JP2772581B2 - Black aluminum nitride sintered body - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an aluminum nitride substrate having a high thermal conductivity capable of efficiently removing heat generated from a semiconductor integrated circuit device. The present invention relates to a black aluminum nitride substrate that can be fired at a low temperature and has excellent mass productivity.

(Prior 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 been rapidly becoming denser and more highly integrated. The problem is how to efficiently remove the heat generated to operate the semiconductor integrated circuit device normally.

In recent years, such a substrate has been replaced with an alumina substrate or a beryllium oxide substrate, which is conventionally known as a high thermal conductive substrate. Aluminum nitride-based sintered bodies having high properties, high thermal conductivity, and excellent properties such as a coefficient of thermal expansion closer to that of silicon single crystal as compared with alumina are attracting attention.

Recently, a blackened aluminum nitride-based sintered body has been demanded from the viewpoints of light-shielding properties and dirt being less noticeable.

However, aluminum nitride is inherently difficult to sinter,
Since the high-density sintered body having a high thermal conductivity can not be obtained in plain, periodic table III a group element oxide such as Y ₂ O ₃ as a sintering aid, or the periodic table such as CaO A method of increasing the density by adding a Group IIa element oxide has been adopted.

(Problems to be Solved by the Invention) However, in the conventional method, a high-density aluminum nitride sintered body is obtained at a temperature of 1700 ° C. or more, and sometimes 19
It was necessary to fire at a high temperature of 00 ° C. or higher. When the sintering temperature is high, for example, when sintering is performed simultaneously with the metal conductor pattern formed on the substrate, there is a problem that the bonding strength between the conductor and the substrate is reduced due to the metal conductor grain growth, and The structure of the firing furnace itself also requires heat resistance, so that there is a problem that the cost of production equipment and the like becomes high, and the cost of the substrate itself becomes extremely high.

Therefore, in order to achieve low temperature firing, a method of simultaneously adding a rare earth element oxide and an alkaline earth oxide is described in JP-A-61-117160, but the firing temperature is at most 1700 ° C. At a firing temperature of about 1600 ° C. or lower, densification cannot be achieved, and there is a problem that stains and the like are easily generated in the porcelain.

In addition, with respect to the above aluminum nitride sintered body, for the purpose of increasing the density and the thermal conductivity, the periodic table IVa, Va, V
It has been proposed in JP-A-62-153173 to add at least one member selected from the group consisting of Group Ia, VIIa and VIII elements. However, even in this method, the firing temperature is not sufficiently lowered.

Further, a method of lowering the firing temperature by adding a rare earth element fluoride to aluminum nitride has been proposed in 61-209959.
However, the fluoride itself is very expensive, and is not suitable for mass production because the furnace is corroded due to the volatilization of fluorine oxide during firing.

(Object of the Invention) The object of the present invention is to solve the above-mentioned problems, and specifically, a relative density of 95% or more is achieved even by low-temperature firing at 1600 ° C or less, and 1600 ° C. An object of the present invention is to provide a black aluminum nitride substrate having a high thermal conductivity of at least 80 W / m · K in a fired product.

(Means for Solving the Problems) As a result of repeated studies on the above problems, the present inventors have made an oxide of a Group Ia element of the periodic table an essential component as a sintering aid, In addition, Periodic Table IVa, Va, VIa, VIIa
It has been found that the firing temperature is lowered by simultaneously adding at least one oxide selected from Group VIII and Group VIII elements, and the present invention has been achieved.

That is, the aluminum nitride-based substrate of the present invention is mainly composed of aluminum nitride and contains at least one element selected from Group Ia elements of the periodic table in an amount of 0.001 to 5% by weight in terms of oxide. a, VIa, VIIa, and at least one element selected from the group VIII elements in an amount of 0.01 to 10% by weight in terms of oxides, a relative density of 95% or more, and a thermal conductivity of 80% or more.
It is characterized by being composed of a sintered body of W / m · K or more, and further includes a group IIa of the periodic table and / or
Alternatively, at least one element selected from Group IIIa elements is contained at a ratio of 0.01 to 20% by weight in terms of oxide.

 Hereinafter, the present invention will be described in detail.

A great feature of the sintered body forming the substrate of the present invention is that at least one element selected from Group Ia of the periodic table and Group IVa, Va, VIa, VIIa and VIII of the periodic table. It contains at least one element selected from the elements.

At least one element selected from Group Ia elements of the periodic table contains 0.001 to 5% by weight of oxide in the sintered body,
In particular, it is contained at a ratio of 0.01 to 1% by weight,
It is important that at least one element selected from the group consisting of a, Va, VIa, VIIa and VIII is contained in a proportion of 0.01 to 10% by weight, especially 0.05 to 4% by weight in terms of oxide. is there.

