JPH0725772B2 - Group III-Method for producing Group A organometallic compound - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to the following formula M ¹ R _a (wherein M ¹ represents an element of Group III-A of the periodic table, and each R represents , Independently selected from a hydrogen atom, a hydrocarbyl group and combinations thereof, and "a" represents an integer determined by the valency of M ¹ , in particular 3). Alternatively, it relates to a purification method.

[Technical background]

Organometallic compounds having Group III-A elements of the Periodic Table, especially lower alkyl compounds of these elements, are widely used to deposit compounds of their constituent elements on a support by chemical vapor deposition. For example, gallium arsenide semiconductor layers have been deposited on supports by combining vapors of gallium sources such as trimethylgallium and vapors of arsenic sources such as arsine at elevated temperatures in the presence of a suitable support. . Using similar methods, other Group III-A compounds, such as indium phosphide, have been prepared from trimethylindium and phosphine. First
The Group III-Group V compounds are preferably supplied in liquid form from a bubbler, which are vaporized in a carrier gas stream and transported to the deposition chamber. Thus, in this mode of transport, it is desired that the organometallic of the Group III-A compound be volatile and liquid at any temperature between about 0 ° C and 150 ° C.

Group III-A source compounds for chemical vapor deposition, in particular Group III-
Compounds for the preparation of Group V compounds are used to produce coatings of the grade required for electronics and other required applications.
It needs to be exceptionally pure. When these compounds are transported in liquid form from the bubbler, they are of no special significance since the non-volatile impurities are not vaporized in the bubbler device and therefore are not transported to the support. However, volatile impurities must be minimized in the chemical vapor deposition source compound as they are carried into the vapor deposition chamber.
Even parts per million of volatile impurities can have a significant effect on the properties of vapor deposited films. For example, “Analysis of High Purity Metalorgani” by Jones et al.
cs by ICP Emission Spectrometry ", Journal of Crysta
l Growth, Vol.77, pp.47-54 (1986), especially
See page 47, column 1 (note that this paper is not considered a prior art document).

Many interfering solvents and organometallic compounds are volatile,
It is a kind of deterioration factor that it is difficult to separate these by physical means. For example, the aforementioned Jones et al. Document points out that it is difficult to remove volatile trace impurities from Group III-A alkyl compounds by distillation. A specific example of organic fouling of Group III-A alkyl compounds is the presence of complexed ethers of trialkylindiums made in ether solvents. This ether is so complexed that it cannot be separated. Previous attempts to separate this complexed ether involve wasting most of the desired product and repeatedly distilling at elevated temperatures where all the complexed ether cannot be removed. Examples of organometallic contamination are the presence of alkylsilanes such as tetramethylsilane or Group II-B alkylates such as dimethylzinc.

The aforementioned Jones et al. Document discloses that Group III-A organic compounds are formed from organometallic and organic impurities by forming a non-volatile adduct of the desired organometallic compound with 1,2-bis (diphenylphosphino) ethane. It teaches that metal compounds can be separated. Non-adduct-forming materials such as those mentioned above, including ethers, other organic impurities and organo-metals such as tin, silicon and zinc, are not volatile and are not adducts and therefore are not subject to subsequent evaporation and removal. It is possible. The target compound is then separated from the non-volatile 1,2-bis (diphenylphosphino) ethane by distillation and then recovered.

A significant problem with the Jones et al. Method is that it must be decomposed by heating the adduct.
When the decomposition temperature of the adduct is high, there is a possibility that the decomposition temperature of the target compound is approached or exceeded. The second problem is that the adducting agent of Jones et al.
This is to form an adduct with a volatile organometallic compound of an element other than the group A element. As long as the adduct other than the target compound is not decomposed at a temperature substantially higher than the adduct of the organometallic compound of interest, the interfering compound will dissociate when decomposing the organometallic adduct of interest. Therefore, the method of Jones et al. Must be able to separate out all the unwanted impurities.

Various Group III-A alkyls as containing less than about one part per million impurities (such compounds are referred to as "Six Nine" or "Six N", indicating to be at least 99.9999% pure). Are commercially available. Other labeling methods refer to them as containing less than 1 ppm of impurities. The claimed purities of these compounds have not been directly linked to their utility for chemical vapor deposition of films, as non-volatile impurities are less important than volatile ones and volatile impurities are generally not measured.

Volatile impurities (other than solvents) can be measured using inductively coupled plasma atomic emission spectroscopy with the special care that the impurities are retained throughout the analysis of the sample (Barnes et al. To U.S. Pat. No. 4,688,935 issued Aug. 25, 1987, the contents of which are incorporated herein by reference).
Volatile impurities (containing solvent) can also be measured by mass spectroscopy, indicating that the impurities remain in the sample under analysis. Such analysis indicated that the commercially available material was not of optimum purity. These materials are generally believed to have a purity of "six nines" with respect to non-volatile components, but less than or equal to "five nines" with respect to volatile components such as alkyl silicon and alkylzinc (for gallium compounds). ing.

[Definition]

The terms used in the present specification are defined as follows.

Group III-A elements of the periodic table called M ¹ refer to boron, aluminum, gallium, indium and thallium, among which, in order to prepare a Group III-V compound, usually aluminum, Gallium and indium are preferred.

The Periodic Table I-A and Group II-A group element is referred to as M ^2, say hydrogen, lithium, sodium, potassium, rubidium, francium, beryllium, magnesium, calcium, strontium, barium and radium. Of these, lithium, sodium, potassium and magnesium are preferred, and lithium is most preferred. Ammonium also falls within the definition of M ² .

Elements of Group II-B of the Periodic Table include zinc, cadmium and mercury, which are designated M ³ .

