JP6016674B2 - Process for producing silanes - Google Patents

Description

  The present invention relates to a method for producing silanes.

In recent years, with the development of the electronics industry, the demand for silicon-based thin films for semiconductor production such as polycrystalline silicon thin films or amorphous silicon thin films has increased rapidly. Silanes such as monosilane (SiH ₄ ) and disilane (Si ₂ H ₆ ) have recently been gaining importance as raw materials for the production of such silicon-based thin films for semiconductor production. In particular, disilane (Si ₂ H ₆ ) has been refined. As a raw material for the most advanced silicon-based thin films for semiconductor manufacturing, demand is expected to increase significantly in the future.

  As a method for producing silanes starting from a silicon alloy, a method of generating silane by adding magnesium silicide in small portions to an ammonium halide ammonia solution, or a mixture of magnesium silicide and ammonium halide with a liquid A method for producing silane by dropping ammonia (Patent Document 1) is known.

  In the latter method, it is disclosed that a silicon powder having a particle size of 200 mesh or less, a magnesium powder, and a lead powder having a particle size of 200 mesh or less are fired. Further, it is disclosed that a mixture composed of silicon powder, magnesium powder and the like is put in a magnetic crucible and fired, and then the obtained alloy is pulverized in a mortar to 80 mesh or less (Patent Document 2).

In addition, it is disclosed that a mixture of magnesium silicide and ammonium chloride having a molar ratio of 1: 2 is continuously supplied to a reactor using a rotary feeder (Patent Document 3).
However, these methods still have many variations in the production of silanes, and there is room for improvement in order to obtain silanes stably and continuously in a high yield on an industrial scale.

Shoko 42-12060 JP-A 62-56314 JP 62-292614 A

  In accordance with the recent increase in demand for silanes, the present invention produces silanes by reacting an alloy containing magnesium silicide, which is one of its production methods, in an ammonia solution in which ammonium halide is dissolved. In particular, the present invention provides a method for producing monosilane and disilane, which makes it possible to continuously and stably carry out the production on an industrial scale.

  The method for producing silanes of the present invention is a process for producing an alloy containing magnesium silicide by continuously supplying a mixture containing silicon powder and magnesium powder to a firing furnace and continuously firing the mixture. (I), an alloy containing magnesium silicide and ammonium halide are mixed in a liquid ammonia solvent to produce silanes (II), wherein the silicon powder is JIS R 9301-2 -2, the angle of repose measured in accordance with -2 is 30 to 70 °, and the average particle size is 5 to 200 µm.

  The firing in the step (I) is preferably performed at 400 to 900 ° C. in an inert gas, and the step (I) and the step (II) are preferably performed continuously. In addition, that the process (I) and the process (II) are continuously performed means that the product is supplied to the next process without extracting the product between the two processes. Therefore, it is also included in the present invention that a storage tank, a hopper, a mixer and the like are installed between step (I) and step (II) and supplied to step (II).

The alloy containing magnesium silicide preferably has an angle of repose measured according to JIS R 9301-2-2 of 30 to 70 °.
Further, the mixture includes a powder containing at least one metal element selected from Groups 3 to 16 of the periodic table (however, excluding silicon), and the powder contains 1 atomic% of silicon in the mixture. And 0.5 to 30 atomic% is preferable.

  Moreover, the alloy containing magnesium silicide of the present invention continuously feeds a mixture containing silicon powder and magnesium powder to a firing furnace, and continuously in a inert gas at 400 to 900 ° C. The silicon powder obtained by firing has an angle of repose measured according to JIS R 9301-2-2 of 30 to 70 ° and an average particle diameter of 5 to 200 μm.

Furthermore, the silanes of the present invention can be obtained by mixing the alloy containing magnesium silicide and ammonium halide in a liquid ammonia solvent.
In the method for producing an alloy containing magnesium silicide of the present invention, a mixture containing silicon powder and magnesium powder is continuously fed into a firing furnace, and the mixture is continuously produced at 400 to 900 ° C. in an inert gas. And the step (I) of producing an alloy containing magnesium silicide, the silicon powder has an angle of repose measured according to JIS R 9301-2-2 of 30 to 70 °, And an average particle diameter is 5-200 micrometers.

