JPH06329474A - Sintered aluminum nitride and its production - Google Patents

Abstract

PURPOSE:To improve the thermal conductivity, strength and heat-dissipation property of a sintered aluminum nitride by mixing a specific AlN raw material powder with an element oxide and an Si component, forming the mixture and sintering in a non-oxidizing atmosphere. CONSTITUTION:A mixed powder is produced by mixing AIN powder having an impurity cation (Fe, Mg, etc.) content of <=0.2wt.% and an average particle diameter of 0.05-2mum with 1-10wt.% of an oxide of at least one kind of element selected from the group IIIa element of the periodic table, Ca, Sr and Ba, 0.01-0.2wt.% of an Si component such as SiO2 and Si3N4 and 5-10wt.% of an organic binder. The mixed powder is formed, heated at 400-800 deg.C in a non- oxidizing atmosphere to eliminate the organic binder and sintered at 1650-1900 deg.C for 2-10hr in a non-oxidizing atmosphere to obtain a sintered AlN material having an average crystal grain diameter of 1-4mum, a thermal conductivity of >=150w/m.k and a three-point bending strength of >=50kg/mm<2>.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum nitride sintered body used for a semiconductor substrate or the like and a method for manufacturing the same, and in particular, it significantly improves strength without impairing the thermal conductivity peculiar to aluminum nitride. The present invention relates to an aluminum nitride sintered body excellent in heat dissipation and a manufacturing method.

[0002]

2. Description of the Related Art Sintered ceramics, which are superior in properties such as strength, heat resistance, corrosion resistance, wear resistance, and lightness, compared with conventional metal materials, are used in semiconductor substrates, electronic equipment materials, engine members, It is widely used as a material for high speed cutting tools, nozzles, bearings, and other mechanical parts, functional parts, structural materials and ornamental materials used under severe temperature, stress and wear conditions that conventional metal materials do not have.

In particular, an aluminum nitride (AlN) sintered body is an insulator having a high thermal conductivity and has a coefficient of thermal expansion close to that of silicon (Si). Therefore, the aluminum nitride (AlN) sintered body is used as a heat sink or a substrate of a highly integrated semiconductor device. Expanding applications.

Conventionally, the above-mentioned aluminum nitride sintered body is generally mass-produced by the following manufacturing method. That is,
A sintering aid to the aluminum nitride raw material powder, an organic binder, and various additives and solvents as required, to prepare a raw material mixture by adding a dispersant, the resulting raw material mixture doctor blade method or A thin plate-shaped or sheet-shaped molded body is formed by the slurry casting method, or a raw material mixture is press-molded to form a thick plate-shaped or large-sized molded body. Next, the obtained molded product is heated and degreased in an atmosphere of air or nitrogen gas to remove and degrease the hydrocarbon components and the like used as the organic binder from the molded product. The degreased compact is heated to a high temperature in a nitrogen gas atmosphere or the like and densified and sintered to form an aluminum nitride sintered compact.

In the above manufacturing method, when an ultrafine raw material powder having an average particle diameter of about 0.5 μm or less is used as the raw material AlN powder, a considerably dense sintered body can be obtained by using the AlN powder alone. However, a large amount of impurities such as oxygen adhering to the surface of the raw material powder and the like are solid-solved in the AlN crystal lattice at the time of sintering, or Al-O- which hinders the propagation of lattice vibration.
As a result of producing a compound oxide such as an N compound, the thermal conductivity of the AlN sintered body that did not use a sintering aid was relatively low.

On the other hand, when AlN powder having an average particle size of 1 μm or more is used as the raw material powder, the sinterability of the raw material powder alone is not good. Was difficult to obtain, and there was a drawback that mass productivity was low. Therefore, in order to efficiently manufacture a sintered body by the atmospheric pressure sintering method, in order to prevent the densification of the sintered body and the impurity oxygen in the AlN raw material powder from forming a solid solution in the AlN crystal grains. In addition, as a sintering aid,
It is generally practiced to add rare earth oxides such as yttrium oxide (Y ₂ O ₃ ) and alkaline earth metal oxides such as calcium oxide.

These sintering aids react with the impurity oxygen and Al ₂ O ₃ contained in the AlN raw material powder to form a liquid phase to achieve the densification of the sintered body, and at the same time, to form the impurity oxygen into particles. It is believed that it can be fixed as a phase phase and achieve high thermal conductivity.

[0008]

However, in the above-mentioned conventional production method, since the wettability between AlN and the liquid phase compound is originally low and the liquid phase itself tends to segregate, the liquid after the sintering is dissolved. When the phase solidifies, the liquid phase is AlN
It tends to remain so as to be unevenly distributed in the interstices of the grains and to solidify to form a coarse and brittle grain boundary phase. Further, the grain growth of crystal grains is likely to proceed, and as shown in FIG. 2, the average grain size is 5 to 1
Coarse crystal grains with a size of 0 μm are easily formed, and minute pores do not disappear but remain in the crystal grains, hindering the densification of the sintered body, and finally the three-point bending strength is 35-40 kg / mm. There is a problem that only a low-strength aluminum nitride sintered body of about ² can be obtained.