The I-A group elements of the periodic table often has identified the first II-A group elements of the periodic table is referred to as a M ^4.

A "hydrocarbyl group" is broadly defined as any organic group that forms an organometallic compound with a Group III-A metal. Particularly preferred hydrocarbyl groups are alkyl groups, especially lower alkyl groups (defined as having 1 to 4 carbon atoms). Specifically, all isomers of methyl, ethyl, propyl and butyl groups are the preferred hydrocarbyl groups. Other exemplary hydrocarbyl groups are saturated or unsaturated cycloalkyl groups, preferably about 5 to 12 carbon atoms, most preferably cyclopentadienyl groups, aryl, preferably phenyl or 1 Included are phenyl groups substituted with the above alkyl groups, as well as any of the above groups substituted with nitrogen, oxygen or other heteroatoms.

“A” is an integer determined by the valence of M ¹ , and specifically refers to the integer 3. “B” is an integer determined by the valence of M ² , and specifically means an integer of 1 when each of M ² is selected from Group IA of the periodic table. When selected from Group A, it refers to the integer 2.

“X” includes, but is not limited to, halides, carboxylates (eg, acetates), nitrates, preferably halides, most preferably pure and chlorides of Group III-A compounds. Is an anion including chloride since it is commercially available at a relatively low cost.

"Distillation" is meant to include all steps in which the components of a mixture are separated into one or more of them by selective evaporation (including sublimation) and separation transport as a vapor. Thus, distillation also includes steps that do not collect or agglomerate vapor.

"Trace impurities" refers to detectable impurities present as less than about 20 ppm of the target compound.

“Substantially containing no ...” means containing less than one part per million of the above-specified impurities.

"Parts per million" is abbreviated as "ppm" and means the weight of impurities per million parts of the total weight of the compound containing impurities.

Two types of compounds are “separable” means that one is substantially separated from the other by a physical separation means such as distillation without performing a chemical reaction that affects one of the separable compounds. It refers to the case where it can be in a free state. The term "unseparable" of a compound means that the compound cannot be separated by the aforementioned means.

The term "solvent" is used in a broad sense to include a suspension or slurry liquid medium as well as a practical solution liquid medium. All solvents and materials described herein are anhydrous.

The “complexing solvent” refers to a solvent that cannot be separated from the target compound because it forms a complex resistant to decomposition by distillation. All other solvents are "non-complexing" solvents. In this respect, the predominant complexing solvent is ether. Specific examples of non-complexing solvents for the purposes of the invention include all solvents that do not contain electron donating atoms such as oxygen, nitrogen or sulfur atoms. Acceptable non-complexing solvents include aliphatic hydrocarbons (eg pentane or hexane), chlorinated aliphatic solvents (eg chloroform, or carbon tetrachloride), aromatic solvents (eg benzene or naphthalene), fatty acids. Group substituted aromatic solvents (eg toluene or xylene), and heteroatom substituted aromatic solvents (eg chlorobenzene)
Are included.

“Ether” means diethyl ether in the examples. Elsewhere, "ether" also includes other ethers that are complexing solvents, including cyclic ethers such as tetrahydrofuran.

"Volatile" compounds are those that have a room temperature vapor pressure of 30 mTorr or less.

"Production" refers to the production of the compound itself, or the purification of a given prepared compound by forming an adduct of the compound, separating and then decomposing.

[Summary of Invention]

One of the objects of the present invention is to produce Group III-A organometallic compounds, which preferably have less than 1 ppm total volatile organometallic impurities.

A first aspect of the present invention is a method for producing a compound represented by the following formula M ¹ R _a , wherein
In the process, the following formula _{^{[M 1 R (a + 1}} )] ▲ - b ▼ [M 2] + nonvolatile intermediate represented by ^b (adduct) is prepared.

The adduct is formed in the presence of volatile impurities that are removed, and the impurities are inseparable from the target compound once the adduct is formed. Volatile impurities co-existing with adducts (including any complexed ethers) are then removed by evaporation thereof and separating their vapors from the intermediate. next,
This adduct is decomposed to form the target compound. Decomposition, the following reaction formula _{^{c [M 1 R (a +}} 1)] ▲ - b ▼ [M 2] + b + dM 1 X a → eM 1
R _a + fM ² X _b (where X represents any suitable anion, preferably a halogen atom, and c, d, e and f represent balanced integers) It is preferable to carry out according to the reaction described above.

Finally, a secondary distillation step is performed to separate the target compound from the remaining organometallic (particularly alkylsilicon) impurities.

Surprisingly, according to the invention, Jones et al.
Contrary to teaching that "trace amounts of impurities of volatile organometallic compounds cannot be removed from objective volatile organometallic compounds by distillation", it was found that residual alkylsilicones and other impurities can be removed by distillation .

One of the advantages of the method of the present invention is that the decomposition agent is a metal compound of the target compound, so that the yield of the target compound is increased. The second advantage of utilizing this reaction is that the decomposition product is a volatile target compound and a non-volatile IA compound.
It is a group II or group II-A metal compound. This volatile product can be easily separated by a distillation method by utilizing the difference in volatility between the two kinds of products of the decomposition reaction. A third advantage of this method is that it does not have to rely on heating everything to decompose the adduct and separate the target compound. A dissimilarity to the prior art adduct treatment methods is that the present invention allows the adduct to be decomposed in most cases at room temperature or even lower temperatures.

Fourthly, since the compound of M ¹ is used as a decomposing agent, it is possible to avoid introducing other metal that may remain as a contaminant.

The intermediate in the above method can be formed by various methods. Some synthetic examples are described later in this specification.