  According to the production method of the present invention, the production of silanes due to variations in production over time, which is manifested in continuous production on a large scale, which is not a problem when silane production is performed on a laboratory scale. Yield reduction is improved, and silanes can be continuously produced in a high yield stably and economically on an industrial scale.

FIG. 1 is an example of a method for producing silanes of the present invention.

  The inventors of the present invention have provided a method for producing silanes by supplying an alloy containing magnesium silicide into a liquid ammonia solution of ammonium halide, and collecting silanes that are manifested in large-scale continuous production. As a result of intensive investigations to solve the manufacturing problem that the rate is reduced, the crystal structure of magnesium silicide is formed as high as possible, and the alloy containing magnesium silicide is a liquid of ammonium halide. It came to the conclusion that it is very important to supply the ammonia solution quantitatively, stably and continuously without variation.

  That is, magnesium silicide is an intermetallic compound formed by reaction of silicon and magnesium at an atomic ratio of 1: 2, and usually takes the crystal structure of magnesium silicide only with this stoichiometric composition. If the supply of silicon and magnesium deviates from this composition, excess silicon or magnesium remains unreacted and cannot contribute to the formation of silanes in a liquid ammonia solution of ammonium halide, resulting in a decrease in the yield of silanes. become. The atomic ratio of silicon and magnesium supplied during firing is more preferably a ratio close to the stoichiometric composition from the viewpoint of silane yield.

  Magnesium silicide is generally manufactured by firing silicon and magnesium metals, but it is also important that the crystal structure of magnesium silicide be formed to a high degree by this firing, resulting in insufficient crystallinity. Then, the reaction rate becomes low in the ammonium halide ammonia solution, and the yield of silanes becomes low. In addition, if the crystallinity is not stable, the generation of silanes becomes irregular due to the reaction in liquid ammonia, and the production amount varies, which may hinder the subsequent purification and collection steps.

  In the production of magnesium silicide, a method for producing silanes by firing a metal as a raw material and then supplying an alloy containing magnesium silicide obtained after firing into an ammonia solution in which ammonium halide is dissolved. If it is, there is no particular problem even if other steps are included in the middle, but furthermore, in industrial production, economic efficiency must be taken into consideration, and continuous production in as short a time as possible is required. It is done. Therefore, in the industrial production of magnesium silicide, the metal as a raw material is usually continuously supplied, for example, to a rotary kiln capable of continuous firing, and fired and continuously extracted from the firing furnace. It is preferable that the alloy containing magnesium silicide is continuously supplied in an ammonia solution in which ammonium halide is continuously dissolved to produce silanes.

  In the present invention, the formation of an alloy containing magnesium silicide described above in such a series of industrial manufacturing processes is carried out stably and continuously at a constant rate, and silanes are stably added. The method of manufacturing is found out.

Hereinafter, the present invention will be described in detail.
(Manufacture of alloys containing magnesium silicide)
An alloy containing magnesium silicide is manufactured in a powder form so as to easily react with an ammonia solution in which ammonium halide is dissolved.

  Accordingly, silicon is preferably powder, the particle size is 200 μm or less, and the average particle size is 5 to 200 μm, preferably 5 to 100 μm. If the particle size is too large, the crystallinity of the magnesium silicide-containing alloy is not lowered, and it is too small to increase the crystallinity. However, it is fine, so it sticks to the wall, dust is flying, etc. It is not difficult to handle. Magnesium silicide is formed by entering magnesium into the silicon particles. Therefore, when the silicon particle size is increased, the magnesium cannot sufficiently enter and the crystallinity is lowered. The purity of silicon is not particularly limited, but is preferably 90 to 99.999%, more preferably 93 to 99.999%, and still more preferably 97 to 99.999%.