In recent years, the above-mentioned aluminum nitride material having high thermal conductivity (high heat dissipation) is becoming widespread in order to cope with the heat generation amount which is increased with the high integration and high output of semiconductor elements. As for sex, generally satisfactory results have been obtained. However, as described above, the strength as a structural member is insufficient. Therefore, for example, a slight bending stress that acts when mounting a semiconductor substrate formed of an aluminum nitride sintered body on a mounting board or an impact force that acts during handling There is a problem that the semiconductor substrate is damaged and the manufacturing yield of the semiconductor circuit substrate is significantly reduced.

The present invention has been made in order to solve the above problems, and suppresses grain growth of an AlN sintered body and refines the structure of the sintered body to improve the strength and make the sintered body uniform. To improve the mechanical strength without sacrificing heat dissipation characteristics
An object is to provide an IN sintered body and a method for manufacturing the same.

[0011]

In order to achieve the above-mentioned object, the inventors of the present invention have variously changed the types and amounts of the sintering aids and additives to be added to the raw material aluminum nitride powder, and Experimental studies were conducted on the effects on the crystal structure, strength characteristics and heat transfer characteristics.

As a result, when a small amount of Si component as an additive is added in addition to a predetermined sintering aid, a sintered body structure having a fine crystal grain size of 1 to 4 μm is obtained, An AlN sintered body having excellent strength characteristics was obtained. The present invention has been completed based on the above findings.

That is, the aluminum nitride sintered body according to the present invention contains 1 to 10% by weight of an oxide of at least one element selected from the group IIIa elements of the periodic table, Ca, Sr and Ba, and Si Component concentration is 0.01-0.2
It is characterized in that it is wt%. The Si component is Si
It may be contained as at least one silicon compound selected from O ₂ , Si ₃ N ₄ , SiC and Si ₂ N ₂ O. Furthermore, Ti, Zr, Hf, Nb, Ta, Mo,
At least one metal element selected from W may be contained in an amount of 0.1 to 0.5% by weight in terms of oxide. Also F
The content of impurity cations such as e and Mo is preferably 0.2% by weight or less. Furthermore, the average crystal grain size of the sintered body is 1 to 4
It is characterized by being μm. The AlN sintered body having the above composition has a thermal conductivity of 150 W / m · K or more and a three-point bending strength of 50 kg / mm ² or more.

In the method for producing an aluminum nitride sintered body according to the present invention, an aluminum nitride raw material powder containing 0.2% by weight or less of impurity cations such as Fe and Mg is added to a group IIIa element of the periodic table. , 1 to 10% by weight of an oxide of at least one element selected from Ca, Sr and Ba,
A mixed powder added with 0.01 to 0.2 wt% of Si component is molded, and the obtained molded body is subjected to 165 in a non-oxidizing atmosphere.
It is characterized in that it is sintered in a temperature range of 0 to 1900 ° C.

The aluminum nitride raw material (AlN) powder used in the method of the present invention, which is the main component of the sintered body, has an impurity oxygen content of 1.3% by weight or less in consideration of sinterability and thermal conductivity. The average particle size is 0.05 to
A fine AlN powder having a size of about 2 μm, preferably 1 μm or less is used.

The oxide of group IIIa element of the periodic table, Ca, Sr, and Ba acts as a sintering aid, and in order to densify the AlN sintered body, 1 to 10% by weight based on the AlN raw material powder.
It is added in the range of. Specific examples of the above-mentioned sintering aid include oxides of rare earth elements (Y, Sc, Ce, Dy, etc.), nitrides, oxides of alkaline earth metals (Ca), or compounds obtained by a sintering operation. Materials are used, especially yttrium oxide (Y ₂ O ₃ ), cerium oxide (Ce
O) and calcium oxide (CaO) are preferred. When the amount of the sintering aid added is less than 1% by weight, the effect of improving the sinterability is not sufficiently exerted, the sintered body is not densified and a low-strength sintered body is formed, or AlN Oxygen dissolved in the crystal,
A sintered body having a high thermal conductivity cannot be formed. On the other hand, if the addition amount exceeds 10% by weight, not only the effect as a sintering aid reaches a saturated state and becomes meaningless, but
On the contrary, the thermal conductivity of the AlN sintered body obtained by sintering is lowered, while a large amount of the grain boundary phase remains in the sintered body, and the volume of the grain boundary phase removed by heat treatment is large. Voids may remain in the tying body, increasing the shrinkage rate and making it more likely to cause deformation.