The reason for limiting the amount of such additives to the above range is as follows.
If the content of the group a element is less than 0.001% by weight, the sinterability is greatly reduced and the powder is not densified. If it exceeds 5% by weight, the thermal conductivity is reduced. If the amount of the group IVa, Va, VIa, VIIa, and VIII element is less than 0.01% by weight, the sinterability is deteriorated and the coloring property of the sintered body is reduced. Thermal conductivity is undesirably reduced.

In a more preferred embodiment of the present invention, it is desirable that the above system further contain a Group IIa element and / or a Group IIIa element of the periodic table. In this case, these elements are used in a total amount of 0.1 to 20 in terms of oxide.
When the content is contained in the ratio of weight%, higher density can be realized by low-temperature firing.

According to the present invention, the amount of impurity oxygen in the sintered body containing the sintering aid is 0.1 to 6% by weight, particularly 0.4 to 2.5%.
% By weight. Such an impurity oxygen amount refers to the total oxygen amount in the sintered body, and among the additives, the periodic table Ia, IIa, IIIa, IVa, Va, VIa, VIIa, VIII
It is the amount of oxygen excluding oxygen contained in the oxide of the group III element,
It mainly corresponds to oxygen as an unavoidable impurity in the aluminum nitride raw material powder. This impurity oxygen also greatly contributes to the sinterability of the entire system. If the amount is less than 0.1% by weight, high density by low-temperature sintering cannot be achieved, and 6% by weight.
If it exceeds, the thermal conductivity decreases.

Further, according to the present invention, it is desirable that the average crystal grain size of aluminum nitride in the sintered body is 0.8 μm or more, particularly 1.2 μm or more. The larger the crystal grain size, the higher the thermal conductivity. That is, when the particle size is smaller than 0.8 μm, the volume (area) occupied by the grain boundaries between the crystal grains is large, so that the grain boundaries become obstacles for phonon conduction, and the thermal conductivity is reduced.

Incidentally, as the Group Ia element of the periodic table used in the present invention, Li, Na, K, Rb, as the Group IVa element, Ti,
Zr, Hf, Group Va elements as V, Nb, Ta, Group VIa elements as W, Mo, Cr, Group VIIa elements as Mn,
Group VIII elements include Co, Ni and the like. Also,
Group IIa elements include Ca, Sr, Ba, and Group IIIa elements include Y, Yb, Er and the like.

Next, a method for manufacturing such an aluminum nitride sintered body will be described.

First, the aluminum nitride raw material powder is manufactured by a known method such as a direct nitriding method, an alumina reducing method,
Powders with an average particle size of 3 μm or less, with an impurity oxygen content of 1.5 wt% or less, a carbon content of 0.2 wt% or less, a cationic impurity content of 0.1 wt% or less excluding aluminum, and particularly a Si content and a Fe content of both 100 ppm or less. It is preferably used.

Additive components, in addition to using any of the oxide powders of any of the above-described Group Ia to VIII Group elements in the periodic table, compounds that can be converted to oxides by firing, for example, compounds such as carbonates, chlorides, and hydroxides Can also be added. Also, the Ia
As the group compound, a fluoride or the like can be used.

A mixed powder in which the above-mentioned additive component is blended with the aluminum nitride raw material powder is mixed in an organic solvent if desired. At this time, the amount of water contained in the organic solvent is set to 0.4% by weight or less. Thereby, the dispersibility of the aluminum nitride powder can be improved, and oxidation of the surface of the aluminum nitride particles can be prevented by a reaction with moisture in the inside.

The obtained mixed powder is formed into a desired shape by a known molding method, for example, press molding using a mold or hydrostatic pressure, sheet molding, extrusion molding, or the like, and then fired.

Firing is performed in a non-oxidizing atmosphere containing nitrogen gas, and as the firing means, normal pressure firing, hot press firing, nitrogen gas pressure firing, or the like is employed.
By setting the firing temperature at this time to about 1500 ° C. or more, it is possible to densify to a relative density of 95% or more, and the average crystal grain size of aluminum nitride is slightly larger than that of the primary particles in the raw material.

As the firing temperature is further increased above 1500 ° C, the sinterability improves and the average crystal grain size of aluminum nitride gradually increases.However, when the temperature exceeds 1700 ° C, the heat resistance of the firing furnace is required, so The structure becomes large-scale. Therefore, in consideration of mass productivity, it is preferable that the firing temperature is set to 1700 ° C. or lower, particularly 1650 ° C. or lower, and firing at normal pressure is performed, whereby a continuous furnace or the like can be used.

Further, in consideration of coloring properties, it is possible to reduce each element by adding carbon, carbon monoxide, hydrogen, and the like in the firing atmosphere to enhance the coloring property.

