JPH06191955A - Production of aluminum mitride sintered compact - Google Patents

Abstract

PURPOSE:To obtain an AlN sintered compact excellent in thermal conductivity and mechanical strength at low cost in a practical way. CONSTITUTION:AlN powder >=12.0m<2>/g in specific surface area is added with an oxygen-contg. and nonfluorine base rare earth metal compound as sintering auxiliary followed by molding, and the resultant form is then sintered in a nonoxidative atmosphere at <=1650 deg.C, thus obtaining the objective AlN sintered compact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an aluminum nitride sintered body.

[0002]

2. Description of the Related Art With the progress of higher integration and higher power consumption of semiconductor elements represented by ICs and the like, along with this, there has been a demand for an electrically insulating material having a good heat dissipation property. Among them, in particular, an insulating substrate made of an aluminum nitride sintered body is excellent in terms of thermal conductivity, thermal expansion property, electrical insulating property, etc., and therefore, it has been noticed and put into practical use.

However, the aluminum nitride sintered body is very expensive because the raw material aluminum nitride powder is expensive and it is difficult to sinter and requires high temperature firing at 1750 ° C. or higher. For this reason, a method of manufacturing an aluminum nitride sintered body has been proposed in which the firing temperature is lowered to reduce the cost. Aluminum nitride powder,
As a sintering aid, it has been proposed to use a fluoride or oxide of a rare earth element and a fluoride or oxide of an alkaline earth element in combination (JP-A 61-209959, USP 4,746, 63
(Specification No. 7). Here, it is said that a dense aluminum nitride sintered body having a high thermal conductivity can be obtained by firing at a low temperature of 1550 to 1700 ° C. However, the above method has the following problems.

When a fluoride is used as a sintering aid, elemental fluorine produced by decomposition of the sintering aid during firing easily becomes a corrosive or toxic gas such as HF, which may adversely affect the health of workers. It is not practical because problems such as damage to the firing furnace occur. When a rare earth compound and an alkaline earth compound are used together as a sintering aid, the liquidus formation temperature is lower than that when the rare earth compound is used alone, which enables sintering at a low temperature. However, since grain growth due to liquid phase formation becomes remarkable at the same time, it is advantageous for increasing the thermal conductivity but disadvantageous in terms of mechanical strength. Further, in the case of alkaline earth, diffusion is likely to occur during firing, uneven distribution is likely to occur in the sintered body, burning unevenness of the aluminum nitride sintered body, and a sintering furnace or a jig setter. Problems such as deterioration due to adhesion reaction occur. In addition, since the liquid phase forms a thick grain boundary layer and surrounds the grains, the fracture mode is grain boundary fracture. In general, the mechanical strength is lower than that of the rare earth compound alone. Rare earth compounds are Y ₂
Taking O ₃ alone as an example, Al ₂ O ₃ at 1760 ° C.
A liquid phase is formed between and, and this liquid wets the grains of aluminum nitride, but without forming a grain boundary layer, it is easy to gather at the triple points of the grain boundaries and the grain boundary layer is very thin. As a result, the fracture mode is likely to be intragranular fracture rather than intergranular fracture. Intragranular fracture generally has higher mechanical strength than intergranular fracture.

[0005]

In view of the above circumstances, the present invention aims to provide a practical method capable of inexpensively obtaining an aluminum nitride sintered body excellent in thermal conductivity and mechanical strength. And

[0006]

In order to solve the above-mentioned problems, a method for producing an aluminum nitride sintered body according to the present invention is a method of forming a molded body obtained by adding a sintering aid to aluminum nitride powder and molding the same. When sintering by firing in an oxidizing atmosphere, a molded body formed by adding a sintering aid to aluminum nitride powder and molding the sintered body is sintered by firing in a non-oxidizing atmosphere. In the production method, the aluminum nitride powder has a specific surface area of 12.0 m ² / g or more, the sintering aid is a non-fluorinated rare earth compound containing oxygen, and Is fired at a temperature of 1650 ° C. or lower.

