JPH1036173A - Manufacturing method of aluminum nitride sintered body - Google Patents

Abstract

(57) [Problem] When an AlN molded body is subjected to a binder removal treatment in a state of being sealed in a container, organic substances are not completely removed and pores remain in the sintered body, and the sintered body is warped. And inconveniences such as carbonization of the metal wiring occur. For this reason, conventionally, a two-stage processing method is employed in which a binder removal treatment is directly performed without coating the AlN molded body or the like, and then the processed AlN molded body is sealed in a container and then subjected to a firing treatment. In addition, since it is necessary to take out the AlN compact on the way, there is a problem that productivity is poor. SOLUTION: The AlN molded body 20 has a porosity of 10 to 40.
Porous AlN container 10 having a volume percentage of 20 mm or less in thickness
Debinding process and baking process are carried out in the state of being stored in the container.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an aluminum nitride sintered body (hereinafter referred to as an AlN sintered body).
More specifically, the present invention relates to a method for producing an AlN sintered body having excellent thermal conductivity and used for an insulating substrate, a heat sink, a semiconductor package, and the like.

[0002]

2. Description of the Related Art In recent years, as the control speed and signal processing speed of electronic equipment have been increased, and the performance and size of electronic equipment have been increased, the dissipation of heat generated from semiconductor elements has become an important technical issue. ing. Particularly, in the case of a substrate on which an element generating a large amount of heat, such as a power transistor for IC, LSI, microwave communication or optical communication, or a laser diode, is mounted. To prevent the temperature of the
Development of a substrate having high thermal conductivity has become an essential issue.

Conventionally, alumina sintered bodies have been widely used as a substrate material for mounting a semiconductor element. Recently, for the above-mentioned reason, a material having better heat radiation characteristics has been demanded. Development of a high thermal conductive substrate material is desired.

Recently, aluminum nitride (AlN) has been used as one of high thermal conductive substrate materials which can satisfy such requirements.
Is attracting attention. This AlN has excellent thermal conductivity of about 10 times that of alumina and has various properties required for the substrate material, such as electrical resistivity, dielectric strength, relative permittivity, mechanical properties, and thermal expansion coefficient of Si. Since matching and other properties are equal to or higher than those of the alumina sintered body, active research and development of heat sinks and substrate materials are being promoted.

In order to manufacture a substrate using the above-mentioned AlN as a main raw material, a sintering aid, a binder (a resin and a solvent) and the like are added to an AlN raw material powder and mixed to form a slurry. A green sheet is formed by molding by a method or the like. Next, a conductive paste containing a conductive metal powder such as W or Mo is printed on the green sheet as necessary, and a green sheet laminate (AlN molded body) is produced by laminating these green sheets. . Next, this green sheet laminate (AlN molded body)
A binder removal process is performed to decompose and eliminate organic substances such as the binder contained therein, and thereafter, a baking process is performed to promote densification, thereby manufacturing a substrate made of an AlN sintered body.

The slurry is dried and granulated using a spray drier or the like, and then molded to form a molded body having a predetermined shape. The molded body is subjected to a binder removal treatment and a calcination treatment. There is also a method of forming a wiring on the substrate.

[0007] The wiring formed on the surface of the AlN substrate is further plated with Au or the like in order to improve the wire adhesion and the like when electrically connecting to the semiconductor chip by a method such as wire bonding. In the manufacture of a heat sink or a substrate, there is a case where the step of forming wiring and the like is not necessary among the above steps.

[0008] In the above manufacturing process of the AlN sintered body,
The binder removal step is generally performed by subjecting the molded body to heat treatment in an appropriate atmosphere gas. In the case of oxide ceramics that can be heat-treated in an oxidizing atmosphere, the combustion reaction between the organic matter in the compact and oxygen can be performed by heating in air or oxygen, and the removal can be performed relatively easily. Binder treatment can be performed.

However, since AlN is a non-oxide ceramic containing no oxygen as a constituent element, there is a possibility that AlN itself is oxidized by heating in an oxidizing atmosphere.
Therefore, the binder removal treatment is usually performed in an inert gas atmosphere. In this case, the binder in the AlN molded body needs to be thermally decomposed and volatilized, so that a high-temperature and long-time heat treatment is required. . Also, low-boiling components generated by thermal decomposition of the binder are easy to volatilize, but high-boiling components are hard to volatilize, and carbon may be generated from a part thereof,
If this carbon remains in the AlN molded body, it becomes difficult for the AlN molded body to proceed to densification. In order to prevent such carbon residue and promote the oxidation reaction of the binder, there has been disclosed a method of performing a binder removal treatment in an atmosphere in which a carbon dioxide gas is mixed into an inert gas (JP-A-7-3304).
No. 4). According to the above method, the binder removal treatment of the AlN formed body can be performed relatively favorably.

