JP2735227B2 - Manufacturing method of aluminum nitride sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for producing an aluminum nitride sintered body.

(Conventional technology) Aluminum nitride (AlN) has many excellent properties such as maintaining high strength from room temperature to high temperature, not getting wet with molten metal, high electrical insulation, high thermal conductivity, etc. Therefore, it is attracting attention as a new material. In particular, in recent years, Al
Active research on application of N sintered bodies to semiconductor substrates has been actively conducted, and the thermal conductivity of AlN sintered bodies that can be mass-produced was 40-60 W / m until several years ago.
・ The value of k was reduced to ~ 20 by adopting a special sintering method.
It has been improved to 0W / mk.

The first factor in increasing the thermal conductivity of such an AlN sintered body is that it has become possible to mass-produce a high-purity AlN raw material, particularly an AlN powder having a low oxygen content. AlN with low oxygen content
AlN sintered bodies with high thermal conductivity have been obtained by optimizing sintering aids with powder as the main component.On the other hand, sinterability tends to decrease with decreasing oxygen content. In order to obtain a dense sintered body, sintering at a higher temperature and for a longer time has been required as compared with the related art. That is, although the sintered body obtained by using the AlN powder having a high oxygen content as a raw material has low thermal conductivity, it has excellent sinterability and can be densified.

When considering application to a semiconductor mounting substrate, an alternative to the alumina substrate that is currently widely used is conceivable.However, in the situation described above, thorough cost reduction is required, and the sintering temperature rises and the time becomes longer. Is unfavorable because the production cost increases.

By the way, when an AlN sintered body is to be obtained by a method other than hot pressing, in order to densify the sintered body and prevent solid solution of impurity oxygen in the AlN raw material powder into the AlN grains, a conventional method is used. Rare earth element oxides, alkaline earth element acid compounds and the like have been added as binders (Japanese Patent Application Laid-Open No.
-127267, JP-A-61-10071, JP-A-60-71575, etc.). These sintering aids react with the impurity oxygen in the AlN raw material powder to form a liquid phase to achieve the densification of the sintered body, and fix the impurity oxygen as a grain boundary phase (oxygen trap) to increase the heat It is believed that conductivity is achieved.

By adding the sintering aid to the AlN powder raw material in this way, it is possible to certainly achieve the densification and high thermal conductivity of the AlN sintered body.
Since high-temperature sintering is required at a high temperature of ~ 1900 ° C, Al
This was an obstacle to the low cost of the N sintered body.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned conventional problems, and has achieved a reduction in sintering temperature and a reduction in sintering time without impairing high thermal conductivity. An object of the present invention is to provide a method for manufacturing an AlN sintered body.

[Constitution of the Invention] (Means for Solving the Problems) A method for producing an aluminum nitride sintered body according to the present invention comprises aluminum nitride as a main component, and (A) aluminum fluoride; and (B) yttrium oxide. Additives containing and as essential components are converted to elemental elements of cation species of 0.
It is characterized in that it is added at 1 to 20% by weight, molded, and then sintered at a temperature of 1700 ° C. or less.

Another method for producing an aluminum nitride sintered body according to the present invention comprises aluminum nitride as a main component, and (A) aluminum fluoride, (B-1) yttrium oxide, and (B-2) alkaline earth. Element oxides, fluorides, carbides; alkaline earth element rare earth compound; alkaline earth aluminum compound; rare earth aluminum compound;
And at least one compound selected from the group consisting of an alkaline earth element and a rare earth element aluminum compound;
It is characterized by adding 1 to 20% by weight and sintering.

Still another method for producing an aluminum nitride sintered body according to the present invention comprises aluminum nitride as a main component, and (A) aluminum fluoride, and (B) an oxide, fluoride, or carbide of an alkaline earth element;
At least one compound selected from the group consisting of rare earth element compounds (excluding yttrium oxide); alkaline earth element rare earth element compounds; alkaline earth aluminum compounds; rare earth element aluminum compounds; and alkaline earth element rare earth aluminum compounds; The additive used as a component is 0.
It is characterized by adding 1 to 20% by weight and sintering.

