JP4190368B2 - Process for producing B, B ', B "-trialkyl-N, N', N" -trialkylborazine - Google Patents

Description

  The present invention relates to a process for producing B, B ′, B ″ -trialkyl-N, N ′, N ″ -trialkylborazine. The borazine ring-containing compound, which is a low dielectric material produced by the production method of the present invention, can be used, for example, to form an interlayer insulating film for semiconductor, a barrier metal layer, and an etch stopper layer.

  As the performance of information equipment increases, LSI design rules become finer year by year. In the manufacture of LSIs with fine design rules, the materials that make up LSIs must also have high performance and function on fine LSIs.

  For example, regarding materials used for interlayer insulating films in LSIs, a high dielectric constant causes signal delay. In a fine LSI, the influence of this signal delay is particularly great. For this reason, development of a new low dielectric material that can be used as an interlayer insulating film has been desired. In addition, in order to be used as an interlayer insulating film, not only the dielectric constant is low, but also properties such as moisture resistance, mechanical strength, heat resistance, and mechanical strength are required to be excellent.

  As a response to such a demand, a borazine ring-containing compound having a borazine ring skeleton in the molecule has been proposed (see, for example, Patent Document 1). Since the compound having a borazine ring skeleton has a low molecular polarizability, the formed film has a low dielectric constant. In addition, the formed film is excellent in heat resistance.

  Various compounds have been proposed as borazine ring-containing compounds. For example, a borazine ring-containing compound in which a boron moiety is substituted with an alkyl group has very excellent characteristics as a low dielectric material (see, for example, Patent Document 2). As a method for producing a borazine ring-containing compound in which a boron moiety is substituted with an alkyl group, a halogenated borazine such as N-alkyl-B-trichloroborazine is used as a starting material, and the halogenated borazine is halogenated using a Grignard reagent. A method of substituting an alkyl group with an atom is known (for example, see Non-Patent Document 1).

When a borazine ring-containing compound is synthesized by the Grignard method using halogenated borazine as a raw material, a certain amount of halogen is inevitably contained in the product. When a borazine ring-containing compound is applied to a semiconductor material, halogen, which is an impurity contained in the borazine ring-containing compound, has a large adverse effect on the characteristics of the material. Therefore, the halogen contained in the borazine ring-containing compound must be removed to the smallest possible extent. As a method for producing an organic compound, distillation, recrystallization, sublimation purification, and the like are known. Sublimation purification is useful for purification of an organic compound that is difficult to be distilled, such as hexamethylborazine. However, purification by sublimation has low purification efficiency, and even if a borazine ring-containing compound containing halogen as an impurity is sublimated and purified, halogen remains in the resulting product at a concentration of several hundred ppm or even higher.
JP 2000-340689 A JP 2003-119289 A D. T. T. HAWORTH and L.H. F. HOHNSTEDT, J.A. Am. Chem. Soc. , 82, 3860 (1960)

  The object of the present invention is to provide a means for producing B, B ', B "-trialkyl-N, N', N" -trialkylborazines with low halogen content.

  In the present invention, a trialkylborane represented by the following chemical formula 1 is reacted with an alkylamine represented by the following chemical formula 2 under pressure, B, B ′, B ″ -trialkyl-N, N ′, This is a method for producing N ″ -trialkylborazine.

(Wherein R ¹ is an alkyl group having 1 to 6 carbon atoms, and R ¹ may be the same or different)

(Wherein, ^{R 2} is an alkyl group having 1 to 6 carbon atoms, when three of ^{R 1} in Chemical Formula 1 are identical, ^{R 2} is different from ^{R 1)}
That is, in the production method of the present invention, B, B ′, B ″ -trialkyl-N, N ′, N ″ -trialkylborazine (hereinafter also referred to as TATAB) is synthesized by the following reaction.

  If the manufacturing method of this invention is used, a halogen atom will not be contained in the compound used as a raw material. For this reason, TATAB containing a very small amount of halogen or containing no halogen is obtained. TATAB produced by the production method of the present invention is suitable for various applications where a low halogen content is desired. For example, when TATAB manufactured by the manufacturing method of the present invention is used, an interlayer insulating film having a low halogen content and excellent characteristics can be formed.

