WO2017033855A1 - Aluminum nitride sintered body and method for producing same - Google Patents

Abstract

This aluminum nitride sintered body has one main surface and contains a plurality of aluminum nitride crystal grains. With respect to the aluminum nitride crystal grains, the (11-20) planes of all the aluminum nitride crystal grains, or alternatively, the (11-20) planes of some aluminum nitride crystal grains and the (10-10) planes of the other aluminum nitride crystal grains are oriented to be parallel to the main surface. Consequently, an aluminum nitride sintered body having a main surface that is easy to be mirror finished and a method for producing this aluminum nitride sintered body are provided.

Description

Aluminum nitride sintered body and method for producing the same

The present invention relates to an aluminum nitride sintered body and a method for producing the same.
This application claims priority based on Japanese Patent Application No. 2015-164958 filed on August 24, 2015, and cites all the contents described in the above Japanese application.

Since the aluminum nitride sintered body has high heat dissipation due to high thermal conductivity, it is suitably used as a substrate for semiconductor devices, a substrate for semiconductor device circuits, and the like.

Japanese Patent Laid-Open No. 2002-201072 (Patent Document 1) has 15 to 30 AlN crystal particles included in a linear distance of 50 μm, and has a thermal conductivity of 200 W · m ⁻¹ · K ⁻¹ or more, Disclosed is a highly abrasive AlN sintered body having a surface roughness Ra of 0.01 μm or less and 5 or less degranulation traces having a maximum diameter of 5 μm or more contained per unit area of 50 μm × 50 μm on the surface.

Japanese Patent Application Laid-Open No. 2002-249379 (Patent Document 2) has aluminum nitride as a main component, rare earth metal element in an oxide conversion of 0.4 mol% to 2.0 mol, and aluminum oxide in an amount of 0.5 mol% to 2.0 mol. Disclosed is an aluminum nitride sintered body that contains no more than%, Si content is not more than 80 ppm, and the average particle size of aluminum nitride particles is not more than 3 μm, which is resistant to degranulation and has a relatively high thermal conductivity.

Japanese Patent Laid-Open No. 2002-293637 (Patent Document 3) discloses that in a method for producing an aluminum nitride sintered body, the surface of the sintered body has a concentration of 15 to 15 prepared with an abrasive having JIS abrasive grain size # 240 to # 320. It is disclosed that defects on the surface of a sintered body can be reduced by spraying 30 vol% polishing slurry at 0.3 to 0.5 MPa and polishing the surface.

Japanese Patent Application Laid-Open No. 2004-107096 (Patent Document 4) describes an oriented carbonization in which α-type silicon carbide particles and a solvent are mixed to prepare a raw material slurry, and this raw material slurry is solidified by a magnetic field of 1 T or more and sintered. A method for producing a silicon sintered body is disclosed. Such a slurry can generally have a pH of 9 or more. For example, the pH is about 9 to 12 as an aqueous slurry.

Japanese Patent Laid-Open No. 2002-193672 (Patent Document 5) is characterized in that a non-ferromagnetic powder having a crystal structure other than equiaxed crystals is dispersed in a solvent, and the slurry is solidified and molded in a magnetic field and then sintered. A method for producing an oriented ceramic sintered body is disclosed.

JP 2002-201072 A JP 2002-249379 A JP 2002-293637 A JP 2004-107096 A JP 2002-193672 A

The aluminum nitride sintered body of the present disclosure has one main surface and includes a plurality of aluminum nitride crystal particles. The aluminum nitride crystal particles are the (11-20) plane of all the aluminum nitride crystal particles, or a part of the aluminum nitride crystal particles. The (11-20) plane of the aluminum nitride crystal grains and the (10-10) plane of the remaining aluminum nitride crystal grains are oriented parallel to one principal plane.

The method for producing an aluminum nitride sintered body of the present disclosure includes a step of forming a raw material slurry by dispersing a raw material powder containing an aluminum nitride powder in a solvent, and after adjusting the pH of the raw material slurry to 1 to 6 A step of forming a molded body including a step of forming a molded body having one principal surface by slip casting in a magnetic field and a step of forming an aluminum nitride sintered body by sintering the molded body. The magnetic field is applied in a direction parallel to one main surface of the compact.

