JP2003100939A - Heat radiation substrate and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pyrogenic conductive substrate that is a heat radiation substrate where ceramic having insulation properties is adopted as the material of the substrate and a diamond layer is formed on the upper surface by a vapor phase method, and is formed with high coherency for preventing a diamond film from peeling off easily even in, for example, machining such as cut-off. SOLUTION: On the mount surface of a ceramic substrate such as aluminum nitride having the mount surface for mounting an element, a green sheet is formed. The green sheet gives ceramic having substantially the same quality as that of ceramic for composing the ceramic substrate, and contains 1×10<4> to 1×10<10> diamond particles per 1 cm<2> of the green sheet. Additionally, the green sheet is sintered for forming a ceramic layer where at least one portion of the diamond particle is exposed on a surface, and a diamond layer is formed on the ceramic layer by a vapor phase method, thus manufacturing the heat radiation substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a highly heat conductive substrate which can be suitably used as a heat sink for radiating heat energy generated from a heat source and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the increase in information density, the processing capacity of electronic parts has been significantly improved. Therefore, a large amount of heat is currently generated from each component. In order to operate these electronic components stably, it is preferable to keep them at a constant temperature, and various measures have been taken to cool them. Generally, high-temperature electronic components are generally mounted and used on a “heat sink” that is a “material capable of absorbing heat, a device using such a material for thermally protecting a component or system”. Target.

As a material which has been put into practical use as a heat sink material from early on, a metal having high heat conductivity such as Cu or Cu-W, a metal alloy, or a semiconductor or insulating high heat conductive ceramic material such as SiC or AlN is used. However, it has been found that there is a limit to cooling the heat generated due to the improvement of the performance of electronic parts by using a heat sink made of only such a material. Has the highest thermal conductivity (about 2
Those using diamond having 000 W / mK) have been developed. As such a heat sink, there is a general one in which a plate-shaped or film-shaped single crystal diamond is brazed or soldered as a so-called submount on a substrate made of copper or the like called a stem. In the heat sink, single crystal diamond is very expensive, so that a large shape cannot be used, and the above-mentioned brazing material and soldering material become resistance to heat conduction, so that the heat radiation efficiency is not always satisfactory. It wasn't going to happen. Therefore, it has been attempted to form a polycrystalline diamond film on a substrate by a vapor phase synthesis method, and a semiconductor element is mounted as a heat sink manufactured by such a method and having no problem as described above. A heat-dissipating component whose mounting surface is covered with a vapor-phase synthetic diamond layer has been proposed (JP-A-5-13843). The heat-dissipating component is for suppressing characteristic deterioration due to heat generation of the semiconductor laser device, and is a microwave plasma CVD (Chemical Vapor Depositio) on the substrate (stem).
The polycrystalline diamond layer having a thickness of 10 to 500 μm is directly formed by the method n). It is considered that the heat dissipation component can be used as a submount by downsizing.

In a heat sink such as the above-mentioned heat dissipation component, the optimum material for the substrate forming the polycrystalline diamond film differs depending on the application, but when forming an electric circuit on it, it has good insulating properties. In many cases, ceramics are used, and in recent years, there has been an increasing demand for a heat dissipation substrate having a diamond film formed on a ceramic substrate.

By the way, the formation of a diamond film by the vapor phase method as described above can be applied not only to ceramics but also to metal substrates and the like. The present situation is that the adhesion between the substrate and the diamond is not satisfactory. As an attempt to improve the adhesion between the substrate and the diamond film, before the diamond film is formed by the vapor phase method, the substrate is subjected to a fine scratch treatment using diamond powder, or the diamond powder is embedded, Alternatively, in addition to the method of forming unevenness on the surface by subjecting the substrate to mechanical treatment or plasma treatment,
A method of inducing crystal nucleus formation by applying a DC voltage to the substrate during vapor phase synthesis of the diamond film can be mentioned.

