JP5546723B2 - Method for producing N-alkylborazine - Google Patents

Description

  The present invention relates to a method for producing N-alkylborazine. N-alkylborazine is used, for example, to form a semiconductor interlayer insulating film, 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. Further, in order to be used as an interlayer insulating film, it is necessary not only to have a low dielectric constant but also to be excellent in characteristics such as moisture resistance, heat resistance and mechanical strength.

  As a response to such a demand, borazine compounds having a borazine ring skeleton in the molecule have been proposed (see, for example, Patent Document 1 and Patent Document 2). Since a borazine 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.

  As one of borazine compounds, there is N-alkylborazine in which a nitrogen atom constituting a borazine ring is bonded to an alkyl group. N-alkylborazine itself can be used as a raw material for an interlayer insulating film for semiconductors. It also serves as an intermediate when producing other borazine compounds. For example, a hexaalkylborazine is produced by replacing a hydrogen atom bonded to boron of N-alkylborazine with an alkyl group.

In consideration of application to precision equipment such as an interlayer insulating film, it is preferable to reduce the content of impurities contained in the N-alkylborazine to a very small amount, and various purification methods can be employed. For example, N-alkylborazine contains N-alkylcycloborazanes and boron ether compounds by-produced in the synthesis reaction of N-alkylborazine, but the content of these impurities is reduced by distillation purification and filtration. (See Patent Document 3).
JP 2000-340689 A JP 2003-119289 A JP 2006-213642 A

  However, when the liquid after completion of the synthesis of N-alkylborazine is purified by distillation for the purpose of removing impurities, a large amount of precipitate may adhere to the cooler or the distillation line. If the deposit adheres and accumulates, the distillation column may be clogged, so that stable operation becomes difficult. Furthermore, in order to periodically remove and wash such precipitates, it is necessary to stop distillation, which causes problems such as a decrease in productivity.

  Therefore, the object of the present invention is to solve the problem of deposits adhering to the cooling section of the distillation apparatus during the distillation purification after the completion of synthesis during the production of N-alkylborazine, and provide means for improving productivity. It is to be.

In view of the above problems, the present inventors examined impurities contained in the synthesized N-alkylborazine. In the process, in addition to the above-mentioned N-alkylcycloborazane and boron ether compound, amine borane (RNH ₂ -BH ₃ , where R is an alkyl group) as a reaction intermediate causes the above-mentioned precipitates I found out that Further, the present inventors distillatively purify a solution having a content of the amine borane with respect to the N-alkylborazine in a solution containing the synthesized N-alkylborazine, thereby preventing the deposits from adhering. As a result, it was found that clogging of the distillation tower was prevented and the present invention was completed.

That is, the present invention relates to an alkali borohydride represented by ABH ₄ (A is a lithium atom, a sodium atom or a potassium atom), (RNH ₃ ) _n X (R is an alkyl group, and X is sulfuric acid. A method of producing N-alkylborazine, which comprises a step of reacting an amine salt represented by a group or a halogen atom and n is 1 or 2 in a solvent to synthesize N-alkylborazine. a liquid containing the N- alkylborazine, and the _RNH 2 _-BH 3 (R is an alkyl group) or less 3 mol% relative to the N- alkylborazine content of amine borane represented by the liquid A method for producing N-alkylborazine, comprising a step of purifying N-alkylborazine by distillation.

The present invention also relates to an alkali borohydride represented by ABH ₄ (A is a lithium atom, a sodium atom or a potassium atom), (RNH ₃ ) _n X (R is an alkyl group, and X is sulfuric acid. A method of producing N-alkylborazine, which comprises a step of reacting an amine salt represented by a group or a halogen atom and n is 1 or 2 in a solvent to synthesize N-alkylborazine. , reduce the content of amine borane represented by _RNH 2 _-BH 3 from the first liquid is a liquid containing the N- alkylborazine (R is an alkyl group) below 3 mol% relative to the N- alkylborazine A method for producing N-alkylborazine, comprising a step of obtaining a second liquid, and a step of purifying N-alkylborazine from the second liquid by distillation purification.

In addition, the present invention includes N-alkylborazine, amine borane represented by RNH ₂ -BH ₃ (R is an alkyl group), and a solvent, and the content of the amine borane is 3 mol with respect to the N-alkylborazine. % Or less.

The present invention _further, RNH (the R is an alkyl group) 2 _-BH 3 or less 0.5 mol% with respect to the amine borane content is N- alkylborazine represented by a N- alkylborazine.

  According to the present invention, a problem that precipitates are generated in the cooling section during distillation purification of N-alkylborazine is prevented. Moreover, the purity of the distilled purified product can be improved.

In the first aspect of the present invention, an alkali borohydride represented by ABH ₄ (A is a lithium atom, a sodium atom or a potassium atom), (RNH ₃ ) _n X (R is an alkyl group, X is A method of producing N-alkylborazine, which comprises a step of reacting an amine salt represented by a sulfuric acid group or a halogen atom and n is 1 or 2 in a solvent to synthesize N-alkylborazine. And a liquid containing an N-alkylborazine and an amine borane content represented by RNH ₂ -BH ₃ (R is an alkyl group) of 3 mol% or less with respect to the N-alkylborazine. It is a manufacturing method of N-alkyl borazine including the process of refine | purifying N-alkyl borazine by distilling.

