JPS62182182A - Aluminum nitride sintered body with metallized surface - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an aluminum nitride sintered body, and more specifically, an aluminum nitride sintered body having a metallized surface with reliable and practical bonding strength. It is related to.

2. Description of the Related Art In general, semiconductor devices or devices and equipment using them include various active and passive elements, but these have the problem of heat generation. Therefore, in order to operate these elements stably and reliably, it is necessary to perform the best thermal design during mounting, which is extremely important in the design and manufacture of semiconductor devices and the like.

Furthermore, in recent years, there has been a major trend toward faster operation and higher integration of semiconductor devices, and especially in large-scale integrated circuits (LSI), the degree of integration has been significantly improved. Along with this, the amount of heat generated per package also increases significantly. For this reason, importance has been placed on the heat dissipation properties of substrate materials.

On the other hand, alumina has traditionally been used as ceramics for integrated circuit (IC) substrates, but the thermal conductivity of conventional alumina sintered bodies is insufficient for heat dissipation, and it is not sufficient to cope with the increased heat generation of IC chips. It's starting to become impossible. Therefore,
Substrates or heat sinks using aluminum nitride, which has high thermal conductivity, have attracted attention as an alternative to such alumina substrates, and many studies have been conducted to put them into practical use.

Aluminum nitride is a material that inherently has high thermal conductivity and high insulation properties, and unlike aluminum nitride, it is non-toxic, so it is viewed as a promising material in the semiconductor industry, especially as an insulating material and packaging material. There is.

Since aluminum nitride (AIN) sintered bodies have high thermal conductivity, they are attracting attention as IC substrates or heat sinks as described above. However, while having such interesting properties, AIN sintered bodies have problems in bonding strength with metals, glass, etc.

By the way, when mounting an LSI on these sintered bodies, it is necessary to provide a metallized surface on the surface of the sintered body in advance.

For this purpose, methods are known in which a vapor deposition film is deposited by a thick film method in which a commercially available metallizing paste is applied directly onto the surface of a sintered body, or by a physical/chemical vapor deposition method.

However, it is not possible to obtain a bonding strength sufficient for practical use by such methods, and in reality, the surface is modified by some method before or during the metallization operation, and other methods such as metals, etc. It is necessary to improve bondability with

As a conventional method for surface modification of such an AIN sintered body, a method is known in which the surface of the AIN sintered body is subjected to oxidation treatment or the like to form an oxide layer. That is, for example, AIN
5I02, Al2O5, mullite, Fe2 on the sintered surface
This is a method of forming an oxide layer of O, CuO, etc. However, although the oxide layer as exemplified above has good affinity with the glass layer, alumina layer, etc. and forms a strong bond, it has low affinity with the AIN sintered body itself.
There seems to be a problem with reliability.

Problems to be Solved by the Invention As stated above, AIN sintered material has extremely good electrical insulation and thermal conductivity, and is therefore expected to be used as an IC insulating substrate or heat sink material that requires good heat dissipation. The body is often used with its surface metallized, but there have been problems in terms of bonding strength to these metals. Therefore, various methods such as those described above have been considered, but all of them are insufficient, and an AIN sintered body having a metallized surface sufficient for practical use has not yet been obtained.

That is, the conventional thick film method of coating an AIN sintered body with a metallized paste (for example, a commercially available frit or chemical bond type) has not been able to provide good bonding strength. This is because the conductor paste is originally for Al2O3 and does not have good reactivity with the A18 layer.

Therefore, if aluminum oxide is formed on the A18 layer, it is expected that the wettability of the conductive paste will be improved.

However, the wettability, the strength of the interface between the aluminum oxide layer and the A18 layer, and the heat dissipation properties are greatly influenced by the thickness of the aluminum oxide. That is, when forming aluminum oxide, it is necessary to accurately define the thickness of the layer.

Therefore, an object of the present invention is to define the thickness of the aluminum oxide layer in order to improve the bonding strength between the metallized layer, which has excellent insulation and heat dissipation properties, and the AIN sintered body. That is,
AIN with excellent bonding strength and highly reliable metallized surface
The objective is to provide a sintered body.

Means for Solving the Problems In view of the above-mentioned current state of the conventional methods for applying a metallized surface to an AIN sintered body, the present inventors have developed a method for applying a metallized surface that is advantageous in terms of cost and productivity. We chose a thick film method by applying a metallized paste, and for the surface treatment, we chose to apply an aluminum oxide film that has a relatively good affinity for both the AIN sintered body and the metallized layer, and various conditions for the formation method. consider,
The present invention was completed based on the knowledge that the thickness and the amount of metal and glass components in the metallized layer are particularly important for bond strength.