A second aspect of the invention includes a method for separating a volatile Group III-A organometallic compound from a volatile Group II-B organometallic compound. One of the advantages of this method is similar to the first step in the first method.
The first step of this separation method consists of one or more volatile first
Volatile group containing trace impurities of II-B group compounds
It is carried out by supplying a Group III-A compound.
The Group III-A compound and the trace impurities are each represented by the following formula.

M ¹ R _a and M ³ R ₂ This mixture is reacted with a less than stoichiometric amount of the adducting agent with respect to the M ¹ compound. The adduct-forming ability of the M ¹ compound is preferably slightly higher than that of the M ³ compound. Thus, as a result, the following formula _{^{[M 1 R (a + 1}} )] ▲ - b ▼ [M 2] + b selective formation of the adduct occurs indicated by.

A small amount of M ¹ R ₂ and virtually all traces of M ³ R _a remain as unreacted residue. Since both of these starting materials are volatile, while the adduct is non-volatile, these starting materials can be removed from the adduct by distillation. Next, the adduct is decomposed as described above, and the target compound (M ¹ R _a ) can be collected from the nonvolatile decomposition product by distillation.

[Description of preferred embodiments]

The first step has the formula _{^{[M 1 R (a + 1}} )] ▲ - b ▼ and forms a non-volatile intermediate represented by [M ^{2] + b.} This adduct can be formed in various ways.

In some embodiments, the starting material is an impure variant of the target compound. In this case, the adduct formation and its final decomposition are the purification methods. Intermediates, the following reaction formula _{^{bM 1 R a + M 2 R}} b → [M 1 R (a + 1)] ▲ - b ▼ according to the reaction represented by [M ^{2] + b,} and organometallic compounds of M ² and the target compound By reacting with, it can be formed from an impure target compound.

In this reaction, the preferred adducting agent (M ² R _b ) is an alkyllithium (preferably methyllithium),
A complex is formed with a volatile organometallic compound of Group II-B and Group III-A according to the reaction described above. This one is
Does not react with volatile compounds of other elements forming non-volatile adducts. Volatile compounds of other elements can be easily removed from the adduct by distillation, even though non-volatile compounds of other elements remain thereafter, and then the adduct is decomposed and the volatile target compound is distilled. Separated by.

Another advantage of these adducting agents is that any of the reactants will eventually be complexed by the ether, but in the intermediate the ether will be more loosely complexed, thus heating the adduct mildly. The fact is that the ether can be removed. Even though the ether is complexed, it is understood to be a separable impurity for the purposes of the present invention in view of its ability to be removed from the intermediate by distillation.

A second method of forming the intermediate of similar target compound from impure starting materials, the following reaction formula _{^{cM 4 + dM 1 R a →}} c [M 1 R (a + 1)] ▲ - b ▼ [M 4] + b
+ EM ¹ (in the above reaction, c, d and e represent integers of values required to maintain equilibrium, and M ⁴ represents a Group IA metal excluding Group II-A) The metal M ⁴ is reacted with the starting material according to the reaction represented by (indicating the selected metal). This method is generally inferior to the first reaction described above for intermediate formation. One of the non-volatile products is the free metal of the target compound, as some of the target compound is not regenerated at the end of the process. This problem can be mitigated by recycling the free metal to regenerate it to an alkyl metal or other compound. When practicing this method, lithium or sodium is preferred as M ⁴ .

The third method of forming the intermediate is the following reaction scheme By carrying out the reaction shown in.

In this method, the preferred alkyl metal is also alkyl lithium, most preferably methyl lithium. The preferred M ¹ X _a reactant is the metal chloride of the target compound. The advantage of this reaction, without first forming a common ignition compound M ¹ R _a, non-pyrophoric reactant (M ¹ X _a)
To form a general non-incendive adduct. This method is a method of forming pure compounds rather than purification.

The next step is to isolate it from all volatile impurities by distillation in order to color the intermediate formed. This step can remove volatile starting materials that do not form non-volatile adducts. Also,
It is also possible to remove the uncomplexed solvent, since there are also no particular obstacles to solvent evaporation and removal. Although not as evidence, complexing solvents (especially ethers) are removed by this process because the adduct-ether complex is not so close that it is difficult to separate from the complex of the desired organometallic compound and ether. It This is
This is particularly clear when the target compound is an indium compound, which is generally formed only in ether solvents and is inseparable from ether. It can be seen that this ether is loosely complexed with the [M ² ] ^{+ b} ion of the adduct rather than the [M ¹ R _{(a + 1)} ] ⁻ ion by associating before the adduct is formed.

Separation of volatile impurities and starting materials can be carried out by heating the reaction product, partially or completely depressurizing the vessel holding the adduct, or a combination of these methods.

After removing the volatile impurities, the adduct is decomposed and the volatile target compound is collected from the residue of the non-volatile adduct.

When carrying out the adducting method described above in the Technical Background section of the present specification, it is less preferred except when it is allowed that the intermediate is decomposed by heating. To practice this method, the disadvantages of other adducting methods can also be anticipated.

A preferred method of degrading the adduct is to react the adduct with a reagent. Preferred reagent (M ¹ X
_a ) can also increase the yield if it is a metal compound of the target compound. A preferred reaction scheme for decomposing the intermediate is as follows.

_{^{That, c [M 1 R (a}} + 1)] ▲ - b ▼ [M 2] + b + dM 1 X a → eM 1
R _a + fM ² X _{b In} the above reaction formula, c, d, e and f represent integers necessary for maintaining balance.

If an adduct is formed by adding M ¹ X _a , the adduct can also be degraded by adding an additional amount of the same reagent. Therefore,
When utilizing this formation and decomposition mode, it is not important to add an excess of adduct former first, which may avoid premature regeneration of the desired compound. However, this precaution is not critical, for example, if some of the target compound is formed when the adduct is formed, the target can be collected during the process of removing volatile impurities.

