JPS63170292A - 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 The present invention relates to an aluminum nitride sintered body, and more particularly to an aluminum nitride sintered body having a metallized surface with a highly reliable and practical bonding strength.

2. Description of the Related Art Semiconductor devices and devices and equipment using them generally 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 in particular, there has been a remarkable increase in the integration density of LSIs and the like. 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 IC boards, but the thermal conductivity of conventional alumina sintered bodies is insufficient for heat dissipation, and it is becoming increasingly difficult to cope with the increased heat generation of IC chips. . Therefore, as an alternative to such alumina substrates, substrates or heat sinks using aluminum nitride, which has high thermal conductivity, have attracted attention, 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 beryllia, it is non-toxic, making it particularly promising as an insulating material and packaging material in the semiconductor industry. .

Aluminum nitride (CMN) sintered bodies have high thermal conductivity, so as mentioned above, they are attracting attention as substrates for integrated circuits (I(2)) or as heat sinks.However, while having such interesting properties, However, MN sintered bodies have a problem in bonding strength with metals, glass, etc. By the way, this sintered body can be manufactured by applying a commercially available metallizing paste directly onto the surface of the MN sintered body, or by using the thick film method, or by applying active metals or metals. It is common to use a metallized layer by using a thin film method, in which a thin film is formed by a method such as vapor deposition.However, depending on this method, it is difficult to achieve a bonding strength that is sufficient for practical use. In fact, it is necessary to modify the surface by some method before metallization or during the metallization operation to improve bondability with other materials, such as metals.

As a conventional method for surface modification of such a MN sintered body, a method is known in which an oxidation treatment or the like is performed on the surface of the MN sintered body to form an oxide layer. That is, for example, SiO*, Am! on the surface of the MN sintered body. srs, mullite, Pe5
This is a method of forming an oxide layer such as oss Cu.

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 little affinity with the MN sintered body itself and is reliable. It is thought that there is a problem with sexuality.

Problems to be Solved by the Invention As mentioned above, MN 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 a MN sintered body having a metallized surface sufficient for practical use has not yet been obtained.

That is, good bonding strength could not be obtained by the conventional thick film method of applying M, N sintered bodies and metallizing paste (for example, commercially available frit or chemical pound type). This is because the conductive paste is originally for M2O3 and does not have good reactivity with the MN layer.

In addition, a method is known in which metallization is applied while or after the oxide layer is formed. Oxide treatment of the surface of N sintered bodies is known. However, the above SiOs
,M! Oxide layers such as Js, mullite, Pe*Os, and CuO have poor reactivity with MN. Moreover, even if a reaction layer is formed, the reaction layer is essentially similar to an oxide layer, so the reactivity with the MN surface is hardly improved, and therefore the bonding strength with the MN sintered body is is not improved either.

Furthermore, this oxide treatment has problems in terms of density and film bonding strength.

That is, the oxide treatment of the MN surface is expressed, for example, by the following formula: 2MN+-Ox→N15Os+Nx↑Nitrogen gas may be generated as a result of this reaction, and the resulting oxide film is extremely porous. It becomes a film of quality.

Further, it is difficult to expect sufficient bonding strength even by thick film methods or thin film methods using active metals.

In other words, even when active metals that are highly reactive with nitrides are used, MN is extremely chemically stable, so sufficient bonding strength cannot be obtained between them, making bonding difficult. This seems to be due to

As described above, all attempts to achieve a bond strength sufficient for practical use between the MN sintered body and the metallized layer have not been satisfactory. Therefore, by setting a structure that has affinity for both the metal layer or metal oxide, etc. and the MN sintered body, the bond between them is guaranteed, and the bonding strength between the metallized layer and the MN sintered body is strengthened. The development of new technology that can improve this is desperately needed.

Therefore, an object of the present invention is to improve the bonding strength between a metallized layer having excellent insulation properties and heat dissipation properties and an AIN sintered body. That is, the object of the present invention is to provide a MN sintered body having excellent bonding strength and a highly reliable metallized surface.

In view of the above, various studies and researches were conducted in order to obtain an aluminum nitride sintered body having a metallized surface as described above. It has been found that it is advantageous to realize a highly concentrated layer of binder and form a metallized surface via this, leading to the present invention.

That is, the aluminum nitride sintered body having a metallized surface of the present invention comprises an aluminum nitride sintered body substrate and an oxide of a group Ua element of the periodic table of elements provided thereon or a mixture thereof. It is composed of a high concentration layer of a sintering aid for aluminum (hereinafter also referred to as a high concentration sintering aid layer) and a metal layer provided on the sintered body substrate via the high concentration layer. This is a characteristic feature.

