JPH09169507A - Production of aluminum nitride - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce AlN having a low C content without requiring oxidation treatment and firing in ammonia. SOLUTION: When an organoaluminum compd. and ammonia are brought into a vapor phase reaction to produce AlN powder, the compd. is evaporated at the b.p. or below with carrier gas and the evaporated compd. is transferred to a reactor at the b.p.+20 deg.C or below within 100sec. It is fed into a zone at 200-600 deg.C in the reactor and allowed to react with ammonia at 300-600 deg.C. The resultant precursor of AlN is decarbonized by firing at 1,100-1,900 deg.C in inert gas. By this firing, decarbonization can be easily and very effectively carried out and the objective high purity AlN for a semiconductor substrate having very low O and C contents and high heat conductivity is more easily obtd. as compared with conventional treatment in an oxidizing atmosphere or in an atmosphere of ammonia. This method is low-cost and industrially advantageous from the viewpoint of processes and apparatus.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing aluminum nitride powder. More specifically, the present invention relates to a method for producing an aluminum nitride powder having a low carbon content for obtaining an aluminum nitride sintered body that is preferably used as a semiconductor peripheral material and heat resistant / corrosion resistant ceramics.

[0002]

2. Description of the Related Art Conventionally, the following two methods have been industrialized as methods for producing aluminum nitride powder. One is a direct nitriding method of nitriding metallic aluminum powder with nitrogen or ammonia gas, and the other is an alumina reduction method of firing a powder mixture of alumina and carbon in a reducing atmosphere. On the other hand, recently, since the organic aluminum method uses organic aluminum that can be refined by distillation or the like as a raw material, it has the merit that it is easy to make the product highly purified, and therefore, it has attracted attention.

[0003]

However, the organoaluminum method has a problem in that the obtained product contains about 3 wt% of carbon as impurities due to the alkyl group of the raw material. However, the raw material powder for sintering is required to have a low carbon content as well as an oxygen content, and the upper limit is generally set to about 0.1 wt%. Therefore, in order to remove this carbon, the aluminum nitride precursor produced by the reaction of organoaluminum and ammonia is fired in an oxidizing gas atmosphere (such as in air), or as disclosed in JP-A-2-199009. , It was necessary to reduce the carbon content by firing in NH ₃ .

In the case of oxidation treatment, as a result, it is excessively oxidized and contains a few percent of oxygen, which causes deterioration of thermal conductivity when the product is sintered. Also, NH ₃
Although calcination inside is a very effective method for removing carbon in the precursor, it is an economic problem such as deterioration of NH ₃ and power consumption, and there is no material that can withstand NH ₃ atmosphere at high temperature. There is also a problem in terms of safety. For example, Japanese Patent Publication No. 4364/1996 discloses a method of producing aluminum nitride powder by reacting organic aluminum with ammonia gas. This method uses these compounds
Although the reaction is carried out at 600 to 1300 ° C. after mixing at 200 ° C. or less, when these compounds are mixed at 200 ° C. or less, clogging occurs at the mixing part, and long-term operation becomes difficult. Furthermore, the reaction temperature is as high as 600 to 1300 ° C, which is uneconomical, and there is no material that can withstand an ammonia atmosphere at high temperatures, so there is a problem in terms of safety. There are problems in industrialization.

Further, a method for producing aluminum nitride powder by reacting an organoaluminum gas with an ammonia gas is disclosed in JP-A-2-141408 (aluminum nitride production method) and JP-A-2-217311 (organic aluminum is supplied by a double pipe). Operation for a long time) and Japanese Patent Laid-Open No. 2-239109 (homogenization of produced particles by the ratio of organoaluminum and ammonia and the total gas in the system), and the evaporation temperature and the transport temperature are described. After that, if the transportation time to reach the reactor is 100 seconds or more, some of the organoaluminum will decompose,
The content of carbon as a decomposing species in the obtained aluminum nitride precursor increases, the decomposing species are difficult to evaporate during firing, and the carbon content in the obtained aluminum nitride also increases.

[0006]

In order to solve the above-mentioned problems, the inventors of the present invention have conducted earnest research on a method for inexpensively producing high-purity aluminum nitride powder. As a result, it was possible to develop a method for producing aluminum nitride powder having a low carbon content without oxidation treatment or firing treatment in ammonia, and completed the present invention.