Finally, trace impurities are removed by a decomposition step followed by distillation. The distillation pot is heated sufficiently for the target compound to melt, and the trace impurities are distilled off from the target compound. The unexpected aspect of this secondary distillation step is that the large amount of impurities cannot be removed directly by distillation,
Even if it has to be removed by the adduct formation and decomposition process, the secondary distillation process can provide the target compound substantially free of trace impurities.

Taking trimethylindium (InMe ₃ ) as an example,
The method of the present invention will be described in detail.

Step A: InCl ₃ / Et ₂ O and MeLi / Et ₂ O reflux temperature of ether,
That is, they are reacted at 36 ° C. to form LiInMe ₄ .
This reflux is maintained by the addition rate of MeLi.

Step B: After decanting the LiInMe ₄ ether solution, most of the ether is removed at 40-45 ° C. by atmospheric distillation. The final solvent is removed by reducing the pressure to 200-400 Torr and finally below 100 Torr. The solid LiInMe ₄ thus obtained is dried at 120 ° C./0.1 mmHg for 5-10 hours. Then, after crushing, 120-130 ℃ /
Bake for 15 to 20 hours at 0.1 mmHg.

Step C: This intermediate is decomposed by reacting with InCl _{3 in} the presence of benzene. This reaction has a reaction temperature of 80.
It is carried out by maintaining the temperature below ℃.

Step D: The product, Me ₃ In, is then sublimed at 50 ° C./0.1 mmHg. It is then maintained under vacuum in an oil bath at 90-110 ° C for 5-15 minutes to allow further sublimation.

A second aspect of the present invention is a method for separating Group II-B impurities from volatile Group III-A organometallic compounds. This method can be used as a pretreatment for carrying out one of the above-mentioned methods or for any other purpose separating these organometallic compounds.

The first step is to provide a mixture of a major portion of the Group III-A compound and a volatile Group II-B organometallic compound. The target compound and trace impurities are represented by the following formulas M ¹ R _a and M ³ R ₂ , respectively.

Since each component of this mixture is volatile, it is difficult to separate these components by physical means so that the target compound is substantially free of trace impurities. The mixture is reacted with less than stoichiometric amount of the adducting agent. The adducting agent can be any of the aforementioned reactants or combinations of reactants that are capable of forming the aforementioned intermediates.

A particular embodiment of this method is that when both compounds coexist, M ¹
The compound of ³ ) forms a complex more easily than the compound of M ³ . If less than the stoichiometric amount of adducting agent is used, only the compound of M ¹ present will form the adduct.

The volatile components are then separated from the adduct as described above. Since the compounds of M ³ are unable to complex and are volatile, they are removed by separation methods such as those used for other volatile impurities. After that, the target compound of M ¹ is regenerated by the decomposition of the adduct as described above. The decomposition product of the adduct is an organometallic compound of M ¹ and is substantially free of a compound of M ³ .

〔Example〕

The following examples illustrate various aspects of the invention, but do not limit the scope of the invention.

All the operations in the examples were carried out in vacuum or under an inert atmosphere of nitrogen or argon gas. Also, all reactants and products described herein are anhydrous.

Example 1. Production of InMe ₃ (1) Production of LiInMe _{4 In} this section, the following reaction was carried out (“Me” represents a methyl group).

In a glove bag, 1500 g (6.78 mol) of InCl ₃ were weighed into a 12-necked, three-neck flask that had been previously evacuated and filled with nitrogen. The 12 flasks were placed in a heating mantle and placed on a large jack stand. Then add a dropping funnel, a mechanical stirrer, and a 46 cm (18 inch) Vigreux column to the Claisen Head (Claize Head).
isen head) installed in 5 three-necked receptacles of 12 flasks ("Bigelow" and "Claisen").
Can't believe that is a trademark). The receiver of No. 5 was connected to a nitrogen bubbler. One dropping funnel was connected via a stainless steel tube to a source of methyllithium (1.5 mol, low halide in diethyl ether).

Since MeLi has reactivity with grease made of halogenated carbon, the dropping opening of the dropping funnel was extended below the grease joint.

About 2 diethyl ethers were siphoned to 12 flasks to prepare a stirrable slurry with InCl ₃ .

After the receiver of 5 and the dry ice condenser were cooled with a mixture of isopropanol (IPA) and dry ice, the addition of MeLi was started. The reaction was continued under reflux, and the ether was distilled using a Vigreux column to prepare the above 5
Collected in the receiver. The reaction was not required to heat the reaction flask as the heat of reaction was sufficient to maintain reflux.

The addition of MeLi was continued until there was 4.4 mol of MeLi per mol of Incl ₃ . MeLi concentration is standard acid solution (0.1N hydrochloric acid)
It was measured by titrating a known amount of several tens of ml. 12
When the reaction flask was full, the addition of MeLi had to be stopped and the ether had to be distilled off by heating the reaction mixture to reflux using a heating mantle. The receiver was emptied several times by siphoning off the distilled ether. The total amount of MeLi solution is about 20 (In
It was 4.4 mol MeLi per mol Cl ₃ .

After adding MeLi to the 12 reaction flask, the dropping funnel was removed and replaced with a nitrogen inlet tube equipped with a shut-off valve. Heat the reaction flask with a heating mantle until the reaction mixture is 5
The ether was continuously distilled off until the following was reached. at this point,
The stirring was stopped and the reaction mixture was allowed to stand overnight.

The Vigreux column, Claisen head and receiver were removed from the reaction flask. The reaction mixture consisted of a white precipitate (polymer of LiCl and methyllithium) that had settled below the orange solution.