After the binder removal treatment, a baking treatment is performed. In the case of AlN, the baking treatment is usually performed at 1600 to 2000.
A high temperature of ℃ is required, and firing must be performed in a non-oxidizing atmosphere so that the AlN itself and the metal wiring are not oxidized. As a firing furnace for firing AlN under such a high temperature and non-oxidizing atmosphere, a carbon furnace, a metal furnace, an alumina refractory furnace and the like have been conventionally used.

[0011]

However, when firing AlN in a metal furnace, the AlN sintered body and its metal wiring are contaminated by Cr, Fe, etc. in stainless steel used for the furnace wall. When AlN is fired in a refractory furnace, there is a problem that impurities such as SiO ₂ and Fe ₂ O ₃ contained in the refractory contaminate the AlN sintered body and its metal wiring. Was. In order to solve these problems, for example, a method of covering an AlN compact with an AlN fired body to prevent contaminants from contacting the AlN surface (Japanese Patent Laid-Open No. 6-144935) is disclosed.

When AlN is fired in a carbon furnace, metal wires formed inside and on the surface of the AlN sintered body are carbonized by the carbon used for the inner wall of the furnace and the heater, thereby increasing the electric resistance. There was a problem of doing. In order to solve the above problem, for example, a method in which an AlN molded body is sealed in a BN container and firing is performed in a state where the AlN molded body is shielded from the surrounding atmosphere (Japanese Patent Laid-Open No. 2-167)
No. 863) and the like.

However, in the binder removal step, AlN
If the surface of the molded body is covered with the AlN fired body or the AlN molded body is sealed in a container, the removal of organic substances in the AlN molded body becomes incomplete and carbon remains in the molded body. As a result, there are problems such as pores remaining inside the AlN sintered body and warping of the AlN sintered body. There is also a problem that the metal wiring is carbonized. For this reason, conventionally, the above-described treatment method is not used in the binder removal step. For example, an AlN molded body that has not been subjected to any treatment such as coating in an inert atmosphere containing carbon dioxide gas is subjected to binder removal treatment, and then the binder removal treatment is performed. After the applied AlN molded body is covered with an AlN fired body, or the AlN molded body is sealed in a BN container, a firing treatment is performed.
Since the treatment method has a stepwise process, and it is necessary to take out the AlN compact on the way, there is a problem that productivity is poor.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is possible to continuously perform a binder removal treatment and a baking treatment, and to substantially completely remove organic substances and the like in an AlN molded body in the binder removal step. And the AlN sintered body itself does not undergo discoloration, warpage, oxidation or the like.
The metal wiring formed inside or on the surface of the N sintered body does not discolor or deteriorate, and is dense and has excellent properties such as thermal conductivity.
It is an object of the present invention to provide a method for manufacturing an AlN sintered body capable of manufacturing an N sintered body.

[0015]

In order to achieve the above object, a method (1) for producing an AlN sintered body according to the present invention comprises:
The method is characterized in that a binder removal treatment and a baking treatment are performed in a state where the N molded body is housed in a porous AlN container.

According to the method (1) for producing an AlN sintered body, since the AlN container is porous, the atmosphere gas is A
It is easy to enter the inside of the 1N container, and the organic matter generated when performing the binder removal treatment easily escapes to the outside of the AlN container, so that the residual carbon amount of the AlN molded body can be reduced, and the subsequent firing Densification at the time can be favorably advanced. Further, the container is made of the same material as the AlN molded body, and SiO ₂ is added to the outside atmosphere of the AlN container during firing.
And when contaminants such as Fe ₂ O ₃ are present,
Since the surface portion and the porous portion of the AlN container preferentially trap contaminants, it is possible to suppress the occurrence of warpage and discoloration of the internal AlN sintered body. Therefore, it is possible to continuously and efficiently manufacture a dense AlN sintered body having excellent properties such as thermal conductivity.

Further, the method (2) for manufacturing an AlN sintered body according to the present invention is the method for manufacturing an AlN sintered body (1), wherein the conductor paste layer for forming a wiring is formed on the surface or inside of the AlN molded body. It is characterized by being formed.

According to the manufacturing method (2) of the AlN sintered body, it is possible to prevent the wiring formed on the surface or inside of the AlN sintered body from being lowered in resistivity due to deterioration such as discoloration or carbonization. be able to.