In the present invention, the form in which the reduction treatment is performed before or after the firing or during the firing is, as described in detail below, the obtained aluminum nitride sintered body (hereinafter,
It is effective in increasing the thermal conductivity of the "AlN sintered body" and can be said to be a useful form. In the present invention, the reason for using the aluminum nitride powder having a specific surface area of 12.0 m ² / g or more and having a fine particle diameter (hereinafter, referred to as “AlN powder”) is that a non-fluorinated rare earth compound containing oxygen (rare earth) is used. (Oxygenated compounds of group elements), that is, rare earth oxides, non-fluorinated compounds that become rare earth oxides when fired, are used at a temperature of 1650 ° C or lower. This is because it becomes possible to sinter by low temperature firing.

As described above, when a rare earth element fluoride or oxide and an alkaline earth element fluoride or oxide are used in combination, AlN powder having a specific surface area of less than 12.0 m ² / g can be sintered. However, there are problems such as a decrease in mechanical strength due to grain growth, uneven burning of the AlN sintered body, deterioration of a firing furnace and a setter, and the like. According to the present invention, it is possible to eliminate the above-mentioned inconvenience of the combined use that the sintering can be performed by low temperature firing without using the combined form.

A typical rare earth element oxygen-containing compound
Y₂O₃Take, for example, Y₂O₃And AlN powder surface A
l₂O₃To form a eutectic melt at 1760 ° C or higher
Therefore, in order to perform liquid phase sintering, firing at a temperature higher than this is required.
Will be required. According to the study by the inventors, the specific surface
Product is 3.0m²/ G using a coarse AlN powder ₂
O₃If you try to sinter it alone, the above liquid phase sintering will not work.
It is indispensable, and high temperature firing at 1760 ° C or higher is essential.
Therefore, the inventors continued to study, and the specific surface area was 12.0.
m²If it is fine AlN powder of / g or more, it is not liquid phase sintering but solid.
It seems that phase sintering is possible and the firing temperature can be reduced.
I found it. Specific surface area is 12.0m²/ G not
Full AlN powder requires firing temperature over 1700 ° C
The specific surface area is 12.0m²/ G or more of AlN
If it is a powder, it is possible to use only sintering aids of non-fluorinated rare earth compounds
We found that sintering is possible at a firing temperature of 50 ° C or less
I did.

If sintering can be performed by firing at 1650 ° C. or lower, there is an advantage reflected in reduction of firing cost. Specifically, it is possible to significantly extend the life of an expensive BN container used as a firing container, and it is also possible to use an inexpensive alumina-based container instead of the expensive BN container. Can be mentioned. An inexpensive alumina-based container cannot be used in the past because it is significantly deformed by high temperature creep when fired above 1650 ° C. Further, the running cost of the firing furnace can be reduced by saving power consumption.

Next, the thermal conductivity and mechanical strength of the AlN sintered body obtained by the present invention will be described. As we saw above,
In the case of the present invention, fine non-alloyed AlN powder having a specific surface area of 12.0 m ² / g or more is used, and sintering is performed at a firing temperature of 1650 ° C. or less only with a sintering aid of a non-fluorinated rare earth compound. The sintering mechanism is considered to be solid phase sintering, not liquid phase sintering. Therefore, the grain size of the AlN sintered body is smaller than that when an alkaline earth compound that forms a liquid phase is used as a sintering aid even at 1650 ° C. or lower, and as a result, the mechanical strength is increased. However, AlN
The thermal conductivity usually tends to decrease as the grain size of the sintered body decreases. This is because the heat conduction mechanism in the AlN sintered body is phonon conduction, and this phonon conduction easily causes scattering in the grain boundary portion, and in the case of the AlN sintered body having a small grain size, there are many grain boundary portions.
This is because this phonon scattering is large and heat conduction is hindered.

Further, the impurity oxygen in the AlN powder, which causes a decrease in thermal conductivity, generally increases as the specific surface area of the AlN powder increases (the particle size becomes finer). This is because the impurity oxygen exists in the surface layer of the AlN powder. Therefore, in the present invention in which the fine AlN powder having a specific surface area of 12.0 m ² / g or more is used, the amount of impurity oxygen inevitably increases as compared with the case of using the AlN powder having a large particle size.