(2) Vacuum drying of LiInMe ₄ Having a three-necked glass lid (O-ring seal) 5
A stainless steel Kettlehead type dry flask was equipped with a nitrogen inlet tube with a shutoff valve and a stir bar. The dry flask was connected by a U-tube to a three-necked receiver equipped with a dry ice condenser of 5. A condenser, a valve, a liquid nitrogen reservoir, a vacuum gauge, a second valve, and a vacuum pump are arranged in this order, and the stainless steel is placed in an oil bath installed on an apparatus combining a heating / stirring table and a jack stand connected by a vacuum tube. A dry steel flask was heated. The device was evacuated and backfilled with nitrogen several times.

Take the 12 reaction flasks containing the reaction mixture of (1) above, and make sure that no LiCl and excess of polymeric MeLi are sucked out of the reaction flask into the 5 stainless steel dry flask. The orange solution was siphoned through a flexible tube from.

LiInMe _{4 in} ether (intermediate) from 12 reaction flasks
After removing most of the orange solution of ## STR3 ## the ether was added to the flask to wash the precipitate. The mixture was stirred for at least 1 hour and then left overnight.

Meanwhile, a vacuum was gradually applied to the drying flask of 5 in order to remove ether. The oil bath temperature was maintained at about 30 ° C to compensate for the heat loss due to the evaporation of the ether. The receiver and condenser were cooled with a dry ice / IPA slurry. Throughout this process, distilled ether was intermittently withdrawn from the receiver.

After the volume of material in the dry flask of 5 was reduced to less than 2, the pale yellow supernatant washed from the 12 reaction flask was again washed with care to ensure that no precipitate was released from its bottom. Transferred to a dry flask.

At the beginning of drying, the vacuum was gradually applied again and the temperature of the oil bath was gradually increased. This operation was continued until a sufficient vacuum was obtained, then the temperature of the oil bath was 120 ° C. LiInMe ₄ was dried under full vacuum and maintained at 120 ° C for several hours. The apparatus was then charged with nitrogen through the inlet tube shutoff valve on flask 5 and then cooled to room temperature.

The U-tube and receiver were removed from the 5 stainless steel dry flask. The stainless steel flask was replaced with an empty five-necked three-neck glass flask equipped with a mechanical stirrer and two nitrogen inlet tubes with shut-off valves, a stainless steel motor and pestle, a funnel and a spatula. Moved into a glove bag. Remove the glass lid from this stainless steel dry flask and use a motor and pestle to remove light brown solid LiInMe ₄
The adduct was ground until it became a fine powder. After grinding the adduct, it was transferred to the glass flask described in 5 above.

The flask containing LiInMe ₄ was placed in an oil bath and then directly connected to a liquid nitrogen reservoir equipped with a vacuum tube. The flask was evacuated thoroughly and then the temperature of the oil bath was raised to 120 ° C. After drying LiInMe ₄ under these conditions for 2 hours or more, nitrogen was charged into the flask of No. 5 and cooled to room temperature. The dry LiInMe ₄ was then weighed in order to determine the calculated amount of InCl ₃ used in the next reaction.

(3) Decomposition of LiInMe ₄ The dry LiInMe ₄ prepared in (2) above was weighed and the weight of InCl ₃ required for the final reaction was calculated.

InCl in a 1-neck flask of 2 in a glove bag
Weighed the theoretical amount of ₃ . The flask was equipped with a single large diameter tube about 2 feet long with a male flask at the end and a small flask. This Li
About 5 benzenes were poured into the 5 flasks containing InMe ₄ to obtain a stirrable slurry. The 5 flask was placed in an oil bath and equipped with a Y-tube in its one neck, to which was fixed a dry ice condenser and thermowell. Remove a small "dummy" flask from the end of the tube connected to the InCl ₃ flask,
The male joint on the end of the tube was connected to the 5 flask. InCl ₃ was transferred into the LiInMe ₄ / benzene slurry in small portions at a time. The transfer rate was such that the reaction temperature was kept below the reflux temperature of benzene (80 ° C). During the addition of known small amounts of InCl _3, InCl ₃ was tightly shut off the tube so as not clog wetness and the tube with benzene vapor. It took several hours to add InCl ₃ .

After the addition of InCl ₃ was complete, the reaction mixture was cooled to room temperature with stirring. The InCl ₃ addition flask and tube were removed and fitted with a nitrogen inlet tube with shut-off valve. The Y-tube, dry ice condenser and thermowell were removed.

(4) Removal of Benzene and Trace Impurities by Distillation The reaction flask described in 5 of (3) above was equipped with a 46 cm (18 inch) Vigreux column connected to 3 receivers by a Westcott water-cooled condenser. (Westcott is not believed to be a trademark).
The receiver was cooled in an ice bath and benzene was distilled from the reaction mixture at atmospheric pressure. The oil bath was maintained at about 110 ° C and the heating temperature was about 80-83 ° C. After distilling off most of the benzene, the reaction mixture showed thickening. The stir bar was raised a few inches so that the stirrer blade floated above the level of the molten reaction mixture, and the stir bar was fixed in that position while the reaction flask was cooled overnight.

The next day, the stir bar was removed from the 5 reaction flask containing the solid mixture of InMe ₃ , LiCl and benzene. A 3-necked flask containing a stir bar and a dry ice condenser of 3 were connected to the flask of 5 using a U-shaped tube. The U-tube was wrapped with heating tape. A dry ice condenser was connected by a vacuum tube (in that order) to the valve, liquid nitrogen reservoir, pressure gauge, valve and vacuum pump.

