JPH0712993B2 - Aluminum nitride sintered body having metallized surface - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an aluminum nitride sintered body, and more particularly to an aluminum nitride sintered body having a metallized surface with highly reliable and practical bonding strength on the surface. It is about.

2. Description of the Related Art Generally, a semiconductor device or a device or device using them includes various active / passive elements, but these have a problem of heat generation. Therefore, in order to operate these elements and the like stably and reliably, it is necessary to perform the best thermal design at the time of mounting, which is extremely important in the design and manufacture of the semiconductor device and the like.

Further, in recent years, there has been a great trend such as high-speed operation and high integration of semiconductor devices, and particularly in LSI and the like, the degree of integration is remarkably improved. Therefore, the heat dissipation of the substrate material has come to be emphasized.

On the other hand, although alumina has been used as the ceramics for IC substrates in the past, the heat conductivity of conventional alumina sintered bodies is not sufficient to dissipate heat, and it is becoming difficult to cope with the increase in heat generation of IC chips. . Therefore, as a substitute for such an alumina substrate, a substrate or a heat sink using aluminum nitride having a high thermal conductivity has attracted attention, and many studies have been conducted for its practical use.

Since aluminum nitride originally has high thermal conductivity and high insulating properties as a material and is not toxic unlike beryllia, it is regarded as particularly promising as an insulating material or a packaging material in the semiconductor industry.

Since the aluminum nitride (AlN) sintered body has a high thermal conductivity, it has attracted attention as a substrate for integrated circuits (ICs) as described above, or as a heat sink. However, while having such interesting characteristics, the AlN sintered body has a problem in bonding strength with metal or glass. By the way, the metallization layer of this sintered body is directly applied to the surface thereof by using a thick film method in which a commercially available metallizing paste is applied or a thin film method in which a thin film of an active metal or a metal is formed by a method such as vapor deposition. It is generally used in a given state. However, it is not possible to obtain a bonding strength that can withstand practical use by such a method, and in practice, the surface is modified by some method before or during the metallization operation, and another metal such as metal is used. It is necessary to improve the bondability with.

As a conventional method for modifying the surface of such an AlN sintered body, there is known a method of forming an oxide layer by subjecting the surface of the AlN sintered body to oxidation treatment or the like. That is, for example, it is a method of forming an oxide layer of SiO ₂ , Al ₂ O ₃ , mullite, Fe ₂ O ₃ , Cu or the like on the surface of the AlN sintered body. However, the oxide layer as exemplified above has a good affinity for the glass layer, the alumina layer, etc. and causes a strong bond, but the affinity with the AlN sintered body itself is small, and the reliability is high. It is thought that there is a problem with sex.

Problems to be Solved by the Invention As described above, since the electric insulation and the thermal conductivity are extremely good, AlN sintering expected as an IC insulating substrate or heat sink material that requires good heat dissipation is required. The body is
Although its surface is often used after being metallized, there is a problem in terms of bonding strength to these. Therefore, various methods such as the above were considered, but none of them are sufficient.
AlN sinters with a metallized surface of sufficient practicability have not yet been obtained.

That is, good bonding strength could not be obtained by the conventional thick film method of applying the AlN sintered body and the metallizing paste (for example, commercially available frit or chemical bond type). This is because the conductor paste was originally for Al ₂ O ₃ ,
This is because the reactivity with the lN layer is not good.

Further, there is known an oxide treatment on the surface of an AlN sintered body, which is known as a method of performing metallization while or after forming an oxide layer. However, the above SiO ₂ , Al
Oxide layers such as ₂ O ₃ , mullite, Fe ₂ O ₃ and CuO have poor reactivity with AlN. Also, even if a reaction layer is formed, the reaction layer is essentially similar to the oxide layer.
The reactivity with the AlN surface is hardly improved, and therefore the bonding strength with the AlN sintered body is not improved. Further, this oxide treatment also has problems in terms of denseness and film bonding strength. That is, AlN
The surface oxide treatment is represented, for example, by the following formula: Nitrogen gas may be generated along with the reaction, and the obtained oxide film becomes a remarkably porous film.

In addition, it is difficult to expect sufficient bonding strength by the thick film method and the thin film method using an active metal. In other words, this is because even when an active metal highly reactive with nitride is used, AlN is extremely chemically stable, so sufficient bonding strength between them cannot be obtained, and bonding is difficult. It seems to be due to.