As described above, the AlN sintered body obtained by the present invention is disadvantageous in terms of thermal conductivity because of its small grain size and the large amount of impurity oxygen in the starting AlN powder.
However, in the present invention, the thermal conductivity can be improved if the reduction treatment is performed before or after the firing or during the firing. This reduction treatment reduces the amount of impurity oxygen in the AlN powder, and the heat conductivity increases accordingly. However, since this reduction treatment hardly changes the grain size in the sintered body, it seems that the reduction in thermal conductivity due to the grain size cannot be eliminated at all. Oxygen in the surface layer of the AlN powder is partially taken into the aluminum grains, which improves the thermal conductivity of the grains themselves, so that a certain degree of elimination of the decrease in thermal conductivity due to the grain size can be expected. . As described above, when the reduction treatment is also performed, the grain size is small, but the high thermal conductivity can be achieved by the high purification.

The above points can be summarized as follows. In the present invention, a raw material is used for sintering at low temperature of 1650 ° C. or lower, which does not use an alkaline earth compound or a fluorine-based sintering additive that causes various problems and enables economical firing cost. As the powder, AlN powder having a particle size of 12 m ² / g or more and an oxygen-containing compound of a rare earth element are used. As a result, the grain size in the sintered body becomes smaller than that in the case where the alkaline earth compound is used, so that the mechanical strength can be improved. Further, the thermal conductivity can be improved by reducing the impurity oxygen of the AlN powder by adopting the reduction treatment.

The rare earth elements in the fluorine-free rare earth compound (oxygen-containing compound of rare earth elements) used as a sintering aid include Y, La, Dy, Er, Ce, Sm, Pm,
NdEu, Gd, Tb, Pr, Tm, Lu, Ho, Yb
And oxides such as carbonates, nitric oxides, hydroxides, and oxalates as compounds that become rare earth oxides upon firing. When using sintering aids, multiple rare earth oxides may be used in combination, multiple compounds that become rare earth oxides by firing may be used in combination, and rare earth oxides and compounds that become rare earth oxides by firing may be used. You may make it use together with. Regarding the addition amount of the sintering aid, if the total amount of the obtained AlN sintered body is 100% by weight, the sintering aid will occupy 0.1 to 10% by weight.

Firing is from about 1400 to 1650 ° C
The firing range is 1 to 6 hours.
Not limited to the case. The reduction treatment is performed before or after firing or after sintering.
It can be done during firing, but before sintering has not progressed
However, oxygen is easily removed. For example, sintering at 1650 ° C
In the case of
You may make it sinter in a neutral atmosphere, or
A reducing atmosphere is used, and the sintering process and the reducing process are performed simultaneously in parallel.
However, it may be performed for the same period. Can be used for reduction processing
The reducing atmosphere is H ₂, CO, NH₃, CH_Four, C
₂H_Four, C₂H₆, C₃H₈A reducing gas atmosphere such as
To reduce these reducing gases to N_2,Neutral gas such as Ar
Achieve an effective processing atmosphere by combining with the atmosphere
can do. In addition, the firing furnace is a carbon heater
If it is a carbon furnace using carbon furnace material, vapor phase
It is easy to form a reducing atmosphere with carbon.

[0017]

In the case of the present invention, a non-fluorine-based AlN powder having a specific surface area of less than 12.0 m ² / g is used without using an alkaline earth compound or a fluorine-based sintering aid which causes various problems. Sintering is performed by firing at a low temperature of 1650 ° C. or less using only a sintering aid of a rare earth compound.

Since it is not necessary to use an alkaline earth compound or a fluorine-based compound as a sintering aid, uneven burning of the AlN sintered body, warpage, deterioration due to diffusion into a furnace or a setter are prevented, and 1650 ° C. Since the firing is performed at a low temperature as described below, it is possible to prolong the life of the firing container and to reduce the cost of the material, as well as to reduce the running cost such as saving the power consumption.

Further, since the grain size in the obtained AlN sintered body becomes small, the mechanical strength is improved. In addition, since the firing is performed at a low temperature of 1650 ° C. or less, it is possible to extend the life of the sintering container, reduce the cost, and reduce the running cost such as power consumption.

When a reduction treatment is carried out before or after the firing or during the firing, A having a high thermal conductivity is removed by removing impurity oxygen.
The 1N sintered body can be obtained.

