JPS5997518A - Purification of chlorosilanes - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Background of the Invention The present invention relates to the production of pure trichlorosilane for the production of silicon for electronic devices, and more particularly to the production of pure trichlorosilane for the production of silicon for electronic devices, and more particularly to the production of pure trichlorosilane for the production of silicon for electronic devices, and more particularly to the production of pure trichlorosilane for the production of silicon for electronic devices. The present invention relates to a novel method for removing compounds of other Group I elements.

Very advanced electronic applications such as semiconductors and transistors require ultra-high purity silicon. As is well known, trace amounts of impurities can significantly impair the performance of silicon-containing electronic components.

In general, elemental silicon for semiconductors is silicon halide such as silicon tetrachloride (SLCf4), 1-lichlorosilane (1-ISLCR3) or dichlorosilane (H2SL
C92) with hydrogen, zinc, sodium or metal hydride. Silicon is silane (SL
Silane can also be obtained by thermal decomposition of Ha ), but silane is difficult to process because it combusts explosively when it comes into contact with air.

One of the most difficult impurities to remove from silicon is phosphorus. Although impurities such as copper, iron, and manganese can be removed relatively easily by conventional methods (e.g., zone melting refining, crystal pulling, etc.), phosphorus has a strong resemblance to silicon. Therefore, the only way to separate them is through repeated trials. Furthermore, since phosphorus forms compounds with similar properties to starting materials such as chlorosilanes, the purification and concentration of these starting materials is also difficult.

Methods C that have been proposed to date for removing impurities such as phosphorus from silicon or silicon halides typically involve adsorption of impurities by conjugation with a solid hydrated metal oxide complexing agent. or to form a stable adduct and then precipitate or distill pure silicon or silicon halide. Regarding the details of such processing, C, for example,
U.S. Patent No. 2.971.607 Thirsty Caswell), No. 3
, No. 069.239 (Winter et al.), No. 3,071°444 (Sweller), No. 3.188.168 (Brazdley) and British Patent No. 929.696 (Siemens Sückertwerke Ltd.). Please refer. In addition, the applicant's U.S. patent application [Applicant's Docket]
339-1696 (608,1-609/614)
6081-708/710/711/716)],
An improved method is disclosed.

However, these methods also have problems such as impurity formation and difficulty in mass processing.

The above-mentioned patents and patent applications are cited and included in C Honkawa Hosoen.

Invention IF! It has been discovered that phosphorus compounds and other compounds containing these elements can be removed from chlorosilane solution b) by utilizing the property that Group V elements of the periodic table can be trivalent as well as trivalent. Ta. The normally trivalent impurities present in the ultrapure chlorosilane solution are oxidized to the trivalent state by conventional distillation (or preferably by further combining the impurities with a complexing agent and then It was discovered that chlorosilanes can be easily separated from these impurities by distillation. For example, phosphorus trichloride (f) CF2)
is an impurity that commonly remains in ultrapure 1-lichlorosilane. In the present invention, phosphorus oxychloride (+) ○C! 3. Boiling point 105.3
℃), but this phosphorus oxychloride (yoP(43(
Trichloro-1-1 silane (boiling point 75.5℃)
It is easy to separate by distillation from 31.8°C). Alternatively, this p Q CJ 3 can be reacted with certain complexing agents according to the present invention to form a more thermally stable KiJ form to facilitate subsequent distillation.

This J: sea urchin, the object of the present invention is dichlorosilane, 1-
The object of the present invention is to provide a new method for purifying cyclosilanes such as cyclosilanes, silicon tetrachloride, or mixtures thereof.

Another objective of the present invention is to provide a method for removing phosphorus compounds and other n-type impurities from chlorosilane solutions.

Still another object of the present invention is to provide a purification method that is irreversible and applicable to large-scale purification systems.

Another object of the present invention is to provide a new method for oxidizing n-type impurities such as phosphorus in chlorosilane solutions.

Historically, another object of the present invention is trivalent linen thin resin [
” to provide a new means for removal from rosilane.