In the second aspect of the present invention, an alkali borohydride represented by ABH ₄ (A is a lithium atom, a sodium atom or a potassium atom) and (RNH ₃ ) _n X (R is an alkyl group, X is a sulfuric acid group or a halogen atom, and n is 1 or 2). A method for producing N-alkylborazine comprising a step of synthesizing N-alkylborazine by reacting in a solvent The content of amine borane represented by RNH ₂ -BH ₃ (R is an alkyl group) from the first liquid which is a liquid containing the N-alkylborazine is ₃ mol% with respect to the N-alkylborazine. It is a manufacturing method of N-alkyl borazine including the process of obtaining the 2nd liquid reduced below, and the process of refine | purifying N-alkyl borazine by distillation purification from said 2nd liquid.

  In the production method of the present invention, an N-alkylborazine is synthesized by reacting an alkali borohydride and an amine salt in a solvent. Thereafter, the synthesized N-alkylborazine is further purified by distillation purification.

  When amine borane, which is one of the reaction intermediates, is contained in the liquid containing N-alkylborazine obtained by synthesis, amine borane having a vapor pressure is used in the cooling section and distillation of the distillation apparatus during distillation purification. Deposits and adheres to the exit line. Further, when the liquid is heated at a high temperature, precipitates are generated in the cooling section or the like. In the present invention, a method for effectively suppressing the adhesion and accumulation of precipitates is provided.

  In the first aspect of the present invention, a solution containing the N-alkylborazine and having a content of amine borane as a reaction intermediate of the N-alkylborazine is purified by distillation. In the second aspect of the present invention, a step of obtaining a second liquid having a reduced content of amine borane from the first liquid, which is a liquid containing the N-alkylborazine, is performed, and the obtained second liquid is purified by distillation. To do. By using a solution having an amine borane content of a predetermined value or less during distillation purification, precipitates derived from amine borane in distillation purification can be suppressed, and blockage of the distillation apparatus can be prevented. Here, the liquid containing N-alkylborazine means a liquid containing N-alkylborazine produced in the step of synthesizing N-alkylborazine (reaction step). The liquid containing N-alkylborazine may be in a slurry form or a liquid component after separating the liquid component and the solid component. Examples of the liquid containing N-alkylborazine include a liquid (reaction liquid) obtained in a synthesis step (reaction step) and a liquid obtained by purification. The liquid obtained by the purification may be a final purified product, such as a liquid obtained in the middle of purification, such as a liquid obtained by rough purification (crude distillation) of the reaction liquid. Also good.

  Next, the present invention will be described in detail.

First, an alkali borohydride represented by ABH ₄ (A is a lithium atom, a sodium atom or a potassium atom) and (RNH ₃ ) _n X (R is an alkyl group, X is a sulfate group or a halogen atom) And n is 1 or 2) to react with an amine salt in a solvent to synthesize N-alkylborazine.

In alkali borohydride (ABH ₄ ), A is a lithium atom, a sodium atom or a potassium atom. Examples of alkali borohydrides include sodium borohydride, lithium borohydride, and potassium borohydride. A combination of alkali borohydrides having different As may be used.

In the amine salt ((RNH ₃ ) _n X), R is an alkyl group, and X is a sulfate group or a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. And when X is a sulfate group, n is 2, and when X is a halogen atom, n is 1. When n is 2, R may be the same or different. In consideration of the yield of the synthesis reaction and the ease of handling, R is preferably the same alkyl group. The alkyl group may be linear, branched or cyclic. Although carbon number which an alkyl group has is not specifically limited, Preferably it is 1-8, More preferably, it is 1-4, More preferably, it is one. Specific examples of the alkyl group include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group, hexyl group, heptyl group. Octyl group, nonyl group, decyl group, cyclopropyl group, cyclopentyl group, cyclohexyl group, and the like. Alkyl groups other than these may be used. Examples of amine salts include monomethylamine hydrochloride (CH ₃ NH ₃ Cl), monoethylamine hydrochloride (CH ₃ CH ₂ NH ₃ Cl), monomethylamine hydrobromide (CH ₃ NH ₃ Br), monoethylamine Examples thereof include hydrofluoric acid salt (CH ₃ CH ₂ NH ₃ F) and monomethylamine sulfate ((CH ₃ NH ₃ ) ₂ SO ₄ ). Two or more types of alkylamine salts can be used in combination.

  N-alkylborazine is a compound represented by the following formula.