However, the above-mentioned method is limited to a substrate material having electrical conductivity, and cannot be applied to a substrate made of a ceramic material. Further, the above-mentioned method has not only a problem in reproducibility but also a maximum nucleation density of about 1 × 10 ³ cm ^−2, which is not so effective. Further, in the above method, the concave portion formed on the surface of the substrate is used as the center of the crystal nucleus, and in the case of using the plasma treatment as described in, for example, JP-A-5-156445, nucleation is performed. Although it is possible to increase the density to about 1 × 10 ¹³ cm ⁻² , the diamond film formed is only in physical contact with the substrate and is in intimate contact therewith, and there is a problem in that it easily peels off. Therefore, among the above methods, the method of homoepitaxially growing the vapor-phase synthetic diamond on the embedded diamond powder is considered to be the best method as far as the crystallinity and the adhesion to the underlayer (diamond powder) are concerned.

[0007]

As an attempt to grow vapor-phase synthetic diamond on diamond powder embedded in a base material, the technique is disclosed in JP-A-4-297045. According to the publication, 1 to 100
It describes a method of vapor-phase synthesis of diamond on the surface of a ceramic sintered body containing 1 to 75% by volume of diamond fine particles of μm. According to this technique, vapor-phase synthetic diamond can be vapor-phase synthesized on the fine diamond particles exposed on the surface of the ceramic substrate, and the number of exposed diamond particles is controlled by controlling the filling amount. It seems that you can do it. However, since diamond becomes thermally unstable and changes or disappears from around 1000 ° C., in consideration of the fact that the sintering temperature of the ceramic material that becomes the base is generally 1000 ° C. or higher, diamond is contained in the ceramic when the ceramic base is sintered. Even if it is carried out, it is extremely difficult to maintain its shape, and it seems that it is difficult to obtain the above-mentioned ceramic sintered body containing diamond fine particles. It should be noted that the above publication does not describe detailed conditions of the method for manufacturing the ceramic substrate.

Therefore, as a new attempt to incorporate fine diamond particles on a ceramic substrate, JP-A-8-119 has been proposed.
The following technology is disclosed in Japanese Patent Publication No. 795. That is, a paste made by mixing metal powder such as Ti, which does not dissolve carbon, carbon powder, and diamond particles having an average particle size of 10 μm is coated on a substrate made of molybdenum and the like, and a high melting point ceramics There is disclosed a method of forming an intermediate layer made of a diamond sintered body in which diamond particles are dispersed in the matrix, and forming a diamond film thereon by a vapor phase synthesis method. According to the art, the intermediate layer experiences a temperature of 1000 ° C. or higher during formation, but it is explained that the diamond particles contained in the intermediate layer are not damaged because the time is instantaneous and extremely short. There is. However, since the substrate and the intermediate layer are different materials, no study has been made on the adhesion between the substrate and the intermediate layer.

In a heat sink using a diamond thin film, it is important not only to form a diamond film having good heat dissipation characteristics with good reproducibility but also to prevent the vapor phase synthetic diamond film from being separated from the substrate. Therefore,
According to the present invention, a ceramic having an insulating property is selected as the material of the substrate, and a high-quality polycrystalline diamond layer is formed on the substrate made of such a material, and a diamond film is formed at the time of processing even if it is processed. An object of the present invention is to provide a high thermal conductive substrate formed with high adhesiveness that is difficult to peel off.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems. As a result, high thermal conductivity is obtained when a layer made of a green body containing diamond particles is formed on a plate-shaped ceramic substrate, and this is fired to form a polycrystalline diamond film on it by the vapor phase method. We have come to the knowledge that a high-quality polycrystalline diamond film having properties can be formed with high adhesion. As a result of further examination based on the findings, when the amount of diamond particles added to the green body is within a specific range, a diamond film having high adhesion and good crystallinity can be stably formed. The present invention has been completed and the present invention has been completed.

That is, according to the present invention, a ceramic substrate having a mounting surface for mounting an element, on the mounting surface, is made of a ceramic of substantially the same quality as the ceramic constituting the ceramic substrate, and diamond particles are provided. 1 × 10 ⁴ to 1 × 1
It is a heat dissipation board characterized by comprising a laminated body in which a ceramic layer containing 0 ¹⁰ pieces / cm ² and a diamond layer are laminated in this order.

