JPH06172038A - Aluminum nitride sintered compact - Google Patents

Abstract

PURPOSE:To provide an aluminum nitride sintered compact capable of firmly joining a metallic layer formed by metallizing treatment to an aluminum nitride sintered compact. CONSTITUTION:This aluminum nitride sintered compact has a grain boundary phase consisting essentially of 3Y2O3.5Al2O3 compound and a 2Y2O3.Al2O3 at >=0.60 to <=0.95 component ratio (C) (atomic ratio) of the grain boundary phase when the ratio 3Y2O3.5Al2O3/(3Y2O3.5Al2O3+2Y2O3.Al2O3) is assumed as the (C). The aluminum nitride sintered compact preferably has <=15% area ratio of the grain boundary phase occupying the sintered compact surface.

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 which is subjected to a so-called metallizing treatment for forming a metal film on its surface.

[0002]

2. Description of the Related Art In recent years, the density and integration of semiconductors have been rapidly increasing, and along with this, the amount of heat generated from the semiconductor tends to significantly increase. Therefore, how to dissipate the generated heat is an important issue. Conventionally, a beryllia (BeO) sintered body has been used for such an application, but the application is limited because it is toxic. Instead, an aluminum nitride sintered body, which has a thermal conductivity of 7 times or more that of alumina (Al ₂ O ₃ ) and a thermal expansion coefficient close to that of silicon, is attracting attention as a substrate and a package for heat dissipation. Since aluminum nitride is a covalent bond substance, it is difficult to sinter as it is, and a sintered body can be obtained by adding a sintering aid such as rare earth. This sintering aid plays a role of accelerating the sintering by reacting with alumina or the like existing on the surface of the aluminum nitride particles to form a liquid phase.

When the aluminum nitride sintered body is used for a substrate or a package, it is necessary to bond the aluminum nitride sintered bodies to each other or to other ceramics or metal. The aluminum nitride sintered body is hard to be wet with a metal, and a metallizing treatment for forming a metal layer on the surface of the aluminum nitride sintered body is performed in advance, and the aluminum nitride sintered body is joined by soldering or the like. For the metallizing treatment at this time, a physical vapor deposition method such as ion plating or sputtering is often used. In addition, a metallizing treatment is often performed to form a metal layer which becomes a conductive path on the surface of the aluminum nitride sintered body. For the metallizing treatment at this time, powder of refractory metal such as Mo and W is mainly added.
Conductor paste to which various inorganic compounds and organic compounds are added is screen-printed on the sintered body to form a pattern,
A thick film method of forming a metal layer by firing this and a thin film method of forming a metal layer by forming a thin film on a sintered body using ion plating, sputtering, etc. are often used. .

[0004]

The surface of the aluminum nitride sintered body which is subjected to the above-mentioned metallizing treatment must be of such a quality that the metal layers to be formed can be joined with sufficient strength.
The surface condition of the aluminum nitride sintered body is the atmosphere during sintering,
Due to the influence of the sintering temperature and the like, a phenomenon occurs in which the liquid phase oozes out on the surface of the sintered body and the sintering aid volatilizes from the surface. As an attempt to obtain a surface of an aluminum nitride sintered body which can obtain a high bonding strength with a metal phase, JP-A-2-9
No. 766, in which the grain boundary phase in the substrate is unevenly distributed on the surface of the substrate; A method has been proposed in which the concentration of the phase component is 3% by weight or less.

Further, as described above, in the sintering process for obtaining the aluminum nitride sintered body, the liquid phase oozes out from the grain boundaries, so that a striped pattern is generated on the surface of the sintered body, and the appearance is deteriorated. May be defective. The nonuniformity of color tone such as a striped pattern causes local nonuniformity of physical properties such as thermal conductivity, specific resistance and dielectric constant. As an aluminum nitride sintered body which has solved the appearance defect and the local nonuniformity of the physical properties due to the generation of such a striped pattern, there is disclosed in
In No. 204367, the temperature decreasing rate at the time of sintering is adjusted so that the grain boundary layer between the aluminum nitride particles is a garnet-type oxide (Y ₂ O ₃ is a sintering additive containing a sintering additive as a main component). in the case of _{3Y 2 O 3 · 5Al 2 O} 3, (3: 5)) and the perovskite oxide (Y ₂ when O ₃ is sintering aid _{Y 2 O 3 · Al 2 O} 3, ( It is disclosed that the color tone and the physical properties are made uniform by using a sintered body composed of a mixture of approximately the same amount of 1: 1)).