That is, the AIN sintered body having the metallized surface of the present invention is AIN
A sintered body substrate and a thickness of 10 to 40 μm formed thereon
and an aluminum oxide layer provided on the AIN sintered body substrate via the aluminum oxide layer.
and at least one metallization layer selected from the group consisting of g-PdSCuSWSMoSMn.

The AIN sintered body having a metallized surface according to the present invention can be formed as follows.

First, AIN sintered bodies can be manufactured by any conventionally known method, but since the AIN powder itself has extremely poor sinterability, many AIN sintered bodies obtained by sintering after powder compaction are In this case, it has a large number of pores and has poor thermal conductivity. This is because the heat conduction mechanism of insulating ceramics such as AIN sintered bodies is mainly based on phonon conduction due to anharmonic interaction between lattice vibrations, since this AIN consists of ionic bonds and covalent bonds. Therefore, if there are a large number of defects such as pores and impurities, phonon scattering will be significant and only a low thermal conductivity can be obtained.

Therefore, the method of producing an AIN sintered body having dense quality and good thermal conductivity developed by the present inventors (see JP-A-60-184635) or the above-mentioned JP-A-Sho! It is advantageous to use the one disclosed in '19-121175 Invention.

An aluminum oxide layer is then formed on the surface of the AIN sintered body thus obtained. This is done by oxidizing the surface of the AIN sintered body in the air or in an air stream (heating to 900-1250°C), or by physical or chemical vapor deposition such as chemical vapor deposition (CVD) or ion blating. It can be implemented by law.

In particular, in consideration of adhesive strength, it is preferable to use a vapor deposition method.

Next, a paste of a predetermined composition is applied onto the aluminum oxide layer and baked to complete the metallized surface. Baking conditions vary depending on the type and properties of the paste.

Generally, it is carried out at a temperature within the range of 800 to 1700° C., for example, in the air, in humidified hydrogen, or in a nitrogen atmosphere.

The quality of the AIN sintered body with the metallized surface thus obtained is generally determined by tensile strength measurement or scanning electron microscopy (SEM).
This is done by observing the structure using EMPΔ and examining the element distribution (particularly at the bonding interface) using EMPΔ.

LS sintered body with excellent electrical insulation and thermal conductivity
When using the AIN sintered body as a substrate, it is necessary to metallize its surface in advance, but due to the unique characteristics of the AIN sintered body, there are various difficulties as described above. Therefore, in the present invention, we chose the thick film method, which is advantageous in terms of cost and tooth productivity.
The formation of an aluminum oxide layer was selected as the surface treatment at that time, and the method of forming the aluminum oxide layer, its thickness,
The relationship with the metallized layer material was examined in detail, and the following findings were obtained.

Even in the invention disclosed in JP-A-59-121175,
As a surface treatment for the IN sintered body, oxidation treatment is performed, that is, 1
By heating at 000 to 1.400°C for 30 minutes to 2 hours, the oxygen concentration on the surface becomes 0.05 to 0.2 mg.
/cnf. however,
With such treatment, an oxide film with a thickness of about 1.0 μm can be obtained at most, and with such pre-treatment (surface treatment), even if metallized using a thick film method, the adhesive strength is low and is at a practical level (2 kg). /mm2) was found to be insufficient to achieve the strength. That is, unlike A1□03, AIN inherently has poor chemical affinity and wettability with metals, and therefore has a significantly low adhesive strength between them. However, even if an aluminum oxide film with relatively excellent chemical affinity and wettability for both of these is provided as described above,
．． A layer as thin as about 0 μm is insufficient to achieve the above-mentioned practical level of strength because it is difficult to form a uniform aluminum oxide layer. Even if formed,
Due to its small volume, most of it diffuses into the metal layer and is consumed during metallization, so the wettability and chemical affinity between AIN and metal are hardly improved. No improvement in adhesive (bonding) strength could be expected.

Therefore, in the present invention, the thickness of the aluminum oxide layer was studied in detail, and it was found that a thickness in the range of 10 to 40 μm is advantageous.

All of these numerical ranges are critical in the present invention,
As demonstrated in the following examples, if the thickness of the aluminum oxide film is less than the lower limit, a practical level of bonding strength cannot be achieved due to the reasons mentioned above, and if it exceeds the upper limit, Although satisfactory bonding strength can be obtained, the presence of thick aluminum oxide makes the mechanical strength insufficient and new problems such as peeling of the metallized layer occur, so neither is preferable.

According to the present invention, by configuring the AIN sintered body having a metallized surface as described above, various drawbacks caused by the poor chemical affinity and wettability of the AIN sintered body with other metals can be avoided. This problem is solved, and an AIN product with a metallized surface formed with sufficient bonding strength is realized, making it possible to put the AIN sintered body into practical use.