The method of manufacturing an AlN sintered body (3) according to the present invention is the method of manufacturing an AlN sintered body according to the method (1) or (2), wherein the porosity of the AlN container is 10 to 40% by volume. And the thickness is not more than 20 mm.

According to the above method (3) for producing an AlN sintered body, since the porosity and thickness of the AlN container are set to appropriate values, the organic matter generated during the binder removal treatment is made of AlN. It is easier to remove from the outside of the container, and the densification at the time of firing can be further favorably advanced. Further, even when a contaminant is present in the external atmosphere of the AlN container at the time of firing, the ability of the AlN container to trap the contaminant is high, and the warping and discoloration of the AlN sintered body, and the discoloration and deterioration of the wiring are suppressed. It can be prevented more reliably.

Further, the method (4) for producing an AlN sintered body according to the present invention comprises the above-mentioned method (1) for producing an AlN sintered body.
(3) The method according to any one of (3), wherein the binder removal treatment is performed in an atmosphere in which carbon dioxide is mixed into an inert gas.

Further, the method (5) for producing an AlN sintered body according to the present invention is characterized in that, in the method (4) for producing an AlN sintered body, the temperature of the binder removal treatment is 900 to 1000 ° C. I have.

The method (4) for producing the AlN sintered body,
According to (5), since the inert gas contains carbon dioxide, the binder is easily oxidized and decomposed, the amount of residual carbon is further reduced, and the sintered body is further densified.

Further, the method (6) for producing an AlN sintered body according to the present invention comprises the above-mentioned method (1) for producing an AlN sintered body.
(5) In any one of (5), the calcination treatment is performed in an inert gas atmosphere or a reducing gas atmosphere.

Further, a method (7) for producing an AlN sintered body according to the present invention is characterized in that, in the above-mentioned method (6) for producing an AlN sintered body, the firing temperature is 1550 to 1700 ° C. .

A method (6) for producing the AlN sintered body,
According to (7), since the residual carbon and the like are easily scattered, the densification of the sintered body further proceeds.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing an AlN sintered body according to the present invention will be described below with reference to the drawings.

The AlN compact can be produced by a known method. That is, as a sintering aid AlN powder was added Y ₂ O _3, CaCO _3, etc., then, after forming a slurry by adding a resin and a solvent as a binder, the slurry doctor blade method or the like To form a green sheet. If necessary, processing such as punching is performed on this green sheet, and a conductive paste containing W powder or the like is filled or printed, and laminated to produce a green sheet laminate (AlN molded body).

The AlN compact produced by the above method is subjected to a binder removal treatment and a baking treatment.
A binder removal treatment and a baking treatment are performed in a state where the molded body is placed in an AlN container.

FIG. 1 shows an AlN according to an embodiment of the present invention.
FIG. 3 is an exploded perspective view schematically showing an AlN container and an AlN molded body used in a method for manufacturing a sintered body.

The AlN container 10 has a bottom portion 11 and an intermediate portion 1.
2 and a lid 13, and the AlN container 10 is completed by sequentially laminating the above three members. Further, when the above three members are stacked, each member is subjected to uneven processing (not shown) so that the members are not easily shifted from each other. Has become. An AlN molded body 20 for a substrate or the like is placed in the AlN container 10 having the above configuration. In FIG. 1, one AlN molded body 20 is accommodated in the AlN container 10, but the AlN container 10 can accommodate a plurality of AlN molded bodies 20 therein. It may be configured. Also, a method of stacking the bottom portion 11 and the intermediate portion 12 and then placing a member having a shape that also serves as the bottom portion 11 and the lid portion 13 thereon, and placing another AlN molded body 20 on the member In this case, the above members can be stacked in multiple stages, and a large number of AlN molded bodies 20 can be stored in one AlN container at a time.

The AlN container 10 is made of a porous AlN sintered body so that the atmosphere gas during binder removal and firing can easily flow through the inside thereof, and the gas generated by decomposition of the binder during heating can easily escape. Having a porosity of preferably 10 to 40% by volume and a thickness of 20% by volume.
mm or less is preferable.

When the porosity of the AlN container 10 is less than 10% by volume or when the thickness exceeds 20 mm, the removal of organic substances and the like generated from the AlN molded body 20 in the binder removal step becomes poor, and AlN due to carbon etc.
The density of the sintered body may not be increased, warpage may occur, or the metal wiring on the surface and inside of the AlN sintered body may be carbonized, and the electrical resistivity of the metal wiring may increase. When the porosity of the AlN container 10 exceeds 40% by volume, the AlN container 1
0 Because the effect of trapping contaminants on the outer surface is weakened,
The AlN sintered body and the metal wiring on the surface and inside thereof are easily discolored or deteriorated.

