JPH0470247B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing silicon hydride by reacting an alloy containing magnesium and silicon (hereinafter referred to as silicon alloy) with an acid. More specifically, at least one ether group (C-
The silicon alloy is reacted with an acid in a solvent of an ether compound containing (O-C bond), and the general formula Si _o
The present invention relates to a method for producing silicon hydride represented by H _2o+2 (n is a positive integer). In recent years, with the development of the electronics industry, the demand for silicon for semiconductors such as polycrystalline silicon or amorphous silicon has increased rapidly.
Silicon hydride, Si _o H _2o+2 , has recently become more important as a raw material for manufacturing silicon for semiconductors, and in particular, silane (SiH ₄ ) and disilane (Si ₂ H ₆ ) are used as raw materials for semiconductors for solar cells, etc. Therefore, demand is expected to increase significantly in the future. Conventionally, several methods are known as methods for producing silicon hydride, such as those exemplified below. Mg ₂ Si＋4HClaq→2MgCl ₂ +1/nSi _o H _2o+2 + (1−1/n)H ₂ Mg ₂ Si＋4NH ₄ Br−33℃ ――――――――→ in lig.NH ₃ 2MgBr ₂ +4NH ₃ +1/nSi _o H _2o+2 +(1-1/n)H ₂ SiCl ₄ +LiAlH ₄ -----→ in etherLiCl +AlCl ₃ +SiH ₄ Si+SiCl ₄ +2H ₂ →SiHCl ₃ +SiH ₃ Cl (2SiHCl ₃ →SiCl ₄ +SiH ₂ Cl ₂ 2SiH ₂ Cl ₂ →SiHCl ₃ +SiH ₃ Cl 2SiH ₃ Cl→iH ₄ +SiH ₂ Cl ₂ ) Among these conventionally known methods, there is a method in which a silicon alloy such as magnesium silicide is reacted with an acid in an aqueous solution. The method does not require expensive reducing agents, as in the reaction of, for example, nor does it need to be reacted at low temperatures or under _pressure , as in the reaction _of This is basically the easiest method to implement, as it does not have the drawbacks of using expensive hexachlorodisilane (Si ₂ Cl ₆ ) as a raw material as in the reaction. However, the fatal drawback of this method is that the conversion rate (hereinafter referred to as yield) of silicon in silicon alloys to monosilane (SiH ₄ ), disilane (Si ₂ H ₆ ), and other highly useful silicon hydrides is low. There is. This low yield is said to be due to the unavoidable by-product of a silicon compound having a siloxane bond due to an inevitable mechanism during the reaction process as shown in the following formula. Mg ₂ Si + 2H ₂ O → H ₂ Si (MgOH) ₂ (1) H ₂ Si (MgOH) ₂ +4HCl → SiH ₂ +2MgCl ₂ +2H ₂ O
_{+ H 2 ( 2 ) XSiH 2 → ( SiH 2 ) _} ′ (SiH ₂ ) ₄ + H ₂ O → SiH ₂ O + Si ₃ H ₈ (4)″ In other words, the intermediate H ₂ Si generated in formula (1)
(MgOH) ₂ reacts with, for example, hydrochloric acid to form SiH ₂ radicals (2), which immediately polymerize (3) and subsequently hydrolyze to form various silanes and prosiloxanes (4). , (4)′, (4)″, ...