The Si component has the effect of improving the sinterability and lowering the sintering temperature, but grain growth of the sintered body can be suppressed by adding it in combination with the above-mentioned sintering aid. , Is added to form a fine AlN crystal structure and enhance the structural strength of the sintered body. Examples of the Si component include SiO ₂ , Si ₃ N ₄ , SiC and Si ₂ N.
It is desirable to use silicon compounds such as ₂ O. The content of this silicon compound is 0.01 to 0.
It is adjusted to the range of 2% by weight. The content of Si component is 0.
If it is less than 01% by weight, the effect of suppressing the grain growth becomes insufficient, and the crystal structure becomes coarse, so that a high-strength AlN sintered body cannot be obtained. On the other hand, the content is 0. ． If the amount exceeds 2% by weight, the thermal conductivity of the sintered body may decrease and the bending strength may decrease.

Ti, Zr, Hf, Nb, Ta, Mo, W
The oxide of is effective for improving the characteristics of the AlN sintered body such as forming an opaque sintered body by coloring while lowering the sintering temperature to improve the sinterability. It may be added in the range of 0.1 to 0.5% by weight. If the added amount is less than 0.1% by weight, the above characteristic improving effect is insufficient, while if the added amount is more than 0.5% by weight, the heat of the AlN sintered body is increased like other impurities. Reduces conductivity.

Impurity cations such as Fe and Mg are Al
Since it is easy to form a compound that inhibits the heat conduction of the N sintered body,
The content in the AlN sintered body is set to 0.2% by weight or less. The AlN raw material powder, various sintering aids and Si compound for Si component are put into a pulverizing mixer such as a ball mill and mixed for a predetermined time to form a raw material mixture. Next, the obtained raw material mixture is filled in a mold having a predetermined shape and pressure-molded to form a molded body. At this time, by adding 5 to 10% by weight of an organic binder such as paraffin and stearic acid to the raw material mixture in advance, the molding operation can be smoothly carried out.

As a molding method, a general-purpose die pressing method, a slurry casting method, a hydrostatic pressing method, or a sheet forming method such as a doctor blade method can be applied.

Subsequent to the above molding operation, the molded body is heated in a non-oxidizing atmosphere, for example, in a nitrogen gas atmosphere at a temperature of 400 to 400 ° C.
By heating to 800 ° C., the previously added organic binder is thoroughly degreased and removed.

Next, the plurality of sheet-shaped compacts that have been degreased are stacked in multiple stages in a firing furnace through a sieving powder made of, for example, ceramics sintered powder. And sintered at a predetermined temperature. For the sintering operation, the molded body is heated to a temperature of 16 in a non-oxidizing atmosphere such as nitrogen gas.
It is carried out by heating at 50 to 1900 ° C. for about 2 to 10 hours. In particular, by adding the Si component, 1720-1
It becomes possible to sinter at a temperature of about 780 ° C., which is lower than the conventional temperature. The sintering atmosphere may be a non-oxidizing atmosphere that does not react with AlN, but is usually a nitrogen gas or a reducing atmosphere containing nitrogen gas. H ₂ gas or CO gas may be used as the reducing gas. The sintering may be performed in an atmosphere including vacuum (including a slight reducing atmosphere), reduced pressure, increased pressure and normal pressure. When sintered at a low temperature such as a sintering temperature of less than 1650 ° C., although it depends on the particle size of the raw material powder and the amount of oxygen contained, it is difficult to densify, and problems such as strength and thermal conductivity tend to occur. When firing at a temperature higher than ℃, the vapor pressure of AlN itself in the firing furnace becomes high, which may make densification difficult and the thermal conductivity may sharply decrease. Therefore, the sintering temperature is set to the above range. .

Then, a raw material mixture having a predetermined composition in which a sintering aid and a Si component are added to the above AlN raw material powder is molded, degreased and sintered to obtain an average crystal grain size of 1 to 1.
It has a fine crystal structure of about 4 μm and a thermal conductivity of 1
50 W / mK or more, and bending strength of 50 kg / mm
A high-strength AlN sintered body of ² or more can be obtained.

[0024]

According to the aluminum nitride sintered body and the method of manufacturing the same having the above-described structure, the group IIIa elements, Ca, and S of the periodic table are used.
A predetermined amount of S together with a sintering aid composed of oxides of r and Ba
Since an iN component is added in combination to form an AlN sintered body, S
The crystal grain growth is effectively suppressed by the i component, and a fine crystal structure is obtained. Therefore, an aluminum nitride sintered body having excellent strength characteristics can be obtained.

[0025]

EXAMPLES Next, the aluminum nitride sintered body according to the present invention will be described more specifically with reference to the following examples.

Examples 1 to 26 0.8 wt% oxygen was contained as an impurity, and the average particle size was 1 μm.
As shown in Table 1, with respect to the aluminum nitride powder of m, Y ₂ O ₃ , WO ₃ , and T as Si components and sintering aids were used.
iO ₂ , ZrO ₂ , HfO ₂ , Nb ₂ O ₅ , Ta
₂ O ₅ , MoO ₃ , CaO, BaO, SrO, Nd ₂ O
₅ was added in a predetermined amount, and ethyl alcohol was used as a solvent and mixed in a ball mill for 20 hours to prepare a raw material mixture. Next, 5.5 wt% of polyvinyl alcohol (PVA) as an organic binder was added to this raw material mixture to prepare granulated powder.