[0021]

Embodiments of the present invention will be described below. This invention is not limited to the following embodiments. - the AlN powder of Example 1 a specific surface area of 12.0m ² / g, and as a sintering aid, were added Y ₂ O ₃ 3.0 wt%, a wet ball mill mixing, after drying sizing, uniaxial 20m diameter by press
m to 1.5 mm after being molded into a disk with a height of 10 mm
CIP was performed at a pressure of n / cm ² to obtain a disk-shaped molded body.

Subsequently, the molded body was placed in a crucible made of BN, covered with a loose lid made of BN, stored in a carbon furnace, and a N ₂ gas containing 4% H ₂ was flowed while flowing 120.
After the temperature was raised to 0 ° C., the gas was switched to 100% N ₂ gas, the temperature was raised to 1650 ° C., and the temperature was maintained for 3 hours to obtain an AlN sintered body. - by way of example 2-sintering agent, changing the Y ₂ O ₃ in Y (NO _{3) 3,}
An AlN sintered body was obtained in the same manner as in Example 1 except that the sintering temperature was set to 1600 ° C.

-Example 3-A AlN powder having a specific surface area of 15.0 m ² / g was added with 3.0% by weight of Y ₂ O ₃ as a sintering aid, and circled in the same manner as in Example 1. After obtaining a plate-shaped molded body, the molded body was placed in an alumina setter, covered with an alumina plate, and housed in a carbon furnace, while flowing N ₂ gas containing 4% H ₂ at 1600. The temperature is raised to ℃ and kept for 3 hours.
An N sintered body was obtained. N ₂ gas containing 4% H ₂ was used in all steps.

[0024] - to the Example 4 sintering aid, except for changing the Y ₂ O ₃ to La ₂ O _3, thereby obtaining the AlN sintered body in the same manner as in Example 3. -Example 5-In place of the alumina setter and the alumina plate, the crucible made of BN and the lid made of BN of Example 1 were used, and 100% in all steps
An AlN sintered body was obtained in the same manner as in Example 3 except that N ₂ gas was used.

-Comparative Example 1-AlN powder having a specific surface area of 10.0 m ² / g was added with 3.0% by weight of Y ₂ O ₃ as a sintering aid, and circled in the same manner as in Example 1. After obtaining a plate-shaped molded body,
Put it in an N crucible, cover it with a loose BN lid, store it in a carbon furnace, and let 100% N ₂ gas flow,
The temperature was raised to 1650 ° C. and maintained for 3 hours to obtain an AlN sintered body.

-Comparative Example 2-3.0% by weight of Y ₂ O ₃ and Ca as a sintering aid.
An AlN sintered body was obtained in the same manner as in Comparative Example 1 except that 0.5% by weight of O was added. -Comparative Example 3-AlN powder having a specific surface area of 3.0 m ² / g as AlN powder
An AlN sintered body was obtained in the same manner as in Comparative Example 2 except that the powder was used.

Tables 1 and 2 show the main firing conditions in Examples and Comparative Examples, and the density, grain size, thermal conductivity and bending strength measured for each AlN sintered body obtained in Examples and Comparative Examples. Note in 2.

[0028]

[Table 1]

[0029]

[Table 2]

As shown in Table 2, the AlN sintered bodies of Examples were sufficiently densified without using an alkaline earth-based or fluorine-based sintering aid, and had high thermal conductivity. Although it also has bending strength, the AlN sintered body of the comparative example did not have these characteristics.

[0031]

In the method for manufacturing an AlN sintered body according to the present invention, since the firing is performed at a low temperature of 1650 ° C. or lower, the life of the firing jig container can be extended and the low-priced material container can be used and consumed. Running costs can be reduced by saving electricity, and since alkaline earth-based and fluorine-based sintering aids are not used, uneven burning, warpage, and deterioration due to diffusion into the furnace or setter can be prevented. Not only that, the grain size becomes smaller, an AlN sintered body having excellent mechanical strength can be obtained at low cost, and in addition, when the reduction treatment is performed, the thermal conductivity of the AlN sintered body can be improved, Therefore, the present invention is practical and very useful.

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[Procedure amendment]

[Submission date] February 24, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Method for producing aluminum nitride sintered body

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an aluminum nitride sintered body.

