JPH0482892A - Production of highly pure alkoxysilane - Google Patents

Abstract

PURPOSE:To industrially produce the subject silane useful as a raw material for the insulating films of semiconductors by bringing a crude alkoxysilane into contact with a chitosan chelate resin to remove remaining volatile liquid organic compounds in the silane. CONSTITUTION:(A) A crude alkoxysilane is brought into contact with (B) a chitosan chelate resin and vacuum-distilled to separate the alkoxysilane from the component B as a distillate. An inert gas is fed into the distillate under vacuum to evaporate volatile components readily contained or freshly by- produced in the system, thereby producing the objective silane. The components A and B are preferably brought into contact with each other with a rotary evaporator with rotating and subsequently subjected to a vacuum-distillation process.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for purifying crude alkoxysilane to obtain highly pure alkoxysilane.

Conventional technology <Alkoxysilane> Alkoxysilanes such as tetraethoxysilane and triethoxymedylsilane are well known as raw materials for the chemical industry, and are used, for example, as starting materials for the production of glass and ceramics by the sol-gel method, and for the production of catalysts. It is often used as a starting material.

<Method for producing alkoxysilane> As a method for producing alkoxysilane, JP-A-50-7
Methods disclosed in Japanese Patent Publication No. 1632 and Japanese Patent Publication No. 60-35351 (Japanese Unexamined Patent Publication No. 51-13725) are known.

That is, in the former, silicon, iron silicide, or silica chain is reacted with 125 to 25
By reacting at 0°C, orthosilicate tetraalkoxyalkyl ester is obtained.

In the latter, when alkoxysilanes are produced continuously by direct esterification of chlorosilanes with alcohols, the reactants are added through separate conduits to the top of a column distillation apparatus, the hydrogen chloride is distilled off, and the product is A method is adopted in which water flows out continuously from an overflow pipe.

<Method for Purifying Alkoxysilane> Several methods have been adopted for purifying alkoxysilane.

For example, in Japanese Patent Application Laid-open No. 50-47931,
Triethoxysilane obtained by reacting silicon powder with ethanol is refluxed or distilled while being brought into contact with an inert gas to remove impurities.

The explanation of the prior art in this publication states that the main impurities in triethoxysilane are unreacted ethanol, various chlorine compounds resulting from the cuprous chloride catalyst, various hydrocarbons as side reaction products, It is said that these impurities are ethyljethoxysilane, ethyl ether, etc., and that conventionally these impurities have been separated by rectification using the difference in their boiling points.

In JP-A-62-114992, when purifying alkoxysilane containing impurities caused by chlorine, (1) heating the alkoxysilane in the presence of acid clay or metal halide during the entire purification process. , (i
The process includes a step of neutralizing with an il neutralizing agent and (iii) a step of removing the neutralized salt in order.

In the description of the prior art of this publication, it is stated that alkoxysilanes can be obtained by catalytically reacting the corresponding chlorosilane and alcohol in the liquid phase or gas phase, and that the purification of the obtained alkoxysilane has been conventionally carried out. It is stated that this was carried out by neutralization using a neutralizing agent, and then separation from non-volatile components such as neutralized salts by distillation of alkoxysilane. In addition, as a method for removing non-hydrolyzable chlorine, conventional methods include heat treatment in the presence of lithium aluminum hydride, tetramethylglinicine, magnesium oxide, dibutyltin dihydride, or sodium metal, followed by distillation. It is also stated that

Problems to be Solved by the Invention In the method for purifying alkoxysilane described above, volatile or liquid organic compounds remaining in alkoxysilane are targeted for removal.

However, in recent years, alkoxysilanes have been used as Si in semiconductor devices.
It has been confirmed that when used as a raw material compound for forming insulating films, it is possible to form insulating films at lower temperatures (e.g., 650°C or lower) than silane gas, etc., and as a result, alkoxysilanes are being used in the semiconductor industry as a new application. It is expanding.

The insulating film of such a semiconductor element may contain Na, alkali or alkaline earth metal ions such as Ca, or As, which increase the concentration of mobile ions, in the insulating film formed.
Various metal and non-metal cations remain, such as non-metal cations such as , P, and B that cause P-N junctions, as well as heavy metal ions that cause precipitates and transitions such as Fe, Cr, and Cu. The essential condition is that the

However, the conventional purification methods described above do not have the main purpose of removing these metal/nonmetal ions, so these metal/nonmetal ions still remain in the alkoxysilane purified by the above purification method. Cations are not removed sufficiently, e.g. 1-5 w/w pp in total.
Currently, about 100,000 m of cations remain.