Next, the obtained granulated powder is filled in a molding die of a press molding machine and compression-molded in a uniaxial direction with a pressing force of 1200 kg / cm ² , to obtain a length of 50 mm × width of 50 mm × thickness. A large number of 5 mm square plate-shaped compacts were prepared. Subsequently, each molded body was heated in a nitrogen gas atmosphere at 700 ° C. for 1 hour to be degreased.

Next, the degreased compacts were placed in an AlN firing container, and densified and sintered at a firing lower limit temperature of 1720 to 1780 ° C. shown in Table 1 for 4 hours in a firing furnace.
After that, cooling was performed at a cooling rate of 200 ° C./hr to manufacture AlN sintered bodies according to Examples 1 to 26, respectively.

Comparative Example 1 On the other hand, the raw material preparation, molding, degreasing and sintering were carried out under the same conditions as in Example 1 except that the Si component was not added at all and only the conventional sintering aid was added and sintered at 1800 ° C. Then, an AlN sintered body according to Comparative Example 1 having the same dimensions was manufactured.

Comparative Example 2 Also, an excessive amount of SiO ₂ as a Si component was 0.3% by weight.
An AlN sintered body according to Comparative Example 2 was manufactured by treating under the same conditions as in Example 3 except that (Si conversion) was added.

Comparative Example 3 An excess amount of 15% by weight of Y ₂ O ₃ as a sintering aid was added,
An AlN sintered body according to Comparative Example 3 was manufactured in the same manner as in Example 3 except that it was sintered at 1800 ° C.

Comparative Example 4 In addition to Y ₂ O ₃ as a sintering aid, 1% by weight of WO ₃ was added, and Si ₃ N ₄ as a Si component was added in an excessive amount of 0.3% by weight (converted to Si). And the same treatment as in Example 11 except that the AlN sintered body according to Comparative Example 4 was manufactured.

In order to evaluate the strength characteristics and heat dissipation characteristics of the AlN sintered bodies according to Examples 1 to 26 and Comparative Examples 1 to 4 thus obtained, the three-point bending strength, thermal conductivity and average of each sample were evaluated. The crystal grain size was measured and the results shown in Table 1 below were obtained.

[0034]

[Table 1]

As is clear from the results shown in Table 1 above,
In the AlN sintered bodies according to Examples 1 to 26 in which a small amount of the Si component was added in addition to the sintering aids such as Y ₂ O ₃ and CaO, the crystal grain size was extremely 2.5 to 4 μm. It was found to be fine and both bending strength and thermal conductivity were excellent.

On the other hand, Comparative Example 1 in which no Si component is added
The AlN sintered body according to Example 1 has a thermal conductivity of Examples 1 to 1.
Although it is superior to No. 26, it has low bending strength and has problems in durability and handleability. Further, the samples of Comparative Examples 2 and 4 in which the Si component was added in an excessive amount had insufficient thermal conductivity, and the samples of Comparative Example 3 in which the conventional sintering aid Y ₂ O ₃ was added in an excessive amount. Then, it was confirmed that the thermal conductivity and the strength were both reduced, despite the addition of the Si component.

Further, the surface portions of the AlN sintered bodies according to Examples 1 to 26 were observed by a scanning electron microscope (SEM). As a result, as shown in FIG. It was confirmed that the boundary phase was uniformly dispersed and formed. On the other hand, in the sintered body according to Comparative Example 1, Si
Since the grain growth suppressing effect by the addition of the components is small, the AlN particles themselves are also coarse as shown in FIG.
It was formed so that a coarse grain boundary phase was aggregated around the N particles.

[0038]

As described above, according to the ceramic sintered body and the method of manufacturing the same according to the present invention, a predetermined amount of the sintering aid including the group IIIa element of the periodic table, oxides of Ca, Sr, and Ba is used. Since an AlN sintered body is obtained by adding a Si component in combination, the crystal grain growth due to the Si component is effectively suppressed, and a fine crystal structure is obtained. Therefore, an aluminum nitride sintered body having excellent strength characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph showing a crystal structure of an aluminum nitride sintered body according to the present invention.

FIG. 2 is a scanning electron micrograph showing a crystal structure of a conventional aluminum nitride sintered body.

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[Procedure amendment]

[Submission date] May 17, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Aluminum nitride sintered body and method for producing the same

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum nitride sintered body used for a semiconductor substrate or the like and a method for manufacturing the same, and in particular, it significantly improves strength without impairing the thermal conductivity peculiar to aluminum nitride. The present invention relates to an aluminum nitride sintered body excellent in heat dissipation and a manufacturing method.