(Z.Anorg.Allgem.Chem., 303 , 283 (1960), JA
CS, 57 , 1349 (1935)). According to the probable reaction mechanism as shown above,
When focusing on monosilane and disilane, the maximum total yield is theoretically about 44%, and in practice it is even lower, at most in the 30% range. Therefore, when the yield approaches 40%, this value approaches the theoretical limit value as mentioned above, and it is thought that it would not be easy to increase this by a few percentage points using conventional methods. It will be done. The present inventors have conducted intensive studies to improve the low conversion rate (yield) of silicon to silicon hydride in silicon alloys, which is an unavoidable drawback of the above method, and as a result, the above siloxane bonds have been It has been discovered that the by-product of silicon compounds is mainly caused by the presence of water in the system, and by conducting the reaction in the presence of a specific organic solvent and under substantially anhydrous conditions. The present invention was completed by discovering that these drawbacks could be solved. That is, the present invention provides an alloy containing magnesium and silicon (hereinafter referred to as silicon alloy) and an acid,
At least one ether group (C-O-
C) A compound of the general formula Si _o H _2o+2 (n is 1,
The present invention provides a method for producing silicon hydride represented by a positive integer of 2, 3, . . . The present invention will be explained in detail below. The silicon alloy used in the present invention has silicon and magnesium as essential components, and may also contain a third component metal. The gram atomic ratio of magnesium to silicon (Mg/Si) is preferably in the range of 1/3 to 3/1. Specific examples of the silicon alloy include Mg ₂ Si, Mg ₂
SiNi, Mg ₂ SiAl, Mg ₂ Si ₂ Ba, MgSiBa, CeMg ₂
Examples include Si ₂ , Mg ₆ Si ₇ Cu ₁₆ , Mg ₃ Si ₆ Al ₈ Fe, etc. These can be used alone or as a mixture of two or more. Further, the grain size of the alloy is not particularly limited, but the finer the grain size, the better. However, for economical or handling reasons, a range of 20 to 300 meshes is desirable. The silicon alloy used in the present invention is easily available commercially and can be used as is. Alternatively, it may be manufactured by a known method. For example, Mg ₂ Si can be easily obtained by mixing silicon powder and magnesium and heating the mixture at 500 to 1000°C, preferably 550 to 850°C, for about 4 hours in a hydrogen stream or the like. In the present invention, such a silicon alloy is reacted with an acid, and examples of the acid include hydrogen chloride, hydrogen bromide,
Inorganic acids such as hydrogen fluoride, sulfuric acid, pyrosulfuric acid, phosphoric acid, pyrophosphoric acid, metaphosphoric acid, and nitric acid; and organic acids such as acetic acid, formic acid, propionic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, benzoic acid, and phenolic acid. Examples include acids, which are used in a substantially anhydrous state after dehydration. Among these, hydrogen chloride and sulfuric acid are preferred in view of the yield of silicon hydride. The present invention deals with the reaction of the above-mentioned silicon alloy with an acid, and at least one ether group (C-O
-C bond) The reaction is carried out in the presence of a solvent and under substantially water-free conditions; such ethers include dimethyl ether, diethyl ether,
Ethyl methyl ether, di-n-propyl ether, di-n-butyl ether, ethyl-1-chloroethyl ether, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether,
vinyl ethyl ether, tetrahydrofuran, dioxane, diphenyl ether, anisole,
Examples include 1,1-diethoxyethane. Among these, those with boiling points in the range of 0 to 200℃ are
This is desirable in terms of the yield of silicon hydride and the ease of controlling the reaction temperature. Moreover, these can also be used as a mixed solvent of two or more types. Note that there is no particular restriction on the dehydration method for making the ether substantially anhydrous, and any commonly used method can be employed. For example, the purpose can be sufficiently achieved by using dehydrating agents or adsorbents such as sodium, potassium, calcium chloride, sodium sulfate, phosphorus pentoxide, and molecular sieves. Of course, it is also desirable to treat acids such as hydrogen chloride with these to render them anhydrous. The ratio of ether to be used is 0.001 to 2000 times the volume of the acid, preferably 0.01 to 50 times the volume, and the amount used is based on the molar ratio (ether/acid) to the acid.