Since the heat dissipation substrate of the present invention uses a ceramic substrate having excellent insulating properties, it is easy to form a circuit, and since a diamond layer having high thermal conductivity is formed on the surface, the heat dissipation substrate as a whole is formed. Good endothermic and heat dissipation properties. Further, the diamond layer has high adhesion strength to the underlayer and the base body, and it is possible to make the diamond having large crystal grains from the vicinity of the underlayer and having particularly good heat dissipation characteristics. Among the heat dissipation boards of the present invention, the one in which the base body and the ceramic layer are made of a ceramic material containing aluminum nitride as a main component has not only the above-mentioned characteristics but also a high thermal conductivity as a whole and is preferable.

The second aspect of the present invention provides, on the mounting surface of the ceramic base having a mounting surface for mounting an element, ceramic of substantially the same quality as the ceramic constituting the ceramic base. A green sheet, wherein the diamond particles are 1 × 10 per 1 cm ^{2 of the} green sheet.
⁴ to 1 × 10 ¹⁰ green sheets included are formed,
Then, the green sheet is sintered to form a ceramic layer in which at least some of the diamond particles are exposed on the surface, or after the ceramic layer is formed, diamond is formed on the formed ceramic layer by a vapor phase synthesis method. A method for manufacturing a heat dissipation substrate according to the present invention, which comprises forming a layer.

According to the above manufacturing method of the present invention, the heat dissipation substrate of the present invention can be efficiently manufactured. In particular, the surface roughness Ra of the mounting surface of the ceramic substrate is 0.
When the thickness is from 03 to 5 μm, the adhesion strength between the layer derived from the green sheet layer and the base material is high, and by extension, the heat dissipation substrate having the diamond film firmly adhered can be obtained. In addition, the thickness of the green sheet is 0.05
By setting the thickness to 200 μm, it becomes possible to sinter the green sheet at the substrate heating temperature at the time of forming the diamond film, and the heat dissipation substrate can be manufactured more efficiently.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The heat dissipation substrate of the present invention has a structure in which a diamond layer is laminated on a ceramic substrate having a mounting surface on which elements are mounted, and semiconductor elements, resistors, capacitors, etc. are formed on the diamond layers. It can be used as a heat sink by mounting various elements of. Here, the heat sink means a material capable of absorbing the heat generated by the element as described above, a device using such a material for thermally protecting a component or system, and a so-called submount. Is a concept that includes. Since the heat dissipation substrate of the present invention uses a ceramic substrate having high insulation as a substrate,
An electric circuit can be easily formed, and for example, a portion where a diamond layer is not stacked can be provided and a circuit for wiring can be drawn on the portion. Further, when a ceramic substrate having aluminum nitride as a main component having a high thermal conductivity is used as the material of the substrate and the ceramic layer, the total thermal conductivity is lowered even when a laminate with a diamond layer is formed. Can be suppressed.

The substrate used in the present invention is not particularly limited as long as it is made of ceramics and has a shape having at least one flat surface on which a diamond layer on which elements are mounted is formed. For example, aluminum nitride powder, Alumina powder, zirconia powder, silicon carbide powder, silicon nitride powder, silicon oxide powder, boron nitride powder, and other various inorganic oxides or inorganic nitride powders are added with sintering aids and then formed by pressure, etc., and then sintered. A plate-shaped body produced by doing the above, or a plate-shaped one obtained by processing a polycrystalline body can be preferably used. Among these, from the viewpoint of high thermal conductivity, a substrate made of a ceramic containing aluminum nitride, silicon carbide, boron nitride or the like as a main component, particularly aluminum nitride as a main component because the thermal expansion coefficient is close to that of diamond. It is preferable to use a substrate made of ceramic. In addition, since the substrate used in the present invention has high adhesion to the ceramic layer described later, the surface roughness of the mounting surface of the substrate is Ra of 0.03 to 5 μm, particularly 0.05 to 4 μm. Is preferred.

The diamond layer formed on the mounting surface of the base body through a ceramic layer described later may be either a polycrystalline body or a single crystal body, and may be either natural diamond or synthetic diamond. From the viewpoint of cost and easiness of film formation, it is preferable that the polycrystalline diamond film is synthesized by a vapor phase method. The area, shape, thickness, etc. may be appropriately determined according to the element to be mounted, desired heat dissipation characteristics, time and cost required for manufacturing, but generally heat dissipation characteristics are higher when the thickness of the diamond layer is thicker. On the contrary, the time and cost required for production decrease as the thickness of the layer decreases. Therefore, it is preferable to set the layer thickness to 10 μm to 300 μm, particularly 20 μm to 250 μm in view of the balance between the two. Further, the higher the thermal conductivity, the more desirable.