Furthermore, in the present invention, the angle of repose of silicon is very important, and is 30 ° or more and 70 ° or less. More preferably, it is 60 ° or less. In the present invention, the angle of repose is measured as described in the examples. If the angle of repose is smaller than 30 °, the fluidity is too high, and there is a concern that the mixture may be classified with magnesium or transferred. While moving in the firing furnace or when transferring to the firing furnace, the raw material mixed powder is classified little by little due to the good fluidity of the silicon particles, and gradually deviates from the assumed mixing ratio of magnesium and silicon. will have to go. For this reason, the crystal structure of magnesium silicide is not sufficiently formed in the reaction in the firing furnace (unreacted magnesium and silicon remain by classification), and the production amount of silanes decreases. If the angle of repose is greater than 70 °, the movement of the particles is adversely affected, and there is a concern that the transfer of particles varies.
Furthermore, if the movement of the silicon particles and the magnesium particles is poor, the particles may be stagnated in the firing furnace, and the reaction may be hindered.

  In addition, by using silicon powder having an angle of repose within the above range, the atomic ratio of silicon and magnesium can be quantitatively and stably supplied to the firing furnace without variation in a ratio close to the stoichiometric composition, Furthermore, as will be described later, it becomes easy to control the movement of particles in an arbitrary baking furnace (baking apparatus) such as a belt furnace, a rotary furnace, a cart furnace, or the like. Therefore, highly silicified magnesium silicide can be obtained, and silanes can be obtained in high yield.

  Magnesium is not particularly limited in shape, and any shape having a granular shape, a chip shape, a ribbon shape, or the like can be suitably used. The particle diameter or major axis is more preferably 1 mm or less. The fact that the particle size of magnesium is small is not particularly limited with respect to the formation reaction of magnesium silicide, but it is preferably 20 μm or more because safety problems such as dust explosion occur in handling. The angle of repose of magnesium is not particularly limited, but is preferably 30 to 70 ° for stable and continuous supply.

  Moreover, if it is a range which does not inhibit the reaction to the mixture of silicon and magnesium, there is no problem even if an additive is added, and in particular, when it is desired to increase the yield of disilane, groups 3 to 16 of the periodic table are included. A powder containing at least one metal element selected from the above (excluding silicon) may be contained in the mixture in an amount of 0.5 to 30 atomic% with respect to 1 atomic% of silicon. Specific examples of the metal element include Tl, In, Ga, Al, B, Pb, Sn, Ge, C, Bi, Sb, As, P, Po, Te, Se, and S, and preferably Pb. , Sn, Al, Bi.

  The repose angle of these metal powders is not particularly limited, but is preferably 30 ° or more and 70 ° or less. The particle diameter of these metal powders is not particularly limited, but the particle diameter is preferably 200 μm or less, more preferably the average particle diameter is 5 to 200 μm, and further preferably 5 to 100 μm.

  These raw materials are preferably mixed with a mixer before firing in order to improve the uniformity of the mixture. The mixer is not particularly limited as long as it can mix particles, and a V-type mixer, a paddle mixer, a ribbon blender, a nauter mixer, and the like can be used.

  The crystal structure of an alloy containing magnesium silicide can be obtained by manufacturing silicon and magnesium with additives, if necessary, by heat-firing, compaction under mechanical stress, plastic working such as rolling, or both. Although it can be obtained, industrially, a method of heating and baking is generally preferred in order to manufacture in a short time.

  It is preferable that the mixture of silicon and magnesium and optionally added additional elements is quantitatively and continuously supplied to the firing furnace. At this time, it is more preferable that there is no variation in the supply amount from the viewpoint of suppressing the variation in crystallinity of magnesium silicide. For quantitative supply, it is preferable to store the mixed raw material once in a hopper and use a screw feeder, a rotary valve, a vibratory feeder, a table feeder, a belt feeder, etc. It is not limited.

  Originally, silicon and magnesium react at an atomic ratio of 1: 2 stoichiometric composition as described above to produce magnesium silicide, but it is very difficult to completely react in industrial firing. There are many cases. In this case, the unreacted raw material is discarded as it is, which increases the manufacturing cost. In view of this, it is generally carried out by charging the cheaper raw material cost more than the stoichiometric composition and consuming as much of the expensive raw material as possible. Specifically, the mixing ratio of silicon and magnesium (silicon: magnesium) is preferably 1: 1.2 to 1: 2.8, more preferably 1: 1.5 to 1: 2.5, most preferably 1: 1.8 to 1: 2.2. In firing that does not take into account economic efficiency, the preparation of raw materials does not need to be focused on the stoichiometric composition.