Still another method for producing an aluminum nitride sintered body according to the present invention comprises aluminum nitride as a main component, and (A) aluminum fluoride, and (B) an oxide, fluoride, or carbide of an alkaline earth element;
At least one compound selected from the group consisting of a rare earth element compound; an alkaline earth element rare earth element compound; an alkaline earth aluminum compound; a rare earth aluminum compound; and an alkaline earth element rare earth aluminum compound; And at least one compound selected from the group consisting of aluminum oxides;
It is characterized by adding 1 to 20% by weight and sintering.

It is preferable to use AlN containing 0.1 to 20% by weight of oxygen and having an average particle diameter of 0.1 to 2.5 μm by a centrifugal sedimentation method.

Examples of the additive include the following forms.

. An additive consisting only of the components (A) and (B).

. An additive comprising the component (A), the component (B) and a transition metal compound.

. An additive comprising the above component (A), component (B) and aluminum oxide.

. An additive comprising the above components (A) and (B), a transition metal compound and an aluminum oxide.

As the oxide, fluoride and carbide of the alkaline earth element, for example, oxides, fluorides and carbides of Mg, Ca, Sr and Ba are used.

Examples of the rare earth element compound in the component (B) include Sc, Y, La, Ce, Sm, Eu, Tm, Tb, Dy, Nd, Gd, Pr,
Examples thereof include oxides, fluorides, nitrides and carbides of Ho, Er and Yb, and particularly preferred are compounds of Y, La and Ce.

As the alkaline earth element rare earth compound in the component (B), for example, when the alkaline earth element is R and the rare earth element is Ln, R-Ln-O, R-Ln-F, R-Ln-C , R-Ln-N, particularly RLn ₄ O ₇ , RLn
₂ O ₄ and RLn ₄ F ₁₄ are desirable.

As the alkaline earth element aluminum compound in the component (B), for example, when the alkaline earth element is R,
Examples include oxides represented by R ₂ Al ₂ O ₅ , RAl ₂ O ₄ , R ₁₂ Al ₁₄ O ₃₃ , and R ₃ Al ₂ O ₆ .

As the rare earth element aluminum compound in the component (B), for example, when the rare earth element is Ln, Ln ₃ Al ₅ O ₁₂ , Ln
Oxides represented by nAlO ₃ and Ln ₄ Al ₂ O ₉ can be exemplified.

The aluminum compound of the alkaline earth element and the rare earth element in the component (B) is represented by an R-Ln-Al-O-based composite oxide, where R is the alkaline earth element and Ln is the rare earth element. Yes, RLnAlO ₄ and RLnAl ₃ O ₇ are particularly desirable.

Examples of the transition metal compound contained in the additive include oxides, fluorides, nitrides, and carbides of Ti, Zr, Hf, Ni, Cr, Mn, Fe, Co, and V, and in particular, T
Compounds of i, Zr and Hf are preferred.

Examples of the aluminum oxide contained in the additive include α-Al ₂ O ₃ and γ-Al ₂ O ₃ .

The amount of the above additives with respect to AlN powder is calculated in terms of cation.
It is desirable to be in the range of 0.1 to 20% by weight, more preferably 0.2 to 15% by weight. The reason is that if the amount of the additive is less than 0.1% by weight, the effect of improving the properties of the sintered body is not sufficient, while if the amount exceeds 20% by weight, the properties such as thermal conductivity and high-temperature strength deteriorate. This is because it may not be ignored. The amount of aluminum fluoride in the additive is 0.05
If the content is less than 0.05% by weight, it is difficult to sufficiently achieve the effect of improving the properties. If the content exceeds 5% by weight, bubbles may remain in the sintered body, and the density may be reduced. This is because it becomes difficult to obtain a sintered body. Further, when a transition metal compound and an aluminum oxide are contained in the additive, it is desirable that each component is added in an amount of 0.01 to 3% by weight. The reason is that the addition amount of the transition metal compound is 0.01% by weight.
If the amount is less than the above, it is not possible to sufficiently enhance the strength and the coloring of the sintered body, and if it exceeds 3% by weight, the thermal conductivity of the sintered body may be reduced. If the amount of the aluminum oxide is less than 0.01% by weight, the effect of adding the oxide cannot be sufficiently improved to improve the sinterability. This is because there is a risk of lowering

Each of the above additives has an average particle size of 0.3 to 0.3 centrifugation.
It is desirable to add the powder or liquid phase of 2.0 μm to the AlN raw material powder. As an example of adding as a liquid phase, a method in which nitrate of a cationic species element is dissolved in alcohol and added to the AlN raw material powder, or an alkoxide of the same cationic species element is added to AlN
After adding to the raw material powder, a method of hydrolysis and the like can be adopted.

