JPH0676264B2 - Aluminum nitride sintered body having glass layer and method for producing the same - Google Patents

Description

The present invention relates to an aluminum nitride sintered body. More specifically, an aluminum nitride sintered body having a glass layer, which is useful in the production of an aluminum nitride sintered body having a metallized surface on the surface, which is particularly useful as a thermally conductive substrate, particularly as an insulating substrate for integrated circuits (ICs), and these The present invention relates to a method for manufacturing an aluminum nitride sintered product.

2. Description of the Related Art Generally, a semiconductor device or a device or device using the semiconductor device is equipped with various active / passive elements, and 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. However, since such a trend is accompanied by an increase in the amount of heat generated per package, further improvement in terms of mounting technology is required such as improvement of heat dissipation of the substrate material.

Conventionally, an alumina ceramics substrate has been used as a material for IC substrates, but this alumina sintered body has low thermal conductivity and cannot secure sufficient heat dissipation, increasing the heat generation amount of the IC chip as described above. It is becoming difficult to deal with. Therefore, it has been desired to develop a new substrate material having a high thermal conductivity in place of such an alumina substrate, and attention has been paid to aluminum nitride, and many studies have been conducted for practical use as a substrate or a heat sink.

However, it is difficult to obtain aluminum nitride having satisfactory thermal conductivity because the powder itself is inferior in sinterability.
That is, the aluminum nitride sintered body can be obtained by sintering after powder molding, but because of the poor sinterability as described above, in many cases, only a product having a large amount of pores and low thermal conductivity could be obtained. . Since the insulating ceramics such as aluminum nitride are composed of ionic bonds and covalent bonds, their heat conduction mechanism is mainly phonon conduction due to anharmonic interaction between lattice vibrations. If it contains defects such as pores and impurities, phonon scattering will be significant, resulting in a product with low thermal conductivity. However, very recently, the manufacturing method has been improved and a good thermal conductivity has been obtained.

Since the aluminum nitride sintered body has high thermal conductivity, and is also excellent in electrical insulation and mechanical strength, it has attracted attention as an insulating substrate for ICs. By the way, the aluminum nitride sintered body has a remarkably low wettability with a metal. Therefore, after forming a metal layer on the surface in advance and improving the wettability with the metal on the surface, it is used as an IC substrate or the like. Is the current situation.

However, even if the surface of the aluminum nitride sintered body is directly subjected to metallization or vitrification treatment, since the affinity and wettability for them are essentially low, the adhesion is low, and therefore the surface of the sintered body is not easily treated with metal. A high-affinity oxide layer of aluminum oxide or the like was formed as an intervening layer, and then metallization was performed.

Thus, the metallized layer and the aluminum oxide layer as the intervening layer were firmly bonded, but the problem of adhesion between the intervening layer and the aluminum nitride sintered body remained unsolved. There is. That is, an oxide layer such as aluminum oxide has a vitrification layer or a metallization layer due to its poor affinity or wettability with a nitride such as an aluminum nitride sintered body and low adhesion. The reliability of the aluminum nitride sintered product was insufficient.

Further, as one of the methods of forming the aluminum oxide intervening layer, a method of oxidizing the surface of the aluminum nitride sintered body is known, but the aluminum oxide layer obtained by this method is extremely uneven (thickness, etc.). It's porous. In such an example, the reaction layer generated by oxidizing the sintered body having powders such as Si, Al ₂ O ₃ and Fe on the surface is also non-uniform and porous, and has an adhesion strength and a thermal conductivity. However, the reliability is insufficient, and thus it is difficult to use it as a target IC substrate.

Problems to be Solved by the Invention As described above, research and development on a substrate, a heat sink, and the like, which are suitable for recent trends in semiconductor technology, particularly have excellent heat dissipation and electrical insulation properties, have been extensively conducted, Attention is focused on an aluminum nitride sintered body which is satisfactory in both of these characteristics and mechanical strength. This aluminum nitride
There are some problems that must be solved before they can be put to practical use as substrate materials for semiconductor ICs. As one of them, the technical problem of obtaining a sintered body that is dense and has good thermal conductivity has been almost solved. However, another serious problem, that is, the problem that aluminum nitride has a low affinity for glass and metal, and low wettability, is still unsolved. It has been practiced to provide an intervening layer of aluminum oxide or the like having a good affinity only to the surface to be converted.