[0002]

2. Description of the Related Art With the progress of higher integration and higher power consumption of semiconductor elements represented by ICs and the like, along with this, there has been a demand for an electrically insulating material having a good heat dissipation property. Among them, especially the insulating substrate made of aluminum nitride sintered body,
Since it is excellent in terms of thermal conductivity, thermal expansion, electrical insulation, etc., it has attracted attention and is being put into practical use.

However, the aluminum nitride sintered body is very expensive because the raw material aluminum nitride powder is expensive and it is difficult to sinter and requires high temperature firing at 1750 ° C. or higher. For this reason, a method of manufacturing an aluminum nitride fired body is proposed in which the firing temperature is lowered to reduce the cost. It has been proposed to use a fluoride or oxide of a rare earth element and an oxide of a fluoride of an alkaline earth element in combination with aluminum nitride powder as a sintering aid (Japanese Patent Laid-Open No. 61-209959). , USP
4,746,637). Here, 1550 to 170
0 dense and high thermal conductivity aluminum nitride sintered body at a constant temperature firing that ℃ is to be obtained. Nevertheless, if the above methods have the following problems.

When a fluoride is used as a sintering aid, elemental fluorine produced by decomposition of the sintering aid during firing easily becomes a corrosive / poisonous gas such as HF, which adversely affects the health of workers. It is not practical because problems such as damage to the firing furnace occur. When a rare earth compound and an alkaline earth compound are used together as a sintering aid, the liquidus formation temperature is lower than that when the rare earth compound is used alone, which enables sintering at a low temperature. However, since grain growth due to liquid phase formation becomes remarkable at the same time, it is advantageous for achieving high thermal conductivity but disadvantageous in terms of mechanical strength. Further, in the case of alkaline earth, diffusion is likely to occur during firing, uneven distribution is likely to occur in the sintered body, uneven burning of the aluminum nitride sintered body, sintering furnace or a setter which is a jig. Problems such as deterioration due to adhesion reaction occur. In addition, since the liquid phase forms a thick grain boundary layer and surrounds the grains, the fracture mode is grain boundary fracture. In general, the mechanical strength is lower than that of the rare earth compound alone. Taking the case where the rare earth compound is Y ₂ O ₂ alone, a liquid phase is formed with Al ₂ O ₃ at 1760 ° C., and this liquid phase wets the aluminum nitride grains. Unlike the alkaline earth, it is easy to gather at the triple points of the grain boundaries without forming a thick grain boundary layer, and the grain boundary layer becomes very thin. As a result, the fracture mode is not the intergranular fracture but the intragranular fracture. Intragranular fracture generally has higher mechanical strength than intergranular fracture.

[0005]

In view of the above circumstances, the present invention provides a practical method capable of inexpensively obtaining an aluminum nitride sintered body excellent in thermal conductivity and mechanical strength. It is an issue.

[0006]

In order to solve the above-mentioned problems, a method for producing an aluminum nitride sintered body according to the present invention is a method of forming a molded body obtained by adding a sintering aid to aluminum nitride powder and molding the same. Upon sintering by firing in an oxidizing atmosphere, before Symbol specific surface area of the aluminum nitride powder is not more 12.0m 2 / ^g or more, the sintering aid, rare earth containing oxygen non fluorine system It is a compound, and the firing in the non-oxidizing atmosphere is performed at a temperature of 1650 ° C. or lower.

In the present invention, the form in which the reduction treatment is carried out before or after the firing or during the firing is, as described in detail below, the obtained aluminum nitride sintered body (hereinafter,
Is effective in increasing the thermal conductivity of the referred to as "AlN sintered body"), it can be said that the useful form. In the present invention, a specific surface area of 12.0m 2 / ^g or more micro-grain size of the aluminum nitride powder (hereinafter, referred to as "AlN powder") The reason for using the rare earth compound containing oxygen non fluorine system (rare oxygen-containing compounds s elements), i.e. rare earth compound, firing a rare earth compound comprising a compound only original low temperature sintering of 1650 ° C. or less to the use in rare earth range of compounds consisting of compounds of the non-fluorine-based This is because they can be sintered in.