  In the formula, since R is as described for the amine salt, the description is omitted here. Examples of N-alkylborazines include N, N ′, N ″ -trimethylborazine, N, N ′, N ″ -triethylborazine, N, N ′, N ″ -tri (n-propyl) borazine, N, N ', N ″ -tri (isopropyl) borazine, N, N ′, N ″ -tri (n-butyl) borazine, N, N ′, N ″ -tri (sec-butyl) borazine, N, N ′, N ″ -Tri (isobutyl) borazine, N, N ', N "-tri (tert-butyl) borazine, N, N', N" -tri (1-methylbutyl) borazine, N, N ', N "-tri (2 -Methylbutyl) borazine, N, N ', N "-tri (neo-pentyl) borazine, N, N', N" -tri (1,2-dimethylpropyl) borazine, N, N ', N "-tri ( 1-ethylpropyl) borazine, N, N ′, N ″ -tri ( -Hexyl) borazine, N, N ', N "-tricyclohexylborazine, N, N'-dimethyl-N" -ethylborazine, N, N'-diethyl-N "-methylborazine, N, N'-dimethyl- N "-propylborazine and the like can be mentioned.

  The alkali borohydride and amine salt to be used may be selected according to the structure of the N-alkylborazine to be synthesized. For example, when producing N-methylborazine in which a methyl group is bonded to the nitrogen atom constituting the borazine ring, an amine salt such as monomethylamine hydrochloride, where R is a methyl group, is used as the amine salt. Good.

  The mixing ratio of alkali borohydride and amine salt is not particularly limited, but when the amount of amine salt used is 1 mol, the amount of alkali borohydride used is preferably 0.8 to 2.0 mol, More preferably, it is 1.0 to 1.5 mol.

  The solvent that can be used is not particularly limited, but ether solvents such as tetrahydrofuran, monoethylene glycol dimethyl ether (monoglyme), diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), tetraethylene glycol dimethyl ether (tetraglyme), Pentaethylene glycol dimethyl ether (pentag lime), monoethylene glycol diethyl ether, diethylene glycol diethyl ether, monopropylene glycol dimethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, tetrapropylene glycol dimethyl ether, monopropylene glycol diethyl ether, dipropiate Glycol dialkyl ether solvents such as glycol diethyl ether. Here, the said solvent may be used independently, or 2 or more types may be mixed and used for it.

  The solvent may be selected according to the normal boiling point of the N-alkylborazine to be synthesized. The normal boiling point of N-alkylborazine means the boiling point of N-alkylborazine, which is the object of synthesis, at normal pressure. In addition, since the normal boiling point of N-alkyl borazine may be fluctuate | varied with the kind of substituent, it is not uniquely determined. The standard boiling point of the solvent means the boiling point at normal pressure of the solvent used in the reaction between the alkali borohydride and the amine salt. The upper limit of the standard boiling point of the solvent that can be used is not particularly limited. However, if the boiling point is too high, it is difficult to carry out distillation purification. Therefore, the normal boiling point of N-alkylborazine is preferably + 200 ° C. or less, more preferably +150. A solvent having a normal boiling point of 0 ° C. or lower is used. The lower limit of the normal boiling point of the solvent is not particularly limited, and it is sufficient that boiling does not occur at a predetermined reaction temperature or lower. Preferably, the boiling point is higher than the normal boiling point of N-alkylborazine + 20 ° C., more preferably + 50 ° C. That's it. For example, when synthesizing N, N ′, N ″ -trimethylborazine having a normal boiling point of 133 ° C., triglyme having a normal boiling point of 216 ° C. or dipropylene glycol dimethyl ether having a standard boiling point of 175 ° C. is used as a solvent. Also, N, N ′, N ″ -triethylborazine having a normal boiling point of 184 ° C., N, N ′, N ″ -tri (isopropyl) borazine having a normal boiling point of about 203 ° C., or a normal boiling point of about When synthesizing N, N ′, N ″ -tri (n-propyl) borazine at 225 ° C., tetraglyme having a normal boiling point of 270 ° C. or pentaethylene glycol dimethyl ether having a standard boiling point of about 342 ° C. is used as a solvent. It is preferable.

  The amount of solvent used is not particularly limited. The amount of solvent used may be selected according to the solubility of raw materials and products, the ease of handling of the solvent, and the like. Preferably, 3 to 15 times by mass of solvent is used with respect to the total amount of alkylamine salt and alkali borohydride.

  The reaction conditions between the alkali borohydride and the amine salt are not particularly limited. Reaction temperature becomes like this. Preferably it is 20-250 degreeC, More preferably, it is 50-240 degreeC, More preferably, it is 100-220 degreeC. When the reaction is performed within the above range, the amount of hydrogen generation can be easily controlled. The reaction temperature can be measured using a temperature sensor such as a K thermocouple.

  The synthesized N-alkylborazine is purified by a known purification method from the reaction solution obtained in the step of synthesizing the above-mentioned N-alkylborazine.

  In the above reaction, since alkali borohydride, amine salt, and by-product salt (AX) all have low solubility in organic solvents, the reaction solution containing N-alkylborazine obtained by synthesis is in a slurry state. . The method for purification is not particularly limited, and methods such as filtration, adsorption, evaporation, and distillation can be used. These methods may be used singly or a plurality of methods may be combined. For example, distillation (rectification step) may be performed from the slurry-like reaction liquid described above, and after the liquid component and the solid component are completely separated by filtration or evaporation from the slurry-like reaction liquid, the liquid You may perform distillation (rectification process) about a component. Or after distilling (crude distillation process) from the said slurry-like reaction liquid and obtaining the crude refined liquid (crude distillate) which concentrated the liquid component, you may perform distillation (rectification process).