In view of this situation, the present invention provides a method for producing high-purity alkoxysilane that can also be used for forming an insulating film of semiconductor devices, and more specifically, it is an object of the present invention to provide a method for producing a high-purity alkoxysilane that can also be used for forming an insulating film of a semiconductor element. It is an industrial method that removes metal and non-metal cations to the detection limit (nearly 2 to 10 w/w ppbl or less), and also removes by-product alcohol to the detection limit (nearly 2w/w ppm1 or less). The aim is to provide an advantageous purification method.

Means for Solving the Problems The method for producing high-purity alkoxysilane of the present invention includes a step A in which crude alkoxysilane is contacted with a chitosan-based chelate resin, and after the previous step A, alkoxysilane is extracted from the chelate resin by vacuum distillation. Step B of separating the distillate as a distillate; Step C1 of introducing an inert gas under reduced pressure into the distillate obtained in the previous step B to volatilize and remove volatile components already contained in the system or newly produced by-products; It is characterized by consisting of.

The present invention will be explained in detail below.

AlkoxysilaneAs the alkoxysilane, trimethoxysilane, triethoxysilane, tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethylethoxysilane, dimethyljethoxysilane, trimethylmethoxysilane, trimethylethoxysilane, Methyldimethoxysilane, methyljethoxysilane, dimethylethoxysilane, dimethylvinylmethoxysilane, dimethylvinylethoxysilane, methylvinyldimethoxysilane, methylvinyljethoxysilane, diphenyldimethoxysilane, phenyltrimethoxysilane, diphenyljethoxysilane, phenyl trimethoxysilane Examples include ethoxysilane, and among these, tetraethoxysilane is particularly important.

The crude alkoxysilane may be one that has been purified to some extent by a conventional purification method (or may be one that is produced in the alkoxylation step of chlorosilane).

Process] [Δ Process A is a process in which crude alkoxysilane is brought into contact with a chitosan-based chelate resin.

As the chitosan-based chelate resin, a resin having chitosan as a main chain and a polyamine type, iminodiacetic acid type, or aromatic carboxylic acid type coordination group is used. Depending on the type of metal/nonmetal cation to be removed, it is better to use cations having different coordination groups in accordance with the individual reaction characteristics. A commercially available product of such a chitosan-based chelate resin is "Chelate Chitobal" manufactured by Fujibo Co., Ltd. (For the production method of granular porous chitosan, please refer to Japanese Patent Publication No. 1-1642 filed by Fujibo Co., Ltd.
There is a detailed explanation in Publication No. 0. ) When contacting the crude alkoxysilane with the chitosan-based chelate resin, heat it under a stream of inert gas such as nitrogen, argon, helium, etc. to perform dehydration and degassing treatment.

The reaction time for removing trace amounts of metal cations from crude alkoxysilane by catalytic reaction is several hours to 1 hour.
It is often about 00 hours, for example about 3 to 90 hours.

This catalytic reaction is preferably carried out using a rotary evaporator while rotating the rotary evaporator while keeping the system under an inert gas atmosphere such as nitrogen, argon, or helium. The crude alkoxysilane to be treated may contain alcohol, and even if the pretreatment of dehydration and degassing is performed as described above, trace amounts of water liberated from the chitosan-based chelate resin and the alkoxysilane may be mixed together. Since alcohol is produced as a by-product through the hydrolysis reaction of , a rotary evaporator is suitable for continuously removing such alcohol in the same device.

Step B, which is one mile higher, is a step in which, after the previous step A, the alkoxysilane is separated from the chelate resin as a distillate by vacuum distillation.

The internal temperature and the degree of pressure reduction are appropriately set depending on the type of alkoxysilane. The atmosphere of the system is nitrogen, argon,
Keep under an inert gas atmosphere such as helium. The final vacuum distillation conditions are determined according to the vapor pressure curve, which is a physical property specific to the raw material alkoxysilane, but excessively high temperatures are disadvantageous in terms of the lifespan of the chitosan-based chelate resin, so
Usually set to 100'C or less.