[0002]

2. Description of the Related Art Sintered ceramics, which are superior in properties such as strength, heat resistance, corrosion resistance, wear resistance, and lightness, compared with conventional metal materials, are used in semiconductor substrates, electronic equipment materials, engine members, It is widely used as a material for high speed cutting tools, nozzles, bearings, and other mechanical parts, functional parts, structural materials and ornamental materials used under severe temperature, stress and wear conditions that conventional metal materials do not have.

In particular, an aluminum nitride (AlN) sintered body is an insulator having a high thermal conductivity and has a coefficient of thermal expansion close to that of silicon (Si). Therefore, the aluminum nitride (AlN) sintered body is used as a heat sink or a substrate of a highly integrated semiconductor device. Expanding applications.

Conventionally, the above-mentioned aluminum nitride sintered body is generally mass-produced by the following manufacturing method. That is,
A sintering aid to the aluminum nitride raw material powder, an organic binder, and various additives and solvents as required, to prepare a raw material mixture by adding a dispersant, the resulting raw material mixture doctor blade method or A thin plate-shaped or sheet-shaped molded body is formed by the slurry casting method, or a raw material mixture is press-molded to form a thick plate-shaped or large-sized molded body. Next, the obtained molded product is heated and degreased in an atmosphere of air or nitrogen gas to remove and degrease the hydrocarbon components and the like used as the organic binder from the molded product. The degreased compact is heated to a high temperature in a nitrogen gas atmosphere or the like and densified and sintered to form an aluminum nitride sintered compact.

In the above manufacturing method, when an ultrafine raw material powder having an average particle diameter of about 0.5 μm or less is used as the raw material AlN powder, a considerably dense sintered body can be obtained by using the AlN powder alone. However, a large amount of impurities such as oxygen adhering to the surface of the raw material powder and the like are solid-solved in the AlN crystal lattice at the time of sintering, or Al-O- which hinders the propagation of lattice vibration.
As a result of producing a compound oxide such as an N compound, the thermal conductivity of the AlN sintered body that did not use a sintering aid was relatively low.

On the other hand, when AlN powder having an average particle size of 1 μm or more is used as the raw material powder, the sinterability of the raw material powder alone is not good. Was difficult to obtain, and there was a drawback that mass productivity was low. Therefore, in order to efficiently manufacture a sintered body by the atmospheric pressure sintering method, in order to prevent the densification of the sintered body and the impurity oxygen in the AlN raw material powder from forming a solid solution in the AlN crystal grains. In addition, as a sintering aid,
It is generally practiced to add rare earth oxides such as yttrium oxide (Y ₂ O ₃ ) and alkaline earth metal oxides such as calcium oxide.

These sintering aids react with the impurity oxygen and Al ₂ O ₃ contained in the AlN raw material powder to form a liquid phase to achieve the densification of the sintered body, and at the same time, to form the impurity oxygen into particles. It is believed that it can be fixed as a phase phase and achieve high thermal conductivity.

[0008]

However, in the above-mentioned conventional production method, since the wettability between AlN and the liquid phase compound is originally low and the liquid phase itself tends to segregate, the liquid after the sintering is dissolved. When the phase solidifies, the liquid phase is AlN
It tends to remain so as to be unevenly distributed in the interstices of the grains and to solidify to form a coarse and brittle grain boundary phase. Further, the grain growth of crystal grains is likely to proceed, and as shown in FIG. 2, the average grain size is 5 to 1
Coarse crystal grains with a size of 0 μm are easily formed, and minute pores do not disappear but remain in the crystal grains, hindering the densification of the sintered body, and finally the three-point bending strength is 35-40 kg / mm. There is a problem that only a low-strength aluminum nitride sintered body of about ² can be obtained.

In recent years, the above-mentioned aluminum nitride material having high thermal conductivity (high heat dissipation) is becoming widespread in order to cope with the heat generation amount which is increased with the high integration and high output of semiconductor elements. As for sex, generally satisfactory results have been obtained. However, as described above, the strength as a structural member is insufficient. Therefore, for example, a slight bending stress that acts when mounting a semiconductor substrate formed of an aluminum nitride sintered body on a mounting board or an impact force that acts during handling There is a problem that the semiconductor substrate is damaged and the manufacturing yield of the semiconductor circuit substrate is significantly reduced.

The present invention has been made in order to solve the above problems, and suppresses grain growth of an AlN sintered body and refines the structure of the sintered body to improve the strength and make the sintered body uniform. To improve the mechanical strength without sacrificing heat dissipation characteristics
An object is to provide an IN sintered body and a method for manufacturing the same.

[0011]

In order to achieve the above-mentioned object, the inventors of the present invention have variously changed the types and amounts of the sintering aids and additives to be added to the raw material aluminum nitride powder, and Experimental studies were conducted on the effects on the crystal structure, strength characteristics and heat transfer characteristics.

As a result, when a small amount of Si component as an additive is added in addition to a predetermined sintering aid, a sintered body structure having a fine crystal grain size of 1 to 4 μm is obtained, An AlN sintered body having excellent strength characteristics was obtained. The present invention has been completed based on the above findings.