As described above, none of the various attempts to make the AlN sintered body and the metallized layer have a practically sufficient bonding strength was satisfactory. Therefore, by setting up a structure that has an affinity for both the metal layer or metal oxide and the AlN sintered body, the bond between them is guaranteed, and the bonding strength between the metallized layer and the AlN sintered body is secured. There is a strong demand for the development of new technology that can improve the above.

Therefore, an object of the present invention is to improve the bonding strength between a metallized layer excellent in insulation and heat dissipation and an AlN sintered body.
That is, it has a highly reliable metallized surface with excellent bonding strength.
It is to provide an AlN sintered body.

Means for Solving the Problems In view of the above-mentioned present situation in the practical application research of the aluminum nitride sintered body as a substrate for IC, etc., the present inventors have made the aluminum nitride sintered body having the above-mentioned metallized surface. As a result of various studies and researches for obtaining a high-concentration layer of the sintering aid of the aluminum nitride sintered body on the surface to be metallized of the aluminum nitride sintered body substrate, the metallized surface It has been found that it is advantageous to form

That is, an aluminum nitride sintered body having a metallized surface according to the present invention is formed on the aluminum nitride sintered body substrate containing a sintering aid made of an oxide of a Group IIIa element of the periodic table, and the substrate. In an aluminum nitride sintered body having a metallized surface provided with a metal layer, the sintering aid is distributed in the substrate so that the concentration becomes higher toward the surface to which the metal layer is attached. Is characterized by.

In the AlN sintered body having the metallized layer of the present invention, it is important that the aluminum nitride sintered body substrate has good thermal conductivity without containing defects such as a large number of pores and impurities. .

In the aluminum nitride (AlN) sintered body having a metallized surface of the present invention, group IIIa elements useful as a high-concentration layer material of the above-mentioned sintering aid include yttrium (Y), cerium (Ce), and cadolinium. (Gd), europium (E
u), samarium (Sm), holonium (Ho) or ytterbium (Yb) may be mentioned as preferred examples. The thickness of the high-concentration auxiliary agent layer is preferably set to a value within the range of 1 to 100 μm.

In order to form the high-concentration sintering aid layer on the surface of this AlN sintered body, the following various methods can be adopted. First, for example, cerium oxide as a sintering aid, 5 to 10 wt% with respect to aluminum nitride powder, and an organic binder are added and then kneaded to produce a green sheet having a thickness of 1 to 10 mm. This sheet is formed into an appropriate size, debindered, and then 30 to 120 in nitrogen at 1700 to 2200 ° C.
Bake for minutes. During firing, the sintering aid cerium oxide reacts with the aluminum nitride powder at a temperature of 1600 ° C. or higher to generate a melt and accelerate sintering. However, while the sample is not fully sintered, it is porous, aid components diffuse through the capillary to the surface, and sintering is complete. As described above, most of the 5 wt% auxiliaries were diffused to the surface, so the concentration of the auxiliaries in the sintered body dropped significantly, and the concentration of the auxiliaries at the depth of 1 to 100 μm from the surface It has increased significantly. The auxiliary component of this diffusion layer is increased to about 20 to 50 wt%. For this reason, the amount of the auxiliary component of the diffusion layer is largely influenced by the thickness of the green sheet and the sintering conditions in addition to the amount of the sintering additive added when producing the green sheet. As a sintering aid, any sintering aid for aluminum nitride other than cerium oxide cannot be used.

A predetermined metallization surface is provided on the high-concentration layer of the sintering aid thus formed. The method of forming the metallized surface, the material used, and the like need not be special, and various conventionally known methods and materials can be used. For example, when the metallized surface is formed of Au, Ag, Pt, Pd, or a mixture thereof, for example, Au, Au
-Pt, Pt, Ag, Ag-Pd and other pastes are coated by screen printing method, and then baked in air, oxygen atmosphere or nitrogen atmosphere at a temperature in the range of about 850 to 940 ° C. It can be formed according to the paste method. Similarly, materials for metallization (metallization) are Mo, Mo-Mu,
The thick film paste method can also be used when Cu or W is used. However, the materials exemplified above are merely examples and do not limit the present invention in any way, and the same applies to the following description.