A vacuum was applied to the system at room temperature. The receiver and condenser were kept at room temperature. All evaporating benzene was flushed into a liquid nitrogen reservoir. If the reservoir becomes clogged with frozen benzene, close the valves on both sides of the reservoir, separate it from liquid nitrogen, dissolve benzene at the bottom of the reservoir, and place the reservoir in a Dewar flask with liquid nitrogen. Brought it back (I can't believe "Jewer" is a trademark).

The oil bath was warmed to 30-35 ° C to keep the benzene in the flask of 5 frozen, and the U-tube prevented the benzene from freezing therein by warming the heating tape. When InMe ₃ crystals began to collect in the receiver, the receiver and condenser were cooled with dry ice / IPA. The temperature of the oil bath was raised to 50 ° C and sublimation was continued.

It took about 9 days before 1 kg of InMe ₃ was sublimated. A small amount of benzene was removed from InMe _{3 by} starting the above operation every morning. Several days after the sublimation treatment, the reaction mixture was finely ground in the morning with care with a spatula while cooling. After consecutive days of sublimation treatment, the device was filled with nitrogen via the nitrogen inlet tube on the flask of 5. Part 5
The sublimation was terminated when only a trace amount of light brown solid LiCl remained in the flask.

(5) The apparatus was disassembled using the first sublimation of resublimation the separation InMe ₃ trace impurities, then 1 received with a small dry ice condenser and containing three of the flask sublimated InMe ₃ and stir bar It was connected by a vessel and a U-shaped tube. The device was assembled as described for the first sublimation.

The heating tape on the U-tube was warmed. On the other hand, in order to completely melt InMe ₃ , the flask in ₃ was heated in an oil bath at 90 ° C under atmospheric pressure.
Heated to ~ 110 ° C. Molten InMe ₃ was stirred with a stir bar.

The receiver and condenser were cooled with dry ice / IPA. Next, the nitrogen inlet tube valve on the 3 flask was closed and the system was gradually depressurized until InMe ₃ started to bubble. The system vacuum was carefully continued until about 20-30 g of material collected in the receiver. At this point, the device was filled with 3 flasks of nitrogen and cooled overnight at room temperature.

One receiver containing the first cut was replaced with three three-necked flasks equipped with a dry ice condenser. Sublimation was started again and the starting operation described for the first sublimation was continued. Sublimation was continued until only about 50 g of material remained in the heated flask. The second sublimation treatment was performed the same number of times in the same manner as the first sublimation.

As in the first sublimation treatment, the system was thoroughly evacuated each morning and then cooled to -78 ° C after a while. This operation is In
Helped to remove traces of benzene from Me ₃ .

After the sublimation was complete, the system was nitrogen filled and decomposed. Three flasks containing twice sublimed InMe ₃ were equipped with a nitrogen shutoff valve. After warming InMe ₃ to room temperature overnight,
A liquid nitrogen reservoir was directly connected to the flask of No. 3, and a sufficient vacuum was made at room temperature for 1 hour. Then, the flask No. 3 was placed in a dry box and stored under vacuum.

The product was analyzed by inductively coupled plasma atomic emission spectroscopy. It was found to contain only 1 ppm silicon.

(6) Growth of InP film The product of (5) above and phosphine gas were grown to grow an indium phosphide semiconductor layer by a vapor phase epitaxy method at atmospheric pressure and then tested for electrical properties of this layer. Electron mobility of the layer at 77 ° K (cm ² / Vs)
Was 131,000. This value is understood to be the highest value obtained so far, indicating that the solvent and organometallic impurity concentrations in the starting compounds are extremely low.

Example 2. Removal of Zn and Si from trimethylgallium (1) Preparation of LiGaMe ₄ The following reaction was carried out.

First of all, the starting material trimethylgallium (TMG)
Impurities in silicon and zinc were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP). It was found that the average value of the volatile alkyl silicon compound was 42 ppm and that of the volatile alkyl zinc compound was about 5 ppm. The detection limit for each of these impurities was about 0.5 ppm.

Twelve stainless steel kettle head flasks with 3-neck glass lid, O-ring seal, magnetic stir bar, and 1
Equipped with an addition funnel. This flask is 0.5mmHg pressure (66N
Evacuated to / cm ² ). 1207 ml TMG (1363 g, 11.87 mol)
Was added to the flask via a dropping funnel from a feed tank through a short hose. Then through the addition funnel,
About 11 mol of MeLi (about 1.3 in ether)
M, 8.45) was added. The reaction was exothermic.

At the end of the MeLi addition, the 12 flasks were connected (in that order) with 3 receivers equipped with a dry ice condenser, a liquid nitrogen reservoir and a vacuum pump. The ether was evaporated until the adduct in the flask was dry. Final pot temperature and pressure are 120 ° C each
And 0.4 mmHg (53 N / cm ² ). The apparatus was then filled with nitrogen, the adduct removed from the flask and ground under a stream of nitrogen. After that, in the same device for about 1 hour,
It was dried at 110 ° C. and 0.3 mmHg (40 N / m ² ) pressure. A small amount of unreacted TMG was isolated in the liquid nitrogen reservoir, confirming that slightly less than the theoretical amount of MeLi was initially added. Then, 1607 g (11.75 mol) of LiGaMe ₄ was isolated.

(2) Reproduction of TMG 3LiGaMe ₄ + GaCl ₃ → 4GaMe ₃ + 3LiCl 1598 g (11.68 mol) of the product of (1) above was weighed into a 12-necked glass flask. Toluene 3.79 (1
Gallon) was siphoned into the flask and 325 ml of toluene was placed in the dropping funnel fixed to the flask. 3.89 mol GaCl ₃ (685 g) in toluene in dropping funnel
Was was then dissolved melted, it was used further toluene (about 255 ml) to wash the GaCl ₃ from the top of the ampoule and dropping funnel GaCl _3. This gallium chloride / toluene solution was added to the adduct in the flask over a period of about 2 hours.