In the heat dissipation substrate of the present invention, between the ceramic base and the diamond layer, a ceramic of substantially the same quality as the ceramic constituting the ceramic base is formed,
1 × 10 ⁴ to 1 × 10 ¹⁰ diamond particles / cm
It is essential to interpose a ceramic layer containing ^two . By using the same kind of material as the base material for the ceramic layer, it becomes possible to secure the adhesion between the two. The term “substantially the same quality” means that the main components are the same, and the sintering aid and other trace components may be different. Further, by providing a ceramic layer of the same quality as the base material in which the diamond particles are present with the above-mentioned surface density, nucleation is promoted when synthesizing the diamond film by the vapor phase method, and the crystal grain size from the vicinity of the base interface Not only is it possible to synthesize a diamond film with a large size, but it is also possible to form a diamond film by epitaxial growth on diamond particles firmly bonded to the ceramic layer, and to form a high-quality diamond film with good adhesion. You can As a result, the heat dissipation substrate of the present invention has not only good heat dissipation characteristics, but also the characteristics that the peeling of the diamond film due to a heat cycle such as heating and cooling during use does not easily occur. When the area density of the diamond particles contained in the ceramic layer is smaller than 1 × 10 ^4, when the diamond layer is formed by the vapor phase method,
Unless the thickness of the formed diamond film is considerably increased, the crystal grain size is not increased, and it is difficult to form a good diamond layer. When the areal density of the diamond particles is larger than 1 × 10 ¹⁰ , the effect of increasing the crystal grains does not change, but it is very difficult to disperse and mix the diamond particles with such a density.

The thickness of the ceramic layer is not particularly limited, but from the viewpoint of facilitating the production of the heat dissipation substrate of the present invention, it is 0.05 to 200 μm, particularly 0.1 to 150 μm.
Is preferred. The particle size of the diamond particles contained in the layer is not particularly limited, but is preferably 0.1 to 50 μm for the reason that it is practically available. If it is larger than 50 μm, it may be difficult to set the surface density within the range of the present invention.

The method for producing the heat dissipation substrate of the present invention is not particularly limited, but from the viewpoint of simplicity and efficiency, the ceramic substrate having the mounting surface for mounting the device is mounted on the mounting surface. A green sheet that provides a ceramic of substantially the same quality as the ceramic constituting the ceramic substrate,
A ceramic in which 1 × 10 ⁴ to 1 × 10 ¹⁰ diamond particles are contained per 1 cm ^{2 of the} green sheet to form a green sheet, and then the green sheet is sintered to expose at least a part of the diamond particles on the surface. It is preferable to manufacture by forming a diamond layer on the formed ceramic layer by vapor phase synthesis while forming the layer or after forming the ceramic layer.

The green sheet used in the above method (production method of the present invention) is a thin sheet formed by a doctor blade method by mixing a slurry containing ceramic powder, a sintering aid, an organic binder, a plasticizer, a solvent and the like. It means the one which gives a sintered body by drying and firing. Diamond powder may be mixed in advance with the above slurry to form a green sheet, but in order to obtain a diamond film with good adhesion by the vapor phase method, it is better that the diamond particles are exposed on the surface. Therefore, when the diamond particles are buried in the green sheet, it is preferable to subject at least a part of the diamond particles to the surface by performing a blast treatment or the like before or after sintering the green sheet. is there. Further, after forming a green sheet containing no diamond particles, the diamond particles are arranged by spraying so as to have a predetermined areal density,
It may be embedded by pressing lightly. In any case, it is preferable that the green sheet is temporarily adhered to the substrate by a pressure press or the like. The thickness of the green sheet is not particularly limited as long as at least a part of the diamond particles can be embedded and fixed, but too thick to convert the green sheet into a sintered body. Since it has to be heated at a high temperature for a long time and the diamond particles deteriorate or disappear, it is preferable that the thickness is 0.05 to 200 μm. With such a thickness, the embedded diamond particles function effectively even if the green sheet is sintered. Further, since the green sheet can be sintered at the same time when the diamond layer is formed by the vapor phase method, the thickness of the green sheet is 0.05 to 200 μm, particularly 0.1 to 1 μm.
It is particularly preferable that the thickness is 50 μm. Further, known methods can be used without limitation for forming the diamond layer by the vapor phase method.

