JP2001320002A - Aluminum nitride metallized substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum nitride metallized substrate that has high thermal conductivity and an excellent heat dissipation property, at the same time, can be used even in a high-frequency region of 100 MHz or more, and can be manufactured by the simultaneous sintering method. SOLUTION: In this aluminum nitride metallizing substrate, an aluminum nitride forming body, and conductor paste that is printed to the aluminum nitride forming body so that a specific wiring pattern is formed are sintered simultaneously, thus forming a metallized layer on the aluminum nitride substrate integrally. Also, in the aluminum nitride metallized substrate, the heat resistance of the aluminum nitride substrate should be equal to 5 deg.C/W or less, and at the same time dielectric loss should be equal to 8.5 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metallized aluminum nitride substrate having a metallized layer on the surface of the substrate, particularly having high thermal conductivity and good high-frequency characteristics.
The present invention also relates to an aluminum nitride metallization that can be manufactured by a simultaneous firing method.

[0002]

2. Description of the Related Art In recent years, the miniaturization and high density of electronic devices have been progressing, and the output of semiconductor components has been rapidly increasing, and the amount of heat generated in electronic devices such as semiconductor components tends to increase significantly. It is in. In order to prevent the operation of the electronic device from being hindered by the heat generation, it is an important technical problem to obtain a method for efficiently dissipating heat generated from semiconductor components and the like.

[0003] Aluminum nitride (AlN) has high thermal conductivity, good electrical insulation, and excellent properties such as almost the same coefficient of thermal expansion as Si. It is suitable as a substrate material for mounting semiconductor components.

By the way, in order to use aluminum nitride (AlN) as a substrate for mounting a semiconductor component, it is necessary to use AlN to form a circuit or a mounting portion for an electronic component.
It is necessary to form a metallized layer made of a conductive metal on the substrate surface. One of the ways to perform metallization is
A co-firing method (Co-fire method) is used, and a metallized layer is generally formed on the substrate surface by the following procedure.

That is, a binder and a solvent comprising an organic compound are added to aluminum nitride (AlN) powder to form a slurry, and this slurry is formed into a sheet by a doctor blade method to obtain an AlN green sheet. Then, on the surface of the AlN green sheet, W or M
A conductive paste containing a high melting point metal powder such as o is printed, the obtained molded body is heated and degreased, and then sintered in a non-oxidizing atmosphere to obtain an AlN metallized substrate.

In the simultaneous sintering method, the sintering of the AlN substrate and the baking of the metallized layer on the AlN substrate are simultaneously performed in a single firing. In comparison, there is an advantage that the number of manufacturing steps is small.

On the other hand, with the increase in power consumption of a semiconductor element, an AlN substrate having better heat dissipation and a high thermal conductivity has been increasingly required as a substrate material for mounting the semiconductor element. -An AlN substrate having a high thermal conductivity of K or more is required.

[0008]

SUMMARY OF THE INVENTION
In order to obtain a thermal conductivity of W / m · K or more,
It is necessary to perform sintering at a high sintering temperature exceeding 800 ° C. However, when sintering at a high temperature exceeding 1800 ° C., there are problems such as elution of the glass component in the AlN molded body and infiltration of the glass component. Was.

That is, if the glass component in the AlN compact elutes on the substrate surface during sintering, it causes stains, discoloration, etc. on the AlN substrate surface. In addition, when the glass component infiltrates into the metallized layer and oozes out on the metallized surface, poor appearance of the metallized portion and a decrease in solderability occur, and the bonding strength and durability of electronic components such as various elements are reduced. Resulting in.

Therefore, in order to prevent poor appearance of the metallized portion and deterioration of solderability, conventionally, the glass component does not exude to the metallized surface at 1800 ° C.
It was necessary to fire at the following relatively low temperatures. Therefore, the upper limit of the thermal conductivity of the AlN metallized substrate that can be manufactured by the simultaneous firing method is about 180 W / m · K.
AlN metallized substrates having a thermal conductivity of 190 W / m · K or more and having a metallized layer on the surface by a simultaneous firing method have not been obtained so far.

