JP2011046569A - Method for producing diborane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing high purity diborane having a low higher-order borane content and useful as a dopant and a BPSG (boron phosphor silicate glass) insulating film-forming material in semiconductor manufacturing and solar cell manufacturing, and as a rocket propellant and the like in an easy and inexpensive way in good yield. <P>SOLUTION: The method for producing diborane includes reacting a sodium borohydride with a trihalogenated boron in an atmosphere of an inert gas having hydrogen concentration of 0.01-50 vol.% in the presence of a solvent. Ultrahigh purity diborane required in semiconductor use and the like can be produced industrially efficiently. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing diborane useful as a dopant, a BPSG insulating film forming material, a rocket propellant or the like in semiconductor production or solar cell production.

As a method for producing diborane, a method by reduction of boron trichloride or boron trifluoride is known, and methods for obtaining diborane from sodium borohydride and boron trichloride have been proposed (Patent Documents 1 and 2). ). However, since diborane molecules (B ₂ H ₆ ) are easily polymerized and have the property of producing higher-order boranes (eg, B ₄ H ₁₀ , B ₅ H ₉ , B ₅ H _11, etc.), production of diborane In this case, higher-order borane may be generated to lower the purity. In particular, when ultra-high-purity diborane is required as a boron source suitable for semiconductor manufacturing materials, it is necessary to continue purification after the production of diborane. There are problems such as a decrease in yield. Therefore, development of a production method that can obtain diborane having a low high-order borane content and high purity is desired.

US Pat. No. 3,142,538 Japanese Patent Laid-Open No. 3-197301

  An object of the present invention is to provide a method for producing diborane having a low high-order borane content and high purity in a high yield by a simple and inexpensive method.

  The present invention relates to a method for producing diborane, in which sodium borohydride and boron trihalide are reacted in an inert gas atmosphere having a hydrogen concentration of 0.01 to 50 vol% in the presence of a solvent.

  In the reaction for obtaining diborane from the sodium borohydride and boron trihalide according to the present invention, 0.12 to 0.16 mol of boron trihalide is added at a reaction temperature of -10 to 0.1 mol per 1 mol of sodium borohydride. It preferably comprises a first reaction step for reacting at 40 ° C. and a second reaction step for reacting 0.17 to 0.21 mol of boron trihalide at a reaction temperature of 20 to 60 ° C.

  The reaction temperature in the first reaction step is −10 to 40 ° C., and preferably 0 to 40 ° C. As reaction time, it is preferable to set it as 1-2 hours, for example.

  The reaction temperature in the second reaction step is 20 to 60 ° C, and preferably 30 to 50 ° C. The reaction time is preferably 1 to 6 hours, for example.

  Examples of the boron trihalide include boron trichloride, boron trifluoride, and boron tribromide. Of these, boron trichloride and boron trifluoride are preferred.

  When the boron trihalide is boron trichloride, the first reaction step and the second reaction step according to the present invention are considered to be represented by the following reaction formulas (1) and (2), respectively. It is done.

7NaBH ₄ + BCl ₃ → 4NaB ₂ H ₇ + 3NaCl (1)
6NaB ₂ H ₇ + 2BCl ₃ → 7B ₂ H ₆ + 6NaCl (2)
That is, if the reaction is carried out in two steps by the first exothermic reaction represented by the formula (1) and the second endothermic reaction represented by the formula (2), the target diborane is obtained in a high yield, It is suitable because it is obtained with high purity.

  Examples of the solvent used in the reaction of the sodium borohydride according to the present invention with boron trihalide include ethylene glycol dimethyl ether compounds such as diglyme and triglyme. Among these, diglyme and triglyme are preferably used.

  As the usage-amount of the said solvent, it is preferable that it is 8-30L with respect to 1 kg of sodium borohydride, for example, and it is more preferable that it is 10-18L.

  When the amount of the solvent used is less than 8 L with respect to 1 kg of sodium borohydride, the sodium borohydride may not be sufficiently dissolved and may become difficult to react. When it exceeds 30 L, volume efficiency is low. Not economical.

  Examples of the inert gas include nitrogen, helium, and argon. Among these, nitrogen and helium are preferable, and nitrogen is more preferably used.