  Moreover, if the manufacturing method of this invention is used, TATAB which is a target object will be synthesize | combined by the reaction of one step from the trialkyl borane and alkylamine which are raw materials. For this reason, the production process is simple compared to a reaction route using a Grignard reagent, which requires a two-stage reaction of halogenation and Grignard reaction. Since the manufacturing process is simple, the manufacturing cost and the equipment cost can be reduced.

Furthermore, TATAB produced by the production method of the present invention can be purified by distillation. As hexamethyl borazine, when R ² is identical in R ¹ and Formula 2 in Formula 1, but it was difficult to purify by distillation, TATAB manufactured by the manufacturing method of the present invention, Purified by distillation. Therefore, the manufacturing method of the present invention is easy to apply to an industrial production process.

  Hereinafter, the present invention will be described in detail.

  In the production method of the present invention, a trialkylborane represented by the following formula 1 is used as one of the raw materials.

In the formula, R ¹ is an alkyl group having 1 to 6 carbon atoms. Specifically, R ¹ is a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group, an iso-butyl group, a tert-butyl group, a 1-methylbutyl group, Examples include 2-methylbutyl group, neo-pentyl group, 1,2-dimethylpropyl group, 1-ethylpropyl group, n-hexyl group, cyclohexyl group and the like. In trialkylborane, three alkyl groups are bonded to one boron atom, but the three alkyl groups may be the same or different. In view of synthesis and availability, the three alkyl groups are preferably the same.

  Specific examples of the trialkylborane include trimethylborane, triethylborane, tri (n-propyl) borane, tri (iso-propyl) borane, tri (n-butyl) borane, tri (sec-butyl) borane, and tri (iso). -Butyl) borane, tri (tert-butyl) borane, tri (1-methylbutyl) borane, tri (2-methylbutyl) borane, tri (neo-pentyl) borane, tri (1,2-dimethylpropyl) borane, tri ( 1-ethylpropyl) borane, tri (n-hexyl) borane, tri (cyclohexyl) borane and the like. Of these, triethylborane is preferred from the viewpoint of industrial availability. Trialkylborane may be synthesized using a known production method, or a commercially available product may be used.

  As another raw material, an alkylamine represented by the following formula 2 is used.

Wherein, ^{R 2} is an alkyl group having 1 to 6 carbon atoms. Specifically, R ² is methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, sec-butyl group, iso-butyl group, tert-butyl group, 1-methylbutyl group, Examples include 2-methylbutyl group, neo-pentyl group, 1,2-dimethylpropyl group, 1-ethylpropyl group, n-hexyl group, cyclohexyl group and the like.

R ² in R ¹ and Formula 2 in Formula 1, but each an alkyl group, the three R ¹ and one R ^2, at least one is a different alkyl group. That is, R ¹ and R ² are selected such that not all of R ¹ and R ² are the same alkyl group. Specifically, when three of R ¹ in Chemical Formula 1 are identical, R ² is a different alkyl group R ^1.

The reason why the alkyl group is selected so that all of R ¹ and R ² are not the same is because of the distillation purification of TATAB to be synthesized. B, B ', B "-trimethyl-N, N', N" -trimethylborazine, B, B ', B "-triethyl-N, N', N" -triethylborazine, B, B ', B "- If R ¹ and R ² in TATAB are the same, such as tripropyl-N, N ′, N ″ -tripropylborazine, distillation purification is difficult and it is difficult to apply to products. TATAB produced in the present invention is an alkyl group in which at least one of alkyl groups bonded to a boron atom and a nitrogen atom is different, and can be easily purified by distillation. R ¹ and how to combine the alkyl group constituting the R ² is not particularly limited, considering the easiness of the feed synthesis, three of R ¹ are the same and is an alkyl group R ² is different from R ¹ . For example, trialkylborane is triethylborane and alkylamine is methylamine.