FIG. 1 is a schematic cross-sectional view showing an example of a molding apparatus used for manufacturing an aluminum nitride sintered body according to an aspect of the present invention. FIG. 2 is a schematic diagram showing an example of the orientation of aluminum nitride crystal grains in an aluminum nitride sintered body according to an aspect of the present invention. FIG. 3 is a schematic diagram showing another example of the orientation of aluminum nitride crystal grains in an aluminum nitride sintered body according to an aspect of the present invention. FIG. 4 is a flowchart showing an example of a method for manufacturing an aluminum nitride sintered body according to another aspect of the present invention.

<Problems to be solved by the present disclosure>
Since the AlN sintered body disclosed in Japanese Patent Laid-Open No. 2002-201072 (Patent Document 1) has degranulation traces with a maximum diameter of 5 μm or more, the maximum height roughness Rz becomes large and is attached to the AlN sintered body. There are problems such as peeling of semiconductor devices to be combined and generation of electric discharge.

The aluminum nitride sintered body disclosed in Japanese Patent Application Laid-Open No. 2002-249379 (Patent Document 2) has a problem that as the average particle diameter of aluminum nitride particles decreases, there are more grain boundaries and the thermal conductivity decreases. is there.

In the method for producing an aluminum nitride sintered body disclosed in Japanese Patent Application Laid-Open No. 2002-293637 (Patent Document 3), since the polishing is performed using an abrasive of JIS abrasive grain size # 240 to # 320, degranulation occurs and the maximum There is a problem that the height roughness Rz becomes large and a problem that polishing unevenness occurs because a polishing slurry having a concentration of 15 to 30% by volume is sprayed at a low spraying pressure of 0.3 to 0.5 MPa.

In the method for producing an oriented silicon carbide sintered body disclosed in Japanese Patent Application Laid-Open No. 2004-107096 (Patent Document 4), the pH of the raw material slurry is set to 9 or more, and nitriding as a raw material of the aluminum nitride sintered body is performed. When the pH of the aluminum powder slurry is 9 or more, hydrolysis of the surface of the aluminum nitride crystal particles occurs, the viscosity of the slurry rises, and the aluminum nitride in the aluminum nitride powder in a magnetic field during molding of the slurry. There are problems that it becomes difficult to orient the particles and a dense molded body cannot be obtained. There is also a problem that oxygen remains in the sintered body after sintering and the thermal conductivity of the sintered body is lowered.

In the method for producing an oriented ceramic sintered body disclosed in Japanese Patent Laid-Open No. 2002-193672 (Patent Document 5), when the magnetic flux density is large, the aluminum nitride formed body and the aluminum nitride particles in the aluminum nitride sintered body are: The (0001) plane of some grains and the (000-1) plane of the remaining grains are oriented parallel to the principal plane, and the aluminum atomic plane that is the (0001) plane is a (000-1) plane that is difficult to be polished. Since the nitrogen atom surface is easily polished, there is a problem that the surface roughness of the main surface of the aluminum nitride sintered body after polishing increases.

Therefore, an object of the present invention is to provide an aluminum nitride sintered body in which the main surface is easily mirror-finished by reducing the surface roughness of the main surface by polishing, and a method for producing the same.

<Effects of the present disclosure>
According to the present disclosure, by reducing the surface roughness of the main surface by polishing, it is possible to provide an aluminum nitride sintered body in which the main surface is easily mirror-finished and a method for manufacturing the same.

<Description of Embodiment of the Present Invention>
First, embodiments of the present invention will be listed and described.

[1] An aluminum nitride sintered body according to an embodiment of the present invention has a principal surface and includes a plurality of aluminum nitride crystal particles. The aluminum nitride crystal particles are (11-20) of all the aluminum nitride crystal particles. ) Plane, or the (11-20) plane of some aluminum nitride crystal grains and the (10-10) plane of the remaining aluminum nitride crystal grains are oriented parallel to one principal plane. The aluminum nitride sintered body of the present embodiment can easily be mirror-finished on the main surface.