As mentioned above, when a fluorine compound or oxide of a rare earth element and a fluoride or oxide of an alkaline earth element are used in combination, AlN having a specific surface area of less than 12.0 m ² / g.
Although powder can be sintered, problems such as a decrease in mechanical strength due to grain growth, uneven burning of an AlN sintered body, deterioration of a firing furnace and a setter, and the like occur. According to the present invention, it is possible to eliminate the above-mentioned inconvenience of the combined use that the sintering can be performed by low temperature firing without using the combined form.

Taking Y ₂ O ₂ which is a typical oxygen-containing compound of rare earth elements as an example, Y ₂ O ₃ and A on the surface of AlN powder are
The temperature at which the eutectic melt is formed with l ₂ O ₃ is 1760 ° C. or higher, and in order to perform liquid phase sintering, firing at a temperature higher than this is required. According to a study by the inventors, a coarse AlN powder having a specific surface area of about 3.0 m ² / g was used and Y ₂
When attempting to sinter O ₃ alone, the liquid phase sintering described above is indispensable, and high temperature firing at 1760 ° C. or higher is indispensable.
Therefore, the inventors continued to study and determine the particle size of AlN powder.
It was discovered that further refinement would allow solid-state sintering instead of liquid-phase sintering, thus reducing the firing temperature. AlN powder with a specific surface area of less than 12.0 m ² / g requires a firing temperature above 1700 ° C., but AlN powder with a specific surface area of 12.0 m ² / g or more is non-fluorescent.
It was found that at 1650 ° C. below the firing temperature only sintering aid containing system rare earth compound capable sintering.

If sintering can be performed by firing at 1650 ° C. or lower, there is an advantage reflected in reduction of firing cost. Specifically, it can be mentioned that the life of an expensive BN container used as a firing container is significantly extended, and further, an inexpensive aluminum container can be used instead of the expensive BN container. Can be mentioned. 1 inexpensive alumina container
If the firing temperature exceeds 650 ° C, the deformation due to high temperature creep becomes remarkable, and thus it cannot be used conventionally. Further, the running cost of the firing furnace can be reduced by saving power consumption.

Next, the thermal conductivity and mechanical strength of the AlN sintered body obtained by the present invention will be described. As noted above, in this invention, a specific surface area using the above fine A l N powder 12.0m 2 / ^g, sintering of 1650 ° C. or less only sintering aid non fluorine-based rare-earth compound Since the sintering is performed at a temperature, it is considered that the sintering mechanism is solid phase sintering, not liquid phase sintering. Therefore, the grain size of the AlN sintered body is smaller than that when an alkaline earth compound that forms a liquid phase is used as a sintering aid even at 1650 ° C. or less, and as a result, the mechanical strength is increased. However, Al
The thermal conductivity usually tends to decrease as the grain size of the N sintered body decreases. This is because the heat conduction mechanism in the AlN sintered body is phonon conduction, and this phonon conduction easily causes scattering in the grain boundary portion, and in the case of the AlN sintered body having a small grain size, there are many grain boundary portions. This is because this phonon scattering is large and heat conduction is hindered.

Impurity oxygen in the AlN powder, which causes a decrease in thermal conductivity, generally increases as the specific surface area of the AlN powder increases (particle size decreases). This is because the impurity oxygen is likely to exist in the surface layer of the AlN powder. Therefore, in the present invention in which a fine AlN powder having a specific surface area of 12.0 m ² / g or more is used, the amount of impurity oxygen inevitably increases as compared with the case of using AN powder having a large particle size.

As described above, the AlN sintered body obtained according to the present invention has a small grain size and a large amount of impurity oxygen in the starting AlN powder, which is disadvantageous in terms of thermal conductivity. However, in the present invention, the thermal conductivity can be improved if the reduction treatment is performed before or after the firing or during the firing. This reduction treatment reduces the amount of impurity oxygen in the AlN powder, and the heat conductivity increases accordingly. Sanawa
Even if the impurity oxygen is reduced, the gray color of the sintered body is basically
Since there is not much change in quality, Glenn
Eliminating the decrease in thermal conductivity due to size, that is, high thermal conductivity
On the other hand, but inside the AlN grain during sintering
Part of the oxygen in the surface layer of AlN particles is taken in by
The decrease in the thermal conductivity of AlN grain itself due to
It is alleviated by the reduction of the amount of oxygen by the original treatment. That
Therefore, although the grain size is small, due to high purification
High thermal conductivity can be achieved and effectively depends on the grain size.
This leads to the elimination of the decrease in thermal conductivity.