These and other objects are achieved by the method provided by the present invention, ie, the purification of chlorosilane solutions contaminated with impurities containing trivalent compounds of Group V elements of the Periodic Table. The method of the present invention includes the following steps. That is, (A) a step of oxidizing the impurities to obtain a compound in which the element is in a trivalent state, and a subsequent step (B) of extracting and recovering purified chlorosilane by distillation.

In a preferred embodiment of the invention, the means of oxidizing the impurities comprising Group V elements is by contacting them with an oxidizing agent selected from chromium trioxide or manganese dioxide.

In another preferred embodiment of the invention, the means for oxidizing Group V elemental impurities is to avoid contacting the chlorosilane solution with oxygen under ultraviolet (UV) irradiation.

Other embodiments contemplated by the present invention include the step of oxidizing the impurities to the trivalent state (=Jadd', t2).

In this step, impurities are avoided to come into contact with transition metal compounds or Lewis acids, but these transition metal compounds or Lewis acids act as complexing agents and generate thermally stable 311 bodies,
These complexes are residually removed during distillation of the chlorosilane.

The method of the invention oxidizes compounds of trivalent Group V elements, such as phosphorus, which may be present as impurities in chlorosilane solutions.
C1 includes the step of forming a compound in which this element is in a different state. Impurities can be easily and efficiently removed by treating the chlorosilane thus treated by fractional distillation or distillation of pure chlorosilane after reaction with a complexing agent. The process of the present invention is particularly effective in removing trace amounts of phosphorous and other common 11-type impurities such as arsenic, antimony, bismuth, etc. from chlorosilanes, particularly 1-110 silanes. According to the method of the present invention, for example, Toriku [J
D The phosphorus content in the silane solution can be reduced to 0.5 ppb or less.

The process of the present invention is useful for removing phosphorus and other Group VIIA elements from chlorosilanes, which are then reduced to crystalline silicon for electronic applications. Phosphorus and its sister Group V elements, such as arsenic, antimony, or bismuth, are of particular importance in the production of silicon for electronics because they donate an excess of free electrons. When these elements are added to the silicon 71~x, the excess electrons change the electrical properties (neutral) of the silicon crystal and also the doping contained therein to give the crystal semiconducting properties. interfere with the agent. These excess electrons contribute as negative charges, so impurities such as phosphorus
'II'-type (negative) impurities, but in Suimei III, this term is used to refer to impurities that appear to be present in nearly pure chlorosilane, such as phosphorus compounds, compounds of group V elements, and other electronic It also refers to compounds that are rich in .

The No. IJ Kumoto prefecture to be oxidized and removed according to the present invention is used in mold pieces containing chlorosilane containing particularly high levels (e.g., residual n-type impurities of less than 200 ppb in total). Found in the chloride or trivalent chlorine hydride state. These impurities have the general formula A Hmc9n,
In this formula C1A is selected from phosphorus, arsenic, antimony and bismuth, m and +1 are 0.1.2 or 3 and m+11 is 3 or 5. Although other forms of Group V element compounds may be removed by the method of the present invention, the most concave form of impurity remaining in the chlorosilane is that represented by the above formula. ' A common property of the group V elements that are the targets of the method of the present invention is that they all have five electrons in their outermost electron orbitals and -C
It is that you are. This means that Huck's Chemical Dictionary (l-
1ackh-s Chemical Q 1ctio
nary1 1st V version, Maclj Low L: JL/
(Published) C11500-501 pages, "Periodic Chin" Tt)
e Periodic Chain”, described in 1 and has -C. The most universal 1511 valence of these original threads is +3 (trivalent), but since there are 5 electrons in the outer shell, +
It can also take on 5- or 11-valent states. When a trivalent group V element compound is oxidized, what is the freedom in its outermost orbit? The tlf child can be donated to the acceptor oxygen (valence -2).

