JPH0660059B2 - Aluminum nitride sintered body and manufacturing method thereof - Google Patents

Description

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

Prior Art and its Problems Conventionally, alumina sintered bodies have been used as insulating substrate materials for integrated circuits. However, since the alumina substrate has a poor thermal conductivity and a large thermal expansion coefficient as compared with silicon, it has many drawbacks such as poor adhesion to a large silicon chip.

On the other hand, when beryllium oxide is used, the thermal conductivity is 10 times or more that of alumina, but this material is toxic and expensive, which makes it difficult to supply.

Moreover, although a SiC substrate has also been developed, since hot pressing is used during sintering, it is disadvantageous in terms of cost, has a large dielectric constant, and originally has a low dielectric strength because SiC is a semiconductor. I have a problem.

Therefore, attention has been paid to an AlN sintered body using aluminum nitride (AlN) having high thermal conductivity and high resistance. This has the advantage that the coefficient of thermal expansion is close to that of silicon and the dielectric constant is small.

However, to take full advantage of these advantages, AlN
It is required that the sintered body be dense and have a low oxygen content.

However, since the sinterability is not good when AlN powder having a low oxygen content alone is used, it becomes necessary to use a sintering aid.

So far, several proposals have been made for this sintering aid.

For example, AlN powder with aluminum oxide (Al ₂ O ₃ )
And yttria (Y ₂ O ₃ ) are added and pressureless sintering or hot pressing is performed. Calcium oxide (CaO), barium oxide (BaO), and strontium oxide (SrO) are added to AlN powder and pressureless firing is performed. Binding method (JP-A-48-74166), boron nitride (BN) added to AlN powder, and pressureless sintering or hot pressing in a non-oxidizing atmosphere (JP-A-58-32073), A method in which a mixed powder containing at least one powder selected from compounds containing CaO, BaO, and SrO is added to Al powder and hot-pressed in a non-oxidizing atmosphere (JP-A-59-50077), etc. Is mentioned.

Among these, the method of adding an oxide is insufficient in terms of thermal conductivity.

On the other hand, the method of adding BN is said to give an AlN sintered body having a higher thermal conductivity than other methods, and is also superior in terms of denseness.

However, in any of the conventional AlN sintered bodies produced as described above, burning unevenness is likely to occur and a white pattern on the surface is observable with the naked eye, and due to burning unevenness, the electrical resistivity (volume resistivity) is There are many variations in the values.

Therefore, in order to improve such a point, development of an AlN sintered body using a new sintering aid is desired.

II Object of the invention The object of the present invention is that there is no burning unevenness, and that it is dense, has high thermal conductivity and electrical resistance, has suitable performance as a substrate material for electrical insulation, and is easy to form and sinter and is inexpensive. Another object of the present invention is to provide an aluminum nitride sintered body and a manufacturing method thereof.

III Disclosure of the Invention Such an object is achieved by the following first to fourth inventions.

That is, the first invention is that aluminum nitride is provided with one or more of hydrides of calcium, barium and strontium as a sintering aid,
It is an aluminum nitride sintered body, which is obtained by adding 0.01 to 10% by weight to the aluminum nitride and firing.

Further, the second invention is that one or more kinds of rare earth metal hydrides and nitrides are added to aluminum nitride as a sintering aid in an amount of 0.01 to 3% by weight with respect to the aluminum nitride. An aluminum nitride sintered body characterized by being fired.

In addition, a third aspect of the present invention is that, in addition to the aluminum nitride powder, one or more powders of hydrides of calcium, barium and strontium are added to the aluminum nitride powder in an amount of 0.0% or less.
The method for producing an aluminum nitride sintered body is characterized in that 1 to 10% by weight is added and mixed, followed by molding and firing in a non-oxidizing atmosphere.

Further, a fourth invention is that, in the aluminum nitride powder, one or more powders of a hydride and a nitride of a rare earth metal are added as a sintering aid in an amount of 0.01 to 3% by weight based on the aluminum nitride powder. A method for manufacturing an aluminum nitride sintered body, which comprises adding and mixing, followed by molding and firing in a non-oxidizing atmosphere.

IV Specific Structure of the Invention Hereinafter, the specific structure of the present invention will be described in detail.

In the aluminum nitride sintered body of the present invention, the following is added as a sintering aid to aluminum nitride (AlN) powder.