  Specific examples of the alkylamine include methylamine, ethylamine, (n-propyl) amine, (iso-propyl) amine, (n-butyl) amine, (sec-butyl) amine, (iso-butyl) amine, (tert -Butyl) amine, (1-methylbutyl) amine, (2-methylbutyl) amine, (neo-pentyl) amine, (1,2-dimethylpropyl) amine, (1-ethylpropyl) amine, (n-hexyl) amine , (Cyclohexyl) amine and the like. Of these, methylamine is preferred from the viewpoint of the heat resistance of the synthesized compound. The alkylamine may be synthesized using a known production method, or a commercially available product may be used.

  The reaction between the trialkylborane and the alkylamine proceeds under pressure. Here, “under pressure” means a state where the pressure is higher than the atmospheric pressure. The trialkylborane and the alkylamine react under a predetermined pressure and a predetermined temperature condition. The reaction may proceed in the liquid phase or in the gas phase. Hereinafter, it demonstrates along a process.

  First, trialkylborane and alkylamine are supplied to the reaction vessel. The trialkylborane and alkylamine are preferably supplied such that equimolar amounts of trialkylborane and alkylamine are present. Specifically, the alkylamine is preferably supplied in an amount of 1 to 2 mol, more preferably 1 to 1.2 mol, per 1 mol of the trialkylborane.

  Two or more trialkylboranes and alkylamines may be used in combination in some cases, but it should be noted that when a plurality of types of raw materials are used, a plurality of products are produced and the reaction becomes difficult to control. It is. However, for example, when there are special circumstances such as improving the characteristics of the borazine ring-containing compound obtained by using two or more kinds of trialkylborane or alkylamine together, a plurality of raw materials may be used in combination. Good.

  The timing for supplying the trialkylborane and alkylamine to the reaction vessel is not particularly limited. After supplying the total amount of trialkylborane and alkylamine to the reaction vessel, the pressure and / or temperature may be changed to the reaction conditions, or the pressure and / or temperature inside the reaction vessel containing either one is used as the reaction conditions. After the change, the other may be supplied to the reaction vessel.

  The reaction vessel in which the reaction between the trialkylborane and the alkylamine proceeds is not particularly limited. However, it is necessary to have pressure resistance enough to withstand the reaction pressure described later. When the reaction scale is small, a pressure vessel such as an autoclave can be used. When the reaction is allowed to proceed on an industrial large scale, the apparatus may be designed with reference to known technical knowledge regarding high-pressure equipment.

  When the trialkylborane and the alkylamine are supplied to the reaction vessel, the inside of the reactor is changed to a predetermined pressure and a predetermined temperature to advance the reaction.

  The pressure in the reaction between the trialkylborane and the alkylamine is preferably 10 to 30 atm, more preferably 15 to 25 atm. If the pressure is too low, the reaction may not proceed. Moreover, when the pressure is too high, the reaction proceeds rapidly, and there is a risk that sudden heat generation occurs. The pressure may be unchanged throughout the reaction or may vary. Further, the pressure may not be within the above range throughout the reaction period. For example, in an embodiment in which the reaction is started by gradually increasing the pressure and the reaction proceeds sufficiently, and then the pressure is gradually decreased, the reaction usually proceeds slightly even if the pressure is outside the predetermined pressure range. . Such an embodiment does not depart from the technical scope of the present invention, and may belong to the technical scope of the present invention as long as the reaction proceeds under pressure, preferably within the above pressure range. The pressure during the reaction can be measured using a known pressure gauge such as a pressure gauge. In order to raise the pressure of the reaction system to a predetermined pressure, known pressurizing means can be used.

  The temperature in the reaction between the trialkylborane and the alkylamine is preferably 250 to 500 ° C, more preferably 300 to 450 ° C. If the temperature is too low, the reaction may not proceed. If the temperature is too high, the compound may be decomposed. The temperature may be constant throughout the reaction or may vary. For example, in order to prevent a large amount of reaction heat from being generated, the reaction is allowed to proceed at a relatively low temperature in the initial stage of the reaction, and when the reaction becomes slow, the reaction temperature is increased. In addition, the temperature may not be within the above range throughout the reaction period. For example, in an embodiment in which the reaction is started by gradually increasing the temperature and the reaction proceeds sufficiently, and then the temperature is gradually decreased, the reaction usually proceeds slightly even if the temperature is out of a predetermined temperature range. . Such an embodiment does not depart from the technical scope of the present invention. The temperature during the reaction can be measured using a known temperature measuring means.

