JP3347526B2 - Aluminum nitride sintered body and method for producing the same - Google Patents

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 and a method for producing the same, and more particularly to a sintered body having high thermal conductivity, suitable for electronic parts such as heat-radiating substrates, and co-fired with a conductor material. The present invention relates to a possible aluminum nitride sintered body and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, as information processing apparatuses have become higher in performance and higher in speed, semiconductor integrated circuits constituting the information processing apparatuses have also become higher in density and higher in integration. In order to operate the semiconductor integrated circuit device normally and stably, there is a problem how to efficiently remove the heat.

For this reason, beryllium oxide sintered bodies have been proposed as ceramic materials having a high thermal conductivity in conventional semiconductor packages and the like using alumina as a substrate, but there is a problem in terms of toxicity. .

[0004] Therefore, as a highly thermally conductive substrate material replacing the beryllium oxide sintered body, it has high mechanical strength from room temperature to high temperature, high electrical insulation, high thermal conductivity, and a thermal expansion coefficient higher than that of alumina. Attention has been focused on aluminum nitride-based sintered bodies having excellent properties such as being close to a single crystal.

[0005] However, aluminum nitride is inherently difficult to sinter, and it has been difficult to obtain a high-density sintered body having high thermal conductivity simply. Therefore, conventionally, as a sintering aid, a compound of Group 2a element of the periodic table or a compound of Group 3a element of the periodic table, for example, an alkaline earth metal such as calcium, strontium, barium or a compound of yttrium and a rare earth element is added. As a result, a sintered body having high density and high thermal conductivity has been obtained.

[0006]

It is advisable to reduce the grain boundaries as much as possible to increase the thermal conductivity. For this purpose, it is necessary to remove auxiliary substances such as Y ₂ O ₃ after sintering. However, the firing temperature needs to be set high, and the surface of the sintered body is roughened, so that the smoothness is lost. Therefore, a polishing step needs to be performed. Therefore, high thermal conductivity by removing such grain boundaries is not preferable in terms of mass productivity.

An object of the present invention is to solve the above problems, and specifically, it is possible to achieve high thermal conductivity without requiring a special step such as removal of grain boundaries. It is an object of the present invention to provide a high-density aluminum nitride sintered body having uniform quality and excellent surface smoothness.

[0008]

Means for Solving the Problems As a result of repeated studies on the above problems, the present inventor has found that, among the sintering aids, a Lu compound or a Lu compound among the Group 3a element compounds of the periodic table. And at least one compound of Group 3a elements of the periodic table other than Lu, a sintered body having a small amount of decomposition of the Lu compound and a smooth surface can be obtained even at a high firing temperature. When used, other periodic table No. 3
higher thermal conductivity as compared with the case where a group a element compound is added; the total amount of the oxide equivalent (RE ₂ O ₃ ) of the group 3a element (RE) in the periodic table; RE ₂ O ₃ / Al ₂ O _{3 in} terms of alumina equivalent (Al ₂ O ₃ )
It has been found that by controlling the molar ratio represented by the formula (1), a sintered body having higher thermal conductivity can be obtained, and the present invention has been achieved.

That is, the aluminum nitride sintered body of the present invention has an aluminum nitride crystal phase as a main phase, and contains Lu or a combination of Lu and at least one element of Group 3a of the periodic table other than Lu. , A sintered body containing impurity oxygen, wherein the Group 3a element of the periodic table is 0.3% in terms of oxide.
２．５2.5 mol% (including Lu in an amount of 0.3 mol% or more in terms of oxide), and
The molar ratio (RE ₂ O ₃ ) of the oxide equivalent amount (RE ₂ O ₃ ) of the group a element (RE) to the Al ₂ O ₃ equivalent amount of the impurity oxygen.
/ Al ₂ O ₃ ) is 1 or more. The grain boundary of the sintered body is RE ₄ Al ₂ O ₉ or R
It is desirable that EAlO ₃ be present as the main crystal phase.