  In the present invention, the structure and method of the firing apparatus is not particularly limited as long as the raw material can be continuously fired, and any apparatus can be used. For example, a belt furnace, a rotary furnace, which supplies powder to the high temperature part of the heating furnace, A cart furnace is used.

  The atmosphere at the time of baking is implemented at 400-900 degreeC in inert gas, such as argon and helium. Note that the inert gas may contain a reducing gas such as hydrogen. The firing time varies depending on the temperature, and is not particularly limited as long as the time until the crystallinity of the alloy containing magnesium silicide is sufficiently increased can be maintained.

  The magnesium silicide-containing alloy obtained by the above operation is subsequently transferred for reaction in an ammonia solution in which ammonium halide is dissolved for the production of silanes.

(Manufacture of silanes)
The transferred magnesium silicide-containing alloy (preferably powder) reacts in an ammonia solution in which ammonium halide, preferably ammonium chloride is dissolved, to form silanes. This reaction is also continuous. It is preferable to carry out in an industrial manufacturing method, and it is preferable to quantitatively supply an alloy containing magnesium silicide continuously. Therefore, it is preferable to store the alloy once in a hopper or the like and appropriately employ a supply device such as a screw feeder or a rotary valve. At this time, the angle of repose of the alloy containing magnesium silicide is not particularly limited, but is preferably 30 to 70 ° because it can be stably continuously supplied and silanes can be obtained in a high yield. The reason for this is as described in the above explanation for defining the angle of repose of silicon. In the present invention, since an alloy containing magnesium silicide is produced by a specific step (I), an alloy having a desired angle of repose can be produced, and the alloy can be continuously subjected to step (II). If the angle of repose of the alloy obtained by continuous firing does not fall within this range, the angle of repose can be appropriately fallen within this range by grinding or sieving. However, since the manufacturing cost increases due to an increase in the number of steps, it is preferable to manufacture the product by an inexpensive method as much as possible in industrial production.

  There is no particular limitation on the reaction between the supplied magnesium silicide powder and ammonium halide, preferably ammonium chloride, and various conventional methods can be employed. For example, magnesium silicide and ammonium halide may be premixed to form a mixture, or may be separately charged continuously into liquid ammonia, or a method of continuously supplying liquid ammonia to this mixture But you can. Moreover, after putting either magnesium silicide or ammonium halide into liquid ammonia, the other may be put into the liquid ammonia.

  Alternatively, the ammonium halide may be preliminarily dissolved in liquid ammonia, or a part of the ammonium halide is dissolved in liquid ammonia, and a part of the ammonium halide is mixed with magnesium silicide and then reacted with magnesium silicide. May be.

  The reaction only needs to proceed continuously in an ammonia solution. Therefore, the reactor is not particularly limited, and a reaction method such as a reaction tank attached with a stirrer or a screw kneader is appropriately employed. The generated ammonia is preferably liquefied as appropriate and used as a liquefied ammonia solution.

  It is economically preferable to use a reaction molar equivalent of the alloy containing silicon magnesium and ammonium halide. However, in order to make the alloy containing magnesium silicide react more, the amount of ammonium halide used is actually An excess is preferred in terms of the yield of silanes. For example, the molar ratio of ammonium halide to silicon (ammonium halide / silicon) of the alloy containing magnesium silicide is appropriately selected according to the alloy formation rate, but is preferably 4.0 or more, more preferably 4. It is 4 or more, and it is preferable to make it 6 or less from an economical viewpoint.

  The reaction temperature for silane generation may be equal to or lower than the temperature at which ammonia is liquefied, and the reaction time is not particularly limited as long as magnesium silicide sufficiently reacts, and is carried out under conventionally known conditions.