  The reaction time between the trialkylborane and the alkylamine is not particularly limited. Depending on the amount of trialkylborane and alkylamine used, the size of the reaction vessel, the pressure and the reaction temperature, the reaction time should be determined. The general reaction time is about 1 to 10 hours. However, the reaction time is not limited to this range.

  The atmosphere around the reaction solution is not particularly limited. For example, nitrogen or argon is used. When the reaction product is taken out, the atmosphere around the product is preferably replaced with an inert gas such as nitrogen or argon.

  In the production method of the present invention, as described above, the target TATAB is synthesized from the starting materials trialkylborane and alkylamine in a one-step reaction. In the case of synthesizing TATAB using a Grignard reagent, at least a two-stage reaction of halogenation of a raw material compound and a Grignard reaction is necessary. Therefore, by using the manufacturing method of the present invention, the manufacturing process can be simplified, and the manufacturing cost and equipment cost can be reduced.

  After the TATAB synthesis reaction is completed, TATAB is preferably purified. Preferably, TATAB is purified by distillation. Even if TATAB synthesized by the Grignard method is purified by distillation, it is difficult to greatly reduce the halogen contained in TATAB. Since TATAB of the present invention can be synthesized using a halogen-free compound as a raw material, the halogen content in the product can be reduced to a very small amount. Further, as described above, if the alkyl group bonded to the boron atom and nitrogen atom forming the borazine ring is the same, it is difficult to purify TATAB by distillation. To purify such compounds, other purification methods such as sublimation purification need to be used. Sublimation purification is relatively time consuming and it is difficult to reduce impurities to the order of ppm. On the other hand, TATAB produced by the production method of the present invention can be purified by distillation. For this reason, purification is easy and it is suitable for industrial production.

  The produced borazine ring-containing compound is not particularly limited, but can be used for forming an interlayer insulating film for a semiconductor, a barrier metal layer, an etch stopper layer, and the like. The borazine ring-containing compound used in that case may be TATAB obtained by the above reaction, or may be a borazine ring-containing compound that has been further modified. A polymer obtained by polymerizing a borazine ring-containing compound may be used as a raw material for an interlayer insulating film for a semiconductor, a barrier metal layer, or an etch stopper layer. A polymer formed from a borazine ring-containing compound can be formed using a compound having a borazine ring skeleton as a monomer. A polymerization method and a polymerization form are not particularly limited. The polymerization method is selected depending on the functional group bonded to the borazine ring. For example, when an amino group is bonded, a polymer can be synthesized by condensation polymerization. When a vinyl group or a functional group containing a vinyl group is bonded to the borazine ring, a polymer can be formed by radical polymerization using a polymerization initiator. The polymer may be a homopolymer or a copolymer composed of two or more monomer units. The form of the copolymer may be any of a random copolymer, a block copolymer, a graft copolymer, and the like. If a monomer having three or more functional groups capable of forming a bond with another monomer is used, it is possible to obtain a polymer in which the monomers are bonded in a network.

  In order to form an interlayer insulating film for semiconductor, a barrier metal layer or an etch stopper layer using a borazine ring-containing compound, a solution-like or slurry-like composition containing the borazine ring-containing compound is prepared and applied. A method for forming a coating film can be used. The solvent used to dissolve or disperse the borazine ring-containing compound is not particularly limited as long as it can dissolve the borazine ring-containing compound and other components added as necessary. Examples of the solvent include alcohols such as ethylene glycol and ethylene glycol monomethyl ether; aromatic hydrocarbons such as toluene, benzene and xylene; hydrocarbons such as hexane, heptane and octane; tetrahydrofuran, diglyme and tetraglyme. Can be used. These may be used alone or in combination of two or more. In the case of film formation using spin coating, diglyme is preferred. When diglyme or a derivative thereof is used as a solvent, the uniformity of the produced film is improved. Moreover, the cloudiness of the film can be prevented. The amount of the solvent used for dissolving or dispersing the borazine ring-containing compound is not particularly limited, and may be determined according to the means for producing the low dielectric material. For example, when a film is formed by spin coating, the solvent and the amount of the solvent may be determined so that the viscosity is suitable for spin coating.