Therefore, conventionally, an AlN substrate having a thermal conductivity of 190 W / m · K or more, which has been sintered in advance at a high temperature exceeding 1800 ° C., is previously prepared, and the glass component that has oozed to the surface is removed by polishing or the like. Thereafter, a post-fire method (Post-fire method) in which a refractory metal paste is printed on the AlN substrate surface and baked is adopted.

However, in the case of the post-fire method,
As compared with the simultaneous firing method, the number of processing steps is large, and a complicated process of removing exuded glass components by polishing or the like is required. there were. In addition, it takes time and effort to form an AlN substrate thicker in advance by an amount corresponding to the polishing allowance, and has a problem that the manufacturing efficiency is poor.

In addition to the metallization method by the post-fire method, a method of forming a thin film on a substrate surface is also used. For example, thin film formation by vapor deposition, sputtering or chemical vapor deposition (CVD: che
Although a method such as physical vapor deposition is also used, such a method requires a larger number of manufacturing steps than the post-fire method, and requires the polishing of the substrate surface as in the case of the post-fire method. Had the problem of.

On the other hand, as the speed of the semiconductor device increases and the operating frequency of the semiconductor element increases, the quality of the high-frequency characteristics of the substrate becomes a serious problem. Specifically, the operating frequency of the semiconductor element mounted on the ceramic substrate is 1
If the operation speed is increased to exceed 00 MHz, the operation signal is likely to be deteriorated due to the dielectric loss of the ceramic substrate, and high-frequency signal processing becomes difficult, and the operation reliability of the semiconductor device is greatly reduced. From such a background, it has been a technical problem to realize a substrate material having a smaller dielectric loss.

The present invention has been made in order to solve such a problem, and has a high heat conductivity, excellent heat dissipation, and can be used in a high frequency region of 100 MHz or more. An object is to provide an aluminum nitride metallized substrate that can be manufactured by a simultaneous firing method.

[0016]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies and as a result, by adjusting the thickness of the AlN substrate appropriately, the glass component was changed to AlN.
It has been found that there are firing conditions that do not elute on the substrate surface, have a thermal resistance of 5 ° C./W or less, and a thermal conductivity of 190 W / m · K or more. That is, when the thickness of the AlN substrate exceeds 1.5 mm, the thermal resistance is 5 ° C./W or less and the thermal conductivity is 190 W unless fired at a temperature higher than 1800 ° C.
/ M · K or more. However, when firing at such a high temperature, the glass component not only moves to the back surface of the AlN substrate, but also oozes out to the surface of the AlN substrate, so that a high-quality AlN substrate cannot be obtained as described above.

However, the inventors of the present invention set the thickness of the AlN substrate to 1.5 mm or less, so that even when baked at a temperature of 1800 ° C. or less, the thermal resistance is as low as 5 ° C./W or less. It has been found that an aluminum nitride substrate having a conductivity of 190 W / m · K or more can be obtained. That is,
The thickness of the AlN substrate is 1.5 mm or less, preferably 1.0 mm or less.
If it is less than mm, the glass component in the AlN substrate at the time of firing moves to the back surface of the AlN substrate by gravity and is further absorbed into the setter, so that the glass component does not elute on the surface of the AlN substrate. Therefore, it has been found that the elution of the glass component to the AlN substrate surface does not occur, and problems such as poor appearance are solved. The present inventors have completed the invention based on such knowledge.

That is, the aluminum nitride metallized substrate according to the present invention is obtained by simultaneously firing an aluminum nitride compact and a conductor paste printed on the aluminum nitride compact so as to form a predetermined wiring pattern. In an aluminum nitride metallized substrate in which a metallized layer is integrally formed on a substrate, the aluminum nitride substrate has a thermal resistance of 5 ° C./W or less and a dielectric loss of 8.5 or less.