  The produced silanes are usually separated by distillation after removing ammonia by adsorption, distillation separation, removal by acid neutralization, etc. in an inert gas in an ammonia condenser to obtain a mixture of monosilane and disilane. The mixture can be separated and recovered by distillation separation, adsorption separation, separation by recrystallization method, or the like. The separated ammonia can be recycled as an ammonia solution.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to these Examples.
[Test method]
(1) Method of measuring angle of repose The angle of repose of the powder was measured in accordance with JIS R9301-2-2 (a method of measuring the angle of repose of alumina powder). That is, 200 g of powder was dropped onto the substrate at a rate of 20 to 60 g per minute from the height of 2 to 4 cm of the upper edge of a commercially available glass funnel having a nozzle inner diameter of 6 mm, and the generated conical shape The angle of repose was calculated from the diameter and height of the deposit.
For the measurement, the angle of repose (injection method) described on pages 27 to 28 of the ceramics dictionary second edition (issued on March 25, 1997, Japan Ceramic Society) can be referred to.

(2) Measuring method of average particle diameter The average particle diameter of the powder was measured using a SALD-2000J laser diffraction particle size distribution measuring device (Microtrack) manufactured by Shimadzu Corporation.
That is, a powder was put into water as a dispersion medium, a laser having a wavelength range of 0.03 to 700 μm was applied to a sample which was ultrasonically dispersed for about 10 minutes, and the particle size was measured from the diffraction.

(3) Determination of silanes The silanes produced by the reaction were separated from the ammonia gas that was regularly entrained, and then the monosilane and disilane were liquefied and collected in a container by distillation separation, and the amount produced was determined by weight change. . From the amount produced, the yield (%) relative to the silicon powder of the raw material was calculated.
Monosilane and disilane were confirmed by gas chromatography analysis.

[Example 1]
(Manufacture of alloys)
Silicon powder (Made by former company, 200: average particle size = 39 μm (however, measured with an aqueous solvent by Microtrac), repose angle 43 °, purity 99.3 wt% or more) 201 kg, magnesium powder (Nippon Thermo Chemical Co., Ltd.) (Made by Mg20-50: Purity 99.90% or more, 0.5 to 0.85 mm particle size is 60% by weight or more) 348 kg of each was put into a V-type mixer and mixed thoroughly to obtain mixed metal powder It was. The mixed metal powder was transferred to a hopper and continuously supplied to a firing furnace with a feed rate adjusted to 50 kg / h using a rotary valve.

  The continuous firing was performed by slowly rotating the firing furnace while circulating argon gas at 200 NL / min so that the mixed metal powder charged stayed in an electric furnace at a temperature of 500 ° C. or higher for 3 hours. After firing, the obtained alloy was cooled to 50 ° C. or lower and then transferred to a hopper and stored. The angle of repose of this alloy containing magnesium silicide was 48 °.

(Manufacture of silanes)
A liquefied ammonia is supplied to a biaxial blender reactor rotating at 35 rpm with a capacity of 700 L, and the calcined magnesium silicide stored in the hopper is temporarily stored in the reactor cooled to about −33 ° C. The containing alloy was fed into the biaxial blender reactor at a feed rate of 50 kg / h using a rotary valve in a nitrogen atmosphere. On the other hand, ammonium chloride stored in a nitrogen atmosphere was introduced so as to have a 4.5-fold molar amount relative to silicon in the alloy containing magnesium silicide, and a silane generation reaction was performed.

The produced silane gas is separated from the accompanying ammonia by an ammonia condenser and hydrochloric acid water washing in an inert gas, and then the silane gas is separated by distillation to obtain monosilane (SiH ₄ ) and disilane (Si ₂ H). ₆ ) Separated and collected. After collection, the amount of silane produced was quantified from the collected weight, and the product was confirmed by gas chromatography.
The results are shown in Table 1.

[Example 2]
Except for changing to silicon powder (formerly manufactured by Co., Ltd., 120-180th: average particle size = 81 μm (however, measured with an aqueous solvent by Microtrac), angle of repose 35 °, purity 98.3 wt% or more) Performed as in Example 1.
The results are shown in Table 1.

[Example 3]
Except that 29.6 kg (corresponding to 2 atomic% of Si) of lead powder (manufactured by Wako Pure Chemical Industries, average particle size of 200 mesh or less) was further added to the mixed metal powder of silicon and magnesium, the same procedure as in Example 1 was performed. It was.
The results are shown in Table 1.