That is, the aluminum nitride sintered body according to the present invention contains 1 to 10% by weight of an oxide of at least one element selected from the group IIIa elements of the periodic table, Ca, Sr and Ba, and Si Component concentration is 0.01-0.2
It is characterized in that it is wt%. The Si component is Si
It may be contained as at least one silicon compound selected from O ₂ , Si ₃ N ₄ , SiC and Si ₂ N ₂ O. Furthermore, Ti, Zr, Hf, Nb, Ta, Mo,
At least one metal element selected from W may be contained in an amount of 0.1 to 0.5% by weight in terms of oxide. Also F
The content of impurity cations such as e and Mg is preferably 0.2% by weight or less. Furthermore, the average crystal grain size of the sintered body is 1 to 4
It is characterized by being μm. The AlN sintered body having the above composition has a thermal conductivity of 150 W / m · K or more and a three-point bending strength of 50 kg / mm ² or more.

In the method for producing an aluminum nitride sintered body according to the present invention, an aluminum nitride raw material powder containing 0.2% by weight or less of impurity cations such as Fe and Mg is added to a group IIIa element of the periodic table. , 1 to 10% by weight of an oxide of at least one element selected from Ca, Sr and Ba,
A mixed powder added with 0.01 to 0.2 wt% of Si component is molded, and the obtained molded body is subjected to 165 in a non-oxidizing atmosphere.
It is characterized in that it is sintered in a temperature range of 0 to 1900 ° C.

The aluminum nitride raw material (AlN) powder used in the method of the present invention as the main component of the sintered body has an impurity oxygen content of 1.5% by weight or less in consideration of sinterability and thermal conductivity. Is suppressed to an average particle size of 0.5 to 2
A fine AlN powder of about μm, preferably 1.5 μm or less is used.

The oxide of group IIIa element of the periodic table, Ca, Sr, and Ba acts as a sintering aid, and in order to densify the AlN sintered body, 1 to 10% by weight based on the AlN raw material powder.
It is added in the range of. Specific examples of the above-mentioned sintering aid include oxides of rare earth elements (Y, Sc, Ce, Dy, etc.), nitrides, oxides of alkaline earth metals (Ca), or compounds obtained by a sintering operation. Materials are used, especially yttrium oxide (Y ₂ O ₃ ), cerium oxide (Ce
O) and calcium oxide (CaO) are preferred. When the amount of the sintering aid added is less than 1% by weight, the effect of improving the sinterability is not sufficiently exerted, the sintered body is not densified and a low-strength sintered body is formed, or AlN Oxygen dissolved in the crystal,
A sintered body having a high thermal conductivity cannot be formed. On the other hand, if the addition amount exceeds 10% by weight, not only the effect as a sintering aid reaches a saturated state and becomes meaningless, but
On the contrary, the thermal conductivity of the AlN sintered body obtained by sintering is lowered, while a large amount of the grain boundary phase remains in the sintered body, and the volume of the grain boundary phase removed by heat treatment is large. Voids may remain in the tying body, increasing the shrinkage rate and making it more likely to cause deformation.

The Si component has the effect of improving the sinterability and lowering the sintering temperature, but grain growth of the sintered body can be suppressed by adding it in combination with the above-mentioned sintering aid. , Is added to form a fine AlN crystal structure and enhance the structural strength of the sintered body. Examples of the Si component include SiO ₂ , Si ₃ N ₄ , SiC and Si ₂ N.
It is desirable to use silicon compounds such as ₂ O. The content of this silicon compound is 0.01 to 0.
It is adjusted to the range of 2% by weight. The content of Si component is 0.
If it is less than 01% by weight, the effect of suppressing the grain growth becomes insufficient, and the crystal structure becomes coarse, so that a high-strength AlN sintered body cannot be obtained. On the other hand, the content is 0. ． If the amount exceeds 2% by weight, the thermal conductivity of the sintered body may decrease and the bending strength may decrease.

Ti, Zr, Hf, Nb, Ta, Mo, W
The oxide of is effective for improving the characteristics of the AlN sintered body such as forming an opaque sintered body by coloring while lowering the sintering temperature to improve the sinterability. It may be added in the range of 0.1 to 0.5% by weight. If the added amount is less than 0.1% by weight, the above characteristic improving effect is insufficient, while if the added amount is more than 0.5% by weight, the heat of the AlN sintered body is increased like other impurities. Reduces conductivity.

Impurity cations such as Fe and Mg are Al
Since it is easy to form a compound that inhibits the heat conduction of the N sintered body,
The content in the AlN sintered body is set to 0.2% by weight or less.

The above AlN raw material powder, various sintering aids and Si compound for Si component are put into a pulverizing mixer such as a ball mill and mixed for a predetermined time to form a raw material mixture. Next, the obtained raw material mixture is filled in a mold having a predetermined shape and pressure-molded to form a molded body. At this time, by adding 5 to 10% by weight of an organic binder such as paraffin and stearic acid to the raw material mixture in advance, the molding operation can be smoothly carried out.