The method for producing an aluminum nitride sintered body according to the present invention is characterized in that the aluminum nitride as a main component and a Lu compound or a Lu compound and a compound other than Lu in the periodic table 3a.
And a combination of at least one compound of the group III elements, and the total amount of the group 3a elements of the periodic table in terms of oxides is 0.3 to 2.5 mol% (however, Lu is calculated as oxides). 0.
3% by mole or more) and Al ₂ O ₃ .
RE ₂ with oxide equivalent weight of group elements _{(RE) (RE 2 O 3} )
It is characterized in that a molded body prepared so that the molar ratio represented by O ₃ / Al ₂ O ₃ is 1 or more is fired in a non-oxidizing atmosphere.

Hereinafter, the present invention will be described in detail.

A major feature of the present invention resides in the use of a Lu compound or one or more compounds of a Lu compound and a Group 3a element of the periodic table other than Lu as a sintering aid. In the sintered body of the present invention, Lu alone or a combination of Lu and a Group 3a element of the periodic table other than Lu can be used as a Group 3a element of the periodic table. In this case, the periodic table 3a containing at least Lu in the sintered body
The group element is contained at a ratio of 0.3 to 2.5 mol%, particularly 0.5 to 2.0 mol% in the total amount in terms of oxide. Yttrium, erbium, and ytterbium are preferable as other group 3a elements of the periodic table to be combined with Lu in terms of thermal conductivity.

If the content is less than 0.3 mol%, densification cannot be achieved, and if it exceeds 2.5 mol%, the volume ratio of the grain boundaries containing the Group 3a element compound in the periodic table increases. Thermal conductivity will be reduced. When Lu is combined with another Group 3a element of the periodic table, L
It is necessary to control the composition so that u does not become less than 0.3 mol% in terms of oxide.

The sintered body of the present invention contains impurity oxygen. This impurity oxygen is the remaining oxygen obtained by subtracting the amount of oxygen in the compound added as a sintering aid from the total amount of oxygen in the sintered body, and includes, for example, impurity oxygen in the aluminum nitride raw material powder. . According to the present invention,
Oxide equivalent of Group 3a element (RE) (RE ₂₎
O ₃₎ It is important that the molar ratio to alumina in terms of the impurity oxygen _{(Al 2 O 3) (RE} 2 O 3 / Al 2 O 3) is 1 or more. This is because if the above ratio is smaller than 1, the thermal conductivity will decrease.

[0015] In the grain boundary phase of the sintered body, an alumina of a Group 3a element (RE) of the periodic table generated during firing is present. As such an aluminum alloy, RE ₃ Al ₅
O ₁₂ , REAlO ₃ or RE ₄ Al ₂ O ₉ are known. Among them, in particular, RE ₃ Al ₅ O ₁₂ has a low thermal conductivity and, if present at the grain boundary, lowers the thermal conductivity of the sintered body. Therefore, in the sintered body of the present invention, it is desirable that REAlO ₃ or RE ₄ Al ₂ O ₉ is the main phase as the crystal phase of the grain boundary phase. Such control of the crystal phase can be controlled by the above-mentioned molar ratio (RE ₂ O ₃ / Al ₂ O ₃ ),
By controlling the molar ratio to a value exceeding 0.6, the above crystal phase can be used as the main phase.

According to the present invention, in addition to the above components, alkaline earth elements such as Ca, Sr, and Ba are added to the sintered body in an amount of 0.001 to 5 in terms of oxide for the purpose of improving sinterability. % Of the periodic table 4a, 5a, 6a, and 8 of Ti, Zr, V, Nb, Ta, W, Mo, Co, etc. for the purpose of containing them in a weight percent or blackening the sintered body. Compound was added to 0.
It may be contained at a ratio of 1 to 10% by weight.