  The density | concentration of the hydrogen gas in the mixed gas of the hydrogen gas concerning this invention and the said inert gas is 0.01-50 vol%, and it is preferable that it is 1-30 vol%. When the hydrogen concentration in the mixed gas is less than 0.01 vol%, the formation of higher-order diborane is difficult to suppress, and when it exceeds 50 vol%, there is no effect commensurate with the amount used and it is not economical.

  Next, embodiments of the present invention will be specifically described.

  A stainless steel reaction vessel equipped with a gas blowing tube, a stirrer, and a reflux condenser is charged with a predetermined amount of solvent and sodium borohydride, and a predetermined concentration of hydrogen-containing inert gas is cooled (for example, 30 ° C. or less) B) into the liquid phase to replace the reaction system. Next, a pressurized state (for example, 0.03 MPaG) is set using a hydrogen-containing inert gas having a predetermined concentration, and the first reaction is performed while maintaining a predetermined reaction temperature. In this case, undissolved sodium borohydride may show a suspended state, but as it is, blowing of boron trihalide is started, and a predetermined amount is added and stopped. The first reaction step is preferably completed in 1 to 2 hours. If the time is long, side reactions such as methane formation occur, which is not preferable for improving yield and purity.

  Since a small amount of gas such as methane or methyl chloride is generated in the first reaction, the hydrogen-containing inert gas having a predetermined concentration is discharged from the reaction system prior to the next second reaction step.

  After purging the gas component containing the by-product gas with a hydrogen-containing inert gas having a predetermined concentration, the hydrogen-containing inert gas having a predetermined concentration is subsequently used to be pressurized (for example, 0.04 MPaG). The temperature is raised to the reaction temperature, and a predetermined amount of boron trihalide is blown into the second reaction step.

  As the boron trihalide is blown in the second reaction step, diborane is generated in the reaction solution. The diborane thus obtained can be isolated by condensing and solidifying the diborane together with a hydrogen-containing inert gas, for example, in a cold trap cooled to about −196 ° C. using liquid nitrogen.

  The diborane obtained in this way has a lower high-order borane content and higher purity than those obtained by the conventional method. Can be increased.

  For example, diborane obtained by the production method according to the present invention may be purified by the following method.

That is, the diborane obtained as described above is gasified with a reboiler, and then impurities such as CO ₂ and C ₂ H ₆ that have a boiling point close to that of diborane are packed in a packed tower packed with an adsorbent having uniform pores. It can be purified by adsorbing and removing, condensing with refluxing liquid, condensing with a condenser attached to the upper part of the tower, and refluxing.

  Examples of the adsorbent include silica gel, zeolite molecular sieve, activated alumina, and the like, but those that do not affect the quality of diborane are good, and zeolite molecular sieve is preferably used.

  The distillation pressure is preferably 0.01 to 1.5 MPaG. If it is less than 0.01 MPaG, there is a risk of causing safety problems such as leakage of outside air. If it exceeds 1.5 MPaG, the safety design of the apparatus is costly and not economical.

  The distillation temperature is determined according to the pressure and is preferably -90 to -20 ° C.

  According to the present invention, diborane having a low high-order borane content and high purity can be produced with high yield by a simple and inexpensive method. For example, ultra-high purity diborane required for semiconductor applications can be industrially efficiently produced.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
Made of SUS304 with an internal volume of 10 L equipped with a reflux condenser cooled to −50 ° C. at the outlet of the reactor, followed by a first cold trap cooled to about −78 ° C. and a second cold trap cooled to about −196 ° C. An electromagnetic stirring type reactor was prepared.

  The reactor was charged with 6 L of triglyme, 500 g (13.2 mol) of powdered sodium borohydride was added, and the content liquid was brought to 25 ° C. while blowing 1 vol% hydrogen-containing nitrogen gas at 10 L / min. .

  Next, 221.0 g (1.89 mol) of gaseous boron trichloride was blown into the content liquid of the reactor over a period of 1 hour using a flow meter to perform the first reaction step. The reaction was exothermic and a small amount of methane-containing gas was generated.

  Next, after replacing the inside of the reaction system with nitrogen gas containing 1 vol% hydrogen, the temperature was raised to 40 ° C., and 294.6 g (2.51 mol) of boron trichloride was blown in over 1.5 hours. A second reaction was performed.