[0014] will be as follows: melt summarized briefly the above-mentioned point. In the present invention, a raw material is used for sintering at low temperature of 1650 ° C. or lower, which does not use an alkaline earth compound or a fluorine-based sintering additive that causes various problems and enables economical firing cost. As the powder, AlN powder of 12 m ² / g or more and an oxygen-containing compound of a rare earth element are used. As a result, the grain size in the sintered body becomes smaller than that in the case where the alkaline earth compound is used, so that the mechanical strength can be improved. Further, the thermal conductivity can be improved by reducing the impurity oxygen of the AlN powder by adopting the reduction treatment.

The rare earth elements in the fluorine-free rare earth compounds (oxygen-containing compounds of rare earth elements) used as sintering aids are Y, La, Dy, Er, Ce, Sm, Pm, N.
d, Eu, Gd, Tb, Pr, Tm, Lu, Ho, Yd
And oxides such as carbonates, nitric oxides, hydroxides, and oxalates as compounds that become rare earth oxides upon firing. When using sintering aids, multiple rare earth oxides may be used in combination, multiple compounds that become rare earth oxides by firing may be used in combination, and rare earth oxides and compounds that become rare earth oxides by firing may be used. You may make it use together. Regarding the addition amount of the sintering aid, if the total amount of the obtained AlN sintered body is 100% by weight, the sintering aid will occupy 0.1 to 10% by weight.

The firing is performed in the temperature range of about 1400 ° C. to 1650 ° C. for about 1 to 6 hours, but the firing conditions are not limited to this. The reduction treatment may be performed before or after firing or during firing for sintering, but oxygen is easily removed before the sintering has progressed. For example, when sintering is performed at 1650 ° C., the reducing atmosphere may be performed up to 1200 ° C., and then the sintering may be performed in a neutral atmosphere. You may make it parallel and only perform the substantially same period. The reducing atmosphere that can be used for the reducing treatment includes H ₂ , CO, NH ₃ , CH ₄ ,
A reducing gas atmosphere such as C ₂ H ₄ , C ₂ H ₆ , C ₃ H ₈ or the like is mentioned. By combining these reducing gases with a neutral gas atmosphere such as N ₂ or Ar, an effective processing atmosphere can be obtained. Can be realized. Further, when the firing furnace is a carbon furnace using a carbon heater or carbon furnace material, it is easy to form a reducing atmosphere by vapor phase carbon.

[0017]

In the case of the present invention, a non-fluorine-based AlN powder having a specific surface area of 12.0 m ² / g or more is used without using an alkaline earth compound which causes various problems and a fluorine-based sintering aid. Sintering is performed by firing at a low temperature of 1650 ° C. or less using only a sintering aid of a rare earth compound.

Since it is not necessary to use an alkaline earth compound or a fluorine-based compound as a sintering aid, uneven burning of the AlN sintered body, warpage, deterioration due to diffusion into a furnace or a setter are prevented, and 1650 ° C. Since the firing is performed at a low temperature as described below, it is possible to prolong the life of the firing container and to reduce the cost of the material, as well as to reduce the running cost such as saving the power consumption.

Further, since the grain size in the obtained AlN sintered body becomes small, the mechanical strength is improved .

When a reduction treatment is carried out before or after the firing or during the firing, A having a high thermal conductivity is removed by removing impurity oxygen.
The 1N sintered body can be obtained.

[0021]

Embodiments of the present invention will be described below. This invention is not limited to the following embodiments. - the AlN powder of Example 1 a specific surface area of 12.0m ² / g, as a sintering aid <br/>, added _Y 2 _{O 3} 3.0 wt%, when wet ball mill, dried sized After that, the diameter is 20m by uniaxial press
m, height 5 mm, molded into a disk, then 1.5 ton
CIP was performed at a pressure of / cm ² to obtain a disk-shaped molded body.