In the first step of the present invention, that is, the oxidation step, oxidation of impurities progresses. -1--Contact the chlorosilane solution with an oxidizing agent or introduce oxygen or air under phosphorus conditions. Many oxidizing agents are known in the art and are suitable for use in the present invention as long as they are compatible with the chlorosilane solution and can effectively oxidize residual impurities. However, chromium trioxide and mankan dioxide are particularly suitable for the purification of the present invention, and therefore C
It has been found that oxidizing agents are preferably used in embodiments of the invention in which oxygen is introduced into the system in gaseous form (either pure 02 or mixed with other residues, i.e. air). C is preferably exposed to ultraviolet (U) radiation for oxidation II.
V) Irradiate. When UV irradiation is used at v1, the reaction rate increases, and therefore sufficient oxygen can be supplied even if air, which is cheaper than pure oxygen scum, is used. UV-oxidation is more selective for impurities than chloro[]silane, thereby increasing the efficiency of the operation.

The strength of the oxidizing agent used in the present invention will depend on the type of agent, the concentration of impurities, the chemistry of the particular oxidation reaction employed, etc. In general, excessive use is undesirable from the point of view of the product Y'i balance and because -C inevitably results in partial oxidation of the chlorosilane. On the other hand, it is desirable for impurities to be completely oxidized. For this reason, it is necessary to experimentally confirm the optimal balance between excess and deficiency of oxidation under given conditions. When using chromium trioxide or manganese dioxide from the preferred agents, complete oxidation of impurities in 1 helichloride (1 helichloride) requires about 7 to 10 and about 10 to 14, respectively.
It has been found that molar equivalents of oxidizing agent are required. The oxidizing agent is typically added directly to the chlorosilane and mixed. (Know the culmination of oxidation) Then take out the four novels at appropriate intervals and analyze them using the well-known chroma 1 graph.

When a V elemental compound is brought into contact with air (or M element) with UV illumination for IC oxidation, the amount of air required depends on the amount of impurities, the degree of stirring, the degree of UV illumination, and other factors. Depends on several factors. However, fundamentally, u v
It has been found that when +t+¥, the amount of air passing through the system due to oxidation can be reduced. This point will be explained in detail later. The UV radiation may be applied directly to the reaction vessel receiving the irradiation, but of course the intensity of the UV sludge must be such as to promote oxidation.

Once the oxidation step is complete, it is advantageous to selectively complex the impurities to form stable compounds.

This stable compound will remain in the bulk distillation of pure talolosilane. Complexing agents suitable for this purpose include the oxidized group V which is compatible with the chlorosilane and present in the chlorosilane.
Any material may be used as long as it selectively binds to group elements to form a complex, but it is easy to separate chlorosilane from the thermally stable impurity/complexing agent complex formed by distillation.

This is because 8H-forming agents include transition metal halides and Lewis acid compounds, which react with the electron-rich Group V elements present in the chlorosilacin 1 helix.

Preferred transition metal halides found to be suitable for the purposes of this invention are zirconium tetrachloride and hafnium C tetrachloride. Compounds such as phosphorus A dichloride form a 1:11fi form with tetra]2□zylmonide in 1-rif[][J silane, and this 111 compound forms a 1:11fi compound with [JO silane solution]. It has been found that 99.9% or more of the above impurities can be removed from) C.
o Other transition metal halides of this type can also be used without unnecessary experimentation, as they are compatible with silanes and can efficiently convert common Group V elements with 14 residues to 111. These also satisfactorily achieve the purpose of the present invention 1i)
Ru.

"Lewis acids" accept and accept electron pairs to form covalent bonds (i.e., "-electron pair acceptors") and can be used to achieve the objectives of the present invention. --The Brønsted acid definition includes the concept of 1-pro-1 hydrogen donor.For example, boron trichloride (13F3) has only 6 electrons in the outermost electron orbital, so , ll! type Lewis acid.