That is, the method for producing aluminum nitride of the present invention is a method for producing aluminum nitride powder by subjecting vaporized organoaluminum and ammonia to a gas phase reaction to evaporate the organoaluminum by an entrained gas at a boiling point or lower, And the temperature before reaching the reactor is the boiling point +20
The temperature is kept below ℃, and the time required to reach the reactor after evaporation is transported within 100 seconds and supplied to the zone of 200 to 600 ℃ in the reactor, and the gas phase reaction with ammonia at 300 to 600 ℃. Then, the obtained aluminum nitride precursor is fired at 1100 to 1900 ° C. in an inert gas. Conventionally, aluminum nitride powder obtained by the organoaluminum method needs to be fired at a temperature of 700 ° C. or higher in an oxidizing gas atmosphere in order to remove residual carbon, and as a result, it is excessively oxidized and contains a few percent of oxygen. However, this oxygen atom adversely affected the thermal conductivity.
In the present invention, this problem can be solved by a simple process, which is extremely advantageous industrially.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The organoaluminum used as the raw material of the present invention is AlR ₁ R ₂ R ₃ (R ₁ , R ₂ and R ₃ are CH ₃ , C ₂ H ₅ and nC ₃ H).
₇ , a combination of one or more C _{1 to} C ₄ alkyl groups such as iC ₃ H ₇ ), and typical organic aluminums include trimethylaluminum and triethylaluminum. These have melting points of 15.3 ℃,
It has the physical properties of -45.5 ° C and boiling points of 127.1 ° C and 186.6 ° C. Since they are liquids at room temperature, they can be easily purified by simple means such as distillation and purification, and the obtained aluminum nitride powder is an electronic material. It is possible to achieve ultra-high purification up to the level suitable for use as. Further, the ease of availability when industrially producing can be mentioned as one of the characteristics.

In the present invention, the purified organoaluminum compound is vaporized at a temperature below the boiling point by using an inert carrier gas such as hydrogen, helium, nitrogen and argon. The vaporized organoaluminum and inert carrier gas are transported to the reactor at a boiling point of + 20 ° C or less and an arrival time of 100 seconds or less, and are supplied to the zone of 200 to 600 ° C in the reactor. Although the aluminum nitride precursor obtained after the reaction contains 2.0 wt% or less of carbon, this kind of carbon species is easily gasified and volatilized by thermal decomposition, and the aluminum nitride precursor is heated to 1100 to 1900 ° C in an inert gas atmosphere. It can be easily volatilized and decarburized by firing at the temperature of. The obtained aluminum nitride powder can easily have a carbon content of 0.1 wt% or less.

In the method of the present invention, organoaluminum is preferably vaporized below its boiling point. When the evaporation temperature is higher than the boiling point, decomposition of organoaluminum occurs, and a part of it is vaporized and remains in the product as a decomposed species which is very difficult to decarburize, which is not preferable. The transport of vaporized organoaluminum causes the temperature to rise to the boiling point +
It is recommended to keep the temperature below 20 ° C and transport it within 100 seconds to reach the reactor. It is preferable that the transportation time is 10 seconds or less. If it is 100 seconds or more, some of the organoaluminum remains in the product as a decomposition species that is very difficult to volatilize and decarburize. Even at a boiling point of + 20 ° C or higher, decomposition similarly occurs, and some decomposition species remain in the product, which is not preferable.

Organoaluminum is from 200 to 600 ° C in the reactor.
Blow into the temperature zone. If the temperature is below 200 ° C, there is no problem in quality, but a sticky substance is produced in the process of mixing with ammonia and the reaction process, clogging the inside of the reactor and making long-term operation difficult. On the other hand, when the temperature is 600 ° C. or higher, the decomposition of organoaluminum is promoted, the carbon content remaining in the product as a decomposition species increases, and the decomposition product is clogged at the supply port, which makes it difficult to operate for a long time. The reaction is carried out at 300-600 ° C.

The aluminum nitride precursor obtained is fired at a temperature of 1100-1900 ° C. in an inert gas. As the inert gas, hydrogen, helium, nitrogen, argon or the like can be selected, but nitrogen gas is preferable from the economical point of view. A temperature of 1100 ° C is sufficient, but volatilization of residual organic matter is further improved at 1400 ° C or higher. But,
If the temperature exceeds 1900 ° C, partial sintering occurs and the product yield is deteriorated. The carbon concentration can be easily quantified using a carbon / hydrogen / nitrogen analyzer (made by LECO) in ceramics.

[0013]

EXAMPLES The present invention will now be specifically described by way of examples, but the present invention is not limited to these examples.

Example 1 3.4 Kg / hour and 2.5 Kg / hour of triethylaluminum were fed to the evaporator by using nitrogen gas as a carrier and evaporated at 170 ° C. The evaporated triethylaluminum was transported to the reactor at a temperature of 200 ° C and an arrival time of 1.2 seconds. External heating of the reactor (empty tower reactor, inner diameter 8 cm, length 6 m)
The blow-out part in the reactor inserted into the reactor while controlling the temperature to 480 ° C was 300 ° C. When the fumed reaction product was reacted with ammonia in the reactor and collected with a SUS316 sintered metal filter, about 0.8 Kg of product (aluminum nitride precursor) per hour was obtained. The resulting product was placed in a carbon crucible and placed under a nitrogen gas atmosphere for 1600
The temperature was raised to 0 ° C., the temperature was maintained for 3 hours, and then the temperature was lowered to room temperature to obtain an aluminum nitride powder. Table 1 shows the evaluation results.