  After blowing all the amount of boron trichloride, blowing of nitrogen gas containing 1 vol% hydrogen was further continued at 40 ° C. for 3 hours to complete generation of diborane to be generated. Table 1 shows the yield, purity, and high-order borane content of diborane collected in the second cold trap with respect to sodium borohydride.

  After the obtained diborane was vaporized, a SUS316 tube having an inner diameter of 31 mmφ and an effective length of 1000 mm was adsorbed using a column packed with zeolite molecular sieve (Zeoram 4A (average pore diameter 4 mm) manufactured by Tosoh Corporation) as an adsorbent. Low temperature distillation purification was performed.

  ZEOLAM 4A was previously filled with 700 ml of an extruded cylindrical product having a diameter of 1.6 mmφ × 5 to 7 mm, which was fired at 400 ° C. in a helium stream for 4 hours. Before introducing the raw material gas, the entire system was replaced with nitrogen gas containing 1 vol% hydrogen to make it oxygen-free. Then, while cooling the reboiler jacket with liquid nitrogen, the diborane obtained above was charged, and the condenser was cooled to -80 ° C and the packed tower was cooled to -76 ° C. The temperature of the reboiler was gradually raised to evaporate diborane. In the temperature raising method, the reboiler refrigerant was switched from liquid nitrogen to dry ice methanol solution, and methanol was added thereto to adjust the temperature to about -71 ° C, while evaporating the diborane to perform rectification. The distillation pressure at this time was kept at 0.15 MPaG. After carrying out the total reflux operation, the concentrated low boiling point gas was discharged to the top of the condenser, and the purified liquefied diborane was analyzed, and recovered as purified diborane when the methane concentration became 10 ppm or less. Table 1 shows the yield, purity, and high-order borane content of purified diborane relative to sodium borohydride.

Example 2
In Example 1, dipolane was produced in the same manner as in Example 1 except that 20 vol% hydrogen-containing nitrogen gas was used instead of 1 vol% hydrogen-containing nitrogen gas. In Example 1, the diborane was purified in the same manner as in Example 1 except that 20 vol% hydrogen-containing nitrogen gas was used instead of replacing the entire system with 1 vol% hydrogen-containing nitrogen gas. Got. Table 1 shows the yield, purity, and high-order borane content of the obtained diborane and purified diborane with respect to sodium borohydride.

Example 3
In Example 1, instead of triglyme 6L, diglyme 6L was replaced with 221.0 g (1.89 mol) of boron trichloride in the first reaction step, and 128.1 g (1.89 mol) of boron trifluoride. Was replaced with 294.6 g (2.51 mol) of boron trichloride in the second reaction step, except that 170.2 g (2.51 mol) of boron trifluoride was used. Thus, diborane was produced. Further, in the same manner as in Example 1, the diborane was purified to obtain purified diborane. Table 1 shows the yield, purity, and high-order borane content of the obtained diborane and purified diborane with respect to sodium borohydride.

Comparative Example 1
In Example 1, diborane was produced in the same manner as in Example 1 except that nitrogen gas alone was used instead of 1 vol% hydrogen-containing nitrogen gas. In Example 1, the diborane was purified in the same manner as in Example 1 except that nitrogen gas alone was used instead of replacing the entire system with 1 vol% hydrogen-containing nitrogen gas to obtain purified diborane. . Table 1 shows the yield, purity, and high-order borane content of the obtained diborane and purified diborane with respect to sodium borohydride.

Claims (5)

  A method for producing diborane, in which sodium borohydride and boron trihalide are reacted in an inert gas atmosphere having a hydrogen concentration of 0.01 to 50 vol% in the presence of a solvent.   The reaction comprises a first reaction step in which 0.12 to 0.16 mol of boron trihalide is reacted at a reaction temperature of −10 to 40 ° C. with respect to 1 mol of sodium borohydride; The method for producing diborane according to claim 1, comprising a second reaction step in which 17 to 0.21 mol is reacted at a reaction temperature of 20 to 60 ° C.   The method for producing diborane according to claim 1 or 2, wherein the boron trihalide is boron trichloride or boron trifluoride.   The method for producing diborane according to any one of claims 1 to 3, wherein the solvent is diglyme or triglyme.   The method for producing diborane according to any one of claims 1 to 4, wherein the inert gas is nitrogen, helium, or argon.