 Next, the production method of the present invention will be described more specifically.

First, an additive is added to AlN powder, and ground and mixed using a ball mill or the like to prepare a raw material. However, in the case of normal pressure sintering, a raw material is prepared by adding a binder to the mixture crushed and mixed by the ball mill or the like, kneading and granulating. Subsequently, after the raw material containing the binder is molded by means such as a mold, hydrostatic pressure or sheet molding, the molded body is heated in a stream of N ₂ gas to remove the binder. Next, the compact is set in a container made of graphite, boron nitride or aluminum nitride, and subjected to normal pressure sintering at 1400 to 1850 ° C. in an N ₂ gas atmosphere. On the other hand, in the case of hot press sintering, the raw material crushed and mixed by the ball mill is hot-pressed at a temperature of 1400 to 1800 ° C.

(Action) According to the present invention, aluminum nitride is used as a main component, and (A) aluminum fluoride and (B) oxides, fluorides and carbides of alkaline earth elements; rare earth element compounds;
Addition of at least one element selected from the group consisting of alkaline earth element rare earth element compound; alkaline earth aluminum compound; rare earth element aluminum compound; and alkaline earth element rare earth aluminum compound; By adding 0.1 to 20% by weight and sintering, a dense and high-conductivity AlN sintered body can be produced in a short time at a low sintering temperature. Although this effect is not clear, it is presumed to be due to the following mechanism.

That is, the effect of accelerating the reaction by aluminum fluoride (AlF ₃ ), which is a main component of the additive, can be mentioned. AlF ₃ has no melting point under a normal atmosphere, and sublimates without decomposition when heated. The vapor pressure reaches 1 atm near 1300 ° C. In sintering the AlN raw material powder, it is considered that a liquid phase is generated by a reaction between the additive and the additive, which is inevitably mixed in the AlN raw material powder, and the densification proceeds by the liquid phase sintering. AlF ₃ is considered to have the effect of allowing this reaction to proceed at a lower temperature and in a shorter time. For example, if the Y ₂ O ₃ as an additive consider a system which added to the AlN raw material, is in the vicinity of the grain boundaries after sintering and generates a composite oxide of Y-Al-O system,
These products become liquid phases at the sintering temperature. In this case, if the generated phase is Y ₃ Al ₅ O ₁₂ , the liquidus temperature is considered to be 1760 ° C., and in order to obtain a dense AlN sintered body, sintering is performed at a higher temperature (about 1800 ° C.). There is a need. This is seemingly Y ₂
O ₃ and Al ₂ O ₃ in the reaction are similar to the two-component system, in fact, be heated AlN raw material powder containing oxygen in a non-oxidizing atmosphere 130
The formation of α-Al ₂ O ₃ is confirmed from around 0 ° C.

The present inventors have, Y ₂ O ₃ and Al ₂ O ₃ powder _{3Y 2 O 3 · 5Al 2 O} 3 or
When mixed to a stoichiometric composition such as 2Y ₂ O ₃ and Al ₂ O ₃ and heated to 1500 ° C in air, unreacted
Is Y ₂ O ₃ and Al ₂ O ₃ often exist, the AlF ₃ trace (e.g. 0.5
(About% by weight), all were converted to a stoichiometric composition under the same conditions, and it was confirmed that no unreacted material remained.

Further, as another component (B) of the additive, an alkaline earth element compound, a rare earth element compound, etc. improve the sinterability as described in the prior art, thereby densifying the AlN sintered body and achieving high heat conduction. It contributes to efficiency.