In the following, the case where the heat dissipating substrate A having a structure as shown in FIG. 1 in which the ceramic layer containing the substrate and the diamond particles is made of ceramic containing aluminum nitride as a main component is manufactured by the manufacturing method of the present invention will be described as an example The manufacturing method of the present invention will be described in detail. In the heat dissipation substrate A shown in FIG. 1, the diamond particles 11 are formed on the AlN substrate 100.
Ceramic layer 110 containing 1 and diamond layer 1
20 has a structure laminated in this order.

In this case, as the aluminum nitride powder used as the raw material of the green sheet, known aluminum nitride powder can be used without particular limitation, but the ease of forming the green sheet and the properties of the obtained sintered body are good. From the viewpoint that the average particle size measured by the sedimentation method is 5 μ,
It is preferable to use a powder of m or less, more preferably 3 μm or less, and particularly 0.5 μm to 2 μm. The purity is not particularly limited, but the oxygen content is 3.0% by weight or less, and the cation impurities contained when the aluminum nitride composition is AlN is 0.5% by weight or less, particularly,
The oxygen content is in the range of 0.4 to 1.0% by weight, the content of cationic impurities is 0.2% by weight or less, and among the cationic impurities, Fe, Ca, Si and It is preferable to use an aluminum nitride powder having a total C content of 0.17% by weight or less. When the aluminum nitride powder having such a purity is used, the thermal conductivity of the obtained aluminum nitride sintered body is improved.

Known sintering aids can be used as the green sheet material without particular limitation. Specifically, an alkaline earth metal compound, for example, an oxide such as calcium oxide, a compound containing yttrium or a lanthanide element, for example, an oxide such as yttrium oxide, or the like is preferably used.

As the organic binder as the green sheet material, known ones can be used without particular limitation. Specifically, acrylic resins such as polyacrylic acid esters and polymethacrylic acid esters, cellulosic resins such as methyl cellulose, hydroxymethyl cellulose, nitrocellulose, and cellulose acetate butyrate, polyvinyl butyral, polyvinyl alcohol, vinyl groups such as polyvinyl chloride. One type or a mixture of two or more types of resin containing, hydrocarbon resin such as polyolefin, oxygen containing resin such as polyethylene oxide and the like are used. Among them, acrylic resins are preferably used because they have good degreasing properties. Other known components such as a solvent, a dispersant, and a plasticizer may be used without particular limitation.

When forming an aluminum nitride green sheet using these materials, the mixing ratio of each of the above components is not particularly limited, and for example, aluminum nitride 100
A mixture of 0.01 to 10 parts by weight of a sintering aid and 0.1 to 30 parts by weight of an organic binder with respect to parts by weight can be suitably used. In particular, since the sintering aid is advantageous in achieving high thermal conductivity, it is particularly preferable to mix it in an amount of 2 to 7 parts by weight with respect to 100 parts by weight of aluminum nitride. When the diamond particles are mixed in advance with the slurry, the surface density is set to 1 in consideration of the intended thickness of the green sheet.
Appropriate blending may be carried out so as to be × 10 ⁴ to 1 × 10 ¹⁰ pieces / cm ² . The slurry prepared by mixing these components is formed into a sheet on the mounting surface of the substrate by a doctor blade method, a printing method or the like. This green sheet may have a single layer or a multi-layer structure. Further, when the diamond particles are not mixed in advance with the slurry, the diamond particles may be embedded in the green sheet formed as described above.

In the manufacturing method of the present invention, the green sheet containing diamond particles formed as described above is sintered to form a ceramic layer in which at least a part of the diamond particles is exposed on the surface, and the formed ceramic is formed. A diamond layer is formed on the layer by a vapor phase synthesis method. At this time, the sintering of the green sheet and the formation of the diamond layer can be sequentially performed separately, but from the viewpoint of increasing the manufacturing efficiency by omitting the steps, the above-mentioned sintering is performed by using the substrate heating performed when forming the diamond layer. Is preferably performed. Sintering of green sheet depends on its thickness, but it is 600-12
It can be easily performed by heating at 00 ° C. for about 30 minutes to 20 hours. In the production method of the present invention, since only the surface layer is a green sheet, unlike the case of sintering the entire substrate, the time of exposure to high temperature is short, so that the diamond particles are less likely to deteriorate during the sintering, or disappear. Since there is nothing to do, it can fully function as a seed.