The container 10 made of AlN only needs to have a thickness that can be handled as a container. For example, even if the thickness is about 2 to 3 mm, it has an ability to sufficiently trap contaminants. It is necessary to improve the sealing performance of the AlN container 10 in an environment with a relatively large amount of contaminants. However, it is not always necessary to improve the sealing performance in an environment with a relatively small amount of pollutants. May have an open portion.

The ordinary AlN sintered body is added with a sintering aid comprising a rare earth compound or an alkaline earth compound in an amount of about 3 to 10% by weight. It is included as a secondary phase. However, when the AlN container 10 contains a large amount of the secondary phase, the secondary phase adheres to the surface of the AlN molded body and the metal wiring during firing, causing discoloration. Therefore, it is preferable that the AlN container 10 does not contain the secondary phase as much as possible, and that the AlN purity in the AlN container 10 is 98 wt% or more.

In this embodiment, the binder removal process and the firing process can be continuously and efficiently performed in the same firing furnace.

The baking furnace for performing the binder removal treatment and the baking treatment is not particularly limited, and a conventionally used metal furnace, carbon furnace, refractory furnace, or the like can be used. It is desirable to use a refractory furnace capable of mass processing at a low temperature.

First, the binder removal treatment is performed at 900 to 1000 ° C. in an inert gas atmosphere containing carbon dioxide gas.
Carbon remaining in the AlN molded body 20 is removed by carbon dioxide gas to obtain an AlN molded body 20 having a small residual carbon amount. If the temperature of the binder removal treatment is lower than 900 ° C., the amount of residual carbon increases, and the densification of the AlN sintered body does not easily progress, and at the same time, the warpage and deformation easily occur. When the temperature exceeds 1000 ° C., AlN is easily oxidized by carbon dioxide in the inert gas, and the densification also hardly proceeds. The content of carbon dioxide gas is preferably 10% by volume or more in order to promote the oxidation of residual carbon, and the inert gas is preferably Ar or nitrogen which hardly reacts with AlN.

Since the AlN container 10 according to the embodiment is porous and has excellent gas flowability, an inert gas containing carbon dioxide gas is continuously passed through the open pores.
While the organic matter generated by the binder removal process escapes from the AlN container 10 in a short time, and the organic matter and carbon hardly remain in the AlN molded body 20. Further, even when impurities such as Fe ₂ O ₃ are present in the atmosphere, the outer surface of the AlN container 10 and the open pores inside trap the impurities, so that the inner AlN molded body 2
0 is not contaminated, and naturally the AlN molded body is not contaminated by dust or the like.

After the above-mentioned binder removal treatment, in an inert gas,
Alternatively, a baking treatment is performed in a reducing gas, and the baking temperature is 15
50-1700 degreeC is preferable, and 1550-1650 degreeC is more preferable. If the firing temperature is lower than 1550 ° C., the densification does not easily proceed, while if the firing temperature exceeds 1700 ° C., the life of the refractory tends to be shortened. If moisture is present in the firing atmosphere, the moisture causes Al
Since N is oxidized to Al ₂ O ₃ , densification hardly proceeds. Therefore, it is desirable to remove moisture so that the dew point of the firing atmosphere is -40 ° C or lower.

In the above baking process, the Si
When impurities such as O ₂ and Fe ₂ O ₃ are present, Al
Since the open pores on the outer surface or inside of the N container 10 trap the impurities, the impurities do not enter the inside of the AlN container 10, and the discoloration and warpage of the AlN sintered body caused by the impurities and the residual carbon. Can be prevented, and deterioration such as discoloration of the wiring formed on the surface and the inside of the AlN sintered body and a decrease in resistivity can be prevented.

The binder removal treatment and the calcination treatment can be performed using a continuous sintering furnace having a binder removal zone and a sintering zone. By using the continuous treatment furnace, a large amount of AlN sintered body can be produced at low cost. can do.

[0043]

Examples and Comparative Examples Examples of the method for manufacturing an AlN sintered body according to the present invention will be described below with reference to the drawings.

In this embodiment, the AlN container 10 (FIG. 1) described in the above embodiment is used, and the AlN
AlN molded body 20 produced under the following conditions
The (AlN sintered body) was manufactured with the (green sheet laminate) contained therein. The manufacturing conditions are as follows.