0.001 to 1000, preferably 0.01 to 5. In carrying out the reaction, an inert organic solvent such as benzene, toluene, xylene, propane, butane, pentane, hexane, heptane, octane, 2-methylpropane, etc. may be used in combination with the above ether. Next, the reaction operation will be described. The reaction of the present invention basically involves silicon alloy (particles)
This is a liquid-solid reaction carried out by bringing an acid into contact with an acid in the coexistence of an ether as described above. Therefore, it is thought that acid and ether usually form a continuous phase, in which silicon alloy particles are dispersed as a dispersed phase, and the reaction proceeds near the particle surface. In this case, there are no particular limitations on the method of charging each reaction component such as the acid, ether solvent, silicon alloy, etc. For example, (2) a method of charging a silicon alloy and an acid simultaneously into an ether solvent, (2) or Various reaction methods can be adopted, such as a method in which a silicon alloy is charged into an ether in which a silicon alloy is dissolved, a method in which an acid is charged in an ether in which a silicon alloy is suspended. The balance of amounts of ether, acid, and silicon alloy can be changed depending on the reaction mode and the type of ether solvent, but in terms of the yield of silicon hydride, the amount of acid used must be at least the reaction equivalent of the silicon alloy. It is. The reaction temperature is operationally from -50°C to 300°C, preferably from room temperature to the boiling point of the ether. Further, the reaction is usually carried out under normal pressure or increased pressure, but it can also be carried out under reduced pressure. In carrying out the present invention, an atmospheric gas is not necessarily required, but if necessary, gases such as nitrogen, hydrogen, helium, etc. that do not react with the generated silicon hydride may be used.
An inert gas such as argon may be used. The reaction in the present invention is an exothermic reaction with an intensity close to that of a combustion reaction (approximately 200 Kcal/g-mole Mg ₂ Si),
In order to control this within the above-mentioned predetermined range, efficient cooling is required. Therefore, in the present invention,
The reactor used should preferably have a structure that has a large heat transfer area (cooling area) and is equipped with a stirring means for effective cooling. Examples include a stirred tank type that is equipped with a heat exchanger and the like as an internal heat exchanger or an external heat exchanger. Of course, a tubular reactor can also be used. However, in order to remove by-product magnesium salts formed on the surface of the silicon alloy, it is more desirable to have a material that can grind the contents by stirring to some extent. As a cooling refrigerant, not only water but also ordinary refrigerants can be used. For example, water-methanol brine, sodium chloride brine, ethylene glycol brine, ammonia, chlorofluorocarbon, methylene chloride, silicone oil, etc. can be suitably used. . These are sent to a jacket or shell-and-tube heat exchanger for cooling and temperature control. Since the reaction is a solid-liquid heterophasic reaction accompanied by heat generation as described above, it is particularly necessary to perform sufficient stirring and mixing to prevent local overheating. Therefore, a particularly preferred method for controlling the reaction heat is to use a reflux condenser (a reflux condenser may be attached directly to the top of the reactor, or may be installed independently from the reactor).
The temperature is controlled by refluxing the ether and controlling the temperature. That is, when the reaction is carried out under reflux of ether having a boiling point of 100° C. or lower, the reaction heat generated can be removed as the heat of vaporization of the ether, making it extremely easy to control the reaction temperature. Note that the reaction itself in the present invention is very fast;
Even at low temperatures of -50°C to 0°C, the process is completed quickly in a few seconds to several minutes. The produced monosilane (SiH ₄ ) has a boiling point of -110°C and does not dissolve in the reaction liquid system, so in the above reaction temperature range it leaves the reaction system as a gas, so it is passed through a trap and liquefied with liquid nitrogen. Supplement. In addition, when the reaction temperature is set to a low temperature of 0°C or lower, for example, -15°C or lower, disilane (Si ₂ H ₆ , boiling point -14.5°C), trisilane (Si ₃ H ₈ , boiling point 52.9°C), tetrasilane (Si ₄ Higher silicon hydrides such as H ₁₀ (boiling point 109°C) are of course not gasified and may accumulate in the reactor as a liquid. Therefore, if the purpose is to produce these higher silicon hydrides, the whole reaction solution after the reaction is completed, or a part of the reaction solution is circulated during the reaction operation, and the circulating reaction solution is heated to, for example, room temperature to around 50°C. These higher silicon hydrides must be stripped and recovered as a gas. Note that separation and purification of each component from these product gas mixtures can be carried out by conventional cryogenic separation, adsorption, etc., respectively. According to the present invention, it is also possible to select a reaction temperature that does not require a low-temperature refrigerant under normal pressure or under pressure as a reaction condition, and it is possible to convert silicon in a silicon alloy to silicon hydride, Si _o H _2o+2. Due to the high conversion rate of
Low cost silicon hydride, especially silane (SiH ₄ )
It is possible to manufacture Furthermore, the silicon hydride obtained by the present invention contains few impurities such as oxygen-containing silicon compounds, and silicon hydride of sufficiently high purity can be obtained without going through complicated purification steps. Hereinafter, the present invention will be explained with reference to Examples. Example 1 A separable flask with a capacity of 500 ml was charged with 200 ml of diethyl ether dehydrated using molecular sieve-3A, and the temperature of the ether was lowered to 0.