[2] In the aluminum nitride sintered body of this embodiment, the arithmetic average roughness Ra specified in JIS B0601: 2013 on one main surface is 10 nm or less, and the maximum height specified in JIS B0601: 2013 on one main surface The roughness Rz can be 100 nm or less. As a result, an aluminum nitride sintered body whose main surface is mirror-finished is obtained.

[3] A method of manufacturing an aluminum nitride sintered body according to another embodiment of the present invention includes a step of forming a raw material slurry by dispersing a raw material powder containing an aluminum nitride powder in a solvent, and a pH of the raw material slurry at its pH A step of forming a molded body having one principal surface by slip casting in a magnetic field after adjusting the thickness to 1 or more and 6 or less, a step of forming an aluminum nitride sintered body by sintering the molded body, In the step of forming the molded body, the magnetic field is applied in a direction parallel to one main surface of the molded body. According to the method for manufacturing an aluminum nitride sintered body of the present embodiment, an aluminum nitride sintered body whose main surface can be easily mirror-finished can be obtained.

[4] The method for manufacturing an aluminum nitride sintered body according to this embodiment may further include a step of mirror-finishing one main surface of the aluminum nitride sintered body. Thereby, the aluminum nitride sintered compact by which the main surface was mirror-finished is obtained.

[5] In the method for manufacturing an aluminum nitride sintered body according to the present embodiment, the arithmetic average roughness Ra specified in JIS B0601: 2013 on one main surface is set to 10 nm or less for the aluminum nitride sintered body after the mirror-finishing step. And the maximum height roughness Rz prescribed | regulated to JISB0601: 2013 of one main surface can be 100 nm or less. Thereby, the aluminum nitride sintered compact by which the main surface was mirror-finished is obtained.

[6] The pH of the polishing slurry used for polishing can be 1 or more and 6 or less in the mirror-finishing step of the manufacturing method of the aluminum nitride sintered body of the present embodiment. Thereby, the aluminum nitride sintered compact by which the main surface was mirror-finished is obtained.

<Details of Embodiment of the Present Invention>
[Embodiment 1: Aluminum nitride sintered body]
As shown in FIGS. 2 and 3, the aluminum nitride sintered body 11 of the present embodiment has a main surface 11 m and includes a plurality of aluminum nitride crystal particles 11 p, and the aluminum nitride crystal particles 11 p are all aluminum nitride. The (11-20) face 11pa of the crystal grain 11p, or the (11-20) face 11pa of a part of the aluminum nitride crystal grain 11p and the (10-10) face 11pm of the remaining aluminum nitride crystal grain 11p are mainly used. It is oriented parallel to the surface 11m. The aluminum nitride sintered body 11 of the present embodiment can easily mirror the main surface.

(Orientation of aluminum nitride crystal grains)
In the aluminum nitride sintered body 11 of the present embodiment, the plurality of aluminum nitride crystal particles 11p are (11-20) face 11pa of all the aluminum nitride crystal particles 11p, or (11 of a part of the aluminum nitride crystal particles 11p. −20) The face 11pa and the (10-10) face 11pm of the remaining aluminum nitride crystal grain 11p are oriented parallel to the one principal face 11m. Here, since the (11-20) plane 11pa and the (10-10) plane 11pm of the aluminum nitride crystal particles 11p are nonpolar planes and the density of atoms contained in the plane is also very close, polishing is performed. The chemical and physical properties for are very close. For this reason, the aluminum nitride sintered body 11 has a (11-20) plane 11pa or a plane parallel to the plane formed by the (11-20) plane 11pa and the (10-10) plane 11pm of the aluminum nitride crystal particle 11p. Since one main surface 11m is uniformly polished, mirror processing of one main surface 11m is easy. Here, the (11-20) plane 11pa and the (10-10) plane 11pm of the aluminum nitride crystal particles 11p are measured and identified by the X-ray diffraction method.