In the manufacturing method of the present invention, the diamond film layer is formed by the vapor phase method on the ceramic layer in which at least a part of the diamond particles formed as described above is exposed on the surface. By adopting the vapor phase method, it is possible to epitaxially grow diamond by using the above-mentioned diamond particles as a seed to form a layer composed of a high-quality diamond film firmly bonded to the ceramic layer. As the vapor phase method, a known vapor phase method capable of producing a diamond film such as a chemical vapor deposition method or a laser ablation method can be used without limitation. Among these, the chemical vapor deposition method is preferable because it is possible to reproducibly and stably produce a diamond film having good crystallinity among the existing techniques. Depending on the manufacturing method, the chemical vapor deposition method is classified into methods using high frequency waves, microwaves, hot filaments, etc. Among these methods, the method using microwaves or the method using hot filaments is more preferable.

As the raw material of the diamond film in the method, a gasifiable substance containing carbon such as methane, acetylene, carbon dioxide, carbon monoxide is usually used. These deposition gases may be diluted with non-deposition gases such as hydrogen, oxygen, nitrogen, argon, xenon, neon, krypton. In addition, diborane, phosphine, etc.
It is also possible to synthesize diamond by mixing the above gas with a gasifiable compound containing a group I or group V element. When the diamond film is synthesized by entraining such a gas, a diamond film having a P-type or N-type conductivity type is synthesized. The substrate temperature at the time of diamond film production is not particularly limited, but 600 ° C to 1200 ° C,
Particularly, it is preferably 700 ° C to 1100 ° C. 6
At a temperature lower than 00 ° C., a diamond film containing a large amount of amorphous carbon is formed, so that the thermal conductivity decreases. If the substrate temperature exceeds 1200 ° C, the diamond particles may be damaged. Further, similar to the film formation at low temperature, amorphous carbon may be contained in diamond, which is not preferable. The heating method of the substrate is not particularly limited as long as it can be set within the above temperature range. For example, a method of heating a heater by embedding a heater in a holder for setting a substrate, a method of heating a substrate by high-frequency induction heating, or a microwave plasma CVD method, a method of heating by a microwave applied for plasma formation. Etc. The pressure for diamond synthesis is usually 0.1 mTorr to 300 Torr, especially 50 mTorr in the case of microwave plasma CVD method.
Is in the range of up to 200 Torr. Further, in the case of the microwave plasma CVD method, the plasma generation power source output is appropriately selected depending on the characteristics of the diamond film to be formed, but is usually 300 W to 10 kW. The shape of the diamond film can be arbitrarily changed by etching after forming the film or masking the substrate during film formation.

[0030]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

The heat dissipation boards obtained in the following examples and comparative examples were evaluated by the methods shown in (1) to (6) below.

(1) Surface Roughness The surface roughness Ra was measured by a surface roughness / contour shape measuring instrument manufactured by Tokyo Seimitsu Co., Ltd.

(2) Diamond particle density The number of diamond particles in the range of 100 μm × 100 μm was determined by image processing and converted into the number within the area of 1 cm ² .

(3) Synthesis rate The thickness of the diamond film synthesized on the substrate was determined by a scanning microscope and divided by the time required for synthesis to obtain the synthesis rate.

(4) Crystallinity was evaluated by determining the full width at half maximum of the scattering waveform appearing at 1333 cm ^-1 by crystalline Raman scattering spectroscopy. The smaller the full width at half maximum, the higher the crystallinity.

(5) Thermal conductivity The thermal conductivity was calculated using the following formula. Thermal conductivity (W / mK) = density (g / cm ³ ) × specific heat (J
/ GK) × thermal diffusivity (cm ² / s) × 100 (constant) Here, the density was obtained by the underwater density method, and the thermal diffusivity was determined by the nonlinear regression analysis by the two-dimensional ring method.