Since the metal/nonmetal cations in the alkoxysilane are fixed to the chitosan-based chelate resin, the distillate no longer contains only trace amounts of nonmetal/metal cations.

Industrially, it is advantageous to use a rotary evaporator in step A, and to carry out step B subsequently using the evaporator after step A is completed.

In the Nikoka process C, nitrogen is added to the distillate obtained in the previous process B under reduced pressure.
This is a process in which an inert gas such as argon or helium is introduced to volatilize and remove volatile components that are already contained in the system or are newly produced as by-products.

Through this step, volatile components such as alcohol and water are removed, and purified alkoxysilane with high purity is obtained.

■ High purity alkoxysilane obtained by the method of the present invention can be used not only as a starting material for the production of glasses and ceramics by the sol-gel method, but also as a starting material for the production of catalysts.
It can also be suitably used in applications that require a high degree of purity, such as raw materials for silicon oxide insulating films for semiconductors and raw materials for optical fibers.

In operation step A, various metal and nonmetal cations remaining in the crude alkoxysilane are chemically adsorbed onto the chitosan-based chelate resin.

There are various types of chelate resins, but as described below, chitosan-based chelate resins are most suitable for the purpose of the present invention.

That is, in the present invention, the metal ion sequestration effect when used in metal surface treatment agents, plating agents, industrial detergents, etc., which are the conventional main uses of chelate resins, or when used in wastewater treatment, etc. Like 10-1
00 w/w ppm Augu is not intended for chemical adsorption of high concentration metal cations, but various cations with a content of 1 w/w ppm or less can be detected using stimulated plasma emission method or atomic absorption method. Since the purpose is to remove trace amounts below the limit or near the detection limit, it is preferable that the lower limit value of chemisorption is lower than the amount of chemisorption as a chelate resin. The chitosan-based chelate resin used in Step A satisfies these requirements.

In addition, pH control chemicals often used in conventional methods become a source of contamination of the alkoxysilane itself for purification purposes. Therefore, it is advantageous to have a chelate formation range near neutrality, and the chitosan-based chelate resin used in Step A also satisfies these requirements.

Furthermore, the chitosan-based chelate resin does not have the characteristic odor that is common to other ordinary pure synthetic chelate resins, and the dehydration and degassing treatment that is performed before being subjected to step A is easy, which is another object of the present invention. suitable for

In step B, the alkoxysilane is separated from the chelate resin by vacuum distillation, and the alkoxysilane distillate is no longer substantially free of metal and nonmetal cations.

Then, in Step C, volatile components already contained in the distillate or newly produced by-products are removed by volatilization, and a highly pure alkoxysilane containing virtually no impurities is obtained.

Example Next, the present invention will be further explained with reference to Examples.

Example 1 Three types of chitosan-based chelate resins (Chelate Chitopearl manufactured by Fujibo Co., Ltd.) having chitosan as the main chain and having chelate coordination groups of polyamine, aromatic carboxylic acid, and iminodiacetic acid were prepared.

Among the above, those with polyamine coordination groups (CC-S
Type) exchange capacity is 1.56 meq/ml, particle size distribution is 0.20-0.45 mm, and elastic modulus is 5. OX106
dyne/am2, the exchange capacity of aromatic carboxylic acid as a coordination group (CG-T type) is 1.20 meq/m
l, particle size distribution is 0.20-0.45mm, elastic modulus is 11
．． 5X 106 dyne/cm2, the exchange capacity of iminodiacetic acid coordination group (CG-I quiz) is 0.83
meq/ml, particle size distribution is 0.20-0.45 mm, and elastic modulus is 5.0×10'dyne/Cm2.

After dehydrating and degassing 2 g of each of the above three types of chitosan-based chelate resins (6 g in total) at 120°C under a nitrogen stream, they were put into a rotary flask of a rotary evaporator, and then the amounts shown in column a) of Table 1 were added. 500 ml of crude tetraethoxysilane (chemical grade) containing the same amount of impurities.
was placed in the same rotating flask, and after purging the entire system with nitrogen, a rotating contact reaction was carried out at room temperature for 24 hours.