In the present invention, the liquid contains N-alkylborazine, and the amine borane content is 3 mol% or less, preferably 1 mol% or less, more preferably 0.5 mol% or less with respect to the N-alkylborazine. Is purified by distillation. Alternatively, the content of amine borane contained in the N-alkylborazine-containing liquid (first liquid) is 3 mol% or less, preferably 1 mol% or less, more preferably 0.5 mol% with respect to N-alkylborazine. The liquid (second liquid) obtained by reducing to the following is purified by distillation. Here, the value measured by gas chromatography is used as the content value of N-alkylborazine, and the value measured by ¹¹ B-NMR is used as the content value of amine borane.

Under normal reaction conditions, a certain amount of amine borane represented by RNH ₂ —BH ₃ may be contained in the liquid after reaction containing N-alkylborazine. The crude purified solution may also contain amine borane. Here, R is an alkyl group and is the same alkyl group as R contained in (RNH ₃ ) _n X because it is derived from an amine salt that is a reaction raw material. The production route of amine borane is not clear, but is considered to be a reaction intermediate produced by the reaction between an alkali borohydride and an amine salt. When the liquid containing N-alkylborazine containing amine borane is purified by distillation, it is considered that precipitates are generated in the cooling unit of the distillation apparatus and the like when the liquid is heated to a certain temperature or higher. However, the technical scope of the present invention is not limited by the amine borane produced by the above mechanism.

  An apparatus that can be used for evaporating or distilling the liquid containing the N-alkylborazine is not particularly limited. For example, a device equipped with a distillation can and a condenser (single distillation device) or a device having a multistage distillation column and supplying a part of the condensate to the top of the column (multistage distillation device) Etc. The distillation method is preferably a batch type (batch type) or a continuous type device.

  In the case of a multistage distillation column, the number of stages of the distillation column is not particularly limited, but is preferably 2 or more. Examples of such distillation columns include packed towers filled with packing materials such as Raschig rings, pole rings, interlock saddles, Dixon packing, McMahon packing, and thruzer packing, trays such as bubble bell trays, sieve trays, valve trays ( A generally used distillation column such as a plate column using a plate) is suitable. A composite distillation tower having both a shelf and a packed bed can also be employed. The number of plates indicates the number of plates in a plate column, and the number of theoretical plates in a packed column. The number of stages is preferably 3 to 100 stages, and more preferably 5 to 50 stages. The number of distillation columns is not limited, and one or two distillation columns can be used.

  It does not specifically limit about distillation conditions, What is necessary is just to select suitably according to the target N-alkyl borazine. The reflux ratio at the top of the distillation column is not limited, but is preferably 0.1 to 50, more preferably 0.3 to 30.

  In addition, when the concentration of the light boiling point component to be removed is low when performing batch distillation, the distillation column is maintained at the total reflux and the light boiling point component is concentrated in the reflux tank, so that the composition of the reflux tank is stabilized. By the way, you may remove a light boiling point component by the method of extracting the liquid in a tank in a short time. By repeating this operation a plurality of times, the light boiling point component can be further removed. The time for holding at the total reflux varies depending on the apparatus, but it is desirable to make it longer than the time for distilling twice the amount of liquid in the reflux tank from the top of the column. After the completion of this operation, the liquid remaining in the tower bottom is extracted or distilled from the tower top, whereby a liquid with reduced light boiling point components can be obtained.

  The distillation temperature is preferably the normal boiling point of N-alkylborazine + 100 ° C. or less, more preferably the boiling point of N-alkylborazine + 50 ° C. or less. As particularly preferable conditions, the distillation temperature is the normal boiling point of the N-alkylborazine + 15 ° C. or less, more preferably the standard boiling point of the N-alkylborazine + 5 ° C. or less, and more preferably the standard boiling point of the N-alkylborazine-5. The normal boiling point of the N-alkylborazine is -15 ° C or less. The lower limit of the distillation temperature is not particularly limited, but is actually 20 ° C. As the value of the distillation temperature, a value obtained by measuring the temperature at the bottom of the distillation column when the liquid is distilled is used. Here, the distillation temperature is the normal boiling point of the N-alkylborazine + 100 ° C. or less. The distillation temperature is the standard boiling point of the N-alkylborazine + 100 ° C. or less in at least a part of the distillation period during which the liquid is distilled. Means that. In this specification, the distillation period means the total period during which the liquid is distilled. When the liquid is continuously distilled, it means the period from the start to the end of the liquid distillation.When the liquid is distilled intermittently, for example, when it is kept at a total reflux, the liquid is distilled. It means the total of the period that is taken out, and does not include the time for holding at total reflux. Preferably, the distillation temperature is 50% or more of the distillation period, more preferably 80% or more of the distillation period, more preferably 90% or more of the distillation period, particularly preferably the whole distillation period. The normal boiling point of the N-alkylborazine + 100 ° C. or lower. At this time, the distillation of the liquid may be continuous or intermittent. By controlling the distillation temperature within the above range, side reactions during distillation can be effectively suppressed. It is also expected to suppress the formation of precipitates. Furthermore, effects such as a reduction in utility costs in the apparatus heating unit and a reduction in equipment costs by reducing the load on the apparatus are expected.

  The operation pressure in the distillation tower is preferably 60 kPa or less, more preferably 40 kPa or less, and even more preferably 30 kPa or less under a high reduced pressure. The operating pressure is preferably 1.3 kPa or more, more preferably 1.5 kPa or more, and further preferably 2.0 kPa or more. As the pressure, a value obtained by measuring the pressure at the bottom of the distillation column is used. By controlling the pressure within the above range, it can be expected that the separation between N-alkylborazine and impurities will be improved. Therefore, the equipment cost can be reduced by reducing the number of stages of the distillation column, and the reflux ratio can be reduced. By doing so, the utility cost can be reduced.

  Furthermore, side reactions during distillation can be suppressed by controlling the temperature and pressure during the distillation to a predetermined range. The operating pressure is preferably 1.3 to 60 kPa, more preferably 1.5 to 40 kPa, and even more preferably 2.0 to 30 kPa. At the same time, the distillation temperature is controlled to the standard boiling point of the synthesized N-alkylborazine + 100 ° C. or lower, more preferably the standard boiling point of N-alkylborazine + 50 ° C. or lower. Particularly preferred conditions are the normal boiling point of N-alkylborazine + 15 ° C. or less, particularly preferably the normal boiling point of N-alkylborazine + 5 ° C. or less, and even more preferably the standard boiling point of N-alkylborazine-5 ° C. or less. Most preferably, the N-alkylborazine has a normal boiling point of -15 ° C or lower. Here, a value obtained by measuring the pressure at the bottom of the distillation column is used as the pressure. Moreover, the temperature uses the value which measured the temperature in the tower bottom of the distillation tower at the time of distillation. By controlling the temperature and pressure within the above-mentioned ranges, side reactions during distillation can be suppressed, and it is expected to suppress the formation of precipitates. In addition, effects such as reduction in utility cost in the apparatus heating unit and reduction in equipment cost by reducing the load on the apparatus are expected. Furthermore, since it can be expected that the separation between N-alkylborazine and impurities will be improved, the equipment cost can be reduced by reducing the number of stages of the distillation column, and the utility cost can be reduced by reducing the reflux ratio. Can do. For example, when N, N ′, N ″ -trimethylborazine (standard boiling point 133 ° C.) is distilled and purified from triglyme as a solvent as N-alkylborazine, the distillation temperature is preferably 20 to 233 ° C. The temperature is preferably 20 to 183 ° C. The particularly preferable condition is that the distillation temperature is 20 to 148 ° C., particularly preferably 20 to 138 ° C., particularly more preferably 20 to 128 ° C., and most preferably 20 The pressure is preferably 1.3 to 60 kPa, more preferably 1.5 to 40 kPa, and even more preferably 2.0 to 30 kPa by distillation under reduced pressure, satisfying both the above temperature and pressure. It is particularly preferred to carry out distillation purification under the conditions, in order to obtain a high purity N-alkylborazine with a high recovery rate, at least under the above conditions. It is preferable to perform one multi-stage distillation.

  In order to perform distillation efficiently under the above-described temperature and pressure conditions, it is preferable that the liquid containing N-alkylborazine after the reaction has a N-alkylborazine content of 30% by mass or more in a crude distillation step or the like. Preferably, a liquid having a mass of 60% by mass or more, more preferably 80% by mass or more is used. In particular, when using a solvent having a higher normal boiling point than N-alkylborazine, the higher the content of N-alkylborazine contained in the liquid to be distilled, the lower the temperature during distillation. Can be suppressed. It is also expected to suppress the formation of precipitates. Furthermore, high quality N-alkylborazine can be obtained. In addition, by reducing the amount of the solution, the size of the distillation can can be reduced in the rectification process, so that the equipment cost and the utility cost can be reduced.

  Other distillation conditions may follow known distillation conditions.

  The conditions for filtration are not particularly limited. Means such as atmospheric pressure filtration, pressure filtration, and vacuum filtration may be selected according to the environment and scale. The type of the filter medium is not particularly limited, and a filter paper, a filter plate, a cartridge filter, or the like may be used depending on the environment or scale. Also, the material of the filter medium is not particularly limited. However, considering the reactivity of the borazine compound to be synthesized, it is preferable to use a filter medium made of polytetrafluoroethylene (PTFE) or glass fiber. What is necessary is just to determine the hole diameter of a filter medium according to the quantity and magnitude | size of a precipitate. The pore diameter of the filter medium may be reduced stepwise.

  The conditions for adsorption are not particularly limited. For example, an adsorbent such as an ion exchange resin is used. The treatment with the adsorbent may be a batch type (batch type) or a continuous type, and can be used in any combination of a fluidized bed and a fixed bed. In particular, if the adsorbent is used as a continuous fixed bed, it is advantageous because it is excellent in maintainability. A commercial item can also be used as such an adsorbent. The adsorption time and the amount of adsorbent used may be appropriately selected according to the content of impurities contained therein.

In the second step of the present invention, the step of obtaining the second liquid in which the content of amine borane is reduced is not particularly limited. For example, an amine salt is further added to the first liquid that is a liquid containing the N-alkylborazine. In addition, a method of reducing amine borane contained in the liquid containing the N-alkylborazine may be used. In this case, the amine salt is preferably added in an amount of 0.01 to 100 mol, more preferably 0.05 to 50 mol, preferably 0.5 to 1 mol of amine borane contained in the liquid containing N-alkylborazine. The reaction is performed for -24 hours, more preferably 0.5-12 hours, preferably 20-250 ° C, more preferably 50-200 ° C. The amine salt is preferably the same as the amine salt used during the reaction. Although it does not specifically limit regarding the addition method of an amine salt, You may add to the said 1st liquid directly with a solid, and after mixing with the solvent similar to the above, you may add to the said 1st liquid as a slurry or a solution. You may repeat the additional operation of the above-mentioned amine salt 2 to 50 times.

  Alternatively, amine borane is removed from the first liquid, which is a liquid containing the N-alkylborazine, by distillation (coarse distillation step). As the distillation apparatus and distillation conditions, those described above can be preferably applied. The content of N-alkylborazine in the fraction obtained by distillation (crude distillation step) is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. The content of amine borane contained in the liquid containing N-alkylborazine can be reduced to a predetermined value or less.

  The step of obtaining the second liquid in which the content of amine borane is reduced is the retention of the first liquid, which is a liquid containing the N-alkylborazine, under the above-mentioned conditions, addition of an amine salt, or distillation (crude distillation step). May be performed alone, or two or more of these may be combined.

  A rough distillation process means the distillation process to the rectification process mentioned later after reaction. The crude distillation step may be distillation using a single distillation apparatus (single distillation), distillation using a multistage distillation apparatus (multistage distillation), or a combination thereof. The number of rough distillation steps is not particularly limited, but is preferably performed once or more. Here, the simple distillation may be distillation using a simple distillation apparatus. For example, heat loss may occur in a part of the distillation apparatus, and a slight reflux may occur, which is not true simple distillation. This case is also included in simple distillation.

  In the crude distillation step, it is preferable that at least 50% by mass or more of N-alkylborazine contained in the liquid after the reaction is recovered as a fraction, more preferably 70% by mass or more, and further preferably 90% by mass or more. to recover.

  The rectification step is the final distillation step, and for example, distillation is performed on the slurry-like reaction liquid and the fraction obtained in the above-described rough distillation step. The distillation apparatus that can be used in the rectification step is preferably a batch (batch type) distillation apparatus or a continuous distillation apparatus having a multistage distillation column. As the distillation conditions such as the distillation apparatus, reflux ratio, distillation temperature, distillation pressure, etc., those described above can be applied.

  Distillation purification may be performed using a continuous distillation apparatus or a batch distillation apparatus. However, when a batch distillation apparatus is used, the column is distilled as the distillation operation proceeds under a constant pressure condition. Since the content of N-alkylborazine in the bottom liquid is lowered, when synthesis is performed using a solvent having a higher normal boiling point than N-alkylborazine, the distillation temperature gradually increases as the distillation rate increases. To be high. Here, the distillation rate means the mass of N-alkylborazine in the distillate with respect to the mass of N-alkylborazine in the liquid to be distilled (feeding liquid). In order to suppress an increase in distillation temperature, the distillation pressure may be lowered stepwise as the distillation operation proceeds.

  As mentioned above, by distilling and purifying a solution having a concentration of amine borane below the specified value, it is stable without deposits adhering to the cooler or distillation line or clogging the distillation column during distillation. Operation becomes possible, and high-purity N-alkylborazine having a purity of 99.7% by mass or more can be obtained with a high recovery rate.

The N-alkylborazine provided by the present invention preferably has an amine borane content of preferably 0.5 mol% or less, more preferably 0.3 mol% or less, based on N-alkylborazine, Preferably it is 0.1 mol% or less. When multiple types of amine boranes are mixed, the total content of each component is preferably in the above range. Here, the value measured by gas chromatography is used as the content value of N-alkylborazine, and the value measured by ¹¹ B-NMR is used as the content value of amine borane.

  The N-alkylborazine provided by the present invention preferably has a purity of 99.70% by mass or more, more preferably 99.90% by mass or more, and particularly preferably 99.92% by mass or more. Here, the value measured by gas chromatography is adopted as the purity value of N-alkylborazine. By using such high-purity N-alkylborazine, the performance of products such as semiconductor elements can be improved.