In the aluminum nitride sintered body 11 and the manufacturing method thereof according to the present embodiment, “the (11-20) plane 11pa of all the aluminum nitride crystal grains 11p is oriented in parallel to one principal surface 11m”. The term “all” means “substantially all” in which no other crystal plane is measured and identified in X-ray diffraction. For example, aluminum nitride crystal particles contained in the aluminum nitride sintered body 11 This corresponds to 95% by volume or more of the entire 11p. Further, in “the (11-20) plane 11pa of some of the aluminum nitride crystal particles 11p and the (10-10) plane 11pm of the remaining aluminum nitride crystal particles 11p are oriented in parallel to one principal surface 11m”. “Partial” and “remainder” mean that the total of the part and the remainder is “substantially all” in which no other crystal plane is measured and identified in X-ray diffraction. For example, the sum of “partial aluminum nitride crystal particles” and “remaining aluminum nitride crystal particles” corresponds to 95% by volume or more of the entire aluminum nitride crystal particles 11p included in the aluminum nitride sintered body 11. .

(Roughness of one main surface of aluminum nitride sintered body)
The aluminum nitride sintered body 11 of the present embodiment has an arithmetic average roughness Ra specified in JIS B0601: 2013 of one main surface 11m of 10 nm or less, and a maximum specified in JIS B0601: 2013 of one main surface 11m. A mirror surface having a height roughness Rz of 100 nm or less is preferred. In the aluminum nitride sintered body 11 of the present embodiment, the arithmetic average roughness Ra of one principal surface 11m is preferably 10 nm or less, more preferably 5 nm or less, from the viewpoint that the one principal surface 11m is a flatter mirror surface. The following is more preferable. Further, the maximum height roughness Rz of one principal surface 11m is preferably 100 nm or less, more preferably 50 nm or less, and further preferably 30 nm or less. Here, the arithmetic average roughness Ra and the maximum height roughness Rz of one principal surface 11m are measured by a three-dimensional optical profiler (Zygo New View 7300 manufactured by Canon Inc.).

(Shape and size of aluminum nitride sintered body)
The aluminum nitride sintered body 11 of the present embodiment has one main surface 11m. It is sufficient if it has at least one main surface 11m, and it may have a plurality of main surfaces, and the shape and size thereof are not limited.

(Thermal conductivity of sintered aluminum nitride)
The thermal conductivity of the aluminum nitride sintered body 11 of the present embodiment is not particularly limited, and the high heat radiation point of view, preferably 130W · m ^-1 · K ^-1 or more, 150W · m ^-1 · K ^{- 1} or more is more preferable, and 170 W · m ⁻¹ · K ⁻¹ or more is more preferable. Here, the thermal conductivity of the aluminum nitride sintered body 11 is measured by a laser flash method thermal constant measuring device (TC-9000, manufactured by Advance Riko Co., Ltd.).

(Relative density of aluminum nitride sintered body)
The relative density of the aluminum nitride sintered body 11 of the present embodiment is preferably 98% or more, and more preferably 99% or more, from the viewpoint of improving the workability and thermal conductivity of the sintered body. Here, the relative density means the percentage of the actual mass with respect to the true mass of the substance, and is measured by the Archimedes method.

(Aluminum nitride crystal particles)
The aluminum nitride sintered body 11 of the present embodiment includes aluminum nitride crystal particles 11p. The average particle diameter of the aluminum nitride crystal particles 11p in the aluminum nitride sintered body 11 is not particularly limited, but is preferably 10 μm or less, more preferably 5 μm or less, from the viewpoint of easy mirror finishing of one main surface 11 m. From the viewpoint of improving the workability and thermal conductivity of the bonded body, it is preferably 1 μm or more, and more preferably 3 μm or more. Here, the average particle diameter of the aluminum nitride crystal particles 11p in the aluminum nitride sintered body 11 is measured by a scanning electron microscope (SEM) (JSM-6510 manufactured by JEOL Ltd.). The average particle size of the crystal particles is a value calculated by the area measurement method. Specifically, a rectangle is drawn so that at least 50 or more crystal grains are included on the image, and the total area A and the number N _A of crystal grains existing in the rectangle are obtained. A value obtained by dividing the area A by the number of crystal grains NA (A / N _A ) is an average cross-sectional area a of the crystal grains, and a square root (√a) of the average cross-sectional area a of the crystal grains is an average grain diameter d of the crystal grains. .