B F 3 has a tendency to accept free electron pairs and avoid completing the 8-electron orbital opening. Although a wide range of Lewis acids can be used to bond with the particular Group V element compounds that are the subject of this invention, Lewis acids such as boron trichloride (8Cj3) can be used to bind elemental compounds that are difficult to remove. I will be focusing on the Rosilan series. In particular, the problem of the difficulty in manufacturing boron (CVi) for electronic devices has been raised.
The use of boron is usually avoided because of its potential. For this reason, Lewis acid complexing agents suitable for the purposes of the present invention are
[It is preferable to include elements that are easier to remove from J silane. The most preferred are ferric oxide (FeCf3) and aluminum chloride (#(J3)).

01 of the complexing agent added to the silane solution to prevent contamination
is an amount such that this compound reacts sufficiently with already oxidized IC impurities. In terms of reaction time and complete removal of impurities, for example, 2 to 5
The best results are obtained with a molar excess of 0(8). However, it will be appreciated that any amount that effectively binds to the impurities present in the solution is sufficient.

After mixing the 111 agent into the solution, the ii) compound may be heated to ++ U to promote the reaction between the n-progeny impurity and the complexing agent compound. If the temperature is too high, i.e. above 150 DEG C., the complexes formed will decompose to some extent, and if the temperature is too low, it will not be sufficient to efficiently remove all impurities. For this reason, the reaction temperature is preferably from 0°C to about 125°C. However, as long as the reaction product is not distilled in the same fraction as the chlorosilane and is therefore not contaminated during the purification process, higher temperatures above the above range may also be used. ! do. The best results were obtained by a ratio of 1:1 at temperatures below about 100°C. Pressurization may be applied within the reaction vessel to prevent premature distillation of the rosilane.

Place! A simple experiment can be used to determine the optimum reaction temperature and pressure under these conditions.

As previously described, the reaction is continued until substantially all of the impurities have combined to form a thermally stable complex. Of course, reaction times will vary depending on the materials used, wetness, pressure, etc. Simple experimentation will determine the optimal reaction time required for a given purification.

The final step in the 711 process of the present invention is to distill pure -10 cycine from the reaction solution.

This final distillation step is possible due to the lower volatility of the C impurity relative to the silane.

The distillation may be carried out at atmospheric pressure or the temperature of the liquid may be lower than the temperature of the liquid to remove impurities or impurities formed in previous steps.
) The temperature of the solution is preferably kept below about 200°C.

To assist those skilled in the art in practicing the invention,
Examples are given below for illustrative purposes, but the present invention is not limited thereto.

A standard solution of trichlorosilane containing 500 ppm phosphorous trichloride was placed in the reaction vessel. Mancan dioxide was added while stirring the solution vigorously, samples of the reaction mixture were taken periodically, and the respective concentrations of phosphorus trichloride and phosphorus oxychloride were determined by graphie. 10-14
The molar equivalent of ω of mankan dioxide is required for complete oxidation,
It was found that phosphorus was quantitatively oxidized to the intermediate state within 2 hours.

Example 2 l) Conversion of Cj3 to POC93 by photooxidation5
A standard solution of 1-lichlorosilane containing 1,000 ppm of phosphorus trichloride was placed in a clear container equipped with a dry ice condenser and gas vent.

Dry air was introduced from the inlet at 50cTI13/min and rapidly dispersed with stirring. Dry ice condensate → J- is
This was sufficient to cool and condense one helichlorosilane in the gas stream. A sample of the 1-licrosilane solution was periodically taken out and the relative temperatures of phosphorus trichloride and phosphorus oxychloride were measured by chromatography. 1-5% PCf when 16 molar excess of oxygen (in air) is passed through the system.
It was found that 3L was not oxidized to POCR3.

While introducing air and stirring and dispersing it, the experiment was continued by checking one rimple. A 2.4 molar excess of oxygen was found to be sufficient for complete oxidation of PC93.

The decrease in the amount of oxygen required means that 1) (
This does not imply that the stoichiometric maximum of J 3 is 2.5, but rather suggests that the molar ratio was determined by a mass effect.

Example 3 Trichlorosilane 4 containing 1.5 parts by volume of phosphorous oxychloride
To 50 parts by weight of the solution, 4.6 parts by weight of zirconium tetrachloride was added. After stirring the solution overnight, POC13 was quantitatively removed from the trichlorosilane solution by Croix 1-graph analysis.

