) sufficiently dehydrated with molecular sieves 4A was added. After dissolution, 3 mmol of tetracarboxylic dianhydride powder (TATFBP) of the present invention represented by the formula (11) was added to this solution all at once (solute concentration: 30% by mass). After stirring at room temperature for 24 hours, the solution viscosity increased and it became difficult to stir. Therefore, the solution was appropriately diluted with the same solvent up to 16% by mass and stirred for a total of 72 hours to obtain a uniform and viscous polyimide precursor solution. This polyimide precursor solution did not precipitate or gel at all even when allowed to stand at room temperature and −20 ° C. for one month, and showed high solution storage stability. The intrinsic viscosity of the polyimide precursor measured with an Ostwald viscometer in DMAc at a concentration of 0.5% by mass at 30 ° C. was 1.75 dL / g, which was a high polymer.
The polyimide precursor film obtained by applying this polyimide precursor solution to a glass substrate and drying at 60 ° C. for 2 hours was subjected to thermal imidization on the substrate at 350 ° C. for 1 hour in a vacuum, and then the residual stress was reduced. In order to remove, it peeled off from the board | substrate and heat-processed at 350 degreeC in vacuum for 1 hour, and obtained the pale yellow polyimide film with a film thickness of 20 micrometers. Further, it was possible to easily chemically imidize by adding dropwise an excess amount of acetic anhydride / pyridine (volume ratio 7/3) to the polyimide precursor solution while stirring and stirring at room temperature for 24 hours. At this time, the reaction solution did not gel. After completion of chemical imidation, the reaction solution was dropped into a large amount of methanol, and the polyimide was precipitated and filtered, washed sufficiently with methanol, and then vacuum dried at 100 ° C. to obtain a polyimide powder. When the infrared absorption spectrum was measured, it was confirmed that the chemical imidization was almost completed. This polyimide powder exhibited high solubility (5% by mass or more) at 25 ° C. in a wide range of organic solvents such as DMAc, N-methyl-2-pyrrolidone (NMP), cyclopentanone, and cyclohexanone.
The polyimide film obtained by thermal imidization was flexible without being broken even by a 180 ° bending test. The resulting polyimide film with a film thickness of 20 μm has a glass transition temperature of 268 ° C., and a 5% weight loss temperature of 463 ° C. in a nitrogen atmosphere and 428 ° C. in an air atmosphere, exhibiting sufficiently high heat resistance and thermal stability, The coefficient of linear thermal expansion (CTE) was a relatively low value of 28.9 ppm / K. Further, the dielectric constant estimated from the average refractive index was 2.75, which was a very low value for wholly aromatic polyimides. Also, a polyimide varnish obtained by dissolving the above polyimide powder in DMAc is coated on a glass substrate, dried, and heat-treated under the same conditions. The physical properties were almost the same as the polyimide film prepared. The FT-IR spectrum of the polyimide thin film is shown in FIG.