In the AlN metallized substrate, the thickness of the aluminum nitride substrate is preferably 1.5 mm or less. Further, it is desirable that the thermal conductivity of the aluminum nitride substrate is 190 W / m · K or more.
Preferably, the average crystal grain size of the aluminum nitride substrate is 5 μm or less.

Further, in the present invention, the metallized layer may be composed of at least one of tungsten (W) and molybdenum (Mo) having a high melting point. Further, the aluminum nitride substrate may be configured to have a multilayer structure in which a plurality of substrate elements are stacked.

In the AlN metallized substrate according to the present invention, the thickness of the AlN substrate indicates a substantial thickness of aluminum nitride excluding the thickness of the metallized layer. In other words, when the aluminum nitride substrate has a single-layer structure consisting of one sheet, the thickness of the aluminum nitride substrate excluding the metallized layer is shown. It shows the total thickness of the aluminum nitride substrate excluding the metallized layer.

When the thickness of the AlN substrate exceeds 1.5 mm, the firing temperature becomes higher than 1800 ° C.
The reason why sintering can be performed at a low temperature of 1800 ° C. or less in the case of m or less is as follows. That is. When the thickness of the AlN substrate is 1.5 mm or less, the glass component contained in the aluminum nitride molded body during firing moves to the back side of the substrate due to gravity, and a setter (fired plate) on which the AlN molded body is placed The above glass components are absorbed and removed from the AlN sintered body. For this reason, the glass component does not elute on the surface of the AlN substrate, and the appearance does not deteriorate and the solderability does not decrease. On the other hand, when the thickness of the AlN substrate exceeds 1.5 mm, the glass component is not completely absorbed in the setter, and a part of the glass component oozes out on the surface of the AlN substrate, causing the above-mentioned problem. Therefore, in the present invention, the thickness of the AlN substrate is set to 1.5 mm or less, and more preferably, 1.0 mm or less.

As the metal material constituting the metallized layer,
In particular, in order to maintain a predetermined wiring pattern shape without melting or flowing even at a high temperature at the time of simultaneous firing, it is preferable to use a high melting point metal such as W or Mo as a main component.

The thickness of the metallized layer is not particularly limited, but is desirably 1 μm or more. By setting the thickness of the metallized layer to 1 μm or more, the exudation of the liquid phase component (glass component) can be more effectively prevented. The thickness of this metallized layer is
Preferably 3 to 20 μm, more preferably 5 to 15 μm
m. If the thickness exceeds 20 μm, bleeding of the liquid phase component can be suppressed, but the metallized layer becomes too thick, making it difficult to form a uniform conductive film. Also,
Since the amount of high melting point metal such as W or Mo used as the metallized layer increases, it is not preferable from the viewpoint of cost.

The average crystal grain size of the aluminum nitride substrate is
This has a great effect on the dielectric loss of the AlN substrate, and in the present invention, it is desirable to set the thickness to 5 μm or less. By setting the average crystal grain size of the AlN substrate to 5 μm or less, it is possible to reduce the dielectric loss of the AlN substrate to 8.5 or less, and to mount a semiconductor element for processing a high-frequency signal of 100 MHz or more. In this case, malfunction does not occur, and the operation reliability can be greatly improved. The more preferable range of the dielectric loss of the AlN substrate is 8.4 or less, and further more preferably 8.3 or less.

The aluminum nitride metallized substrate according to the present invention is manufactured, for example, by the following steps. That is, a sintering aid and a binder are added to the aluminum nitride (AlN) raw material powder, and after adjusting the raw materials, an aluminum nitride molded body is obtained, and a high melting point metal paste is applied to the surface of the aluminum nitride molded body, followed by heat degreasing. After that, an aluminum nitride molded body having a substantial thickness of 1.9 mm or less excluding the metallized layer containing the high-melting-point metal as a main component is placed on a setter.
It is manufactured by firing at a temperature of not more than ℃.