(3) Crude distillation of TMG The 12 flasks were equipped with a distillation tube (vacuum jacketed and filled with an effective stainless steel filler plated with silver), a Claisen head, and dry ice.
Equipped with one first catch receiver with condenser. 12
The flask was heated in an oil bath and the receiver maintained at -78 ° C. When the temperature of the pot reached about 50 ° C and the temperature of its head reached about 55 ° C, TMG was distilled into the receiver. About 50 ml of TMG was collected as the first distillate. An ICP analysis of this initial distillate revealed that zinc was not detected but contained about 3 ppm of silicon.

After replacing the initial distillation receiver with the receiver (flask) of 5, the main fraction of TMG was heated to a head temperature of 85 to 106 ° C and a pot temperature of 85 to 106 ° C.
It was heated to 100-116 ° C and distilled. About 2.5 TMGs were collected.

(4) Secondary Distillation Assembling a 20-stage bubble column equipped with a partially separated head and 1 initial flow receiver on a distillation flask,
The TMG was distilled again. The pot temperature was set to 80 ° C and the head temperature was set to 55 ° C. 100 ml of initial distillate was collected. When this initial distillate was analyzed by ICP, silicon and zinc were not detected. A large receiver was attached and the main fraction of TMG was distilled with a pot temperature of 81-109 ° C and a head temperature of 55-56 ° C. Finally, the final distillate was collected in a third receiver. The pot residue was sampled for analysis.

Analysis of the major fractions showed undetectable amounts of silicon and zinc, similar to the analysis of pot residues.

Even when less than stoichiometric amount of MeLi is reacted with TMG, volatile zinc compounds (and all other volatile II-B
This example showed that the family compounds) were removed. The inventors understand that zinc does not form a complex under these conditions and is distilled off when the adduct is dried. This example also shows that the volatile alkyl silicon in the starting material is almost completely removed by a series of adduct formations and decomposition by secondary distillation.

Example 3. Preparation of LiGaMe ₄ from GaCl _{3 The} following reaction scheme was followed.

A 5-necked 3-necked flask was equipped with a dropping funnel, mechanical stirrer and dry ice condenser of 1. After temporarily removing the dropping funnel, 250 g (1.42 mol) of GaCl ₃ was melted and poured into the flask. 400 ml of degassed ether was slowly added to the flask through the dropping funnel and GaCl ₃
Was dissolved. This dissolution was exothermic. Next, 1.3 M MeLi 4.4 (about 5.7 mol) dissolved in ether was added to
It was added to the flask through a copper tube in which a MeLi tank was connected to the dropping funnel. The reaction was exothermic, so the reaction mixture was refluxed during the addition of MeLi.
After the addition was complete, the reaction mixture was stirred and allowed to cool to room temperature. The mixture was then filtered to separate the precipitate and the filtrate was dried. The obtained product (LiGaMe ₄ ) was a brown solid. Volatiles were removed from the product by bringing it to a pressure below 0.5 mm Hg (66 N / m ² ) and maintaining the temperature up to 127 ° C. for about 8 hours. next,
When the dried product was ground and weighed, 131 g (yield,
67%) of LiGaMe ₄ was formed.

LiGaMe ₄ was tested for volatility by starting from 150 ° C. and heating a small sample at a rate of 3 ° C. per minute. At 220 ° C, no signs of melting or decomposition were noted. It started to decompose at 289 ° C but did not melt.

Example 4. Purification of AlEt ₃ (1) Preparation of NaAlEt ₄ The following reaction was carried out (Note, “Et” means an ethyl group).

The three-necked flask of No. 5 was evacuated and filled with nitrogen. 130 g (5.6 mol) of metallic sodium suspended in toluene was added to the flask in a glove bag. next,
The flask was connected to a magnetic stir bar, a dry ice condenser and a dropping funnel of 1 before it was placed in an oil bath. After adding about 3 toluene to the flask,
The dropping funnel was filled with 540 ml (3.95 mol) AlEt ₃ .
The oil bath was heated to 70-75 ° C, then AlEt ₃ was added slowly over 2 hours. The heating of the oil bath was stopped when the exothermic reaction started. After the addition was complete, the flask was heated to 100 ° C, then cooled and left to stand for 3 days. The flask was heated to 65-70 ° C. with stirring, then the stirring was stopped to precipitate the remaining Na and metallic Al by-products.
The supernatant was transferred and hot filtered into a flask of 5 to separate free metal. The filtrate was cooled, causing a crystalline precipitate. The filtrate was cooled in a bath at -78 ° C and after further precipitation, the supernatant was discarded. Under vacuum [final vacuum is lower than 1mmHg (133N / m ² )] for 2 hours,
Toluene was blown out at 70 ° C. Crystalline NaAlEt ₄ was taken from the flask, crushed with a spatula, and the precipitate
It was dried under a pressure of 0.5 mmHg (66 N / m ² ) at 75 ° C. for about 4 hours, and then ground with a motor and a pestle.

263 g (1.58 mol) of NaAlEt ₄ was isolated. The melting point of this product was 122 ° C to 123 ° C. In addition, literature values [J. Gen.
Chem.USSR, Vol.32, page 688 (1962)] is 12
2 ° to 124 ° C.

(2) Reproduction of AlEt ₃ The following reaction formula was followed.

3NaAlEt ₄ + AlCl ₃ → 4AlEt ₃ + 3NaCl In a small flask in a glove bag, AlCl ₃ 65 g (0.4
(9 mol). The tube was connected to a flask (the other end had a frosted glass male insert that was temporarily inserted into a dummy flask).