Further, the metallized surface of the AlN sintered body of the present invention can be realized by utilizing various known thin film forming methods, preferably physical vapor deposition methods such as vacuum vapor deposition method, sputtering method and ion plating method. This method is particularly advantageous when forming a metal mask having a laminated structure of two or more layers, and is a Group IVa element (titanium (Ti),
Zirconium (Zr) or Hafnium (Hf) / (Mo or Pt) / (Ni or Au), eg Ti / Mo / Ni, Ti / Mo / Au,
It can be realized with a three-layer structure such as Ti / Pt / Au, Zr / Mo / Ni, Zr / Mo / Au, and Zr / Pt / Au.

Among the physical vapor deposition methods, the ion plating method is
It is preferable because it is excellent in the adhesiveness of the deposited film, and it is advantageous to use an active metal such as the group IVa element as the lowermost layer, that is, the layer in contact with the high-concentration sintering aid layer, which is oxygen. Alternatively, since it has a high chemical affinity with Group IIIa elements of the Periodic Table of Elements, it is expected to form a strong bond with the high-concentration layer of the sintering aid for the AlN sintered body substrate.

Original AlN has a remarkably poor affinity with glass or metal, and although it has excellent thermal conductivity (heat dissipation characteristics) and electrical insulation, it is far from practical use until now. there were. That is, the AlN sintered body is the IC substrate,
In order to make it applicable as a material for heat sinks, etc., improve the affinity and wettability between this and metals,
High adhesion strength between them must be ensured.
As a solution for that, as described above, a method of performing a surface treatment with an oxide or the like before applying the metallized surface on the AlN sintered body substrate was known, but even if such a treatment is applied, Due to the inconsistency between the layer obtained as a result of such treatment and AlN, it is not possible to achieve sufficient practical adhesion strength, and surface treatment of the AlN sintered body It is complicated and the resulting product is expensive.

According to the present invention, various drawbacks found in the production of the AlN sintered body having the conventional metallized surface as described above are due to the formation of the high-concentration sintering agent layer obtained as a result of the diffusion of the sintering aid on the surface to be metallized. Most of the problems can be solved by using the AlN sintered body having.

Generally, the sintering aid should be selected from compounds having a high chemical affinity for the substance to be sintered,
It is expected that there will be no inconsistency between the high-concentration layer of sintering aid and the AlN layer, and thus the high-concentration layer and the AlN sintered body are considered to be almost "integral". That is, the auxiliary component
It is considered that the AlN particles are sufficiently wet to form a good grain boundary structure. Therefore, the region mainly composed of this grain boundary structure layer, that is, the high-concentration sintering aid layer also
The mechanical strength equivalent to that of the AlN sintered body is recognized, and it is safe to assume that there is almost no inconsistency between them. Moreover, since the auxiliary agent is an oxide of a Group IIIa element, it has extremely good wettability with the glass component or metal contained in the thick film paste, and therefore can firmly adhere to the metallized surface.

That is, for example, the metallized surface is Au, Ag, Pt-based, Mo, Mo-Mn, Cu.
Alternatively, in the case of W, by applying these pastes and then firing under appropriate conditions, the glass component or the metal component contained in the paste is deposited on the surface of the AlN fired body to promote sintering. It is considered that the wettability of the surface of the sintered body is improved by reacting with the agent component or through the aid component, and the metallized surface and the AlN sintered body are bonded with high strength.

In addition, the metallized surface is a group IVa element / Mo or Pt / Au or Ni.
If it has a three-layer structure of
N directly with the sintered body substrate or through a high-concentration sintering aid layer
It is considered that the activated metal layer as a layer in contact with the lN substrate is firmly bonded to the auxiliary component of the high concentration layer to ensure high bonding strength.

In any of the above cases, the Group IIIa element that constitutes the sintering aid and the oxygen bonded to it contributes greatly to the strong bonding between the metallized material and the AlN sintered body. It is clear that Thus, the presence of the high-concentration sintering aid layer on the surface of the AlN sintered body on the metallized side is extremely important, and its thickness is also a critical condition. That is,
The minimum thickness of the high-concentration layer required to achieve a strong bond is about 1 μm, while the thickness of the high-concentration layer is about 100 μm.
When the thickness exceeds μm, AlN is generated due to the existence of this high concentration layer.
Another problem is that the high thermal conductivity, which is a characteristic of the sintered body, may be reduced. Therefore, in the present invention, by limiting the thickness of the high-concentration layer within the range of 1 to 100 μm as described above, the high bonding strength between the metallized surface and the Al sintered body can be improved by the characteristics peculiar to the AlN sintered body. It has become possible to secure it without damaging.