Next, put the rotating flask of the rotary evaporator into a heating bath, and while keeping the liquid temperature at 52 to 55°C, 10To
Distillation was performed under reduced pressure to rr, and the chitosan-based chelate resin that had been charged was left in the rotary flask together with the remaining liquid from the can. When 350 ml of distillate had been distilled into the distillation receiver, the internal pressure of the system was returned to 1 OOTorr using nitrogen gas, heating was stopped, and vacuum distillation was completed.

Finally, nitrogen gas is blown into the distillate obtained in the receiver for 60 minutes at 100 Torr through a gas blowing porous tube to diffuse the trace amount of ethanol contained in the system to the outside of the system and achieve the desired high temperature. Purified tetraethoxysilane with high purity was obtained.

The analysis results of the obtained high-purity tetraethoxysilane were
It is shown in column b) of the table.

The analysis was performed using an induced plasma emission spectrometer (ICPV-100O3, manufactured by Shimadzu Corporation), an atomic absorption spectrometer (AA-680G, manufactured by Shimadzu Corporation), and a thermal conductivity gas chromatograph.

Table 1 The unit of # is v/v ppm.

An 8102 film was formed using the high purity tetraethoxysilane obtained above under the following conditions, and its resistivity was measured.

Vapor deposition method Plasma CVD High frequency output 400W Tetraethoxysilane flow rate 20 cc/mjn O2 flow rate 300 cc/min Vapor deposition substrate 41nch silicon wafer furnace temperature
320°C Deposition rate: 15 nm/min Deposited film thickness: 150 nm The 5iO- film resistivity measured using a digital electrometer (model TR-8411 manufactured by Atopan Test Co., Ltd.) was 6 x 10 + aΩcm, which is sufficient as a semiconductor grade. I was satisfied with it.

In addition, SiO using crude tetraethoxysilane as a raw material
□Membrane resistivity is 9×10”.

Example 2 4 g each of the two chitosan-based chelate resins of the CC-5 type and CC-r type used in Example 1, a total of 8 g, were dehydrated and degassed at 100'C under a nitrogen stream, and then placed in a rotary evaporator. Pour into a rotating flask, then
500 ml of crude triethoxymethylsilane containing the amount of impurities shown in column a) of Table 2 was charged into the same rotating flask, and after purging the entire system with nitrogen, a rotating contact reaction was carried out at room temperature for 32 hours.

Next, place the rotating flask of the rotary evaporator in a heating bath, and keep the liquid temperature at 61-64°C for 40 minutes.
Distillation was performed under reduced pressure to Torr, and the chitosan-based chelate resin that had been introduced was left in the rotary flask together with the remaining liquid from the can. When 350 ml of distillate has been distilled into the distillation receiver, the internal pressure of the system is returned to 1 OOTorr with nitrogen gas, and heating is stopped.
Vacuum distillation was completed.

Finally, nitrogen gas is blown into the distillate obtained in the receiver for 60 minutes at 100 Torr through a gas blowing porous tube to diffuse the trace amount of ethanol contained in the system to the outside of the system and achieve the desired high temperature. Purified triethoxymethylsilane of high purity was obtained.

The analysis results of the obtained high purity triethoxymethylsilane are shown in column b) of Table 2.

The unit of # is v/v ppm.

Effects of the Invention As described above, according to the method of the present invention, it is possible to industrially produce a high-purity alkoxysilane suitable for uses such as a raw material for insulating films of semiconductor devices or a raw material for optical fibers.

Claims (1)

[Scope of Claims] 1. Step A in which crude alkoxysilane is contacted with a chitosan-based chelate resin, Step B in which after completion of the preceding step A, the alkoxysilane is separated from the chelate resin as a distillate by vacuum distillation, and the preceding step High-purity alkoxy characterized by comprising step C of introducing an inert gas under reduced pressure into the distillate obtained in step B to volatilize and remove volatile components already contained in the system or newly produced as by-products. Method of manufacturing silane. 2. The manufacturing method according to claim 1, wherein step A is carried out using a rotary evaporator while rotating the evaporator, and after step A is completed, step B is carried out subsequently using the evaporator. 3. The chitosan-based chelate resin used in step A is a resin that has chitosan as its main chain and at least one type of coordination group selected from the group consisting of polyamine type, iminodiacetic acid type, and aromatic carboxylic acid type. The manufacturing method according to claim 1. 4. The manufacturing method according to claim 1, wherein the alkoxysilane is tetraethoxysilane.