In the comparative example, the container 1 made of AlN was used.
The binder removal process and the firing process were performed directly in a firing furnace without using 0. Other conditions are the same as the conditions in the embodiment described below.

(1) Preparation of slurry AlN raw material powder Average particle size: 2.9 μm, oxygen content: 0.85% by weight Sintering aid (based on 100 parts by weight of AlN raw material powder) Yttrium oxide (Y ₂ O ₃₎ ): 1.5 parts by weight Calcium carbonate (CaCO ₃ ): 3 parts by weight Resin for binder (based on 100 parts by weight of AlN raw material powder) Polyvinyl butyral (PVB): 12 parts by weight Solvent for binder (100 parts by weight of AlN raw material powder) Toluene: 60 parts by weight (2) Preparation of AlN molded body, lamination, and printing of conductive paste Production method of green sheet: doctor blade method Dimensions of AlN molded body 20 Length: 30 mm, width: 30 mm, thickness: 5 mm Printing of conductive paste A conductive paste containing W powder is printed on an AlN molded body. (3) Characteristics of AlN container 10 According to 1 (4) firing furnace (binder removal processing and firing processing) Al ₂ O ₃ refractory furnace (5) binder removal treatment atmosphere: CO ₂ nitrogen ambient temperature containing 10 vol%, Time: AlN in Table 1 below Residual carbon content of molded body 20: described in Table 1 below (6) Firing treatment Atmosphere: Nitrogen Dew point in furnace: -40 ° C Temperature and time: described in Table 1 below (7) Observation of appearance of AlN sintered body , And Measurement of Properties The appearance of the AlN sintered body was observed by the following method, and various properties described below were measured. The results are shown in Table 1 below. i) Appearance observation Determine whether discoloration has occurred by visual inspection (ii) Oxidation amount of AlN sintered body Measured by X-ray diffraction method (iii) Thermal conductivity Measured by laser flash method (iv) Firing density Measured by Archimedes method Measurement (v) Warp A ruler was placed on the diagonal line of the manufactured AlN sintered body, the maximum gap between the AlN sintered body and the ruler was equal in the case of a concave surface, and the gap between both ends was equal in the case of a blister surface. In this case, the gap size is measured, and the ratio to the diagonal length is determined. If the ratio is 0.01 or more, it is determined that warpage has occurred.

[0047]

[Table 1]

As is clear from the results shown in Table 1 above, the AlN sintered bodies according to Examples 1 to 8 were processed in a state of being placed in an AlN container 10 having appropriate characteristics. Therefore, the amount of residual carbon and the amount of oxygen were small, the density was high, no discoloration or warpage occurred, and an AlN sintered body having excellent properties such as thermal conductivity could be obtained.

In the case of Examples 9 to 11, AlN
Since any of the porosity and the thickness of the container 10 was not in the suitable range, discoloration or warpage occurred, but an AlN sintered body excellent in density, thermal conductivity, and oxygen amount could be obtained.

On the other hand, the AlN sintered body according to Comparative Example 1
Since the treatment is not performed in the state of being accommodated in the 1N container 10, both the sintered body and the W wiring are discolored, and the oxygen amount, density, and thermal conductivity are inferior.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view schematically showing an AlN container according to an embodiment of the present invention.

[Explanation of symbols]

 10 AlN container 20 AlN molded body

Claims (7)

[Claims] 1. A binder removing treatment in a state where an aluminum nitride molded body is contained in a porous aluminum nitride container,
And a baking treatment. 2. The method for producing an aluminum nitride sintered body according to claim 1, wherein a conductive paste layer for forming a wiring is formed on the surface or inside of the aluminum nitride molded body. 3. The porosity of the aluminum nitride container is 10
3. The method for producing an aluminum nitride sintered body according to claim 1, wherein the thickness is not more than 20 mm. 4. The method according to claim 1, wherein the binder is removed in an atmosphere in which carbon dioxide is mixed into an inert gas.
3. The method for producing an aluminum nitride sintered body according to any one of items 3. 5. The temperature of the binder removal treatment is 900 to 100.
The method for producing an aluminum nitride sintered body according to claim 4, wherein the temperature is 0 ° C. 6. The calcination treatment is performed in an inert gas atmosphere or a reducing gas atmosphere.
5. The method for producing an aluminum nitride sintered body according to any one of the above items. 7. The firing temperature is 1550 to 1700 ° C.
The method for producing an aluminum nitride sintered body according to claim 6, wherein: