JP4904029B2 - Preservation method of borazine compound - Google Patents

Description

  The present invention relates to a borazine compound. The borazine compound is 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 constant 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, a borazine compound having a borazine ring skeleton in the molecule has been proposed (see, for example, Patent Document 1). Since the borazine compound 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 compounds so far. For example, an alkyl borazine compound in which a boron site is substituted with an alkyl group has very excellent characteristics as a low dielectric constant material (see, for example, Patent Document 2).
JP 2000-340689 A JP 2003-119289 A

  However, borazine compounds are vulnerable to moisture. That is, when a borazine compound (for example, N, N ′, N ″ -trimethylborazine) is brought into contact with moisture, the NB bond is hydrolyzed and a decomposition product (for example, methylamine and boric acid) is generated.

  Conventionally, borazine compounds are usually synthesized only in a small amount at a laboratory level and stored in a reagent bottle or the like. On the other hand, if future mass production is taken into consideration, it will be necessary to store in a larger container for a long period of time.

  Here, when storing a mass-produced borazine compound, let us consider a case where a drum can or the like used for storing a general compound is adopted as a storage container. Such a container normally breathes in an atmosphere of about atmospheric pressure, and the gas in the container and the outside air travel to and from the container to some extent. Therefore, if a container generally used for storing compounds is used for storing a borazine compound as it is, moisture contained in the outside air flows into the container accompanying the inflow of the outside air into the container. , May cause decomposition of borazine compounds.

  Therefore, an object of the present invention is to provide means for suppressing the inflow of outside air containing water vapor into a storage container when storing a borazine compound and preventing decomposition of the borazine compound during storage.

  The present invention is a method for storing a borazine compound having a storage step of storing the borazine compound in a container having a pressure pressure of 0.1 MPa or more.

  The present invention is also a borazine compound storage container having a pressure resistance of 0.1 MPa or more.

  Furthermore, the present invention is a borazine compound characterized in that the purity decrease when stored for 60 days is 1% or less.

  According to the present invention, when storing a borazine compound, inflow of outside air containing water vapor into the storage container can be suppressed, and decomposition of the borazine compound during storage can be prevented.

  The first of the present invention relates to a technique for suppressing decomposition of a borazine compound due to contact with moisture during storage. Specifically, a first aspect of the present invention is a method for storing a borazine compound, which includes a storage step of storing the borazine compound in a container having a pressure resistance of 0.1 MPa or more.

  In the storage method of the present invention, the borazine compound is stored in a container having a predetermined pressure resistance. Thereby, when preserve | saving a borazine compound, inflow of the external air containing water vapor | steam into the preservation | save container is suppressed, and decomposition | disassembly of the borazine compound during preservation | save can be prevented. As a result, a decrease in the purity of the stored borazine compound can be suppressed over a long period of time.

  Then, the 1st preservation | save method of this invention is demonstrated in detail.

  The specific form of the borazine compound to be stored in the storage method of the present invention is not particularly limited, and conventionally known knowledge can be appropriately referred to. The borazine compound is represented by the following chemical formula 1, for example.

In the formula, each R ₁ and each R ₂ may be the same or different, and are a hydrogen atom or an alkyl group. Examples of borazine compounds include borazine, N, N ′, N ″ -trimethylborazine, N, N ′, N ″ -triethylborazine, N, N ′, N ″ -tri (n-propyl) borazine, N, N ', N ″ -tri (iso-propyl) borazine, N, N ′, N ″ -tri (n-butyl) borazine, N, N ′, N ″ -tri (sec-butyl) borazine, N, N ′, N ″ -tri (iso-butyl) 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 (n-he Syl) borazine, N, N ′, N ″ -tricyclohexylborazine, N, N′-dimethyl-N ″ -ethylborazine, N, N′-diethyl-N ″ -methylborazine, N, N′-dimethyl-N "-Propylborazine, B, B ', B" -trimethylborazine, B, B', B "-triethylborazine, B, B ', B" -tri (n-propyl) borazine, B, B', B " -Tri (isopropyl) borazine, B, B ', B "-tri (n-butyl) borazine, B, B', B" -tri (isobutyl) borazine, B, B ', B "-tri (tert-butyl) ) Borazine, B, B ′, B ″ -tri (1-methylbutyl) borazine, B, B ′, B ″ -tri (2-methylbutyl) borazine, B, B ′, B ″ -tri (neopentyl) borazine, B , B ′, B ″ -tri (1,2-dimethylpropyl) bo Razine, B, B ′, B ″ -tri (1-ethylpropyl) borazine, B, B ′, B ″ -tri (n-hexyl) borazine, B, B ′, B ″ -tricyclohexylborazine, B, B Examples include '-dimethyl-B "-ethylborazine, B, B'-diethyl-B" -methylborazine, and B, B'-dimethyl-B "-propylborazine. In view of such stability and handleability, the borazine compound is preferably N-alkylborazine.

  The prepared borazine compound includes B, B ′, B ″ -trimethyl-N, N ′, N ″ -trimethylborazine, B, B ′, B ″ -trimethyl-, wherein the boron moiety is substituted with an alkyl group. Alkyl borazine compounds such as N, N ′, N ″ -triethylborazine, B, B ′, B ″ -triethyl-N, N ′, N ″ -trimethylborazine may be used.

  The route for obtaining the borazine compound to be prepared is not particularly limited. When a borazine compound product is commercially available, a product purchased from the product may be used, or a borazine compound prepared by itself may be used.

The method for preparing the borazine compound by itself is not particularly limited. An example of a method for preparing a borazine compound represented by the above chemical formula 1 is an alkali borohydride represented by ABH ₄ (A is a lithium atom, a sodium atom or a potassium atom), and (RNH ₃ ). An example is a method in which an amine salt represented by _n X (R is a hydrogen atom or an alkyl group, X is a sulfate group or a halogen atom, and n is 1 or 2) is reacted in a solvent. .

In alkali borohydride (ABH ₄ ), A is a lithium atom, a sodium atom or a potassium atom. Examples of alkali borohydrides include sodium borohydride and lithium borohydride.

In the amine salt ((RNH ₃ ) _n X), R is a hydrogen atom or an alkyl group, and X is a sulfate group or a halogen atom. And when X is a sulfate group, n is 2, and when X is a halogen atom, n is 1. As described above, when n is 2, R may be the same or different. In consideration of the yield of the synthesis reaction and 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 ammonium chloride (NH ₄ Cl), monomethylamine hydrochloride (CH ₃ NH ₃ Cl), monoethylamine hydrochloride (CH ₃ CH ₂ NH ₃ Cl), monomethylamine hydrobromide (CH ₃ NH ₃ Br), monoethylamine hydrofluoride (CH ₃ CH ₂ NH ₃ F), ammonium sulfate ((NH ₄ ) ₂ SO ₄ ), monomethylamine sulfate ((CH ₃ NH ₃ ) ₂ SO ₄ ) Can be mentioned.

  What is necessary is just to select the alkali borohydride and amine salt to be used according to the structure of the borazine compound to synthesize | combine. 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 1 to 1.5 mol. .

  The solvent for synthesis is not particularly limited, and examples thereof include tetrahydrofuran, monoethylene glycol dimethyl ether (monoglyme), diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), and tetraethylene glycol dimethyl ether (tetraglyme). .

  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.

  On the other hand, an alkyl borazine compound is prepared by using a halogenated borazine compound such as B, B ′, B ″ -trichloro-N, N′-N ″ -trialkylborazine as a starting material, and using the Grignard reagent as a chlorine. It can be synthesized by substituting an atom with an alkyl group (see DT HOWORTH and LF HOHNSTEDT, J. Am. Chem. Soc., 82, 3860 (1960)).

  The synthesized borazine compound can be purified as necessary. As a purification method of the borazine compound, for example, distillation purification is used.

  The size and type of the distillation purification apparatus may be determined according to the environment and scale. For example, if a large amount of borazine compound is to be processed, an industrial scale distillation column can be used. If a small amount of borazine compound is to be treated, distillation purification using a distillation tube can be used. For example, as a specific example of a distillation apparatus for treating a small amount of a borazine compound, a distillation apparatus in which a Liebig cooling pipe is attached to a three-necked flask with a Claisen type connecting pipe can be used. However, the technical scope of the present invention is not limited to the embodiment using such a distillation apparatus.

  The temperature at the time of distillation purification is not particularly limited, and can be appropriately set according to the type of borazine compound synthesized. For example, the temperature is usually about 100 to 150 ° C.

  The first storage method of the present invention is characterized in that the borazine compound is stored in a container having a pressure resistance of 0.1 MPa or more.

  “Pressure pressure” means that when a sealed container is placed in an atmosphere having a certain initial pressure (0.1 MPa in the present application) and the pressure of the atmosphere is increased, It means the pressure obtained by subtracting the initial pressure (0.1 MPa) from the atmospheric pressure at the time when it can flow into the interior. That is, when the pressure of the atmosphere exceeds “pressure resistance + initial pressure (0.1 MPa)”, the atmosphere can flow into the container. Therefore, in the present invention, when the borazine compound is stored in an atmosphere having an initial pressure of 0.1 MPa (approximately equal to atmospheric pressure), the atmosphere flows even if the atmospheric pressure becomes 0.2 MPa or more. Do not store the borazine compound in a container.

  Note that “storage” of a borazine compound is a concept that encompasses any point in time from when the compound is filled into a storage container after synthesis of the borazine compound to when it is used for a specific application. . Therefore, for example, not only when a borazine compound is filled in a container and stored in a warehouse, but also when it is transported by a truck or the like when shipped, the concept of “preservation” as used in the present invention. include. In addition, the borazine compound may be stored alone in a storage container. However, in some cases, the borazine compound may be stored in a storage container in a state of being dissolved in an appropriate solvent or the like.

  The second aspect of the present invention also provides a storage container used in the first storage method of the present invention. That is, the second of the present invention is a borazine compound storage container having a pressure resistance of 0.1 MPa or more.

  As described above, the pressure resistance of the storage container of the present invention is 0.1 MPa or more, preferably 0.2 MPa or more, and more preferably 0.3 MPa or more. If the pressure resistance of the container is less than 0.1 MPa, the atmosphere during storage of the borazine compound flows into the container, and the borazine compound may be decomposed by contact with moisture contained in the atmosphere. Moreover, the value measured by the method employ | adopted in the Example mentioned later shall be employ | adopted as a value of the pressure | voltage resistance of the container used for preservation | save of a borazine compound.

  Here, the upper limit value of the pressure resistance of the storage container is not particularly limited from the viewpoint of preventing the storage atmosphere from flowing into the storage container. However, from the viewpoint of ease of handling such as the weight of the container, the pressure resistance of the storage container is preferably 2.0 MPa or less, more preferably 0.5 MPa or less. However, forms outside these ranges can also be employed.

  There are no particular restrictions on specific forms such as the size and material of the storage container. In order to store a small amount of borazine compound synthesized at the laboratory level, a small storage container may be used. Moreover, what is necessary is just to use a big storage container in order to preserve | save the large amount of borazine compounds synthesize | combined on the industrial level.

  As a material for the storage container, for example, a metal material such as stainless steel or Hastelloy, a plastic material such as polytetrafluoroethylene (PTFE), or the like may be employed. Among these, from the viewpoint of high pressure resistance, the container is preferably made of stainless steel. In order to further improve the corrosion resistance of the storage container, the inner surface of the container made of a material such as the metal may be coated with a resin. At this time, the resin used for the coating is not particularly limited, and examples thereof include polytetrafluoroethylene (PTFE) and polypropylene. Especially, it is preferable to coat using PTFE from a viewpoint that the improvement effect of corrosion resistance is excellent. Here, although there is no restriction | limiting in particular about the coating thickness of a resin coating, Preferably it is 10-3000 micrometers, More preferably, it is 500-1000 micrometers.