  The composition containing the borazine ring-containing compound is supplied to a desired site and solidified by drying. For example, in order to form a semiconductor interlayer insulating film, it may be applied onto a substrate by spin coating and dried. If a coating with the desired thickness cannot be obtained by a single coating and drying, the coating and drying may be repeated until the desired thickness is obtained. Film formation conditions such as the spin coater rotation speed, drying temperature, and drying time are not particularly limited.

  Application to the substrate may use a technique other than spin coating. For example, spray coating, dip coating, etc. can be used.

  Thereafter, the coating film is dried. The drying temperature of the coating film is usually about 100 to 250 ° C. The drying temperature here means the maximum temperature at the time of drying treatment. For example, when the drying temperature is gradually increased and maintained at 100 ° C. for 30 minutes and then cooled, the drying temperature is 100 ° C. The firing temperature can be measured using a thermocouple. The drying time of the dried film is not particularly limited. What is necessary is just to determine suitably considering characteristics, such as a dielectric constant and moisture resistance, about the low dielectric material obtained.

<Example 1>
The autoclave was charged with methylamine (10.4 g) as an alkylamine and triethylborane (32.7 g) as a trialkylborane, and reacted at 310 ° C. at 20 atm for 4 hours and then at 450 ° C. at 20 atm for 4 hours. After completion of the reaction, the contents were taken out under a nitrogen atmosphere and purified by distillation under reduced pressure at 98 ° C./1.8 mmHg to obtain B, B ′, B ″ -triethyl-N, N ′, N ″ -trimethylborazine (8.2 g). Was taken out. When the halogen content of the obtained B, B ′, B ″ -triethyl-N, N ′, N ″ -trimethylborazine was measured, Cl <0.1 ppm and Br <0.1 ppm were obtained.

<Comparative Example 1>
B, B ′, B ″ -trichloro-N, N ′, N ″ -trimethylborazine (74 g) synthesized from boron trichloride and methylamine hydrochloride was placed in diethyl ether (150 mL). To the reaction solution, a 3.0 M ethylmagnesium bromide / diethyl ether solution (450 mL) was added dropwise at room temperature over 4 hours to initiate the Grignard reaction. After completion of the dropwise addition, the reaction was allowed to proceed by stirring for 24 hours at room temperature. After completion of the reaction, the reaction solution was filtered under a nitrogen atmosphere, and the solvent was distilled off from the filtrate under reduced pressure. The obtained solid was purified by distillation under reduced pressure at 98 ° C./1.8 mmHg, and B, B ′, B ″ -triethyl-N, N ′, N ″ -trimethylborazine (36 g) was taken out. When the halogen content of the obtained B, B ′, B ″ -triethyl-N, N ′, N ″ -trimethylborazine was measured, Cl = 14.4 ppm and Br = 51.7 ppm.

<Evaluation>
When TATAB is produced from alkylamine and trialkylborane according to the production method of the present invention, the halogen content in the obtained TATAB is low. TATAB formed by the production method of the present invention is suitable for applications where halogen contamination is not desirable, such as semiconductor interlayer insulating films.

Claims (3)

B, B ′, B ″ -trialkyl-N, N ′, N ″ -tri, wherein a trialkylborane represented by the following chemical formula 1 is reacted with an alkylamine represented by the following chemical formula 2 under pressure A method for producing alkylborazine.

(Wherein R ¹ is an alkyl group having 1 to 6 carbon atoms, and R ¹ may be the same or different)

(Wherein, ^{R 2} is an alkyl group having 1 to 6 carbon atoms, when three of ^{R 1} in Chemical Formula 1 are identical, ^{R 2} is different from ^{R 1)}   The production method according to claim 1, wherein the trialkylborane is triethylborane and the alkylamine is methylamine.   The production method according to claim 1 or 2, wherein the obtained B, B ', B "-trialkyl-N, N', N" -trialkylborazine is purified by distillation.