[Example 3]
<Synthesis of amide group-containing tetracarboxylic dianhydride>
The amide group-containing tetracarboxylic dianhydride (hereinafter referred to as TATFMB) represented by the formula (12) is 2,2′-bis (trifluoromethyl) benzidine (hereinafter referred to as TFMB) and trimellitic acid. Synthesized from anhydride chloride. First, 4.21 g (20 mmol) of trimellitic chloride was placed in an eggplant-shaped flask, a mixed solvent consisting of 14 mL of ethyl acetate and 20 mL of n-hexane was added and dissolved, and a solution was prepared by sealing with a septum. On the other hand, 1.61 g (5 mmol) of TFMB was dissolved in another flask by adding a mixed solvent consisting of 6.5 mL of ethyl acetate and 7.6 mL of n-hexane, and 0.7 mL (10 mmol) of propylene oxide as a deoxidizer. And a septum was sealed to prepare solution B.
Solution B was added dropwise with stirring to solution A cooled in an ethanol ice bath, and the mixture was stirred for 3 hours, and then stirred at room temperature for 12 hours. The precipitate was filtered off and washed well with an ethyl acetate / n-hexane mixed solvent (volume ratio 1: 1) to remove excess trimellitic anhydride chloride and by-product chloropropanol. It was vacuum-dried at 12 ° C. for 12 hours to obtain a white product with a yield of 81%. This was vacuum-dried at 120 ° C. for 12 hours, recrystallized from an acetic anhydride / toluene mixed solution (volume ratio 1/10), and finally dried at 120 ° C. for 24 hours to obtain white crystals. The product obtained from the FT-IR spectrum and ¹ H-NMR spectrum was confirmed to be the target amide group-containing tetracarboxylic dianhydride represented by the formula (12). The analysis results are shown below.
FT-IR: 3378 cm ⁻¹ (amide group NH stretching vibration), 3108 cm ⁻¹ (aromatic C—H stretching vibration), 1858 cm ⁻¹ , 1782 cm ⁻¹ (acid anhydride group C═O stretching vibration), 1676 cm ⁻¹ (Amido group C = O stretching vibration)
¹ H-NMR: δ 11.06 ppm (s, NH, 2H), δ 8.65 ppm (s, on phthalimide, 3-position C _arom H, 2H), δ 8.37 ppm (on phthalimide, 5- and 6-position C _arom H, 4H ), Δ 7.46 ppm (d, 6 and _6′- position C _arom H, 2H on central biphenyl), δ 8.13 ppm (d, 5 and 5′-position C _arom H, 2H on central biphenyl), δ 8.27 ppm ( s, on central biphenyl, 3 and 3 ′ positions C _arom H, 2H),
DSC: melting point 267 ° C.

[Example 4]
Polyamic acid was polymerized, formed into a film, and thermally imidized in the same manner as described in Example 2 except that TATFMB was used in place of TATFBP as the tetracarboxylic dianhydride component, and physical properties were evaluated. The obtained polyamic acid had an intrinsic viscosity of 0.47 dL / g. The i-line transmittance of the polyamic acid film (10 μm thick) was 32.7%. The polyimide film (thickness 20 μm) was flexible without breaking even by a 180 ° bending test. The glass transition temperature was 303 ° C., and the linear thermal expansion coefficient was a relatively low value of 37.8 ppm / K. The mechanical properties were as high as a tensile modulus of 5.40 GPa and the elongation at break was 5.0%. The FT-IR spectra of the polyimide precursor and the polyimide thin film are shown in FIGS. 5 and 6, respectively.

[Example 5]
Polyamide in the same manner as described in Example 2, using TATFMB instead of TATFBP as the tetracarboxylic dianhydride component, and trans-1,4-cyclohexanediamine (hereinafter referred to as CHDA) instead of TFMB as the diamine component. Polymerization, film formation, and thermal imidization of the acid were performed to evaluate physical properties. The obtained polyamic acid had an intrinsic viscosity of 0.75 dL / g. The i-line transmittance of the polyamic acid film (10 μm thick) was 52.6%, indicating a relatively high transparency. The polyimide film (thickness 20 μm) was flexible without breaking even by a 180 ° bending test. The glass transition temperature was 321 ° C., and the linear thermal expansion coefficient was a relatively low value of 21.8 ppm / K. The mechanical properties were as high as a tensile modulus of 6.69 GPa and the elongation at break was 4.8%. The FT-IR spectrum of the polyimide thin film is shown in FIG.