As a forming method, a general-purpose die pressing method, a slurry casting method, a hydrostatic pressing method, or a sheet forming method such as a doctor blade method can be applied.

Subsequent to the above molding operation, the molded body is heated to 400 to 550 ° C. in air, or in a non-oxidizing atmosphere, for example, a nitrogen gas atmosphere, at a temperature of 400 to 800.
By heating to 0 ° C., the previously added organic binder is thoroughly degreased and removed.

Next, the plurality of sheet-shaped compacts that have been degreased are stacked in multiple stages in a firing furnace through a grain powder made of, for example, ceramics sintered powder, and in this arrangement state, the plurality of compacts are packaged together. And sintered at a predetermined temperature. For the sintering operation, the molded body is heated to a temperature of 16 in a non-oxidizing atmosphere such as nitrogen gas.
It is carried out by heating at 50 to 1900 ° C. for about 2 to 10 hours. In particular, by adding the Si component, 1720-1
It becomes possible to sinter at a temperature of about 780 ° C., which is lower than the conventional temperature. The sintering atmosphere may be a non-oxidizing atmosphere that does not react with AlN, but is usually a nitrogen gas or a reducing atmosphere containing nitrogen gas. H ₂ gas or CO gas may be used as the reducing gas. The sintering may be performed in an atmosphere including vacuum (including a slight reducing atmosphere), reduced pressure, increased pressure and normal pressure. When sintered at a low temperature such as a sintering temperature of less than 1650 ° C., although it depends on the particle size of the raw material powder and the amount of oxygen contained, it is difficult to densify, and problems such as strength and thermal conductivity tend to occur. When firing at a temperature higher than ℃, the vapor pressure of AlN itself in the firing furnace becomes high, which may make densification difficult and the thermal conductivity may sharply decrease. Therefore, the sintering temperature is set to the above range. .

Then, a raw material mixture having a predetermined composition in which a sintering aid and a Si component are added to the above AlN raw material powder is molded, degreased and sintered to obtain an average crystal grain size of 1 to 1.
It has a fine crystal structure of about 4 μm and a thermal conductivity of 1
50 W / mK or more, and bending strength of 50 kg / mm
A high-strength AlN sintered body of ² or more can be obtained.

[0025]

According to the aluminum nitride sintered body and the method of manufacturing the same having the above-described structure, the group IIIa elements, Ca, and S of the periodic table are used.
A predetermined amount of S together with a sintering aid composed of oxides of r and Ba
Since an iN component is added in combination to form an AlN sintered body, S
The crystal grain growth is effectively suppressed by the i component, and a fine crystal structure is obtained. Therefore, an aluminum nitride sintered body having excellent strength characteristics can be obtained.

[0026]

EXAMPLES Next, the aluminum nitride sintered body according to the present invention will be described more specifically with reference to the following examples.

Examples 1 to 26 Oxygen was added as an impurity in an amount of 0.8% by weight, and the average particle size was 1 μm.
As shown in Table 1, with respect to the aluminum nitride powder of m, Y ₂ O ₃ , WO ₃ , and T as Si components and sintering aids were used.
iO ₂ , ZrO ₂ , HfO ₂ , Nb ₂ O ₅ , Ta
₂ O ₅ , MoO ₃ , CaO, BaO, SrO, Nd ₂ O
₅ was added in a predetermined amount, and ethyl alcohol was used as a solvent and mixed in a ball mill for 20 hours to prepare a raw material mixture. Next, 5.5 wt% of polyvinyl alcohol (PVA) as an organic binder was added to this raw material mixture to prepare granulated powder.

Next, the obtained granulated powder is filled in a molding die of a press molding machine and compression-molded in a uniaxial direction with a pressing force of 1200 kg / cm ² , to obtain a length of 50 mm × width of 50 mm × thickness. A large number of 5 mm square plate-shaped compacts were prepared. Subsequently, each molded body was heated in an air atmosphere at 450 ° C. for 1 hour to be degreased.

Next, the degreased compacts were placed in an AlN firing container and densified and sintered at a firing lower limit temperature of 1720 to 1780 ° C. shown in Table 1 for 4 hours in a firing furnace.
After that, cooling was performed at a cooling rate of 200 ° C./hr to manufacture AlN sintered bodies according to Examples 1 to 26, respectively.

Comparative Example 1 On the other hand, the raw material preparation, molding, degreasing and sintering were carried out under the same conditions as in Example 1 except that the Si component was not added at all and only the conventional sintering aid was added and sintered at 1800 ° C. Then, an AlN sintered body according to Comparative Example 1 having the same dimensions was manufactured.

Comparative Example 2 In addition, an excessive amount of SiO ₂ as a Si component was 0.3% by weight.
An AlN sintered body according to Comparative Example 2 was manufactured by treating under the same conditions as in Example 3 except that (Si conversion) was added.