Subsequently, the molded body was placed in a crucible made of BN, covered with a loose lid made of BN, housed in a carbon furnace, and a N ₂ gas containing 4% H ₂ was flowed while flowing 120.
After the temperature was raised to 0 ° C., the gas was switched to 100% N ₂ gas, the temperature was raised to 1650 ° C., and the temperature was maintained for 3 hours to obtain an AlN sintered body. - As Example 2 sintering aids, triple the Y _{(NO 3) 3} in terms _{of Y} 2 _{O 3}
Example 1 except that the sintering amount was 1600 ° C.
An AlN sintered body was obtained in the same manner as in.

[0023] - the AlN powder of Example 3 a specific surface area of 15.0 m ² / g, as a sintering aid <br/>, added _Y 2 _{O 3} 3.0 wt%, as in Example 1 Similarly, after obtaining a disk-shaped molded body, the molded body was placed in an aluminum setter, covered with an alumina plate, and housed in a carbon furnace to contain N ₂ gas containing 4% H _2. While flowing, the temperature was raised to 1600 ° C. and held for 3 hours to obtain an AlN sintered body. N ₂ gas containing 4% H ₂ was used in all steps.

[0024] - as an example of 4-sintering agent, except for changing the _Y 2 _{O 3} to _La 2 _{O 3} is
An AlN sintered body was obtained in the same manner as in Example 3. -Example 5-B of Example 1 was used instead of the aluminum setter and the alumina plate.
Using N crucible and BN lid, 100% N in all steps
A was the same as in Example 3 except that ₂ gases were used.
An IN sintered body was obtained.

[0025] - the AlN powder of Comparative Example 1 a specific surface area of 10.0 m ² / g, as a sintering aid <br/>, added _Y 2 _{O 3} 3.0 wt%, as in Example 1 Similarly, after obtaining a disk-shaped molded body, this molded body was BN
Put it in a crucible made of steel, cover it with a loose BN lid, store it in a carbon furnace, and while flowing 100% N ₂ gas,
The temperature was raised to 650 ° C. and maintained for 3 hours to obtain an AlN sintered body.

[0026] - as a comparative example 2 sintering aids, a _Y 2 _{O 3} 3.0 wt% and CaO
Was added in the same manner as in Comparative Example 1 except that 0.5% by weight of A was added.
An IN sintered body was obtained. -Comparative Example 3-AlN powder having a specific surface area of 3.0 m ² / g
An AlN sintered body was obtained in the same manner as in Comparative Example 2 except that the powder was used.

Table 1 shows the main sintering conditions in Examples and Comparative Examples, and the density, grain size, thermal conductivity and bending strength measured for each AlN sintered body obtained in Examples and Comparative Examples. The results are shown in Table 2.

[0028]

[Table 1]

[0029]

[Table 2]

As shown in Table 2, the AlN sintered bodies of Examples were sufficiently densified without using an alkaline earth-based or fluorine-based sintering aid, and had a high thermal conductivity. Although it also has bending strength, the AlN sintered body of the comparative example did not have these characteristics.

[0031]

In the method for manufacturing an AlN sintered body according to the present invention, since the firing is performed at a low temperature of 1650 ° C. or less, it is possible to extend the life of the firing jig container and use a low-priced material container, and to consume less power. It is possible to reduce running costs by saving energy, and since it does not require the use of alkaline earth or fluorine-based sintering aids, uneven burning, warping, and deterioration due to diffusion into the furnace or setter can be prevented. In addition, the grain size is reduced, and an AlN sintered body having excellent mechanical strength can be obtained at a low cost.
It is also possible to improve the thermal conductivity of the 1N sintered body, and therefore, the present invention is practical and very useful.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasushi Tanaka 1048 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works Co., Ltd.

Claims (2)

[Claims] 1. A method for producing an aluminum nitride sintered body, which comprises sintering a molded body formed by adding a sintering aid to aluminum nitride powder and firing the sintered body in a non-oxidizing atmosphere. Has a specific surface area of 1
2.0 m ² / g or more, the sintering aid is a non-fluorinated rare earth compound containing oxygen, and the firing in the non-oxidizing atmosphere is performed at a temperature of 1650 ° C. or less. A method for producing a characteristic aluminum nitride sintered body. 2. The method for producing an aluminum nitride sintered body according to claim 1, wherein a reduction treatment is also performed before or after firing or during firing.