In the MN sintered body having a metal and chemical layer of the present invention, it is important that the aluminum nitride sintered body substrate has good thermal conductivity and does not contain defects such as a large number of pores and impurities. be.

N) In the sintered body, the Group Ia element useful as the material for the high concentration layer of the sintering aid is particularly calcium (C
a) or barium (Ha) can be mentioned as a preferred example. Moreover, the thickness of this high concentration auxiliary agent layer is 1 to 1
It is preferable to set the value within the range of 00 μm.

In order to form a highly concentrated sintering aid layer on the surface of this MN sintered body, the following various methods can be employed.

First, for example, cerium oxide as a sintering aid, 5 to 10 wt % 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+++a+.

After forming this sheet into an appropriate size, the binder is removed, and then the sheet is heated at 30 to 12
Bake for 0 minutes. During firing, the sintering aid calcium oxide reacts with the aluminum nitride powder at 1600° C. or higher to form a melt, which promotes sintering. However, while the sample is not fully sintered, it is porous and the auxiliary components diffuse through the capillaries to the surface and sintering is complete. In this way, most of the 5 wt% of the auxiliary agent is diffused on the surface, so the concentration of the auxiliary agent in the sintered body decreases greatly, and the The concentration of auxiliary agents is increasing rapidly. The auxiliary component of this diffusion layer is about 20~
The content has increased to 50wt%. Therefore, the amount of the auxiliary component in the diffusion layer is greatly influenced by the thickness of the green sheet and the sintering conditions, in addition to the amount of the sintering auxiliary agent added during production of the green sheet. In addition to calcium oxide, any sintering aid for aluminum nitride can be used as the sintering aid.

A predetermined metallization surface is provided on the thus formed high concentration layer of sintering aid. The method of forming the metallized surface, the material used, etc. do not need to be particularly special, and any of the various conventionally known methods and materials can be used. For example, the metallized surface may be Au, Ag, Pt.
, Pd# or a mixture thereof, for example, Au, Au-Pt5Pt.

Formed according to a thick film paste method in which a paste such as Ag, Ag-Pd, etc. is coated by a screen printing method and then baked at a temperature within the range of about 850 to 940 ° C. in air, oxygen atmosphere, or nitrogen cloud atmosphere. can do. Similarly, the material for metallization is Mo,
The thick film paste method can also be used when the material is Mo-MuSCu or W.

However, the above-mentioned exemplified materials are merely illustrative, and
Accordingly, the invention can be realized by using various thin film forming methods, preferably by using a physical vapor deposition method, such as a vacuum evaporation method, a sputtering method, an ion blating method, etc. This method is particularly advantageous when forming a metallized surface of a laminated structure of two or more layers, and is suitable for metallized surfaces of group IVa elements of the periodic table (titanium (Ti), titanium (Ti),
Zirconium (Zr) or Hafnium (Hf) /
(Mo or Pt) / (Ni or Au), for example Ti/Me/Ni5Ti/O/Au.

Ti/Pt/Au, Zr/Mo/Ni5Zr
It can be realized with a three-layer structure such as /Mo/Au5Zr/Pt/Au.

Among the physical vapor deposition methods, the ion blating method is particularly
It is preferable because it has excellent adhesion of the deposited film, and it is advantageous to use active metals such as the above-mentioned Group 1 Va elements as the bottom layer, that is, the layer in contact with the high concentration sintering aid layer. Also, since it has a high chemical affinity with elements of group nIa 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 MN sintered body substrate.

Function: MN inherently has a very poor affinity with glass or metals, and therefore, although it has excellent thermal conductivity (heat dissipation properties) and electrical insulation properties, it is still far from being put to practical use. there were. In other words, in order to make the MN sintered body applicable as a material for IC substrates, heat sinks, etc., it is necessary to improve the affinity and wettability of the MN sintered body with metals, etc., and to achieve high adhesion strength between them. must be secured.

As a solution to this problem, a method has been known in which, as mentioned above, the MN sintered body substrate is subjected to surface treatment with an oxide or the like before being metallized, but even with such treatment, Due to the incompatibility between the layer obtained as a result of such treatment and the MN, it is not possible to achieve a sufficient adhesion strength for practical use, and surface treatment of the MN sintered body requires a process. This makes the resulting product more complex and more expensive.