Comparative Example 3 Y ₂ O ₃ as a sintering aid was added in an excessive amount of 15% by weight,
An AlN sintered body according to Comparative Example 3 was manufactured in the same manner as in Example 3 except that it was sintered at 1800 ° C.

Comparative Example 4 In addition to Y ₂ O ₃ as a sintering aid, 1% by weight of WO ₃ was added, and an excessive amount of Si ₃ N ₄ as a Si component was added by 0.3% by weight (converted to Si). And the same treatment as in Example 11 except that the AlN sintered body according to Comparative Example 4 was manufactured.

In order to evaluate the strength characteristics and heat dissipation characteristics of the AlN sintered bodies according to Examples 1 to 26 and Comparative Examples 1 to 4 thus obtained, the three-point bending strength, the thermal conductivity and the average of each sample were evaluated. The crystal grain size was measured and the results shown in Table 1 below were obtained.

[0035]

[Table 1]

As is clear from the results shown in Table 1,
In the AlN sintered bodies according to Examples 1 to 26 in which a small amount of the Si component was added in addition to the sintering aids such as Y ₂ O ₃ and CaO, the crystal grain size was extremely 2.5 to 4 μm. It was found to be fine and both bending strength and thermal conductivity were excellent.

On the other hand, Comparative Example 1 in which no Si component is added
The AlN sintered body according to Example 1 has a thermal conductivity of Examples 1 to 1.
Although it is superior to No. 26, it has low bending strength and has problems in durability and handleability. Further, the samples of Comparative Examples 2 and 4 in which the Si component was added in an excessive amount had insufficient thermal conductivity, and the samples of Comparative Example 3 in which the conventional sintering aid Y ₂ O ₃ was added in an excessive amount. Then, it was confirmed that the thermal conductivity and the strength were both reduced, despite the addition of the Si component.

The surface of each AlN sintered body according to Examples 1 to 26 was observed with a scanning electron microscope (SEM). As a result, as shown in FIG. It was confirmed that the boundary phase was uniformly dispersed and formed. On the other hand, in the sintered body according to Comparative Example 1, Si
Since the grain growth suppressing effect by the addition of the components is small, the AlN particles themselves are also coarse as shown in FIG.
It was formed so that a coarse grain boundary phase was aggregated around the N particles.

[0039]

As described above, according to the ceramic sintered body and the method of manufacturing the same according to the present invention, a predetermined amount of the sintering aid including the group IIIa element of the periodic table, oxides of Ca, Sr, and Ba is used. Since an AlN sintered body is obtained by adding a Si component in combination, the crystal grain growth due to the Si component is effectively suppressed, and a fine crystal structure is obtained. Therefore, an aluminum nitride sintered body having excellent strength characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a scanning electron micrograph showing a crystal structure of an aluminum nitride sintered body according to the present invention.

FIG. 2 is a scanning electron micrograph showing a crystal structure of a conventional aluminum nitride sintered body.

Claims (10)

[Claims] 1. A group IIIa element of the periodic table, Ca, Sr, Ba
1 to 1 oxide of at least one element selected from
The content of Si is 0.01 to
An aluminum nitride sintered body characterized by being 0.2% by weight. 2. The Si component is SiO ₂ , Si ₃ N ₄ , S
The aluminum nitride sintered body according to claim 1, which is contained as at least one silicon compound selected from iC and Si ₂ N ₂ O. 3. Ti, Zr, Hf, Nb, Ta, Mo,
The aluminum nitride sintered body according to claim 1, containing 0.1 to 0.5% by weight in terms of oxide of at least one metal element selected from W. 4. The aluminum nitride sintered body according to claim 1, wherein the content of impurity cations such as Fe and Mg is 0.2% by weight or less. 5. The aluminum nitride sintered body according to claim 1, wherein the average crystal grain size of the sintered body is 1 to 4 μm. 6. The aluminum nitride sintered body according to claim 1, which has a thermal conductivity of 150 W / m · K or more. 7. The aluminum nitride sintered body according to claim 1, which has a three-point bending strength of 50 kg / mm ² or more. 8. An aluminum nitride raw material powder containing 0.2% by weight or less of impurity cations such as Fe and Mg, and at least one selected from Group IIIa elements of the periodic table, Ca, Sr, and Ba. 1 to 10% by weight of the oxide of the element
A mixed powder added with 0.01 to 0.2 wt% of Si component is molded, and the obtained molded body is subjected to 165 in a non-oxidizing atmosphere.
A method for producing an aluminum nitride sintered body, which comprises sintering in a temperature range of 0 to 1900 ° C. 9. The method for producing an aluminum nitride sintered body according to claim 8, wherein the oxidation content of the aluminum nitride raw material powder is set to 1.3% by weight or less. 10. The method for producing an aluminum nitride sintered body according to claim 8, wherein the average particle diameter of the aluminum nitride raw material powder is set to 1 μm or less.