In the above manufacturing method, by setting the thickness of the AlN compact to 1.9 mm or less, the AlN
The glass component in the molded body moves to the back surface of the AlN substrate due to gravity and is absorbed into the setter.
Even when firing at a temperature of 800 ° C. or less, a high-quality AlN substrate having a thermal resistance of 5 ° C./W or less and a high thermal conductivity of 190 W / m · K or more can be obtained.

In the above manufacturing method, the glass component in the AlN molded body can be efficiently absorbed into the setter by firing using a setter made of highly purified aluminum nitride by high-temperature sintering or the like. .

In the above method for manufacturing an aluminum nitride metallized substrate, not only the aluminum nitride molded article having a single-layer structure but also an aluminum nitride molded article having a multilayer structure in which a plurality of the aluminum nitride molded articles are laminated. It is also possible to use.

Further, as the AlN sintered body constituting the aluminum nitride substrate, it is preferable to use one obtained by adding a sintering aid to aluminum nitride at a ratio of 10% by weight or less to aluminum nitride. If the addition ratio of the sintering aid exceeds 10% by weight, the amount of the liquid phase component seeping out increases, and the problem that the adhesion strength of the metallized layer decreases is caused.

In the present invention, it is preferable to perform simultaneous firing using a setter made of high-purity AlN. For example,
Such a setter is made of yttrium oxide (Y ₂ O ₃ )
By sintering AlN containing 3% by weight at a predetermined temperature to exude a liquid phase component (glass component) and keeping the sintering temperature until the liquid phase component no longer exudes. The setter made of such an AlN sintered body has substantially no liquid phase component and has AlN of about 97 to 100%. Such high purity AlN
If a setter is used, as described above, an AlN substrate (sintered body)
Since most of the liquid phase component oozing out of the substrate is effectively absorbed by the setter, a co-fired metallized substrate can be efficiently produced.

By using the aluminum nitride metallized substrate manufactured as described above, the thermal resistance of the substrate is reduced by 5%.
Since the heat radiation characteristics can be greatly improved by lowering the temperature to less than or equal to ° C./W, a semiconductor device with little thermal influence can be obtained even when a semiconductor element having a heat generation of 40 W or more is mounted.

According to the aluminum nitride metallized substrate having the above structure, the aluminum nitride substrate has a thermal resistance of 5 ° C.
/ W or less, is excellent in heat dissipation, and has a dielectric loss of 8.5 or less, so that it is possible to mount a high-output semiconductor element having a heating value of 40 W or more,
Even when a semiconductor element for processing a high-frequency signal of 100 MHz or more is mounted, malfunction does not occur and operation reliability can be greatly improved.

[0034]

Next, embodiments of the present invention will be described more specifically based on the following examples and comparative examples.

Examples 1 to 11 and Comparative Examples 1 to 4 Yttrium oxide (Y ₂ O ₃ ) powder was added as a sintering aid to an aluminum nitride (AlN) powder having an average particle size of 1.5 μm in an amount of 5% by weight. The powder was prepared and crushed and mixed by a ball mill. After adding an organic binder and an organic solvent (ethanol) to this raw material powder, they were mixed to form a slurry. This slurry was formed into a sheet by a doctor blade method, and a number of AlN green sheets having a thickness of 0.5 to 2.6 mm were prepared in consideration of shrinkage after firing.

On the other hand, as shown in Table 1, an appropriate amount of a resin binder and a dispersant are mixed with tungsten (W) powder or molybdenum (Mo) powder having an average particle size of 1 μm to prepare a W paste or a Mo paste. Materials for the metallized layers were prepared. To the paste materials for Examples 2, 4, and 11, AlN powder, which is a common material of the AlN substrate, was added.

Next, a W paste or the like was screen-printed on the AlN green sheet and dried. As shown in Table 1, the AlN green sheet coated with the W paste or the like was directly used as an AlN molded body having a single-layer structure, and a plurality of such laminated AlN green bodies (laminates) were obtained.
Then, each molded body and the laminated body are placed in a nitrogen atmosphere at 900
A degreasing treatment was performed at a temperature of ° C. for 3 hours.