Trichlorosilane 4 containing 1.7 parts by weight of phosphorus oxychloride
5.0 parts by weight of aluminum trichloride was added to the 02 parts by weight solution. The mixture was placed in 11 reaction vessels and heated to 100°C. Take out the sample regularly and PQ CR
The concentration of No. 3 was measured. After one period, the upper gas is filled with POC.
13 was not detected.

Claims (1)

[Claims] (1) Period t1! A method for purifying a chlorosilane solution containing C as an impurity with a trivalent compound of a group V element in the table, comprising: (△) oxidizing the impurity and converting the impurity into a trivalent compound of the element; A method for purifying silane, comprising the step of distilling and recovering Cr+ chlorosilane. (2) The method according to claim 1, wherein the element is selected from the group consisting of phosphorus, arsenic, antiseptane, and bismuth. (3) The impurity is mainly of the formula A I-1m c
p. where A is selected from fiY consisting of phosphorus, arsenic, antimony and bismuth, Ill and 1)
is 0.1.2 or 3, and l, m + n = 3C)
The method according to claim 2, characterized in that the method is reduced by: (4) The method according to claim 3, characterized in that the impurity is mainly trichloride. (5) The oxidation step (A>) is characterized in that the impurity is brought into contact with a softening agent selected from the group consisting of chromium trioxide and manganese dioxide. (5) The oxidation step (A') is characterized in that the oxidation step (A') is a step of introducing oxygen into the rosilane solution in the presence of ultraviolet light. Ij method. <7> The method according to claim 4, characterized in that after the I culm (A), it includes an additional step of avoiding contact of the oxidation product with a 111-oxidizing agent. ( 8> The method according to claim 7] J1, wherein the complexing agent is a transition metal halide. (9) The transition metal halide is selected from zyl'nium tetrachloride and hafnium tetrachloride. The method according to claim 8, characterized in that the method is selected from the group consisting of: (10) +iiJ. The method according to <11) 'Igj, wherein the Lewis acid is selected from the group consisting of ferric chloride and aluminum chloride.
The method according to claim 10. (12) A method for removing one or more trichlorides of an element selected from the group consisting of phosphorus, arsenic, antimony, and bismuth from 1 to 2 silane, wherein C1(A) oxidizes the trichloride. (B) obtaining a compound of the element in a pentavalent state by distilling the purified 'H trichlor 1' silane into -C
A method comprising: (13) Claim 12, characterized in that said oxidizing step (A>) consists of contacting said trichloride with an oxidizing agent selected from the group consisting of chromium trioxide and manganese dioxide. 14. A method according to claim 12, characterized in that the oxidation step (A>) consists of introducing oxygen into the Tric-1''rosilane in the presence of ultraviolet light. (15) The method according to claim 12, characterized in that after step (A>) the method comprises an additional step of contacting the oxidation product with a complexing agent. (16) The complexing agent is The method according to claim 15, characterized in that the transition metal halide is selected from zirconium tetrachloride and hafnium tetrachloride. The method according to claim 16. (18) The method according to claim 15, characterized in that the complexing agent is a Lewis acid. (19) The method according to claim 15, wherein the Lewis acid is chloride chloride. Claim 1, characterized in that it is selected from iron and aluminum chloride.
The method described in Section 8. (20) A method for removing trichloride of one or more elements selected from the group consisting of phosphorus, arsenic, antimony, and bismuth from 1 to 1-lichlorosilane, the method comprising: (A) oxidizing the trichloride; (i) contacting said trichloride with an oxidizing agent selected from chromium trioxide and manganese dioxide; and (ii) in the presence of a >M external line. Introducing oxygen into trichlorosilane in such a selected step, (B) consisting primarily of zirconium tetrachloride, nophnium tetrachloride, ferric chloride and aluminum chloride 7JX (
a step of adding a complexing agent selected from iY, and a subsequent step of (C) removing purified trichlorosilane by distillation;
A method consisting of