Next, a method for producing the aluminum nitride sintered body of the present invention will be described. First, an aluminum nitride powder and a Group 3a element compound of the periodic table are prepared as starting materials. As the used aluminum nitride powder,
Powders manufactured by a known method such as a direct nitridation method and an alumina reduction method can be used. In particular, the oxygen content is 0.4 to 1.5% by weight, and the cationic impurities excluding aluminum are 0.1% by weight.
Hereinafter, it is desirable that the carbon content be 1000 ppm or less and the ratio of the fluorescent X-ray intensity of sulfur and aluminum in the powder be 10 ^-3 or less (not including 0).

As the sintering aid, a Lu compound or one or more compounds of a Lu compound and a Group 3a element of the periodic table other than Lu may be added in an amount of 0% in terms of an oxide of a Group 3a element of the periodic table. 0.3 to 2.5 mol%, especially 0.5 to 2 mol%. However, Lu is 0.3 mol% in oxide conversion.
Including the above. As these sintering aids, use is made of simple metals or oxides, carbonates or oxalates which are converted into oxides by firing. In addition, the total amount of oxide (RE ₂ O ₃ ) in terms of oxide of Group 3a element (RE) in the periodic table and RE ₂ O ₃ / A in terms of alumina (Al ₂ O ₃ ) of impurity oxygen are used.
The components are mixed and mixed so that the molar ratio represented by l ₂ O ₃ becomes 1 or more.

The low-temperature sinterability can be enhanced by adding an alkaline earth compound such as CaO, SrO, or BaO at a ratio of 0.001 to 5% by weight in terms of oxide. Also,
TiO ₂ , ZrO ₂ , V ₂ O ₅ , Nb ₂ O ₅ , Ta ₂ O
₅ , periodic table 4a such as WO ₃ , MoO ₃ , CoO,
Blackening can also be achieved by adding a Group 5a, 6a, or Group 8 compound at a ratio of 0.1 to 10% by weight.

The mixed powder thus obtained is formed into a desired shape by a known molding method, for example, doctor blade, press molding, extrusion molding, etc., and the obtained molded body is then subjected to a known firing method. , Normal pressure firing, nitrogen gas pressure firing,
It can be densified by hot pressing. Furthermore, by performing treatment by hot isostatic pressing (HIP) after the firing, densification can be increased, and the thermal conductivity can be further increased. Specific firing conditions are as follows: 1600 ° C. in a non-oxidizing atmosphere such as nitrogen.
Bake at ~ 2000 ° C.

[0021]

The thermal conductivity of an aluminum nitride sintered body is determined by the distance between two crystal faces and the thermal conductivity of the crystal in the grain boundary phase. According to the present invention, Lu has the smallest ionic radius as compared with yttrium and other group 3a elements of the periodic table in the group 3a elements of the periodic table, so that the distance between the two planes between the aluminum nitride crystals is reduced. Can be smaller. Therefore, the scattering of phonons between the two surfaces of the grain boundaries can be reduced, so that the thermal conductivity of the sintered body in which the auxiliary agent remains can be increased. Also,
The binding energy between Lu and oxygen or nitrogen in the Lu compound is large, the vapor pressure is low, and it is difficult to decompose even at a high temperature. Therefore, the surface roughness during firing can be reduced. Therefore, the effect is not reduced even if another element of Group 3a of the periodic table is added at the same time.

Furthermore, the molar ratio (RE ₂ O ₃ / Al ₂ O ₃ ) of the oxide equivalent of group 3a element of the periodic table (RE ₂ O ₃ ) to the Al ₂ O ₃ equivalent of the impurity oxygen is 1 By controlling as described above, the precipitation of RE ₃ A ₁₅ O ₁₂ crystal which lowers the thermal conductivity is suppressed, and by depositing REAlO ₃ (perovskite structure) or RE ₄ Al ₂ O ₉ (melilite structure) as a main phase. High thermal conductivity can be achieved.