On the other hand, yttrium oxide (Y ₂ O ₃ )
A setter (sintered plate) made of an AlN sintered body containing 1% by weight was fired at a high temperature of 1900 ° C. to exude a liquid phase component to prepare a setter made of high-purity AlN.

On this high-purity AlN setter, a degreased AlN green sheet was placed, and baked at a temperature of 1750 to 1800 ° C. for 6 hours in a nitrogen atmosphere as shown in Table 1 to obtain an AlN substrate and a WN The AlN metallized substrate composed of a single layer or multiple layers was prepared by simultaneously firing the layer or the Mo layer.

As shown in Table 1, in the second embodiment,
The thickness of the AlN substrate is 1.5 mm, and W and AlN are used as the composition of the metallized layer. The AlN substrates of Examples 3 to 7 have a thickness of 1.4 mm.
In this case, a single-layer AlN substrate gradually thinned by 0.2 mm is used. In Example 8, 0.5 mm of Al
Two N green sheets coated with W paste are laminated and then sintered to form an AlN substrate having a multilayer structure. The ninth to eleventh embodiments differ from each other in the thickness of the metallized layer. In each of the metallized layers with AlN added, 3% by weight of AlN was used.
It was included. In each of the samples of Examples 1 to 11, the thickness of the AlN substrate excluding the metallized layer was substantially 1.5 mm or less, and the sintering temperature was 1800 ° C. or less. .

Comparative Examples 1 and 2 In this comparative example, samples of 2 mm (Comparative Example 1) and 1.6 mm (Comparative Example 2) in which the substantial thickness of the aluminum nitride (AlN) substrate exceeds 1.5 mm are used. Was. In addition, Al
The procedure for manufacturing the N substrate is the same as in the example.

As shown in Table 1, Comparative Example 1 had a thickness of 2.
The comparative example 2 is a single-layer AlN substrate having a thickness of 0 mm.
After stacking four 4 mm AlN green sheets and sintering, an AlN substrate having a multilayer structure with a substantial AlN substrate thickness of more than 1.5 mm is obtained. The components, thicknesses and sintering conditions of the metallized layer are as shown in Table 1.

COMPARATIVE EXAMPLE 3 In this comparative example, a single-layer 1.5 mm-thick AlN was used during firing, using a boron nitride (BN) setter.
It has a substrate. The procedure for manufacturing the AlN substrate is almost the same as that of the example, and the components, thickness, and sintering conditions of the metallized layer are as shown in Table 1.

Comparative Example 4 In this comparative example, eight AlN green sheets each having a thickness of 0.5 mm were laminated and then fired simultaneously to form a total thickness of 3.2 m.
m of an AlN substrate having a multilayer structure. In addition,
The manufacturing procedure of the AlN substrate is almost the same as that of the example, and the components, thickness, and sintering conditions of the metallized layer are as shown in Table 1.

The external appearance of the AlN metallized substrates according to the respective Examples and Comparative Examples thus obtained was observed.
The external appearance was measured by observing whether or not seepage of the liquid phase component was observed when the surface of the metallized layer was observed with a microscope at a magnification of 20 times. Specifically, 2
When the liquid phase component was not observed when the sample was observed at a magnification of 0, the appearance was determined to be good, and when the liquid phase component was observed, the appearance was judged to be poor. The average crystal grain size, thermal resistance, dielectric loss, and thermal conductivity of each AlN metallized substrate were measured. The thermal conductivity was measured using a laser flash method. The measurement results are shown in Table 1 below.

[0046]

[Table 1]

As is clear from the results shown in Table 1, according to the aluminum nitride metallized substrates according to the respective examples,
Since the thermal resistance of aluminum nitride is 5 ° C./W or less, the heat dissipation is excellent, and the dielectric loss is 8.5 or less, for example, a high-output semiconductor element having a calorific value of 40 W or more is also mounted. Is possible and 100 MH
Even when a semiconductor element for processing a signal of a high frequency of z or more is mounted, malfunction does not occur and operation reliability can be greatly improved.