That is, Ca, Sr, Ba hydrides such as CaH
₂ , BaH ₂ , SrH _2, etc .; hydrides of rare earth metals (Sc, Y, La to Lu), for example YH ₂ to ₃ , La _{2 to} 3, CeH ₂ to ₃ , PrH.
₂ to ₃ , NdH ₂ to ₃ , SmH ₂ to _3, etc .; a rare earth metal nitride, for example, YN, LaN, CeN, P.
rN, NdN, SmN, etc.

In addition, as a material similar to the sintering aid of the present invention, MgH
₂ , Mg ₃ N _{2 and the} like, but these do not realize the effect of the present invention.

The AlN powder is preferably pulverized, and the average particle diameter is preferably 0.1 to 10 μm, particularly preferably 0.5 to 6 μm.

The average particle diameter of the sintering aid is preferably 0.1 to 44 μm, particularly 1 to 30 μm in the case of Ca, Ba, Sr or a rare earth metal, and a hydride or nitride of those metals. Is particularly preferably 0.5 to 20 μm.

Of these sintering aids, the amount of Ca, Ba, Sr hydride added is 0.01 to 10% by weight, particularly 0.01 to 3% by weight, and further 1% to AlN. ~ 3
It is preferably in the weight%.

The amount of rare earth hydride or nitride added is 0.01 to 3% by weight, and particularly preferably 1 to 3% by weight, based on AlN.

This is because if the addition amount is too small or too large, a dense sintered body cannot be obtained especially by firing under normal pressure.

In this case, JP-A-60-1809, which is the prior application of this application,
No. 65 discloses yttrium, yttrium hydride,
The use of yttrium nitride is disclosed.

In this proposal, the lower limit of the amount used is the F point of FIG. 2, and 6.2% by weight of YA10 ₃ may be contained in the sintered body.

On the other hand, in the present invention, the upper limit of these charges is limited to 3% by weight, so that even if Y is used as a metal, YA in the sintered body is
The maximum amount of 10 ₃ is 5.5% by weight, which is a clear difference between the present invention and the proposal of the above publication.

Unlike conventional sintering aids such as alkaline earth metal oxides and yttria, these sintering aids do not contain oxygen, and impurities such as oxygen that inhibit thermal conductivity are generated. Considered difficult.

The AlN sintered body is usually obtained by adding and mixing the above-mentioned sintering aid powder to AlN powder, press-molding at room temperature, and sintering this molded body by the atmospheric pressure sintering method in a non-oxidizing atmosphere. It can be left to cool.

However, when a metal is used as the sintering aid, it is difficult to handle, and it is preferable to add and mix it in a non-oxidizing atmosphere using an inert gas such as N ₂ or Ar.

The pressure at the time of pressure molding is about 500 to 2000 kg / cm ² .

The non-oxidizing atmosphere at the time of sintering may be an inert gas such as N ₂ , Ar, or He, H ₂ , CO, various hydrocarbons, or the like, or an atmosphere in which these are mixed, and further various such as vacuum. .

The non-oxidizing atmosphere is used to prevent the surface of the pulverized AlN from being oxidized.

In this case, the non-oxidizing atmosphere is preferably one containing nitrogen, and with 50% or more of nitrogen, Ar, He may be added as necessary.
Inert gas or the like may be mixed.

The atmospheric pressure may be atmospheric pressure, and is usually in a nitrogen stream.

The temperature during sintering is 1600 to 1900 ° C, preferably 17
50 to 1800 ° C is effective.

If the temperature is lower than 1600 ° C, it will not be sufficiently densified even if it is fired for a long time, and if it is higher than 1900 ° C, AlN
When the temperature is higher than 1800 ° C., the oxygen contained is likely to form a solid solution in AlN, which causes phonon scattering.
That is, it causes a decrease in thermal conductivity.

The sintering time is usually 0.5 to 2 hours, especially 175
At 0 ° C., it is preferably about 1 hour.

At the time of sintering, a hot press method may be used by applying a pressure of about 100 to 300 kg / cm ² .

The AlN sintered body thus obtained has no burning unevenness, has a density of 90% or more of the theoretical density of AlN at room temperature, and has an electrical resistivity of 10 ¹² Ωcm or more and a thermal conductivity at room temperature. 80 W / mk or more. The coefficient of thermal expansion is 5 × 10.
It is about ^-6 .

The electric resistivity is 10 to 20% in the conventional AlN sintered body.
However, in the case of the present invention, since there is no unevenness in baking, only a variation of about 1% occurs.