However, such a treatment merely presented a new problem of adhesion between the intervening layer and aluminum nitride, and did not solve the fundamental problem. Further, when such an intervening layer is formed by the oxidation treatment of the surface of the aluminum nitride sintered body, an oxidation reaction substance (for example, alumina,
The structure of silica, mullite, iron oxide, etc.) becomes remarkably porous, and since the film thickness is non-uniform, it is a serious problem in terms of adhesion and reliability.

Under such circumstances, it is urgently desired to develop a processing technique capable of ensuring high adhesion between aluminum nitride and a glassy or metallized surface, and there is a great demand for this. That is, an intermediate component which has high adhesion to an aluminum nitride sintered body and a metallized surface to be formed later and is useful for producing an aluminum nitride sintered body substrate having improved characteristics and high reliability. That is, it is extremely significant to develop an aluminum nitride substrate material having an improved surface or a treated surface with improved wettability and adhesion to both metal and aluminum nitride sintered body.

Therefore, it is an object of the present invention to provide an aluminum nitride sintered body having a glass layer having improved adhesion and reliability.

Another object of the present invention is to provide a method for producing an aluminum nitride sintered body having a glass layer as described above and useful for later forming a metallized surface thereon.

Means for Solving the Problems In view of the above-mentioned current situation in the practical application research of the aluminum nitride sintered body as a substrate for IC, etc., the present inventors are keen to obtain the above-mentioned objective aluminum nitride sintered body. As a result of study and research, they found that etching the surface of the aluminum nitride sintered body to elute the crystal grains is advantageous for the subsequent vitrification and metallization, and arrived at the present invention.

That is, the aluminum nitride sintered body having the glass layer of the present invention is composed of an aluminum nitride layer, a corroded surface layer, and a glass layer formed via the corroded layer.

The aluminum nitride sintered body having the glass layer according to the present invention has a high adhesion strength between the glass layer and the aluminum nitride sintered body, and the glass layer is also excellent in wettability with metal and adhesion. In addition, a metal layer is formed via this glass layer, and it can be used for various applications requiring high electrical insulation and heat dissipation.

The aluminum nitride sintered body having the vitrified layer of the present invention can be obtained as follows. That is, first, it is important for the aluminum nitride sintered body substrate to have good thermal conductivity without containing many defects such as pores and impurities.

Therefore, it is preferable to use the one obtained by the method for producing an aluminum nitride sintered body which is dense and has good thermal conductivity developed by the present inventors.
At least one solution selected from the group consisting of yttrium and cerium alkoxides is added to aluminum nitride powder having an oxygen content of not more than wt% and yttrium or Ce.
It comprises adding 0.1 to 10% by weight in terms of conversion, mixing and decomposing, molding, and then pressureless sintering at a temperature in the range of 1,700 to 2,200 ° C. in a non-oxidizing atmosphere (JP-A-60-184635). See description). However, the present invention is not limited to this example, and is not limited as long as it is dense and has a good thermal conductivity. For example, in addition to those disclosed in JP-A-59-121175, as the above-mentioned sintering aid, Examples include those using CaO.

Next, the aluminum nitride surface is subjected to etching treatment, which is generally wet etching using an alkaline aqueous solution or the like. As a particularly preferred example, 15
An aqueous solution having a pH of about 10 or more such as NaOH or KOH at about 85 ° C can be used. By this treatment, aluminum nitride crystal grains are eluted over a thickness of about 1 to 20 μm. Therefore, it is preferable to use an aluminum nitride sintered body having a grain boundary structure having an average grain size of about 10 to 30 μm as the substrate.

A glass layer is then applied to the surface of the etched aluminum nitride sinter. It is particularly preferable that the glass layer is formed by applying a metal alkoxide (preferably one in which the alkyl portion is a lower alkyl group) and then sintering.
As the metal alkoxide, silicon alkoxide and aluminum alkoxide are mentioned as particularly preferable examples, and a boron (B) source (1 to 20 mol%) for the purpose of imparting specific physical properties (for example, chemical resistance and wettability improvement). , Zr
A source (5 to 30 mol%) or the like may be added. Preferred B
Sources or Zr sources include alkoxides where the alkyl portion is a lower alkyl group.

Since the aluminum nitride sintered body provided with the glass layer has improved affinity with metal and wettability as described above, application of the metallized layer is easy. Therefore, for example, a thick film paste is applied to a predetermined thickness by a screen printing method and then baked, or a metal layer is formed on the surface of the aluminum nitride sintered body through a glass layer according to a physical vapor deposition method such as an ion plating method. It is possible to form an activated surface.

First, in the case of the thick film paste method, Au, Au-Pt, Pt, A
g, Ag-Pd, etc. can be used, and by coating these pastes by screen printing, and then baking them in the atmosphere, in an oxygen atmosphere or in a nitrogen atmosphere at a temperature in the range of about 850 to 940 ° C. The formation of metallized surfaces can be performed. These exemplified metals achieve strong adhesion with the vitrified layer, and are also exemplified as being excellent as IC conductors, and the present invention is not intended to be limited thereto. Of course, other metals can be used. This thick film paste method is particularly advantageous for forming a single metal layer.

On the other hand, the physical vapor deposition method is particularly suitable for obtaining a metallized surface having a laminated structure of two or more layers, for example, Ti / M as an example of a three-layer structure.
o / Ni, Ti / Mo / Au, Ti / Pt / Au, Zr / Mo / Ni, Zr / Mo / Au, Zr / P
Examples include t / Au. Among the physical vapor deposition methods, the ion plating method is particularly preferable because it is excellent in the adhesion of the deposited film and the like, and it is advantageous to use an active metal such as Ti or Zr as the lowermost layer, that is, the layer in contact with the glass layer. Yes, they are expected to form a strong bond with the grain boundary layer because of their high chemical affinity with oxygen or nitrogen.

Action In order to make the aluminum nitride sintered body practical for use as a material for IC substrates, heat sinks, etc., improve the affinity or wettability between it and metal, etc. Must be secured.

The present inventors wet-etch the surface under the idea that the low affinity or wettability with other substances, which is an inherent property of aluminum nitride, is due to the structure of the surface. This changed its structure. By this treatment, the aqueous solution of alkali, especially NaOH, KOH, preferentially elutes the crystal grains of the aluminum nitride sintered body, and the crystal grains eluted in the network of the grain boundary structure due to the partial loss thereof. A hole having a size corresponding to the particle size of is formed. Due to the existence of such holes, the glass layer forming material to be applied next easily penetrates into the surface of the aluminum nitride sintered body, and as a result, the bonding / adhesion strength between the glass layer and the aluminum nitride layer is greatly increased. Will be improved (so-called anchor effect).

In order to advantageously form such holes, it is important to select the sintering aid used when forming the aluminum nitride sintered body, and an oxide such as CeO _{2 is} used as this aid. Is particularly preferable. This is because the sintered body obtained using this as an auxiliary agent is composed of reaction products containing Al, N, Ce, and O as constituent elements, and such a material has a remarkably high affinity with glass. . In addition to the above CeO ₂ , it is advantageous to use Y ₂ O ₃ , CaO or the like as an auxiliary agent, and the same effect can be expected.

Further, as described above, it is preferable that the etching treatment is performed so that the thickness of the grain boundary structure on the surface of aluminum nitride is about 1 to 20 μm. If the treatment is less than 1 μm, the above anchor effect cannot be expected. On the other hand, even if the treatment exceeds 20 μm, not only the significant improvement in the effect is not observed, but conversely, the surface layer becomes porous, and after the glass layer is formed. Neither is desirable because sufficient strength at the interface cannot be ensured. Corresponding to such restrictions on the surface treatment by etching, it is preferable that the aluminum nitride sintered body used also has an average particle size of about 10 to 30 μm.

In order to allow the glass forming material to sufficiently penetrate into the hole thus formed, it is necessary to select the material to be used sufficiently. Therefore, a liquid metal alkoxide is used as described above. By selecting the liquid as the glass layer forming material in this way, a sufficient amount of the glass layer forming material is introduced into the holes formed by the etching process, and the glass obtained after the vitrification process (baking) is obtained. The layer can realize a state in which it is structurally fitted to the surface of the aluminum nitride sintered body, and when the sintering aid which is advantageous in terms of affinity with the glass layer as described above is selected, the adhesion is improved. An aluminum nitride product having an excellent glass layer can be obtained.

By using the liquid metal alkoxide as the glass layer forming material as in the present invention, the surface flatness and film thickness observed in the conventional intervening layer, especially the oxide layer formed by the surface oxidation treatment It is also possible to solve the problem of non-uniformity of the above, and also from this point, improvement of the characteristics of the metallized surface to be formed later can be expected.

The aluminum nitride product having the glass layer of the present invention thus obtained provides sufficient bonding strength and adhesion with a metal. By providing a metallized surface on this glass layer, a substrate for an IC or a heat sink can be obtained. It is possible to provide a substrate material and the like that can be advantageously used as, for example, and can sufficiently cope with an increase in the amount of heat generated due to high integration, which is a trend of recent semiconductor technology.

Further, according to the present invention, it is possible to further enhance the functionality of the aluminum nitride sintered product, for example, as a glass layer forming material Zr
By using the above alkoxides, B alkoxides, and the like in the amounts described above, the environment resistance, chemical resistance (particularly acid resistance or alkali resistance) and wettability can be improved.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and the effects to be demonstrated will be demonstrated, but the scope of the present invention is not limited to the following Examples.

Example 1 An aluminum nitride sintered body composed of an aluminum nitride substrate 1 having a structure as schematically shown in FIG. 1, a corroded layer 2 thereof, and a glass layer 3 formed via the corroded layer 2. Was prepared as follows. Also, as shown in FIG.
An aluminum nitride sintered body having a metallized surface having the metal layer 4 formed on the glass layer 3 was also prepared, and the bonding strength of each was measured.

CeO ₂ , Y ₂ O ₃ as a sintering aid in a 79 ° C NaOH aqueous solution at pH 13.6
Etching treatment (etching thickness: 1 ~ 3μ
m) Then, on its surface, tetraethoxysilicate, triisopropoxyaluminum, tetraethoxysilicate containing tri-n-butoxyboron (molar ratio B: Si = 1: 9) mixed solution and tetraethoxysilicate containing zirconium methoxide ( Molar ratio Zr: Si ＝
1: 3) Apply the mixed solution to each substrate and leave it in the air at 900 ° C for 10
Bake for minutes. The glass layer thickness produced by each alkoxide was 1-2 μm.

Next, Au, Pt, Au-Pt, and Ag paste are applied to the surface of the aluminum nitride sintered body substrate having the glass layer thus obtained to a thickness of about 25 to 30 μm, respectively, and then 850 to 9 in the atmosphere.
Baking was performed at 40 ° C. for 10 minutes to form an aluminum nitride sintered body having a metallized surface. On the metallized surface thus obtained
A 0.8 mmφ mild steel wire was soldered to obtain the tensile strength, and the results are summarized in the following Tables 1-a to 1-c.

The glass film formed by each alkoxide is SiO ₂ ,
Al ₂ O _3, a B ₂ O ₃ -SiO ₂ and ZrO ₂ -SiO _2.

Incidentally, a glass film was similarly formed without etching treatment, and then a metallized product was similarly prepared, which is also shown in the table as a comparative example.

Example 2 An aluminum nitride sintered body using CeO ₂ as a sintering aid was immersed in a KOH aqueous solution (68 ° C.) having a pH of 12.7, and an etching treatment was performed so that the etching thickness was 1 to 3 μm.
The glass layer was provided by coating the surface with the alkoxide of Example 1 and firing it.