[Example 6]
<Preparation of photosensitive resin composition and positive pattern formation>
2,3,4-tris (1-oxo-2-diazonaphthoquinone-5-sulfoxy) benzophenone as a diazonaphthoquinone photosensitizer was added and dissolved in the DMAc solution of polyamic acid obtained in the same manner as in Example 4. It apply | coated on the silicon wafer, it was made to dry in a hot air dryer at 80 degreeC for 2 hours, and the photosensitive resin composition film | membrane with a film thickness of 10 micrometers was formed. At this time, the concentration of the diazonaphthoquinone photosensitizer in the film is 30% by mass. Further, this film was pre-baked at 100 ° C. for 10 minutes in the air, and then irradiated with i-line (365 nm, irradiation light intensity = 150 mW / cm ² ) of an epi-illumination type high-pressure mercury lamp (Harrison Toshiba Lighting Co., Ltd. Toscue 251) through a photomask. Irradiated for 2 seconds. This was subjected to paddling development at 21 ° C. for 90 seconds in an aqueous solution of tetramethylammonium hydroxide (TMAH) containing 20% by volume of ethanol at 21 ° C., washed with ethanol, dried at 60 ° C., and line width of 20 μm. A clear relief pattern was obtained. Even after the thermal imidization in which this relief pattern was heated at 300 ° C., the pattern was not broken. FIG. 8 shows the SEM photograph.

[Example 7]
A photosensitive resin composition film was prepared in the same manner as in Example 6 except that the polyamic acid obtained in the same manner as in Example 4 was changed to the polyamic acid obtained in the same manner as in Example 5. Pattern formation was performed. At that time, development was performed at 21 ° C. for 20 seconds using a 2.38 mass% TMAH aqueous solution, and then rinsed with water. As a result, as in Example 6, a clear relief pattern having a line width of 20 μm was obtained. Even after the thermal imidization in which the relief pattern was heated at 300 ° C., the pattern was not broken. FIG. 9 shows the SEM photograph.

[Comparative Example 1]
In place of TATFBP of the present invention as tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride was used, and the polymerization reaction with TFMB was conducted in the same manner as described in Example 2. And a polyimide precursor was obtained. When a chemical imidizing agent was added to the varnish of the polyimide precursor, the reaction solution gelled and imidization could not be completed. Therefore, the film physical property was evaluated about the polyimide film produced by forming a polyimide precursor film | membrane and carrying out thermal imidation. The polyimide had a glass transition temperature of 314 ° C. and excellent heat resistance, but had a high dielectric constant of 2.93, which was insufficient as an interlayer insulating film material from the viewpoint of lowering the dielectric constant. Moreover, this polyimide did not show any solubility in solvents other than m-cresol, neither film nor powder, and had no solution processability.

  Since the polyimide of the present invention has low CTE, low dielectric constant, high Tg, oxygen plasma resistance and sufficient film toughness at the same time, it is very useful as an insulating film such as an interlayer insulating film of an integrated circuit.

2 is an FT-IR spectrum of white crystals obtained in Example 1. FIG. 2 is a ¹ H-NMR spectrum of white crystals obtained in Example 1. FIG. 2 is a chart by differential thermal analysis of white crystals obtained in Example 1. FIG. 4 is an FT-IR spectrum of the polyimide thin film obtained in Example 2. 4 is an FT-IR spectrum of the polyimide precursor thin film obtained in Example 4. 4 is an FT-IR spectrum of the polyimide thin film obtained in Example 4. 4 is an FT-IR spectrum of the polyimide thin film obtained in Example 5. 7 is a SEM photograph of a positive pattern of polyimide in Example 6. (Magnification 300 times, L & S = 20μm) 10 is a SEM photograph of a positive pattern of polyimide in Example 7. (Magnification 300 times, L & S = 20μm)

Claims (5)

A tetracarboxylic dianhydride represented by the formula (1).

(In the formula (1), X represents an oxygen atom or an NH group.) The polyimide precursor which has a repeating unit represented by Formula (2).

(In formula (2), X has the same meaning as described in claim 1, Y represents a divalent aromatic group or aliphatic group, R represents a hydrogen atom, a silyl group, or a carbon atom number of 1 to 12. Any one of the straight-chain or branched alkyl groups may be mixed, and these may be mixed.) The polyimide which has a repeating unit represented by Formula (3).

(In formula (3), X and Y are as defined in formula (2).) The polyimide according to claim 3, wherein in the formula (3), the structural unit Y is selected from the following formulas (4) to (6).
An interlayer insulating film of an integrated circuit comprising the polyimide according to claim 3 or 4.