(6) Adhesion test Titanium, platinum and gold were each added to 0.0 on the diamond film.
A film having a thickness of 5 μm, 0.5 μm, and 2 μm was formed by a sputtering method, and nickel-plated pins on the surface of the gold film were vertically soldered. The pin has a flat tip, a pin diameter of 0.5 mm, and is made of 42-alloy. The solder has a composition of 60 wt% tin and 40 wt% lead. This is the Strograph M2 manufactured by Toyo Seiki Co., Ltd.
Then, the breaking strength when the pin was pulled in the vertical direction was measured. The pulling speed was 10 mm / min. Unit is K
It is g / mm ² .

Example 1 The shape is 25 mm × 25 mm × 0.5 mm (t),
A 70 μm thick green sheet adjusted so that the surface density of diamond particles exposed on the surface is 1 × 10 ⁶ / cm ² is applied to a ceramic substrate containing aluminum nitride as a main component having a surface roughness Ra of 0.5 μm. The layers were laminated and pressed at a pressure of 100 Kgf / cm ^{2 in} the atmosphere. The green sheet is 100 parts by weight of aluminum nitride powder, 5 parts by weight of yttria, 2 parts by weight of n-butyl methacrylate as a dispersant, 11 parts by weight of polybutyl acrylate as an organic binder, 7 parts by weight of dioctyl phthalate as a plasticizer, toluene and isopropyl alcohol. 50 parts by weight of the mixed solvent was weighed, 4 mg of diamond powder having a diameter of 1 μm was mixed with 1 cm ^{3 of the} mixed solvent, and the mixture was placed in a ball mill pot and sufficiently mixed with a nylon ball to prepare. And
The paste thus obtained was molded on a substrate using a screen printing machine. Next, in order to synthesize the diamond film, the substrate was set in the substrate holder part in the microwave plasma CVD apparatus. At the same time as the inside of the reaction vessel was evacuated, the substrate mounting base was heated to 1000 ° C. Hold the temperature for about 1 hour until the temperature of the substrate stabilizes, and confirm that the pressure in the reaction vessel has become 5 × 10 ⁻⁶ Torr or less, and the reaction vessel contains 12 cc / min of methane gas and 300 cc / min of hydrogen. The pressure inside the reaction vessel was set to 100 Torr by adjusting the exhaust valve. Next, the microwave was supplied to the reaction vessel by tuning with a tuner so that the reflection loss was minimized at an output of 5 kW from the microwave power source. Microwave power was supplied for about 10 hours to deposit the diamond film on the substrate so that the thickness of the obtained diamond film was 50 μm. After the completion of the reaction, it was confirmed that the temperature of the substrate became 100 ° C. or lower, and then the reaction vessel was opened to the atmosphere to take out the substrate on which the diamond was formed.

When the thickness of the diamond film was observed,
It was confirmed to be about 50 μm. Next, the crystallinity of the diamond formed on the substrate was estimated by Raman scattering spectrum measurement. As a result, the full width at half maximum of the peak appearing at 1333 cm ⁻¹ due to the diamond structure was about 8.2.
It was confirmed to be cm ⁻¹ . Further, when the thermal conductivity of the obtained laminate (heat dissipation substrate) was measured, it was about 36.
It was 0 W / mK. As a result of the adhesion test, 2.5
A tensile strength of Kg / mm ² was obtained.

Example 2 A heat sink was formed in the same manner as in Example 1 except that the surface density of diamond particles exposed on the surface of the green sheet was set to 1 × 10 ⁸ / cm ² . The crystallinity of diamond formed on the substrate was estimated by Raman scattering spectrum measurement, and was found to be 1333 cm ^−1.
It was confirmed that the full width at half maximum of the peak due to the diamond structure appearing in ( ¹⁾ was about 8.0 cm ^-1 . Further, when the thermal conductivity of the obtained laminate (heat dissipation substrate) was measured, it was about 380 W / mK. As a result of the adhesion test, a tensile strength of 2.8 Kg / mm ² was obtained.