Further, by using an additive containing the above-described transition metal compound, it is possible to achieve high strength and coloring of the AlN sintered body. That is, the additive of the system containing the transition metal compound is uniformly distributed in the sintered body without inhibiting the sintering and grain growth of the AlN raw material, and the strength of the sintered body can be increased by the pinning effect. Moreover, when the sintered body is colored and various colors are obtained by combining with other components, the unevenness of the color of the sintered body is concealed to enhance the aesthetic appearance. Light that causes a malfunction of the memory can be blocked. Further, by using an additive containing the above-described aluminum oxide, the sinterability of the AlN sintered body can be improved. In particular, it is possible to effectively improve the sintering of AlN powder having a small amount of impurity oxygen and a large particle diameter and the sintering of a compact having a large amount of residual carbon due to insufficient binder removal after molding.

(Examples of the Invention) Hereinafter, examples of the present invention will be described in detail.

Example 1 First, 0.7% by weight of impurity oxygen was contained, and the average particle size was 1.2%.
Y ₂ O ₃ 3 with an average particle size of 1.0 μm as an additive to μm AlN powder
Wt% (Y equivalent; 2.36 wt%) and Al with an average particle size of 1.3 μm
A raw material was prepared by adding 0.3% by weight of F ₃ (in terms of Al; 0.094% by weight), crushing and mixing using a ball mill. Then,
After adding 7% by weight of an acrylic binder to this raw material and granulating it, it was press-molded at a pressure of 500 kg / cm ² to 50 cm × 50 cm.
A compact having a size of × 8 cm was obtained. Subsequently, the green compact was heated to 700 ° C. in a nitrogen gas atmosphere to remove the acrylic binder. Next, the green compact was set in a carbon container and sintered under normal pressure at 1700 ° C. for 30 minutes under a nitrogen gas atmosphere to produce an AlN sintered body.

Examples 2-11, Comparative Examples 1-3 Thirteen kinds of AlN were prepared in the same manner as in Example 1 except that the raw material was composed of the AlN powder shown in Table 1 below and a mixed powder as an additive. A sintered body was manufactured. However, CaO
Indicates the weight of CaCO ₃ added, and the average particle diameter indicates the centrifugal sedimentation diameter when n-butanol is used as the dispersion medium.

The densities of the AlN sintered bodies obtained in Examples 1 to 11 and Comparative Examples 1 to 3 were measured. Further, each AlN sintered body was ground to produce a disk having a diameter of 10 mm and a thickness of 2.5 mm, and the thermal conductivity was measured by a laser flash method using these as test pieces. The temperature at the time of measurement was 21 ° C. ± 2 ° C. The results are shown in Table 1 below.

As is apparent from Table 1 described later, in Examples 1 to 11
It can be seen that the AlN sintered body is superior to any of the AlN sintered bodies of Comparative Examples 1 to 3 in any of the properties of denseness and thermal conductivity.

Example 12 First, impurity oxygen was contained in an amount of 0.9% by weight and the average particle size was 1.5%.
CaCO _{3 with an} average particle size of 0.8 μm as an additive to μm AlN powder
Was added with 1.0% by weight (calculated as CaO; 0.714% by weight) and 0.5% by weight of AlF _{3 having an} average particle size of 1.3 μm (calculated as 0.161% by weight), and the mixture was crushed and mixed using a ball mill to mix the raw materials. Prepared. Subsequently, an acrylic binder was added to the raw material in an amount of 7% by weight, and the mixture was granulated, followed by press molding at a pressure of 500 kg / cm ² to obtain a green compact having a size of 30 cm × 30 cm × 8 cm. Subsequently, the green compact was heated to 700 ° C. in a nitrogen gas atmosphere to remove the acrylic binder. Next, the green compact was set in a carbon container, and heated at 1600 ° C. in a nitrogen gas atmosphere.
With 10 minutes, 30 minutes, 60 minutes, 180 minutes, 300 minutes and
Six kinds of AlN sintered bodies were manufactured by normal pressure sintering for 720 minutes.

Comparative Example 4 First, impurity oxygen was contained at 0.9% by weight, and the average particle size was 1.5%.
CaCO _{3 with an} average particle size of 0.8 μm as an additive to μm AlN powder
Was added by 1.0% by weight in terms of CaO, and the mixture was crushed and mixed using a ball mill to prepare a raw material. Subsequently, using this raw material, normal pressure sintering was performed in the same manner as in Example 12 to obtain six types of Al.
An N sintered body was manufactured.