[0023]

EXAMPLES Example 1 Oxygen content 0.9% by weight, carbon content 0.05% by weight,
0.1% by weight of cationic impurities except aluminum
Hereinafter, a predetermined amount of aluminum nitride raw material powder having a sulfur content of 5 × 10 ⁻⁴ (fluorescent X-ray intensity ratio to Al) and various rare earth oxide powders were weighed and mixed so as to have the values shown in Table 1, respectively. Some calcium carbonate powder was also added.
In addition, alumina was partially added for adjusting the amount of oxygen. Next, a tape of this mixed composition was formed by a doctor blade method. After degreased, the tape was baked at a predetermined temperature in a nitrogen-containing atmosphere.

The main phase of the grain boundary phase in the obtained sintered body was identified by X-ray diffraction. The thermal conductivity was measured by a laser flash method. Table 2 shows the obtained results.

For the composition of the sintered body, the sample was pulverized, the amount of oxygen was determined by infrared absorption method, the amount of nitrogen was measured by thermal conductivity, and the metal elements of Al and additives were measured by ICP emission spectroscopy. The change from the composition of the compact was small.

[0026]

[Table 1]

[0027]

[Table 2]

According to the results of Tables 1 and 2, Samples Nos. 1 to 3 to which an oxide of another Group 3a element of the Periodic Table containing no Lu element alone were added, and a value calculated as an oxide of a rare earth element. Samples Nos. 11 and 12 having a total content of 0.3 mol% or less, a rare earth element-equivalent total amount of oxide and a molar ratio of impurity oxygen equivalent to alumina of 1 or less, and a grain boundary phase of RE ₃ Al ₅ O ₁₂ Samples Nos. 17 and 18 crystallized in the form of No. 2 and Sample No. 2 in which the total amount of rare earth elements in terms of oxide exceeds 2.5 mol%.
The thermal conductivity of each of Nos. 1 and 22 was reduced. On the other hand, all of the present invention had excellent properties with a thermal conductivity of 182 W / m · K or more.

[0029]

As described in detail above, the aluminum nitride sintered body of the present invention does not need to volatilize the auxiliary agent, and has a high thermal conductivity even if the sintered body has the auxiliary agent remaining. In particular, it is useful as an insulating substrate material on which electronic components and semiconductor elements are mounted, and as various members requiring various high thermal conductivity.

Claims (3)

(57) [Claims] 1. An aluminum nitride crystal phase having a main phase,
u or a combination of Lu and one or more elements of Group 3a of the periodic table other than Lu, and a sintered body containing impurity oxygen, wherein the Group 3a element of the periodic table is converted to oxide. At a rate of 0.3 to 2.5 mol% (provided that L
u is contained in an amount of 0.3 mol% or more in terms of oxide) , and the oxide equivalent amount (RE) of the Group 3a element (RE) in the periodic table.
₂ O ₃₎ wherein the molar ratio in terms of Al ₂ O ₃ amount of impurity oxygen _{(RE 2 O 3 / Al 2} O 3) is 1 or higher aluminum nitride sintered body, characterized in that the. 2. The main crystal phase of the grain boundary of the sintered body is RE ₄ Al ₂
O ₉ or consists REAlO ₃ claim 1 aluminum nitride sintered body according. 3. A composition comprising aluminum nitride as a main component, a Lu compound, or a combination of a Lu compound with one or more compounds of Group 3a elements of the periodic table other than Lu.
0.3 as a total of oxides of the Group 3a element of the periodic table.
~ 2.5 mol% (However, 0.3 mol of Lu is calculated as oxide.)
% Or more , and Al ₂ O ₃ in terms of an oxide equivalent (RE ₂ O ₃ ) of Group 3a element (RE) of the periodic table (RE ₂ O ₃ / A).
A method for producing an aluminum nitride-based sintered body, characterized in that a molded body prepared so that the molar ratio represented by l ₂ O ₃ is 1 or more is fired in a non-oxidizing atmosphere.