Next, this substrate was immersed in a NaOH aqueous solution having a pH of 13.6 and 72 ° C. and thoroughly washed, and then a metallized layer was formed in the same manner as in Example 1. The aluminum nitride sintered body having the metallized layer thus obtained was subjected to the same tensile strength measurement as in Example 1 to examine the alkali corrosion resistance due to the difference in the alkoxide component.

The results are shown in Table 2.

As described in detail above, according to the present invention, the surface of the aluminum nitride sintered body is first subjected to etching treatment with an alkaline aqueous solution or the like to preferentially elute the crystal grains, leaving the grain boundary layer, and Based on the fact that a glass layer was formed by applying an alkoxide solution on the surface, the synergistic effect of the anchor effect based on the elution of crystal grains and the improvement of the affinity with the glass layer,
It has become possible to secure a sufficiently high adhesion strength between the glass layer and the aluminum nitride sintered body.

Further, the coexistence of the B source in the alkoxide component is expected to further improve the adhesion between the aluminum nitride and the glass layer, and the coexistence of the Zr source is expected to improve the environment resistance, particularly the alkali resistance. be able to.

Since the glass layer thus obtained has excellent affinity with metal and wettability, it is necessary to form a metallized layer on the glass layer with sufficient adhesion by screen printing method and physical vapor deposition method, especially ion plating method. Became possible.

Therefore, the aluminum nitride sintered body having the glass layer of the present invention can be used not only as an IC substrate, a heat sink, etc. by forming a metal layer through the glass layer, but also as a composite material of a metal and an aluminum nitride sintered body. It can be advantageously used in all fields in which aluminum nitride is required, and the excellent properties of aluminum nitride such as high thermal conductivity, high electrical insulation and high mechanical strength can be sufficiently exhibited.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view for explaining the structure of an aluminum nitride sintered body having a vitrification layer of the present invention, and FIG. 2 is an application example of the product of FIG. FIG. 3 is a schematic cross-sectional view showing an example in which a metallized layer is provided on the. (Main reference numbers) 1 ... Aluminum nitride sintered body substrate, 2 ... Corrosion surface, 3 ... Glass layer, 4 ... Metal layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location H05K 1/03 7011-4E 3/38 A 7011-4E (56) Reference JP-A-60-166262 (JP, A) JP-A-54-82666 (JP, A) JP-A-60-200884 (JP, A)

Claims (8)

[Claims] 1. An aluminum nitride sintered body substrate having a corroded layer including holes formed by removing crystal grains from a surface to a predetermined thickness, and a glass layer deposited on the corroded layer. An aluminum nitride sintered body having a glass layer, characterized in that a part of the glass layer penetrates into the hole. 2. The aluminum nitride sintered body according to claim 1, wherein the corrosion layer has a thickness of 1 to 20 μm. 3. The aluminum nitride according to claim 1, wherein the grain boundary structure of the aluminum nitride sintered body has an average grain size of 10 to 30 μm. Sintered body. 4. A glass layer is formed by wet etching the surface of an aluminum nitride sintered body substrate with an aqueous solution of NaOH or KOH having a pH of 10 or more and a temperature of 15 to 85 ° C., and then applying an alkoxide and firing. Of manufacturing an aluminum nitride sintered body having a glass layer to be used. 5. The method for producing an aluminum nitride sintered body according to claim 4, wherein the alkoxide is a silicon alkoxide, an aluminum alkoxide or a mixture thereof. 6. The method for producing an aluminum nitride sintered body according to claim 5, wherein the alkyl portion of the alkoxide is a lower alkyl group. 7. The method for producing an aluminum nitride sintered body according to claim 5, wherein the alkoxide contains 1 to 20 mol% of boron alkoxide. 8. The method for producing an aluminum nitride sintered body according to claim 6 or 7, wherein the alkoxide contains zirconium alkoxide in an amount of 5 to 30 mol%.