  Furthermore, the storage container is preferably sealable, and examples of means for enabling sealing of the container include a form in which a valve is provided in a part of the container.

In addition, about the storage temperature conditions in the 1st storage method of this invention, since stability with respect to the temperature also changes according to the kind of borazine compound, it cannot define uniquely, but to maintain desired purity. Suitable temperature conditions can be selected as appropriate. However, in the first storage method of the present invention, the borazine compound is usually stored under a temperature condition of preferably 30 ° C. or lower, more preferably 25 ° C. or lower. If the temperature at which the borazine compound is stored exceeds 30 ° C., impurities in the borazine compound may increase. In particular, when the R ₂ group in the chemical formula 1 is a hydrogen atom or a lower alkyl group having 1 to 2 carbon atoms, this problem tends to be prominent. In the above-mentioned form, it is most preferable that the temperature condition at the time of storage is 30 ° C. or less over the entire period from the start to the end of the storage, but it is not limited to such a form, The temperature condition at the time of storage may be 30 ° C. or less at least at one point of the period from the start to the end, preferably 80% or more of the period, more preferably 90% or more of the period.

  According to the first storage method of the present invention or the second storage container of the present invention, decomposition of the borazine compound during storage can be suppressed, and a decrease in the purity of the borazine compound can be prevented at a very low rate. That is, this invention also provides the borazine compound by which the purity fall was suppressed. At this time, the decrease in purity of the borazine compound provided by the present invention when stored for 60 days is 1% or less, preferably 0.1% or less, and more preferably 0.01%. Note that “the purity reduction of the borazine compound is 1%” means that, for example, when the purity of the borazine compound at the start of storage is 99.8%, the purity of the borazine compound after storage for 60 days is 98.8. Means%. That is, “decrease in purity” means a decrease in absolute purity of the borazine compound, not a relative value before and after storage. In addition, as a purity value of a borazine compound, the value measured by the method employ | adopted in the Example mentioned later shall be employ | adopted.

  The borazine 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. In that case, the borazine compound may be used as it is, or a compound obtained by modifying the borazine compound may be used. A polymer obtained by polymerizing a borazine compound or a borazine compound derivative 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, the “borazine compound”, “derivative of borazine compound”, and “polymer derived therefrom” 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 technique of forming a coating film by applying to a desired site can be used.

  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>
A reaction vessel equipped with a condenser was charged with methylamine hydrochloride (33.5 g), a dehydrated amine salt, and triglyceme (98.6 g) as a solvent while purging with nitrogen, and the reaction system was heated to 100 ° C. The temperature rose.

  On the other hand, sodium borohydride (21.0 g), which is an alkali borohydride, was prepared and added to separately prepared triglyme (88.7 g) to prepare a slurry.

  The sodium borohydride slurry prepared above was slowly added to the reaction vessel heated to 100 ° C. over 1 hour.

  After the addition of the slurry, the reaction system was heated to 200 ° C. over 2 hours and further aged at 200 ° C. for 2 hours to synthesize N, N ′, N ″ -trimethylborazine.

  The obtained N, N ′, N ″ -trimethylborazine was distilled at 150 to 220 ° C. to purify N, N ′, N ″ -trimethylborazine. The purity of the obtained purified N, N ′, N ″ -trimethylborazine was measured and found to be 99.8%. The purity of the borazine compound was measured using gas chromatography. The measurement conditions were as follows. Street.

  As a borazine compound storage container, a stainless steel container having an inner surface coated with PTFE (coating thickness: 500 μm) was prepared. The pressure resistance of the prepared storage container was measured and found to be 0.2 MPa. At this time, the pressure resistance of the storage container is measured by installing a leak valve in the container, filling the container with nitrogen gas at 23 ° C., and leaking nitrogen gas from the container through the leak valve. The filling pressure at the start was measured using a pressure gauge and calculated by subtracting the atmospheric pressure from the measured value.