A third aspect of the present invention is a liquid containing N-alkylborazine, amine borane, and a solvent, and the content of the amine borane is 3 mol% or less with respect to the N-alkylborazine. In the liquid, the amine borane content is preferably 3 mol% or less, more preferably 1 mol% or less, and particularly preferably 0.5 mol% or less with respect to the N-alkylborazine content. . Here, the content value of the N-alkylborazine contained in the liquid is a value measured by gas chromatography, and the content value of the amine borane is a value measured by ¹¹ B-NMR. And

  When the first production method of the present invention, the second production method of the present invention or the third liquid of the present invention is used, it is possible to prevent deposits from adhering to a cooler or a distillation line during distillation purification. it can. For this reason, the distillation column does not clog due to deposition and accumulation of deposits, so there is no need to stop distillation for removal of precipitates, washing, etc., stable operation is possible, and N-alkylborazine is highly productive. Can be manufactured. Furthermore, N-alkylborazine having a purity of 99.7% by mass or more can be obtained with a high recovery rate.

4th of this invention is N-alkyl borazine whose content of amine borane is 0.5 mol% or less with respect to N-alkyl borazine. The content of amine borane is more preferably 0.3 mol% or less, and still more preferably 0.1 mol% or less. When multiple types of amine boranes are mixed, the total content of each component is preferably in the above range. Here, the value measured by gas chromatography is used as the content value of N-alkylborazine, and the value measured by ¹¹ B-NMR is used as the content value of amine borane.

  The N-alkylborazine of the present invention 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. In that case, N-alkylborazine may be used as it is, or a compound obtained by modifying N-alkylborazine may be used. A polymer obtained by polymerizing N-alkylborazine or a derivative of N-alkylborazine may be used as a raw material for an interlayer insulating film for a semiconductor, a barrier metal layer, or an etch stopper layer. Hereinafter, “N-alkylborazine”, “derivative of N-alkylborazine”, and “polymer derived from them” are collectively referred to as “borazine ring-containing compound”.

  As a method for forming an interlayer insulating film for semiconductor, a barrier metal layer, or an etch stopper layer using a borazine ring-containing compound, for example, a solution-like or slurry-like composition containing a borazine ring-containing compound is prepared. A method of forming a coating film or a chemical vapor deposition film forming method (CVD method) can be used by applying to a desired site.

  Hereinafter, embodiments of the present invention will be described in more detail using examples and comparative examples. However, the technical scope of the present invention is not limited to the following embodiments.

<Example 1>
(Reaction step 1)
A 100 L reaction liquid equipped with a reflux tube was purged with nitrogen, and then 8.40 kg of dried methylamine hydrochloride as an amine salt and 30.1 kg of triglyme as a solvent were charged, and the temperature was raised to 150 ° C. Thereafter, a mixture of 5.25 kg of sodium borohydride as an alkali borohydride and 22.2 kg of triglyme as a solvent was fed over 7.5 hours. Thereafter, the temperature was raised to 170 ° C., followed by aging for 2 hours. Hydrogen produced during the reaction was cooled in a reflux tube and then removed out of the system. The obtained reaction liquid contained 4.5 kg of N, N ′, N ″ -trimethylborazine. The content of amine borane relative to N, N ′, N ″ -trimethylborazine in the reaction liquid was 10 mol%. It was.

(Rough distillation process 1: Simple distillation)
N, N ′, N ″ -trimethylborazine was concentrated from the reaction solution obtained in the above (Reaction Step 1) by distillation. As a crude distillation, the reaction solution was heated at a tower bottom pressure of 13 kPa, and N, N ′. 6.7 kg of a fraction containing N, N "-trimethylborazine was distilled off. The concentration of N, N ′, N ″ -trimethylborazine in the fraction was 65% by mass. The content of amine borane relative to N, N ′, N ″ -trimethylborazine in the fraction was 5 mol%.

(Step 2 for obtaining the second liquid: addition of an amine salt)
1.3 kg of the fraction obtained in the above (crude distillation step 1: simple distillation) and 13 g of methylamine hydrochloride were reacted at 140 ° C. for 6 hours. It was found that the amount of amine borane relative to N-alkylborazine before and after the reaction was 5 mol% to less than 0.5 mol%.

(Rectification process 1: Multistage distillation)
Using the liquid component after the above (Step 1 for obtaining the second liquid 1: addition of amine salt), rectification was carried out in an Oldershaw distillation column (plate column) having an inner diameter of 32 mm and 10 stages. The above-mentioned fraction of 1.2 kg is charged to the tower bottom, the bottom pressure is 28 kPa, the reflux ratio is 2, and the distillation rate is 94% with respect to the mass of N, N ′, N ″ -trimethylborazine contained in the charged liquid. The fraction with N, N ′, N ″ -trimethylborazine concentration of 99.7% by mass or more has a distillation rate of 25% to 93%, and N, N ′, N ″ -trimethylborazine The recovery rate of the fraction having a concentration of 99.7% by mass or more was 68%, and adhesion of precipitates to the cooler was hardly observed.

  The content of N, N ′, N ″ -trimethylborazine was measured by gas chromatography. Measurement conditions are as follows.

The content of amine borane was measured by ¹¹ B-NMR. The measurement conditions are as follows.

<Example 2>
(Reaction step 2)
The same procedure as in (Reaction step 1) of Example 1 was performed.