On the other hand, in the AlN metallized substrates according to Comparative Examples 1, 2, and 4, spots and discoloration were observed on the surface of the AlN substrate, the appearance was poor, and the thermal conductivity was 190 W /
m · K or less. This is because the thickness of the AlN substrate is 1.5
This is because the liquid phase component lowering the thermal conductivity is not sufficiently absorbed by the AlN setter because the thickness is larger than mm.

On the other hand, in each of Examples 1 to 11, the AlN
The substrate had good appearance without spots or discoloration observed. In each case, the thermal conductivity showed a high value of 190 W / m · K or more, and the thermal resistance was 5 ° C./W or less, and a high-quality AlN metallized substrate excellent in heat dissipation was obtained. .

In Example 10 in which the thickness of the metallized layer was 1 μm, a small amount of seepage of the liquid phase component began to be observed. From this phenomenon, it was found that the thickness of the metallized layer was preferably 1 μm or more. On the other hand, Al
No bleeding was observed in Example 11 to which N was added. From this point, it was found that the addition of AlN to the metallized layer also had an effect of preventing bleeding of the liquid phase component. Comparative Example 3
In the metallized substrate fired using the BN setter of
The amount of the liquid phase component seeping out is large, and it has been difficult to use it as a metallized substrate.

According to the present embodiment, by setting the thickness of the AlN substrate to 1.5 mm or less, even if the sintering temperature is 1800 ° C. or less, the thermal resistance is 5 ° C. /
180 W / m · K, which is less than W
Having a thermal conductivity of 190 W / m · K or more that exceeds
An N substrate can be obtained. Therefore, in the present embodiment, since the co-firing method is applied, the number of manufacturing steps can be reduced, the production efficiency can be improved, and the mass production of the AlN metallized substrate can be achieved.

Further, the A manufactured by the manufacturing method of this embodiment is
The 1N substrate has a high thermal conductivity of 190 W / mK or more,
Since it is excellent in heat dissipation, it can be used as a mounting substrate for a semiconductor component with high output, and further downsizing and high density of electronic equipment can be achieved.

Even when the AlN substrate has a multilayer structure as in this embodiment, since the AlN substrate has excellent heat dissipation properties, the integration density can be increased, and the miniaturization and the density increase of the electronic equipment can be achieved. Can be planned.

[0054]

As described above, according to the present invention,
The thermal resistance of the aluminum nitride substrate is 5 ° C./W or less,
Since it has excellent heat dissipation and dielectric loss of 8.5 or less, it is possible to mount a high-output semiconductor element with a heating value of 40 W or more, and process high-frequency signals of 100 MHz or more. Even when a semiconductor element is mounted, malfunction does not occur and operation reliability can be greatly improved.

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Claims (6)

[Claims] An aluminum nitride substrate having a metallized layer formed integrally with an aluminum nitride substrate by simultaneously firing an aluminum nitride molded body and a conductive paste printed on the aluminum nitride molded body so as to form a predetermined wiring pattern. An aluminum metallized substrate, wherein the aluminum nitride substrate has a thermal resistance of 5 ° C./W or less and a dielectric loss of 8.5 or less. 2. The thickness of an aluminum nitride substrate is 1.5 m.
2. The aluminum nitride metallized substrate according to claim 1, wherein the thickness is not more than m. 3. The thermal conductivity of an aluminum nitride substrate is 19
2. The aluminum nitride metallized substrate according to claim 1, wherein said substrate is 0 W / m.K or more. 4. The aluminum nitride metallized substrate according to claim 1, wherein the average crystal grain size of the aluminum nitride substrate is 5 μm or less. 5. The aluminum nitride metallized substrate according to claim 1, wherein the metallized layer is made of at least one of a refractory metal of tungsten (W) and molybdenum (Mo). 6. The aluminum nitride metallized substrate according to claim 1, wherein the aluminum nitride substrate has a multilayer structure in which a plurality of substrate elements are stacked.