The various drawbacks observed in the production of conventional M'N sintered bodies having metallized surfaces as described above can be solved by using a highly concentrated sintering agent obtained as a result of diffusion of the sintering aid onto the surface to be metallized. This is mostly solved by using a MN sintered body with layers.

Generally, the sintering aid should be selected from compounds that have a high chemical affinity for the material to be sintered;
It is expected that there is no inconsistency between the sintering aid enriched layer and the MN layer, so that this enriched layer and the 7v! The N sintered body is considered to be almost an "integral body". That is, it is considered that the auxiliary component sufficiently wets the MN particles and forms a good grain boundary structure. Therefore, the mechanical strength equivalent to that of the MN sintered body is observed in the region mainly composed of this grain boundary structure layer, that is, the high concentration sintering aid layer, and there is almost no inconsistency between them. I can't help but think about it. Moreover, since the auxiliary agent is an oxide of a Group IIa element, it has excellent wettability with the glass component or metal contained in the thick film paste, and therefore can be firmly bonded to the metallized surface.

That is, for example, the metallized surface is Au, Ag5Pt system, Mo,
M.

- In the case of Mn1Cu or W, the glass or metal components contained in the paste are deposited on the surface of the MN sintered body by applying these pastes and firing them under appropriate conditions. It is thought that the wettability of the sintered body surface is improved by reacting with the sintering aid component or via this aid component, and the metallized surface and the MN sintered body are bonded with high strength. .

In addition, the metallized surface is a group 1 Va element/Mo or Pt/A.
In the case of a three-layer structure of U or Ni, the innermost layer, that is, the activated metal layer as a layer in contact with the MN sintered body substrate directly or through a high concentration sintering aid layer has the above-mentioned high concentration. It is thought that high bonding strength is ensured by strongly bonding with the auxiliary component of the concentration layer.

In any of the above cases, the Group Ia element constituting the sintering aid and the oxygen bonded thereto are 71v! It is clear that this greatly contributes to the strong bonding of N sintered body 7. Like this MN
It is extremely important that a highly concentrated sintering aid layer exists on the metallized surface of the sintered body, and its thickness is also a critical condition. In other words, the minimum thickness of the highly concentrated layer required to achieve a strong bond is approximately 1 μm, whereas if the thickness of the highly concentrated layer exceeds approximately 100 μm, the presence of this highly concentrated layer in MN'11. Another problem may arise in that the high thermal conductivity, which is a characteristic of the feeder, is reduced. Therefore, in the present invention, the thickness of the high concentration layer is set to 1 to 1 as described above.
By limiting the range of 00 μm, the metallized surface and M
The M'N sintered body, which has a metallized surface that ensures high bonding strength with the sintered body without impairing the characteristics unique to the AA'N sintered body, can be used for the already mentioned IC substrates, such as high-voltage ICs ( HI(2
), it can be advantageously used not only as a heat sink, etc., but also in any field where a composite material of metal and MN sintered body is required. properties and high mechanical strength.

EXAMPLES Hereinafter, the MN sintered body having a metallized surface of the present invention will be explained in more detail using examples, and the advantages thereof will be clarified. Further, the manufacturing method will be specifically explained using manufacturing examples. However, the scope of the invention is not limited by the following examples.

Example 1 The attached FIG. 1 schematically shows the structure of an AgN sintered body having a metallized surface according to the present invention, and as is clear from the figure,
It is composed of a MN sintered body 1, a metallized surface 2, and a high concentration layer 3 of a MN sintered body sintering aid interposed between these. Here, the metallized surface 2 can be of various types, as shown in the manufacturing examples below, and its thickness can be within the usual range for products of this type known in the art.

Production Example 1 Au, Au-
Pt, Ag-Pd paste was applied to a thickness of about 25 to 30 μm, and then baked in the air at 850 to 940 tons for 10 minutes to form a MN sintered body having a metallized surface. A mild steel wire of 81φ was soldered onto the metal surface thus obtained, and the tensile strength was determined and summarized in the table below. In addition, a sintered body in which the auxiliary agent (5 wt%) was uniformly dispersed without a diffusion layer on the surface was also metalized in the same manner, and the tensile strength of this was also measured in the same manner as above, and a comparative example was prepared. They are also shown in the table.

Production Example 2 W%Mo was added to three types of AiN sintered bodies having diffusion layers to which 5wt% of CaO and BaO were added as auxiliary agents, respectively.