(Step 2 for obtaining the second liquid (crude distillation step 2): distillation (simple distillation))
N, N ′, N ″ -trimethylborazine was concentrated from the reaction solution obtained in the above (reaction step 2) by distillation. The reaction solution was heated at a tower bottom pressure of 13 kPa, and N, N ′, N ″ — 4.5 kg of a fraction containing trimethylborazine was distilled off. The concentration of N, N ′, N ″ -trimethylborazine in the fraction was 90% by mass. The amount of amine borane relative to N, N ′, N ″ -trimethylborazine in the fraction was 1 mol%. I understood.

(Rectification process 2: Multistage distillation)
Using the fraction obtained in the above (Step 2 for obtaining the second liquid (crude distillation step 2): distillation (simple distillation)), rectification was performed in a glass Oldershaw distillation column having an inner diameter of 32 mm and 10 stages. . The above-mentioned fraction of 1.2 kg was charged into the column bottom, the column bottom pressure was 28 kPa, the reflux ratio was 2, and the distillation rate was 81 with respect to the mass of N, N ′, N ″ -trimethylborazine contained in the charged solution. The fraction having a N, N ′, N ″ -trimethylborazine concentration of 99.7% by mass or more has a distillation rate of 23% to 81%, and N, N ′, N ″ − The recovery rate of the fraction having a trimethylborazine concentration of 99.7% by mass or more was 58%, and adhesion of precipitates to the cooler was hardly observed.

<Example 3>
(Reaction step 3)
The same procedure as in (Reaction step 1) of Example 1 was performed.

(Rough distillation step 3-1: Simple distillation)
The same procedure as in Example 1 (crude distillation step 1: simple distillation) was performed.

(Step 3 for obtaining the second liquid (crude distillation step 3-2): distillation (multistage distillation))
The fraction obtained in the above (coarse distillation step 3-1: simple distillation) was distilled in a glass Oldershaw distillation column having an inner diameter of 32 mm and 5 stages. 1.7 kg of the above fraction was charged into the column bottom, and 1.1 kg of a fraction containing N, N ′, N ″ -trimethylborazine was distilled at a column bottom pressure of 7 kPa and a reflux ratio of 1. The concentration of N, N ′, N ″ -trimethylborazine in the mixture was 99% by mass. It was found that the amount of amine borane relative to N, N ′, N ″ -trimethylborazine in the fraction was 5 mol% to less than 0.5 mol%.

(Rectification process 3: Multistage distillation)
Using the fraction obtained in the above (Step 2 for obtaining the second liquid (crude distillation step 3-2): distillation (multi-stage distillation)), rectification was performed in a glass Oldershaw distillation column having an inner diameter of 32 mm and 10 stages. Went. 1.1 kg of the above fraction was charged into the column bottom, the column bottom pressure was 8 kPa, the reflux ratio was 2, and the distillation rate was 86 with respect to the mass of N, N ′, N ″ -trimethylborazine contained in the charged solution. The fraction having a N, N ′, N ″ -trimethylborazine concentration of 99.7% by mass or more has a distillation rate of 19% to 86%, and N, N ′, N ″ − The recovery rate of the fraction having a trimethylborazine concentration of 99.7% by mass or more was 67%, and no deposits were observed on the cooler when the main distillate was obtained.

<Comparative example>
The fraction (content of amine borane with respect to N-alkylborazine: 5 mol%) obtained in (Coarse distillation step 1: simple distillation) in Example 1 was purified with a glass Oldershaw distillation column having an inner diameter of 32 mm and 10 stages. Distillation (rectification process) was performed. 1.2 kg is charged to the bottom of the tower, the bottom pressure is 28 kPa, and the reflux ratio is 2. Until the distillation rate reaches 96% with respect to the mass of N, N ′, N ″ -trimethylborazine contained in the charged liquid. The fraction having a concentration of 99.7% by mass or more of N, N ′, N ″ -trimethylborazine has a distillation rate of 27% to 68%, and the concentration of N, N ′, N ″ -trimethylborazine is The recovery rate of the fraction having 99.7% by mass or more was 41%, and deposits adhered to the cooler.

  From the results shown in the above Examples and Comparative Examples, it can be seen that the deposition of precipitates on the cooler can be suppressed by distilling and purifying a liquid having an amine borane content of a predetermined value or less.

Claims (2)

An alkali borohydride represented by ABH ₄ (A is a lithium atom, a sodium atom or a potassium atom) and (RNH ₃ ) _n X (R is an alkyl group, X is a sulfate group or a halogen atom) , N is 1 or 2, and a method for producing N-alkylborazine comprising a step of synthesizing N-alkylborazine by reacting with an amine salt in a solvent,
From the first liquid, which is a liquid containing the N-alkylborazine, a method of adding an amine salt to the first liquid, or a method of removing amine borane by distillation from the first liquid, RNH ₂ —BH ₃ A step of obtaining a second liquid in which the content of amine borane represented by (R is an alkyl group) is reduced to 3 mol% or less with respect to the N-alkylborazine, and N- A method for producing N-alkylborazine, comprising a step of purifying alkylborazine.   The manufacturing method according to claim 1, wherein the step of obtaining the second liquid from the first liquid includes distillation of the first liquid under a pressure of 1.3 to 60 kPa.