[Example 4]
The same procedure as in Example 1 was performed except that 17.0 kg (corresponding to 2 atomic% of Si) of tin powder (manufactured by Wako Pure Chemical Industries, average particle size of 200 mesh or less) was further added to the mixed metal powder of silicon and magnesium. It was.
The results are shown in Table 1.

[Example 5]
The same procedure as in Example 1 was performed except that 3.9 kg (corresponding to 2 atomic% of Si) of aluminum powder (pure particle size 250 mesh) was added to the mixed metal powder of silicon and magnesium.
The results are shown in Table 1.

[Example 6]
This was performed in the same manner as in Example 1 except that 29.9 kg (corresponding to 2 atomic% of Si) of bismuth powder (manufactured by Soekawa Rikagaku Co., Ltd., particle size of 200 mesh or less) was added to the mixed metal powder of silicon and magnesium.
The results are shown in Table 1.

[Example 7]
The silicon powder used in Example 2 is sieved, and particles of 160 μm or more are cut and changed to silicon powder (average particle diameter 65.0 μm (measured with a water solvent in a microtrack), angle of repose 38 °). The procedure was the same as in Example 1 except that.
The results are shown in Table 1.

[Example 8]
The same procedure as in Example 1 was performed except that the silicon powder used in Example 1 was sieved to obtain particles having a particle size of 10 μm or less. The average particle size of the silicon powder after sieving was 8.0 μm, and the angle of repose was 60 °.
The results are shown in Table 1.

[Comparative Example 1]
The same procedure as in Example 1 was performed except that the silicon powder used in Example 1 was sieved to remove particles having a particle size of 10 μm or less. The average particle size of the silicon powder after sieving was 27.5 μm, and the angle of repose was 23 °.
When this raw material powder was mixed and then baked, the efficiency of silane generation was reduced.
The results are shown in Table 1.

[Comparative Example 2]
The same procedure as in Example 1 was performed except that the silicon powder used in Example 1 was sieved to obtain particles having a particle size of 10 μm or less. The average particle size of the silicon powder after sieving was 5.1 μm, and the angle of repose was 74 °.
The raw material mixed powder was continuously fired in a state where supply was stagnant and stable feeding could not be performed.
The results are shown in Table 1.

[Comparative Example 3]
The same operation as in Example 1 was performed except that the silicon powder used in Example 2 was sieved to obtain an average particle size of 220 μm. The angle of repose of the silicon powder after sieving was 30 °.
The raw material mixed powder had a silane yield of 10% or more lower than that of Example 1, and could not be stably continuously fired. As a result, the production amount of silanes became unstable and the efficiency decreased.
The results are shown in Table 1.

Claims (6)

Step (I) of producing an alloy containing magnesium silicide by continuously feeding a mixture containing silicon powder and magnesium powder into a firing furnace and continuously firing the mixture;
A step (II) of producing a silane by kneading the magnesium silicide-containing alloy and ammonium halide in a liquid ammonia solvent;
The silicon powder has an angle of repose measured according to JIS R 9301-2-2 of 30 to 70 ° and an average particle diameter of 5 to 200 μm, and a method for producing silanes .   The method for producing silanes according to claim 1, wherein the calcination in the step (I) is performed in an inert gas at 400 to 900 ° C.   The method for producing silanes according to claim 1 or 2, wherein the step (I) and the step (II) are continuously performed.   The silane according to any one of claims 1 to 3, wherein the alloy containing magnesium silicide has an angle of repose measured according to JIS R 9301-2-2 of 30 to 70 °. Manufacturing method. The mixture further includes a powder containing at least one metal element selected from Groups 3 to 16 of the periodic table (excluding silicon),
5. The powder comprising the metal element is contained in the mixture in an amount of 0.5 to 30 atomic% with respect to 1 atomic% of silicon. 6. A method for producing silanes. A mixture containing silicon powder and magnesium powder is continuously fed to a firing furnace, and the mixture is continuously fired in an inert gas at 400 to 900 ° C. to produce an alloy containing magnesium silicide. Including step (I),
The silicon powder contains magnesium silicide having an angle of repose measured according to JIS R 9301-2-2 of 30 to 70 ° and an average particle diameter of 5 to 200 μm. Alloy manufacturing method.

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