According to the present invention, one or more of Ca, Ba, Sr and rare earth metal hydrides and rare earth metal nitrides are used as sintering aids, and a predetermined amount thereof is used. The aluminum nitride powder is added to and mixed with the aluminum nitride powder to obtain a molded body, and the molded body is fired in a non-oxidizing atmosphere, so that an aluminum nitride sintered body having no burning unevenness can be obtained.

In addition, since it is dense, has high thermal conductivity and electrical insulation, and has no baking unevenness, it has good adhesiveness and there is no variation in the value of electrical resistivity. It has suitable performance as a material for the substrate. Moreover, since the atmospheric pressure sintering method is applied for the sintering method, it is easy and cost effective.

VI Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown to explain the effects of the present invention in more detail.

Example An AlN powder having an average particle size of 3 μm has an average particle size of 10 μm.
2% by weight of the sintering aid powder shown in Table 1 of m was added and mixed. Next, this mixture was applied with a pressure of about 1000 kg / cm ² at room temperature to obtain a molded body.

Then, the molded body was heated to 1750 ° C. in an N ₂ gas flow,
After holding at 1750 ° C. for 1 hour, it was allowed to cool.

Thus, the AlN sintered body shown in Table 1 (Samples 101 to 101)
104 and 110).

Also, for comparison, calcium carbonate (Ca
CO ₃ ) was used, and the samples were prepared in the same manner as Samples 101 to 104, except that CO ₃ ) was used in 0.1% by weight, 0.5% by weight, and 1.0% by weight with respect to the AlN powder. Sample 201, sample 202, and sample 203 are provided in this order.

Samples 101 to 10 except that yttria (Y ₂ O ₃ ) was used as the sintering aid and 1.0 wt% was added to the AlN powder.
A sample 301 is prepared in the same manner as in No. 4.

In addition, sample 4 was prepared by adding 3% by weight of BN to AlN.
01.

The above samples 101 to 104, 110, 201 to 203,
The properties for 301 and 401 are shown in Table 1.

The characteristics are measured as follows.

(1) Density and relative density The measured density and its relative value to the theoretical density were obtained.

(2) Electric resistivity and its variation: A sample of 30mmφ, 2mm thick is baked with Ag paste on the front and back to form electrodes, and 10 samples are measured at 23 ° C and 50% relative humidity. The range with the value was calculated.

(3) Thermal conductivity The sample of (2) was measured at room temperature without the silver paste.

(4) Area of baking unevenness The area of baking unevenness precipitated in white was calculated.

From Table 1, the AlN sintered body of the present invention has less firing unevenness,
As a result, it can be seen that there is little variation in the value of electric resistivity. In addition, the denseness, the thermal conductivity, and the electrical resistance are good, and it can be seen that it has suitable performance as an electrically insulating substrate material. Samples 201 and 401 had low densities and did not exhibit practically satisfactory characteristics.

From the above, the effect of the present invention is clear.

When the AlN sintered body of the present invention was applied to an electrically insulating substrate of a semiconductor power module, it showed good resistance to heat cycles. Further, the same effect as in Table 1 was obtained even when other metals or compounds of the present invention or the additive composite of the present invention were added.

However, the effect of the present invention was not obtained with Mg or its hydride or nitride.

Claims (6)

[Claims] 1. An aluminum nitride containing, as a sintering aid, at least one of hydrides of calcium, barium and strontium in an amount of 0.01 to 0.01% with respect to the aluminum nitride.
An aluminum nitride sintered body, which is obtained by adding 10% by weight and firing. 2. Aluminum nitride containing, as a sintering aid, at least one of rare earth metal hydrides and nitrides,
An aluminum nitride sintered body, which is obtained by adding 0.01 to 3% by weight to said aluminum nitride and firing. 3. One or more powders of hydrides of calcium, barium and strontium as a sintering aid are added to aluminum nitride powder in an amount of 0.01 to 10% by weight based on the aluminum nitride powder and mixed. After that, the method for producing an aluminum nitride sintered body is characterized by performing molding and firing in a non-oxidizing atmosphere. 4. The method for producing an aluminum nitride sintered body according to claim 3, wherein the non-oxidizing atmosphere contains nitrogen. 5. An aluminum nitride powder containing, as a sintering aid, at least one powder selected from a hydride and a nitride of a rare earth metal, with respect to the aluminum nitride powder.
A method for producing an aluminum nitride sintered body, which comprises adding 1 to 3% by weight and mixing, and then performing molding and firing in a non-oxidizing atmosphere. 6. The method for producing an aluminum nitride sintered body according to claim 5, wherein the non-oxidizing atmosphere contains nitrogen.