The AIN sintered body having a metallized surface of the present invention can be used for LSI, IC
It can be advantageously used as a substrate for assembly and mounting, such as, or as a heat sink, and can be widely applied in various applications that require high insulation and heat dissipation properties.

EXAMPLES Hereinafter, the IN sintered body having a metallized surface of the present invention will be explained in more detail using examples, and the effects thereof will be demonstrated, but these examples do not limit the scope of the present invention in any way. isn't it.

Example I 1, 2 on AIN sintered substrate in air and 02 airflow
Oxidize by heating to 00°C or CV
Thickness 0.5-60 by D method and ion blating method
An aluminum oxide layer in the μm range was formed. Then,
Ag paste was applied and baked at 920° C. for 10 minutes to form a metallized surface. For each sample thus obtained, a wire (copper wire; 1 mmφ) was welded by soldering.
The tensile strength at that time was measured. The results are shown in Figure 1.

As is clear from the results in Figure 1, the thickness of the aluminum oxide layer that provides practical adhesive strength is in the range of 10 to 40 μm, and higher adhesive strength is achieved when the aluminum oxide layer is formed by vapor deposition. I understand that.

Note that 1 in the figure. P indicates that the aluminum oxide layer was formed by an ion blasting method.

Example 2 Samples with aluminum oxide layers of various thicknesses were obtained by the same operation as in Example 1 except that Au paste was used, and the adhesive strength of each sample was measured in the same manner as in Example 1. The results are plotted in attached Figure 2. It can be seen that, similar to Example 1, the sample according to the invention provides sufficiently high adhesive strength.

In the results shown in Figure 2, the thickness of the aluminum oxide film was 40 mm.
Although the adhesive strength exceeds the practical level (2 kg/mm2) even when the adhesive strength exceeds .mu.m, it has been confirmed that this case involves problems such as peeling for the reasons already mentioned.

Example 3 A paste-like Mo-Mn mixture was applied to the aluminum oxide surface at various thicknesses by CVD on an AIN substrate, and then metallized at 1.450° C. in humidified hydrogen. Next, after Ni plating, the adhesive strength was measured in the same manner as in Example 1. The results are shown in attached Figure 3. Equally excellent results were obtained.

Example 4 Various samples were obtained in the same manner as in Example 3, except that W paste was used. Next, after Ni plating, a tensile strength test was conducted. The results are shown in attached Figure 4.

Results similar to those of the above examples were obtained.

Example 5 As in Examples 3 and 4, aluminum oxide layers were formed in various thicknesses by oxidizing the surface of the AIN substrate in the atmosphere, and then metallized using paste Ag-Pd. After applying Ni plating, a tensile strength test was conducted and the results are shown in FIG. Results similar to those above were obtained.

Example 6 The same procedure as in Example 5 was carried out. However, various samples were prepared by applying Cu paste and baking at 820°C for 5 minutes. The tensile strength was measured in the same manner, and the results are shown in FIG.

Effects of the Invention As explained in detail above, according to the AIN sintered body having a metallized surface of the present invention, the thickness of the aluminum oxide coating as an intervening layer is 10 to 40 μm, which is much thicker than the conventional one. By doing so, various drawbacks seen in the past can be eliminated, and a product with high adhesive strength at a practical level can be obtained.

In addition, if the aluminum oxide layer is formed by a vapor deposition method such as CVD or ion blating, the adhesive strength can be further improved, and the chemical affinity and wettability with conventional metals can be improved. AIN, which had been difficult to put into practical use due to its unique characteristic of extremely poor heat dissipation, can now be effectively utilized as an insulating substrate for ICs, LSIs, etc., heat sinks, etc. due to its high heat dissipation properties.

[Brief explanation of drawings]

FIGS. 1 to 6 are graphs in which the results of measuring the tensile strength of each sample obtained according to an example of the present invention are plotted against the thickness of the aluminum oxide film as an intervening layer.

Claims (4)

[Claims] (1) An aluminum nitride sintered body substrate, an aluminum oxide layer with a thickness of 10 to 40 μm formed thereon, and Au, Ag, Ag- Pd, Cu, W, Mo,
An aluminum nitride sintered body having a metallized surface, comprising at least one metallized layer selected from the group consisting of Mn. (2) The aluminum nitride sintered body having a metallized surface according to claim 1, wherein the aluminum oxide layer is formed by oxidizing the surface of an aluminum nitride substrate. (3) The aluminum nitride sintered body having a metallized surface according to claim 1, wherein the aluminum oxide layer is formed by a physical or chemical vapor deposition method. (4) Any one of claims 1 to 3, wherein the metallized layer is formed by a thick film method.
An aluminum nitride sintered body having a metallized surface as described in 1.