Thus, the AlN sintered body having the metallized surface according to the present invention with the improved bonding strength can be used for the above-mentioned IC substrate such as high withstand voltage I.
Not only as C (HIC), heat sink, etc., but also with metal
It can be advantageously used in all fields where a composite material with AlN sintered body is required, and sufficiently exhibits the interesting properties of AlN, that is, high thermal conductivity, high electrical insulation and high mechanical strength. be able to.

Example Hereinafter, an AlN sintered body having a metallized surface of the present invention will be described in more detail with reference to Examples, and the advantages achieved by the same will be clarified. Moreover, the manufacturing method will be specifically described with reference to manufacturing examples. However, the scope of the invention is not limited in any way by the following examples.

Example 1 The attached FIG. 1 schematically shows the structure of an AlN sintered body having a metallized surface according to the present invention.
N sintered body 1, metallized surface 2, and AlN interposed between these
And a high-concentration layer 3 of a sintered body sintering aid. here,
The metallized surface 2 can be of various types, as will be shown in the production examples below, and its thickness can be within the general range for products of this type known in the art.

Production Example 1 Au, Au-Pt, Ag was added to an AlN sintered body having a diffusion layer (high concentration layer) to which 5 wt% Y ₂ O ₃ , CeO ₂ and Gd ₂ O ₃ were added as auxiliary agents.
The Pd paste was applied to a thickness of about 25 to 30 μm and then baked in the air at 850 to 940 ° C. for 10 minutes to form an AlN sintered body having a metallized surface. On the metal surface thus obtained
Tensile strength was obtained by soldering 0.8 mmφ annealed copper wire and summarized in the table below. A metallized sintered body was also prepared in the same manner as the sintered body in which the auxiliary agent (5 wt%) was uniformly dispersed without having a diffusion layer on the surface. Shown in the table.

Production Example 2 W, Mo and Mo-Mn pastes were added to a thickness of 28 to 3 AlN sintered bodies each having a diffusion layer containing 5 wt% of Y ₂ O ₃ , CeO ₂ and Gd ₂ O ₃ as auxiliary agents. It is applied to about 34 μm, and in the weak reducing atmosphere, the former is 1450 to 1740 ℃ and the latter two are 1310 to 1520 ℃ at 30 ℃.
After baking for minutes, an AlN sintered body having a metal surface was formed. After plating the thus-obtained metal surface with Ni, a 0.8 mmφ annealed copper wire was soldered to obtain the tensile strength, which is summarized in the following table. In addition, there is no diffusion layer on the surface, and the auxiliary agent is uniform (5 wt%).
Similarly, metallized sintered bodies were prepared, and tensile strengths of these sintered bodies were similarly determined and shown in the table as a comparative example.

Production Example 3 A Cu paste was applied to an AlN sintered body having a diffusion layer containing Y ₂ O ₃ , CeO ₂ and Gd ₂ O ₃ as an auxiliary agent in an amount of 5 wt% to a thickness of 10 to 15 μm in a non-oxidizing atmosphere. Baking was performed at 950 to 1050 ° C. for 10 minutes to form an AlN sintered body having a metallized surface.
On this metallized surface, 0.8 mmφ soft copper wire was soldered to obtain the tensile strength, which is summarized in the following table. In addition, a metallized sintered body in which an auxiliary agent (5 wt%) was uniformly dispersed without having a diffusion layer on the surface was prepared as a comparative example, and the tensile strength was obtained in the same manner as above for these comparative examples. Are also shown in the table.

Production Example 4 Three kinds of AlN sintered bodies having a diffusion layer, in which 5 wt% each of Y ₂ O ₃ , CeO ₂ and Gd ₂ O ₃ were added as auxiliaries, were Ti / Mo / Ni, Ti / by the ion plating method. Mo / Au, Ti / Pt / Ni, Ti / Pt / Au,
Zr / Mo / Ni, Zr / Mo / Au, Zr / Pt / Ni, Zr / Pt / Au, Hf / Mo / Ni,
Hf / Mo / Au, Hf / Pt / Ni, and Hf / Pt / Au were laminated in a three-layer structure.
The thickness of Ti, Zr, and Hf is 0.4 to 0.5 μm, and the thickness of Mo and Pt is 0.3.
.About.0.5 .mu.m, and the film thickness of Ni and Au was 2.0 to 2.5 .mu.m. 0.8 mmφ annealed copper wire was soldered on this metallized surface to obtain the tensile strength, which was summarized as follows. In addition, a sintered body in which an auxiliary agent (5 wt%) was uniformly dispersed without having a diffusion layer on the surface was similarly prepared as a comparative example, and the tensile strength was determined in the same manner as above for these comparative examples. The results are also shown in the table.