Me-Mn paste was applied to a thickness of about 25 to 32 μm, and the former was heated at 1400 to 1750 tl in a weak reducing atmosphere:
The latter two were baked at 1320-1630°C for 30 minutes to form MN sintered bodies with metal surfaces. After Ni plating was performed on the metal surface thus obtained, an annealed copper wire of 0.8 ma+φ was soldered to determine the tensile strength, which is summarized in the table below. In addition, metallized sintered bodies in which the auxiliary agent (5 wt%) was uniformly dispersed without a diffusion layer on the surface were prepared in the same way, and the tensile strengths of these were also determined in the same manner and are also shown in the table as a comparative example. Indicated.

Production Example 3 Cu paste was applied to a thickness of 10 to 1 mm on an AgN sintered body having a diffusion layer to which 5 wt% of CaO and BaO were added as auxiliaries.
950-105 in a non-oxidizing atmosphere.
Baking was performed at 0℃ for 10 minutes.
A N sintered body was formed. An annealed copper wire of 0.81φ was soldered onto this metallized surface to determine the tensile strength, which is summarized in the table below. In addition, the auxiliary agent (5 wt.
Comparative examples were prepared using sintered bodies in which %) were dispersed and similarly metallized, and the tensile strengths of these comparative examples were determined in the same manner as above, and the results are also shown in the table.

Table 3 Production Example 4 Ti/Mo/Ni, Ti/Mo/
Au5Ti/Pt/Ni5Ti/Pt/Au,
Zr/Mo/Ni5Zr/Mo/Au.

Zr/Pt/Ni, Zr/Pt/Au, H
f/Mo/Ni, Hf/Mo/Au11ff/
Pt/Ni and If/Pt/Au were laminated in a three-layer structure. The film thickness of Ti, Zr, and Hf is 0.4 to 0.
．． 5tt m, No, Pt film thickness is 0.3 to 0.5
The film thicknesses of Ni and Au were 2.0 to 2.5 μm. An annealed copper wire of 0.8 a Imφ was soldered onto this metal surface to determine the tensile strength, which was summarized as follows. Incidentally, a sintered body having no diffusion layer on the surface and in which the auxiliary agent (5 wt%) was uniformly dispersed was similarly metalized and produced as a comparative example, and the tensile strength was determined in the same manner as above for these comparative rows. The results are also shown in the table.