(Action) By allowing the aluminum nitride to contain a Group Ia element of the periodic table and an element of Groups IVa to VIII of the periodic table,
The sinterability of the system can be improved, and the relative density is 95% at 1500 ° C.
The above densification can be achieved. The Periodic Table IVa-VI
In the sintering process, for example, when the group II element is added as an oxide, it is partially reduced by the sintering atmosphere, and an aluminum nitride substrate that develops a black color by being present as a simple metal or a carbide or a nitride is obtained. Can be

Further, by mixing a Group IIa element and / or a Group IIIa element of the periodic table into the system, a Group Ia element and a Group IIa element oxide or a Group IIIa element oxide can be obtained. A low-melting-point composite oxide is formed between them, whereby the low-temperature sinterability is further enhanced, and stable sinterability is obtained.

 Hereinafter, the present invention will be described with reference to the following examples.

(Example 1) As a raw material powder of aluminum nitride, a BET specific surface area of 2.8 m ²
/ g, a content of impurity oxygen of 0.8% by weight, a carbon content of 0.05% by weight or less, and a commercially available aluminum nitride raw material powder having a cationic impurity content of 0.1% by weight or less excluding aluminum as shown in Table 1 The group a elements were added in the form of carbon salts, chlorides and fluorides, and the elements of groups IVa to VIII were all added in the form of oxides. The Group IIa element was added as a carbonate, and the Group IIIa element was added as an oxide. Next, it was press-molded at room temperature under a pressure of 1000 kg / cm ² . The compact was fired at 1500 ° C., 1550 ° C., and 1600 ° C. in nitrogen gas at normal pressure for 3 hours.

For each sample after firing, based on the Archimedes method,
The relative density was calculated, and the thermal conductivity of the fired product at 1600 ° C. was measured by a laser flash method.

 The results are shown in Table 1.

According to the results in Table 1, the aluminum nitride
Sample No. 28 to which only O ₂ was added and Sample Nos. 29 and 30 to which no Group Ia element was added could not be densified to a relative density of 95% or more at a temperature of 1600 ° C. or less. In the case of adding lithium as a group Ia element, the thermal conductivity decreased in the large amount of No. 31 and in the sample No. 32 in which the added amount of the group IVa to VIIIa element was small, Coloring was insufficient. Sample No. 34 having a large amount of Y ₂ O ₃ as a sintering aid
However, a decrease in thermal conductivity was observed.

In contrast to these comparative examples, samples Nos. 1 to 16 in which the Group IVa to Group VIII element compounds were added together with the Group Ia element compounds according to the present invention had a relative density of 95% even at a firing temperature of 1500 ° C. As described above, it was possible to densify and exhibit high thermal conductivity. In addition, II
In Samples Nos. 17 to 27 to which Group a and IIIa elements were added, the sinterability was further stabilized, and the thermal conductivity could be increased.

(Effect of the Invention) As described in detail above, according to the present invention, the periodic table Ia
The sinterability can be improved by containing the elements of Groups IVa to VIII of the periodic table at a specific ratio together with the elements of the periodic table, and further containing the elements of the groups IIa and IIIa, and the sintering temperature can be increased.
Even at a temperature of 1600 ° C. or less, an aluminum nitride substrate made of a sintered body having a relative density of 95% or more and a high thermal conductivity of 80 W / m · K or more can be obtained. As a result, it is possible to use a continuous furnace without requiring a special heat-resistant structure as a sintering furnace when manufacturing a high thermal conductive aluminum nitride sintered body, thereby reducing manufacturing costs and the like. Thus, an inexpensive aluminum nitride substrate can be provided.

Claims (2)

(57) [Claims] 1. The periodic table is mainly composed of aluminum nitride.
At least one element selected from the group Ia elements in oxide terms
0.001 to 5% by weight, Periodic Table IVa, Va, VIa, VIIa
And at least one element selected from the group VIII elements at a ratio of 0.01 to 10% by weight in terms of oxide, and
A black aluminum nitride substrate made of a sintered body having a thermal conductivity of at least 95% and a thermal conductivity of at least 80 W / m · K. 2. The periodic table mainly comprising aluminum nitride.
At least one element selected from the group Ia elements in oxide terms
0.001 to 5% by weight, Periodic Table IVa, Va, VIa, VIIa
And at least one element selected from Group VIII elements in an amount of 0.01 to 10% by weight in terms of oxides,
III A sintered body containing at least one element selected from Group a elements at a ratio of 0.01 to 20% by weight in terms of oxide, each having a relative density of 95% or more and a thermal conductivity of 80 W / m · K or more. A black aluminum nitride substrate characterized by the above-mentioned.