However, the optimum properties of the grain boundary phase for obtaining high bonding strength have not been specified so far. Especially 3
When using the surface of a sintered body without processing it in three-dimensionally shaped parts, or when the processing amount is small due to processing costs etc., identify the grain boundary phase that has a great influence on the surface properties. Doing is extremely important. The present invention is to provide an aluminum nitride sintered body capable of firmly joining a metal layer formed by a metallizing treatment and an aluminum nitride sintered body.

[0007]

The inventors of the present invention have found that an aluminum nitride sintered body having a high bonding strength is obtained from the relationship between the kind and the amount of the compound forming the grain boundary phase and the bonding strength of the metal layer formed by the metallizing treatment. I came to find out. That is, the present invention provides a 3Y ₂ O ₃ .5Al ₂ O ₃ compound and a 2Y ₂ O ₃ .multidot.
It has a grain boundary phase mainly composed of an Al ₂ O ₃ compound, and the grain boundary phase is 3Y ₂ O ₃ .5Al ₂ O ₃ / (3Y ₂ O ₃ .5Al ₂ O ₃ + 2Y
₂ O ₃ · Al ₂ O ₃ ) = C, the composition ratio C (atomic ratio) is 0.60 or more, 0.
It is 95 or less, preferably the area ratio of the grain boundary phase occupying on the surface of the sintered body is 15% or less, and the aluminum nitride sintered body is characterized.

[0008]

[Act as the sintered aluminum nitride sintered body of yttria sintering aid additive amount, depending on the heating and cooling conditions during _{sintering, 2Y 2 O 3 · Al 2} O 3, 3Y 2 O 3・ 5A
_{l 2 O 3, Y 2 O} 3 · Al 2 O 3 such as Y ₂ O ₃ -Al ₂ O ₃ compound is produced as a grain boundary phase. (Ceramics, vo
l. 26, (1991), 731. See) By changing the amount of yttria added and further changing the sintering temperature, various aluminum nitride sintered bodies having different kinds and amounts of compound phases can be obtained. It has been found that when the grain boundary phase is set in the above range of the composition ratio C, extremely high bonding strength can be obtained between the metallized layer and the sintered body. In the present invention, 3Y ₂ O ₃ .5Al ₂ O ₃ and 2Y
_The main phase of ₂ O ₃ · Al ₂ O ₃ is that the amount of crystal phase is large and the bonding strength is reduced in other cases. In the present invention, the composition ratio C is set to 0.60-0.95,
This is because if the composition ratio is out of this range, the bonding strength between the metallized layer and the sintered body will be reduced. If the amount of the grain boundary phase exuded to the surface is too large, the bonding strength will decrease. Therefore, the grain boundary phase occupying the surface of the sintered body is preferably 15% or less in area ratio.

The aluminum nitride sintered body of the present invention contains 3 to 10 wt% of yttria powder in the aluminum nitride raw material powder.
%, According to the molding method, a binder, a dispersant, a lubricant, a solvent, etc. are added, and mixed by a ball mill or the like. After drying and granulating with a spray dryer, etc., it is used for molding. After the molding, heating is performed up to 1000 ° C. to remove the binder and the like in the molded body, and then sintering is performed. Sintering is performed in a non-oxidizing atmosphere, usually in a nitrogen atmosphere, 1
Perform at 700 to 2000 ° C. for 1 hour or more. If the sintering temperature is too high, aluminum nitride particles will grow and the strength of the sintered body will be significantly reduced.If the sintering temperature is too low, the liquid phase will be insufficiently formed or will not be formed, and sintering will proceed. First, do not densify. The composition of the grain boundary phase in the obtained sintered body largely depends on the production conditions such as the raw material powder composition, the binder removal conditions, and the sintering conditions. Therefore, the production method is not particularly specified in the present invention.

As a method of metallizing the sintered body of the present invention, a conductor paste prepared by adding various inorganic compounds and organic compounds to powder of refractory metal such as Mo and W is screened on the sintered body. A thick film method of forming a conductor layer by printing, forming a pattern, and baking the pattern, and forming a thin film on a sintered body by using ion plating, sputtering, etc., form a conductor layer. Any method such as a thin film method can be used.

The grain boundary phase of the sintered body of the present invention can be specified by an X-ray diffraction method. In addition, 3Y ₂ O ₃ · 5A
surface (211) for l ₂ O _3, d = 2.62 Å peak height of the peak, for _{2Y 2 O 3 · Al 2 O} 3 (22-1) plane, d = 3.01 Å peak The compositional ratio C can be determined from the ratio of the peak heights.