Thus, each of the AlNs obtained in Example 12 and Comparative Example 4
The density and the thermal conductivity at room temperature of the sintered body were measured.
The results are shown in Table 2 below.

As is clear from Table 2 below, in Example 12, 60
It can be seen that an AlN sintered body having a high density and a high thermal conductivity can be obtained even in a short sintering time of one minute.

Examples 13 to 20, Comparative Examples 5 and 6 Except for using AlN powder shown in Table 3 below and a mixed powder as an additive as raw materials, and sintering them under the conditions shown in Table 3 below. By the same method as in Example 1.
Ten types of AlN sintered bodies were produced. However, CaO is obtained by adding CaCO ₃ in terms of weight, and the average particle diameter is the centrifugal sedimentation diameter when n-butanol is used as a dispersion medium.

The AlN sintered bodies of Examples 13 to 20 and Comparative Examples 5 and 6 were measured for density and thermal conductivity at room temperature in the same manner as in Example 1. In addition, each AlN sintered body was ground to produce 6 rods each 4 mm wide, 3 mm thick and 40 mm long,
These are used as test pieces for measuring bending strength, and the distance between fulcrums is 20m.
The three-point bending strength was measured under the conditions of m and a crosshead speed of 0.5 mm / min. Further, the color of each AlN sintered body was observed. These results are also shown in Table 3 below.

As is evident from Table 3 below, Examples 13 to 20
It can be seen that the AlN sintered body of Comparative Example 5 is superior to the sintered bodies of Comparative Examples 5 and 6 in all of the density, thermal conductivity, and three-point bending strength.

[Effects of the Invention] As described in detail above, according to the present invention, a reduction in the sintering temperature and a reduction in the sintering time can be achieved without impairing the high thermal conductivity. It is possible to provide a method capable of manufacturing an AlN sintered body suitable for a substrate or the like at a high yield and at low cost.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akihiko Tsuge 1 Toshiba-cho, Komukai, Sachi-ku, Kawasaki-shi, Kanagawa Inside Toshiba Research Institute, Inc. (56) References JP-A-63-195175 (JP, A)

Claims (4)

(57) [Claims] 1. An additive containing aluminum nitride as a main component and (A) aluminum fluoride and (B) yttrium oxide as essential components in an amount of 0.1% in terms of a cationic species element.
A method for producing an aluminum nitride sintered body, comprising adding -20% by weight, molding, and sintering at a temperature of 1700 ° C or less. 2. An aluminum nitride as a main component, comprising (A) aluminum fluoride, (B-1) yttrium oxide, and (B-2) an oxide, fluoride, or carbide of an alkaline earth element; Earth element rare earth element compound; alkaline earth aluminum compound; rare earth element aluminum compound;
And at least one compound selected from the group consisting of an alkaline earth element and a rare earth element aluminum compound.
A method for producing an aluminum nitride sintered body, characterized in that sintering is performed by adding up to 20% by weight. 3. An aluminum nitride as a main component, comprising (A) aluminum fluoride and (B) an oxide, fluoride or carbide of an alkaline earth element;
At least one compound selected from the group consisting of rare earth element compounds (excluding yttrium oxide); alkaline earth element rare earth element compounds; alkaline earth aluminum compounds; rare earth element aluminum compounds; and alkaline earth element rare earth aluminum compounds; Additives as components are 0.1
A method for producing an aluminum nitride sintered body, characterized in that sintering is performed by adding up to 20% by weight. 4. An aluminum nitride as a main component, comprising (A) aluminum fluoride, and (B) an oxide, fluoride or carbide of an alkaline earth element;
At least one compound selected from the group consisting of: a rare earth element compound; an alkaline earth element rare earth element compound; an alkaline earth aluminum compound; a rare earth aluminum compound; and an alkaline earth element rare earth aluminum compound; and (C) a transition metal compound; And at least one compound selected from the group consisting of aluminum oxide and aluminum oxide.
A method for producing an aluminum nitride sintered body, characterized in that sintering is performed by adding up to 20% by weight.