(f) AIN (CaO: 5wt%) a, thickness of diffusion layer (μm) 1 Metallized film Ti/Mo/Ni Ti/Me/A
u Tensile strength (Kg/mad”) ?, 8 8
．． 9 () is a comparative example (1,1) (1,4)Ti
/Pt/Ni Ti/Pt/Au Zr/Mo/
Ni Zr/ Mu/ Au9.6 9.1
8.0 8.0(1,3) (1
,4) (1,1) (1,0)Zr/P
t/Ni Zr/Pt/Au Hf/Mo/Ni
Hf/Mo/Au7.3 7.5 6.
8 6.0 (1,2) (0,9)
(1,2) (1,3)Hf/Pt/Ni
Hf/Pt/Au6.0 6.0 (1,2) (1,3) b, Thickness of diffusion layer (μm) 10 Metallized film Ti/Mo/Ni Ti/MO/A
n tensile strength (g/ms+') 9.2 9.
1 () is a comparative example (1,2) (1,1)Ti
/Pt/Ni Ti/Pt/Au Zr/Mo/N
i Zr/Mo/Au9.0 g, 9
g, 2 7.8 (1, 3) (1, 1
) (0,9) (1,4)Zr/Pt/
Ni Zr/Pt/Au Hf/Mo/Ni I
ff/Mo/Au6.8 7.3 6.5
5.9(1,3) (1,4) (1,1)
(1,0)Hf/Pt/Ni Hf/Pt/Au
6.4 6.4 (0,9) (1,3) Thickness of C1 diffusion layer (μm) 35 Metallization l! Ti/ No/ Nt Tt
/Mo/Au tensile strength (Kg/ss'') 8.5
8.8 () is a comparative example (1,2) (1,3
) Ti/Pt/Ni Ti/Pt/Au Zr/M
o/Ni Zr/Mo/Au9.6 8.4
7.8 7J(1,0) (1,3
) (0,8) (1,1)Zr/Pt/
Ni Zr/Pt/Au Hf/Mo/Ni H
f/Mo/Au7.3 7.4 6.0
6.5(1,0) (1,2) (
1,1) (1,3)Hf/Pt/Ni revision/
Pt/Au 6,1 6. °2 (0,9) (1,4) (ii) AIN (BaO: 5wt%)a, thickness of diffusion layer (μm) 1 Metallized film Ti/Mo/Ni Ti/Mo/A
u tensile strength (Kg/ms”) 9.2 9.4
Comparative examples in parentheses <1.0) (1,3)Ti/
Pt/Ni Ti/Pt/Au Zr/Mo/Ni
Zr/Mo/Au9.4 9.3 8
．． 2 8.1(1,0) (1,3>
(0,9) (1,3)Zr/Pt/Ni Zr
/Pt/Au Hf/Mo/Ni If/Mo/^
U8.3 8.4 6.6 6.4
(1,1) (1,0) (1,1) (
1,2) If/Pt/Ni Hf/Pt/Au6,
5 6.2 (1,3) (1,2) b, Thickness of diffusion layer (μm) 10 Metallized film Ti/ Mo/ Ni Ti/ M
o/ Au tensile strength (gets ■ 9.4
9.2 () is a comparative example (0,9) (1,2)
Ti/Pt/Ni Ti/Pt/Au Zr/Mo
/Ni Zr/Mo/Au9.4 9.2
g, 5 8.4(1,1) (1,
3) (1,1) (1,2) Zr/Pt
/Ni Zr/Pt/Au Hf/Mo/Ni
Ilf/Mo/Au8.2 8.3 6.
4 6.3 (1,4>(1,2>
(0,9) (1,3)If/Pt/Ni
Hf/Pt/Au6.4 6.4 (1,0) (1,4) Thickness of C9 diffusion layer (μm) 35 Metallized M Ti/Mo/Ni, Ti/No/A
u tensile strength (Kg/a+one 9.2 9.4(
) is a comparative example (1,1)(1,1)Ti/Pt/Ni
Ti/Pt/Au Zr/Mo/Ni Zr/
Mo/Au9.4 9.0 8.4
8.3(1,2) (0,9) (0,
8) (1,1) Zr/Pt/Ni Zr/P
t/Au Hf/Mo/Ni Hf/Mo/Ni8
．． 1 g, 0 6.4 6.6 (
0,9) (1,1) (0,8>
(1,2) 11f/Pt/Ni fir/Pt/A
u6.3 6.2 (0,9> (1,3) Effects of the Invention As described in detail above, the M having the metallized surface of the present invention
- In the N sintered body substrate, a highly concentrated layer of sintering aid that has good chemical affinity, i.e., good wettability, both for the MN sintered body itself as well as for the metallization material applied thereon. By providing the Aj! The unique properties of the N sintered body itself, ie, high electrical insulation, thermal conductivity, and mechanical strength, can be sufficiently maintained and exhibited.

Furthermore, in the present invention, by selecting an oxide of an element of group IV a of the periodic table as an auxiliary agent, a high concentration layer of this substance can be combined with a glass component or metal in a thick film paste, or alternatively with Ti, Zr by a thin film method. , Metalized M!, which is strongly bonded to the Hf vapor deposition film and has sufficient bonding strength for practical use.
A N sintered product can be obtained.

[Brief explanation of the drawing]

FIG. 1 attached hereto shows a schematic cross-sectional view of the structure of a MN sintered body having a metallized surface according to the present invention. (Main reference number) 1...MN sintered body

Claims (7)

[Claims] (1) An aluminum nitride sintered body substrate, a high concentration layer of the sintering aid for aluminum nitride made of an oxide of Group IIa element of the Periodic Table of Elements formed thereon, and the high concentration sintering aid. An aluminum nitride sintered body having a metallized surface, comprising a metal layer provided on the substrate with an agent layer interposed therebetween. (2) The aluminum nitride sintered body having a metallized surface according to claim 1, wherein the high concentration sintering aid layer has a thickness within the range of 1 to 100 μm. (3) The aluminum nitride sintered body having a metallized surface according to claim 1 or 2, wherein the Group IIa element is calcium or barium. (4) The sintering aid layer is formed by the sintering aid being uniformly dispersed during sintering and being diffused by capillary action. An aluminum nitride sintered body having a metallized surface according to any one of items 1 to 3. (5) Any one of claims 1 to 4, wherein the metal layer is made of at least one metal selected from the group consisting of Ag, Au, Pt, and Pd. An aluminum nitride sintered body having a metallized surface according to item 1. (6) The metal layer is Mo, Mo-Mn, Cu or W
An aluminum nitride sintered body having a metallized surface according to any one of claims 1 to 4. (7) The metal layer is formed from the surface side of the aluminum nitride sintered body by (group IVa element)/(Mo or Pt)/(N
The sintered aluminum nitride having a metallized surface according to any one of claims 1 to 4, characterized in that it has a three-layer structure provided in the order of i or Au). body.