(I) AlN (Y ₂ O ₃ : 5wt%) a. Diffusion layer thickness (μm) 1 b. Diffusion layer thickness (μm) 10 c. Diffusion layer thickness (μm) 35 (Ii) AlN (CeO ₂ : 5wt%) a. Diffusion layer thickness (μm) 1 b. Diffusion layer thickness (μm) 10 c. Diffusion layer thickness (μm) 35 (Iii) AlN (Cd ₂ O ₃ : 5wt%) a. Thickness of diffusion layer (μm) 1 b. Diffusion layer thickness (μm) 10 c. Diffusion layer thickness (μm) 35 Effect of the Invention As described in detail above, Al having a metallized surface of the present invention
In the N sintered body substrate, a high-concentration layer of a sintering aid that has good chemical affinity, that is, wettability, with respect to both the AlN sintered body itself and the metallized material applied on it. By providing them, the bonding strength between them is remarkably improved, and by limiting the thickness of the high-concentration layer within a predetermined range, the unique characteristics of the AlN sintered body itself, that is, high electrical insulation and heat The conductivity and the mechanical strength can be sufficiently maintained and exhibited.

Furthermore, in the present invention, by selecting an oxide of a Group IIIa element of the periodic table as an auxiliary agent, a high concentration layer of this substance and a glass component or metal in a thick film paste, or Ti by the thin film method, Zr, It is possible to obtain a metallized AlN sintered body product which is firmly bonded to the vapor deposition film of Hf and has a bonding strength sufficient for practical use.

[Brief description of drawings]

The attached FIG. 1 is a schematic sectional view showing the structure of an AlN sintered body having a metallized surface according to the present invention. (Main reference numbers) 1 ... AlN sintered body, 2 ... metallized layer, 3 ... high-concentration sintering aid layer,

Continuation of front page (56) Reference JP-A-63-55179 (JP, A) JP-A-62-197373 (JP, A) JP-A-62-207789 (JP, A)

Claims (7)

[Claims] 1. An aluminum nitride having a metallized surface including an aluminum nitride sintered body substrate containing a sintering aid made of an oxide of a group IIIa element of the periodic table, and a metal layer formed on the substrate. In the sintered body, the sintering aid is distributed in the substrate so that the concentration increases toward the surface to which the metal layer is attached, the aluminum nitride sintered body. 2. A layer in the substrate, wherein the concentration of the sintering aid with respect to the aluminum nitride sintered body is 20% by weight or more,
The aluminum nitride sintered body having a metallized surface according to claim 1, having a thickness within a range of 1 to 100 µm. 3. The metallized surface according to claim 1 or 2, wherein the Group IIIa element is yttrium, cerium, gadolinium, europium, samarium, holonium or ytterbium. Aluminum nitride sintered body. 4. The distribution of the sintering aid is such that the sintering aid, which had been uniformly dispersed in the substrate material before the sintering, becomes a liquid phase during the sintering to cause a capillary phenomenon in the sintered body. The aluminum nitride sintered body having a metallized surface according to any one of claims 1 to 3, which is formed by diffusing. 5. The metal layer is formed of at least one kind of metal selected from the group consisting of Ag, Au, Pt and Pd.
An aluminum nitride sintered body having the metallized surface according to any one of items 1 to 7. 6. The metallization according to any one of claims 1 to 4, wherein the metal layer is formed of Mo, Mo-Mn, Cu or W. Aluminum nitride sintered body having a surface. 7. The metal layer is (element of group IVa) / (Mo or Pt) / from the surface side of the aluminum nitride sintered body.
Claims 1 to 4 having a three-layer structure in which (Ni or Au) are provided in this order.
An aluminum nitride sintered body having the metallized surface according to any one of items 1 to 7.