[0012]

【Example】

(Example 1) Aluminum nitride powder having an oxygen content of 1.0% was used as a raw material powder, and 5 wt% of Y ₂ O ₃ was added,
After adding an organic solvent, an organic binder, and a lubricant, mixing and pulverizing with a ball mill, granulation was performed with a spray dryer to obtain an aluminum nitride granulated powder. These powders were mold-molded to obtain a molded body. 40 these molded bodies
After degreasing at 0-800 ° C, 1750-1830 ° C,
Sintering was performed in nitrogen at atmospheric pressure to obtain sintered bodies having various surface states shown in Table 1. The resulting sintered body _{3Y 2 O 3 · 5Al 2 O} 3 and _{2Y 2 O 3 · Al 2 O} 3 other than phase phase was not detected by X-ray diffraction analysis, these phases in which the main phase is there.

From the results of X-ray diffraction analysis, it was confirmed that Y ₂ O ₃ .5Al
The composition ratio C of the ₂ O ₃ phase and the 2Y ₂ O ₃ .Al ₂ O ₃ phase was determined. The area ratio of the grain boundary phase occupied on the surface of the sintered body was obtained by image analysis. After that, in order to further increase the bonding strength between the metallized layer and the sintered body, the surface area of some of the samples was removed at the grinding depth shown in Table 1 by changing the processing amount of the sample. . The obtained sample was coated with a paste containing Mo as a main component and then baked at 1700 ° C. to prepare a metallized substrate having a Mo layer with a thickness of 30 μm. After plating 0.5 μm of Ni and 0.5 μm of Au on these metallized substrates in this order, the metallized substrate was cut to a size of 5 mm × 5 mm, and Kovar pins were soldered to the metallized peel strength test pieces. The bonding strength was measured from the strength required for peeling. The results are shown in Table 1.

[0014]

[Table 1]

As shown in Table 1, when the composition ratio C of the grain boundary phase of the present invention is 0.60 to 0.95, even if the surface is not ground (grinding amount = 0), 8 kgf / mm ² It can be seen that the above high bonding strength can be obtained. Further, since the sintered body of the present invention can obtain the maximum bonding strength by grinding about 2 μm, it is understood that it is not necessary to secure the bonding strength by a large amount of grinding as in the comparative example.

(Embodiment 2) Using a sintered body similar to that of Embodiment 1, the surface was machined by changing the grinding depth, and then a thin film of Ti 0.5 μm and Ni 0.5 μm was sequentially formed by ion plating. Formed, Ni 1.0 μm, Au 0.5 μ
m plating was performed. The bonding strength of the metallized layer was measured on this metallized substrate in the same manner as in Example 1. The results are shown in Table 2.
Shown in.

[0017]

[Table 2]

As shown in Table 2, even if the surface of the sintered body of the present invention having a composition ratio C of the grain boundary phase of 0.60 to 0.95 is not ground (grinding amount = 0), It can be seen that a bonding strength of 6.5 kgf / mm ² or higher, which is higher than that of the comparative example, can be obtained. Further, the sintered body of the present invention can obtain the maximum bonding strength by grinding about 2 μm as in Example 1, so that it is not necessary to secure the bonding strength by a large amount of grinding as in the comparative example.

[0019]

According to the present invention, by defining the composition of the grain boundary phase of the aluminum nitride sintered body, a metallized phase, which is essential when joining aluminum nitride to other members, is formed with high bonding strength. Therefore, it is extremely useful for applications in which airtightness and bonding strength with other members are required.

Claims (2)

[Claims] 1. A 3Y ₂ O ₃ .5Al ₂ O ₃ compound and 2Y ₂ O ₃
-Has a grain boundary phase mainly composed of an Al ₂ O ₃ compound, and the grain boundary phase is 3Y ₂ O ₃ .5Al ₂ O ₃ / (3Y ₂ O ₃ .5Al ₂ O ₃ + 2Y
₂ O ₃ · Al ₂ O ₃ ) = C, the composition ratio C (atomic ratio) is 0.60 or more, 0.
An aluminum nitride sintered body characterized by being 95 or less. 2. The area ratio of the grain boundary phase on the surface of the sintered body is 1
It is 5% or less, The aluminum nitride sintered compact of Claim 1 characterized by the above-mentioned.