Example 2 An aluminum nitride powder was obtained in the same manner as in Example 1 except that the time required for the evaporated triethylaluminum to reach the reactor was 3.7 seconds. However, the residence time of the evaporated triethylaluminum was changed by changing the pipe diameter and length from the evaporator to the reactor. Table 1 shows the evaluation results.

Example 3 An aluminum nitride powder was obtained in the same manner as in Example 1 except that the time required for the evaporated triethylaluminum to reach the reactor was 8.6 seconds. Table 1 shows the evaluation results.

Example 4 An aluminum nitride powder was obtained in the same manner as in Example 1 except that the time required for the evaporated triethylaluminum to reach the reactor was 53.2 seconds. Table 1 shows the evaluation results.

Example 5 Example 1 was repeated except that the reactor was controlled at 700 ° C. and the temperature of the blowing portion of triethylaluminum in the reactor was 300 ° C.
Aluminum nitride powder was obtained in the same manner as in. Table 1 shows the evaluation results.

Example 6 Product obtained in Example 2 (aluminum nitride precursor)
In a carbon crucible at 1200 ° C under a nitrogen gas atmosphere.
The temperature was raised to, held at the same temperature for 3 hours, and then cooled to room temperature.
An aluminum nitride powder was obtained. Table 1 shows the evaluation results.

Comparative Example 1 An aluminum nitride powder was obtained in the same manner as in Example 1 except that the evaporation temperature of triethylaluminum was 200 ° C. Table 1 shows the evaluation results.

Comparative Example 2 An aluminum nitride powder was obtained in the same manner as in Example 1 except that the evaporation temperature of triethylaluminum was 240 ° C. Table 1 shows the evaluation results.

Comparative Example 3 The temperature of evaporated triethylaluminum to the reactor was measured.
Aluminum nitride powder was obtained in the same manner as in Example 1 except that the treatment was carried out at 240 ° C. Table 1 shows the evaluation results.

Comparative Example 4 An aluminum nitride powder was obtained in the same manner as in Example 1 except that the time required for the evaporated triethylaluminum to reach the reactor was 112 seconds. Table 1 shows the evaluation results.

Comparative Example 5 The temperature of the outlet of triethylaluminum in the reactor was adjusted to
The same procedure as in Example 1 was repeated except that the test was carried out at 160 ° C. However, the temperature of the blowing part in the reactor was changed by changing the blowing position by utilizing the temperature distribution of the reactor. As a result of operation, after 13 hours, the supply line pressure increased and operation was stopped.When the equipment was disassembled and inspected, an off-white solid was stuck from the supply section to the inside of the reactor and the reactor was blocked. .

Comparative Example 6 Example 1 was repeated except that the reactor was controlled at 700 ° C. and the temperature of the blowing portion of triethylaluminum in the reactor was 630 ° C.
After 7 hours, the supply line pressure increased and operation was stopped.The equipment was disassembled and inspected, and a white silver solid adhered to the supply section and the supply port was blocked. Was there. Table 1 shows the evaluation results of the obtained aluminum nitride powder.

[0026]

[Table 1]

[0027]

According to the method of the present invention, the carbon in the aluminum nitride precursor produced after the reaction is easily gasified and volatilized by firing in an inert gas atmosphere, and effectively decarbonized. be able to. This is extremely easy in terms of process and equipment and is advantageous in terms of cost. Further, it is possible to industrially obtain an aluminum nitride powder excellent in quality.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobuhisa Iwane 1-6 Takasago, Takaishi-shi, Osaka Mitsui Toatsu Chemical Co., Ltd.

Claims (2)

[Claims] 1. A method for producing an aluminum nitride powder by subjecting vaporized organoaluminum and ammonia to a gas phase reaction, wherein vaporization of organoaluminum is carried out by an entrained gas at a temperature not higher than the boiling point and before reaching the reactor. The temperature is kept below the boiling point + 20 ° C, and the time required to reach the reactor after evaporation is transported within 100 seconds and the temperature of 200 to 60
A method for producing aluminum nitride, characterized in that the aluminum nitride precursor is supplied to a zone of 0 ° C., gas-phase reacted with ammonia at 300 to 600 ° C., and the obtained aluminum nitride precursor is fired at 1100 to 1900 ° C. in an inert gas. . 2. The method for producing aluminum nitride according to claim 1, wherein the organic aluminum is trialkylaluminum.