Example 3 A radiator plate was formed in the same manner as in Example 1 except that the ceramic substrate containing aluminum nitride as the main component had a double-sided roughness Ra of 3 μm. As a result of estimating the crystallinity of diamond formed on the substrate by Raman scattering spectrum measurement, the full width at half maximum of the peak appearing at 1333 cm ⁻¹ due to the diamond structure is about 8.2.
It was confirmed to be cm ⁻¹ . Further, when the thermal conductivity of the obtained laminated body (heat dissipation substrate) was measured, it was about 37.
It was 0 W / mK. The result of the adhesion test was 3.1.
A tensile strength of Kg / mm ² was obtained.

Example 4 A heat sink was formed in the same manner as in Example 1 except that the thickness of the green sheet was changed to 5 μm. As a result of estimating the crystallinity of diamond formed on the substrate by Raman scattering spectrum measurement, 1333c
It was confirmed that the full width at half maximum of the peak appearing at m ⁻¹ due to the diamond structure was about 8.3 cm ⁻¹ . Further, when the thermal conductivity of the obtained laminate (heat dissipation substrate) was measured, it was about 360 W / mK. As a result of the adhesion test, a tensile strength of 3.3 Kg / mm ² was obtained.

Comparative Example 1 A heat sink was formed in the same manner as in Example 1 except that the surface density of diamond particles exposed on the surface of the green sheet was set to 1 × 10 ² / cm ² . The crystallinity of diamond formed on the substrate was estimated by Raman scattering spectrum measurement, and was found to be 1333 cm ^−1.
It was confirmed that the full width at half maximum of the peak due to the diamond structure appearing in ¹ was about 10 cm ⁻¹ . Further, when the thermal conductivity of the obtained laminated body (heat dissipation substrate) was measured, it was about 300 W / mK. As a result of the adhesion test,
A tensile strength of 1.8 Kg / mm ² was obtained.

Comparative Example 2 A heat dissipation substrate was prepared in the same manner as in Example 1 except that the material of the green sheet was alumina. The green sheet containing alumina as the main component used alumina powder as the ceramic powder, polyvinyl butyral resin as the binder, and toluene as the solvent. After the diamond was formed, when the substrate was taken out of the reaction vessel,
It was confirmed that the upper layer was peeled from the interface with the base material.

[0045]

Since the heat dissipation board of the present invention uses the ceramic base having excellent insulating properties, the circuit can be easily formed.
Furthermore, since the diamond layer having high thermal conductivity is formed on the surface, the heat dissipation property and the heat dissipation property of the heat dissipation substrate as a whole are good. Furthermore, since the diamond layer has high adhesion strength to the underlayer and the base, it is difficult to peel off during processing such as cutting or peel off due to a heat cycle when the device is mounted and used. The substrate can be used stably for a long period of time. Moreover, according to the manufacturing method of the present invention, such a heat dissipation substrate of the present invention can be efficiently manufactured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a typical heat dissipation board of the present invention.

[Explanation of symbols]

A: Heat dissipation board 100: AlN substrate 110: Ceramic layer 111: Diamond particles 120: Diamond layer

Claims (4)

[Claims] 1. A ceramic substrate having a mounting surface for mounting an element, on the mounting surface, a ceramic substantially the same in quality as the ceramic constituting the ceramic substrate,
1 × 10 ⁴ to 1 × 10 ¹⁰ diamond particles / cm
A heat dissipation substrate comprising a ceramic layer including ² and a diamond layer, which are laminated in this order. 2. A green sheet for providing a ceramic of substantially the same quality as the ceramic constituting the ceramic base on the mounting surface of a ceramic base having a mounting surface for mounting an element, the diamond being a diamond sheet. A ceramic layer in which particles form 1 × 10 ⁴ to 1 × 10 ¹⁰ particles per 1 cm ^{2 of the} green sheet and then the green sheet is sintered to expose at least a part of the diamond particles on the surface. 2. The method for manufacturing a heat dissipation substrate according to claim 1, wherein a diamond layer is formed on the formed ceramic layer while forming or after forming the ceramic layer by a vapor phase synthesis method. 3. The manufacturing method according to claim 2, wherein the surface roughness Ra of the mounting surface of the ceramic substrate is 0.03 to 5 μm. 4. The green sheet has a thickness of 0.05 to
It is 200 micrometers, The manufacturing method of Claim 2 or 3 characterized by the above-mentioned.