  The purified N, N ′, N ″ -trimethylborazine obtained above is filled in a prepared storage container, sealed, and stored at 25 ° C. for 60 days under a pressure of 0.1 MPa with nitrogen gas. The purity of N, N ′, N ″ -trimethylborazine after storage was measured and found to be 99.8%, and no decrease in the purity of the borazine compound was observed.

<Comparative example>
N, N ′, N ″ -trimethylborazine was synthesized by the same method as in Example 1 and purified by distillation.

  As a borazine compound storage container, a stainless steel container having an inner surface coated with PTFE (coating thickness: 500 μm) was prepared. The pressure resistance of the prepared storage container was measured and found to be 0.05 MPa.

  The purified N, N ′, N ″ -trimethylborazine obtained above was filled in a prepared storage container, sealed, and stored for 60 days at 35 ° C. N, N ′, N ″ after storage. -When the purity of trimethylborazine was measured, it was 95.1%, and a 4.7% decrease in the purity of the borazine compound was observed.

<Example 2>
In a reaction vessel equipped with a condenser, B, B ′, B ″ -trichloro-N, N ′, N ″ -trimethylborazine (41.2 g), which is a halogenated borazine compound, and a solvent while purging with nitrogen. Diethyl ether (80 g) was charged, and an ethyl magnesium bromide diethyl ether solution (3 M, 200 mL) was added dropwise at 20 ° C. over 3 hours. Thereafter, the mixture was aged for 2 hours under reflux conditions, and the reaction liquid was cooled to room temperature, and then impurities were separated by filtration.

  Diethyl ether was distilled off from the filtrate obtained by the above filtration, followed by further filtration, and the filtrate was distilled under reduced pressure to purify B, B ′, B ″ -triethyl-N, N ′, N ″ -trimethylborazine. did. The purity of the obtained purified B, B ′, B ″ -triethyl-N, N ′, N ″ -trimethylborazine was measured by the same method as in Example 1 and found to be 99.5%.

  The purified B, B ′, B ″ -triethyl-N, N ′, N ″ -trimethylborazine obtained above is filled and sealed in the same storage container as in Example 1 above, and nitrogen gas is used. It was stored for 60 days at 25 ° C. under a pressure of 0.1 MPa. The purity of B, B ′, B ″ -triethyl-N, N ′, N ″ -trimethylborazine after storage was measured and found to be 99.5%, and no decrease in the purity of the borazine compound was observed.

< Reference Example 3>
B, B ′, B ″ -triethyl-N, N ′, N ″ -trimethylborazine was synthesized and purified by the same method as in Example 2 except that the temperature condition during storage was set to 60 ° C. And saved. The purity of B, B ′, B ″ -triethyl-N, N ′, N ″ -trimethylborazine after storage was measured to be 98.8%, and a 0.7% decrease in the purity of the borazine compound was observed. It was.

From the results shown in the above examples , reference examples and comparative examples, the borazine compound is effectively decomposed by storing the borazine compound in a storage container having a predetermined pressure and pressure under a predetermined temperature condition. It can be shown that it can be suppressed.

  Therefore, according to this invention, the quality of the use (for example, interlayer insulation film for semiconductors) for which a borazine compound is used can be further improved.

Claims (3)

A temperature of 30 ° C. or less, under nitrogen, in a container having the above withstand pressure 0.1 MPa, have a storage step of storing a borazine compound purified by distillation, the borazine compound represented by the following formula 1:
In the formula, each R ₁ and each R ₂ may be the same or different, and each is a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.
The preservation | save method of the borazine compound which is represented by these .   The storage method according to claim 1, wherein the temperature condition is 30 ° C. or less in 80% or more of a period from the start to the end of storage.   The preservation | save method of Claim 2 whose period which makes the said temperature conditions more than 30 degreeC is 12 days or less.