NaAlEt ₄ with about 1 benzene in a 3-necked 3 flask
263 g (1.58 mol) was slurried. The male solid part of the tube was inserted into one neck of a three-necked flask, and AlCl ₃ was transferred little by little to the three-necked flask over about 30 minutes. The solid component of the slurry turned into a fine, light salt precipitate.

Volatiles were distilled from the precipitate for about 15 hours under vacuum at 60-80 ° C. The precipitate was discarded. At pot temperature 20 ° to 45 ° C
Benzene was separated from AlEt ₃ by vacuum distillation. The second receiver was replaced and AlEt ₃ and some benzene were redistilled (pot residue consisting essentially of solids). Further, the second receiver (flask) is vacuumed (0.2 mmHg,
Benzene was removed by maintaining at 60 ° C. under 27 N / cm ² ) for 3 hours. No secondary distillation was performed.

ICP analysis of the product (AlEt ₃ ) showed the presence of about 5 ppm volatile alkyl silicon.

This example shows that even if the adduct formation and decomposition steps are performed, an undesired concentration of alkyl silicon remains in the reaction product if the secondary distillation step is not performed. This example also shows an example of another reaction for forming an adduct from a target compound.

Example 5. Magnesium adduct of TMG The following reaction was carried out and the final product was purified as in Example 2.

Me ₂ Mg + 2Me ₃ Ga → Mg (GaMe ₄ ) ₂ 3Mg (GaMe ₄ ) ₂ + 2GaCl ₃ → 8GaMe ₃ + 3MgCl _{2 The} first reaction is with a slight excess of Me ₃ Ga to avoid the formation of zinc impurity adducts. Insufficient molar amount of Me ₂
It was carried out using Mg and. ICP analysis cannot detect the amount of volatile zinc and silicon compounds (0.5 p
less than pm).

Example 6. Purification of Other Group III Alkyls The following reaction was carried out and the final product was purified as in Example 2.

MeLi + Et ₃ Ga → LiGaMe _x Et _y (x + y = 4) 3LiGaMe _x Et _y + GaCl ₃ → 3GaMe _z Et _w + 3LiCl (z + w = 3) Expressed in another way, the product is a mixture of the following species:

GaMe ₃ GaMe ₂ Et GaMeEt ₂ GaEt _{3 When the} above mixture is distilled off from the decomposition by-products,
Substantially GaMe ₃ and GaEt ₃ (about 55 ° C and 104 respectively)
Boiled at 0 ° C.) and then separated by distillation.

A slight molar excess of Et ₃ Ga was used in the first step to avoid the formation of zinc impurity adducts. ICP analysis
It was shown that the amounts of silicon and zinc in the product were undetectable.

Continued Front Page (72) Inventor Steven Jay. Manzic United States, New Hampshire 03865, Plaistow, Keller Avenue 3 (72) Inventor Thomas Mitchell USA, Massachusetts 02054, Millis, Maple Avenue 4 (56) Reference JP 62-132888 (JP, A) JP Sho 62- 185090 (JP, A) JP-A-2-67230 (JP, A) Special table Sho 61-502056 (JP, A)

Claims (12)

[Claims] 1. The following formula M ¹ R _a containing impurities of a volatile metal compound in a total amount of less than 1 ppm (wherein M ¹ represents an element of Group III-A of the periodic table, and each R is Independently selected from a hydrogen atom, a hydrocarbyl group and combinations thereof, and a represents an integer 3), the method comprising the steps of: A. ¹ R _{(a + 1)} ] ▲ ⁻ _b ▼ [M ² ] ^{+ b} (In the above formula, M ¹ represents an element of Group III-A of the periodic table, and M ² represents Group I-A of the periodic table and Selected from Group II-A elements and ammonium, a represents the integer 3, b is selected from the integers 1 or 2 and each R
Independently forming a non-volatile intermediate represented by a hydrocarbyl group, a hydrogen atom and combinations thereof, B. distilling out most of the volatile impurities from the intermediate,
Step of providing said intermediate comprising a residue of the volatile organic impurities, C. The following reaction scheme _{^{c [M 1 R (a +}} 1)] ▲ - b ▼ [M 2] + b + dM 1 X a → eM 1
R _a + fM ² X _b (wherein c, d, e and f represent integers selected to maintain equilibrium, and X represents an anion), and the intermediate Decomposing the body and thereby supplying said M ¹ _Ra with said residue, and D. secondary distilling said MR _a with said residue from _a liquid, whereby said product Selectively distilling off the residue of the MR _a such that the residue contains less than 1 ppm;
A method comprising. 2. The method according to claim 1, wherein M ¹ is indium. 3. The method according to claim 1, wherein M ¹ is gallium. 4. The method according to claim 1, wherein M ¹ is aluminum. 5. The method according to claim 1, wherein each R is an alkyl group. 6. The method according to claim 5, wherein M ¹ R _a is trimethylindium. 7. The method according to claim 1, wherein M ² is lithium. 8. The method according to claim 1, wherein X is chloride ion. 9. The method of claim 1, wherein the product of the method comprises less than 0.5 ppm silicon and zinc. 10. The method of claim 1 wherein the product of said method contains less than 0.5 ppm of volatile organometallic impurities. 11. The method of claim 1 wherein the product of the method is suitable for growing a semiconductor layer having an electron mobility of at least 131,000 cm ² / Vs at 77 ° K. 12. The forming step comprises reacting an impure starting material represented by the following formula M ¹ R _a with _a less than theoretical amount of an adducting agent to preferentially form the non-volatile intermediate. The method of claim 1.