℃, hydrogen chloride gas dehydrated with phosphorus pentoxide was blown into it. The amounts of hydrogen chloride and water dissolved in the ether are 16% by weight and 5% by weight, respectively.
It was ppm. Next, in a hydrogen gas atmosphere, about 100 ml of glass beads (diameter 3 mm) were added to this ether solution, and while grinding and stirring, 6.0 g of magnesium silicide (Mg ₂ Si) (particle size 100 to 200 mesh, 78.2 mmol) was added. Si) was continued to be added at a constant rate for 40 minutes. During this time, the reaction temperature was maintained at 0° C. by cooling the liquid with a refrigerant. The generated gas is collected in a trap cooled at the temperature of liquid nitrogen, and after the reaction is completed (after the magnesium silicide injection is completed), the amount of SiH ₄ , Si ₂ H ₆ , and Si ₃ H ₈ in the collected gas is It was analyzed and quantified by gas chromatography. Furthermore, the amounts of SiH ₄ , Si ₂ H ₆ , and SiH ₈ dissolved in the reaction solution were determined using gas chromatography. The amounts of SiH ₄ , Si ₂ H ₆ , and Si ₃ H ₈ produced are
They were 52.7mmol, 3.6mmol, and 0.3mmol. The amounts of these three types of silicon hydrides correspond to 77.7% of the silicon in the magnesium silicide subjected to the reaction. The gas obtained in the cylinder was also measured using a gas chromatograph mass spectrometer, but no compound having a silyl ether bond (Si--O--Si bond) was detected. Examples 2 to 6 In Example 1, di-n-propyl ether, 2,2'-dichlorodiethyl ether, ethylene glycol dimethyl ether, dioxane, and tetrahydrofuran were used instead of diethyl ether, and the reaction temperatures are shown in Table 1. The experiment was conducted in the same manner as in Example 1, except that the temperature was set to 1. The results are shown in Table 1. 【table】

Claims (1)

[Claims] 1. An alloy containing magnesium and silicon (hereinafter referred to as silicon alloy) and an acid are combined into a chain and/or cyclic ether containing at least one ether group (C-O-C bond) in the molecule. The general formula Si _o H _2o+2 (n is 1, 2, 3,...
A method for producing silicon hydride represented by a positive integer. 2. The method according to claim 1, wherein the silicon alloy is magnesium silicide. 3. The method according to claim 1, wherein the acid is a hydrogen halide other than hydrogen iodide, sulfuric acid, phosphoric acid, or an organic acid. 4. The method according to any one of claims 1 to 3, wherein ether is added to the acid in advance and allowed to coexist. 5. The method according to any one of claims 1 to 4, wherein the reaction temperature is -50 to 100°C. 6. The method according to claim 5, wherein the reaction is carried out at the boiling point of the ether. 7. The method according to claim 6, wherein the temperature is controlled by refluxing the ether. 8. The method according to claim 7, wherein the reflux is carried out by a backflow condenser installed in the upper part of the reactor.