The content of the aluminum nitride crystal particles in the aluminum nitride sintered body 11 is not particularly limited, but is preferably 95% by mass or more and 99% by mass or less from the viewpoint of increasing the density and thermal conductivity of the sintered body. 97 mass% or more and 98 mass% or less are more preferable. Here, the content of the aluminum nitride crystal particles 11p in the aluminum nitride sintered body 11 is measured by an inductively coupled plasma (ICP) emission spectrometer (ICPS-7510 manufactured by Shimadzu Corporation).

(Sintering aid)
From the viewpoint of increasing the density of the sintered body and the purity of the aluminum nitride of the main phase by lowering the melting point during sintering, the aluminum nitride sintered body 11 of the present embodiment is a group 2 element as a sintering aid. It preferably contains an oxide, nitride, fluoride or the like of a group 3 element or a group 13 element. Preferred examples of the Group 2 element include magnesium (Mg), calcium (Ca), and strontium (Sr). Group 3 elements include scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), and europium (Eu). , Gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), lutetium (Lu) and the like. Preferred examples of the group 13 element include aluminum (Al). Further, the content of the sintering aid in the aluminum nitride sintered body 11 is not particularly limited, but the density of the sintered body and the purity of the main phase aluminum nitride are increased by lowering the melting point during sintering. From the viewpoint of doing, 1 mass% or more and 5 mass% or less are preferable, and 2 mass% or more and 3 mass% or less are more preferable. Here, the kind and content of the sintering aid in the aluminum nitride sintered body 11 are measured by an ICP emission analyzer (ICPS-7510 manufactured by Shimadzu Corporation).

[Embodiment 2: Manufacturing method of aluminum nitride sintered body]
With reference to FIGS. 1 to 4, the method of manufacturing the aluminum nitride sintered body 11 of the present embodiment includes a step S10 of forming a raw material slurry 9 by dispersing a raw material powder containing aluminum nitride powder in a solvent, By adjusting the pH of the raw material slurry 9 to 1 or more and 6 or less and then performing the slip casting in the magnetic field B to form a molded body 10 having one main surface 10m, and sintering the molded body 10 In the step of forming the molded body 10, the magnetic field B is applied in a direction parallel to the one main surface 10 m of the molded body 10. According to the method for manufacturing an aluminum nitride sintered body of the present embodiment, an aluminum nitride sintered body whose main surface can be easily mirror-finished can be obtained.

{Process of forming raw material slurry}
The manufacturing method of the aluminum nitride sintered body 11 of the present embodiment first includes a step S10 of forming a raw material slurry 9 by dispersing a raw material powder containing an aluminum nitride powder in a solvent.

(Aluminum nitride powder)
The purity of the aluminum nitride powder contained in the raw material powder is not particularly limited, but is preferably 98% by mass or more, and more preferably 99% by mass or more from the viewpoint of increasing the density and thermal conductivity of the sintered body. The content of the aluminum nitride powder in the raw material powder is not particularly limited, but is preferably 95% by mass or more and 99% by mass or less, and 97% by mass or more and 98% by mass from the viewpoint of increasing the density and thermal conductivity of the sintered body. % Or less is more preferable. The average particle size of the aluminum nitride crystal particles is not particularly limited, but is preferably 10 μm or less, more preferably 5 μm or less, and more preferably 5 μm or less from the viewpoint of improving the workability and thermal conductivity of the sintered body. From the viewpoint of increasing the thermal conductivity, 1 μm or more is preferable, and 3 μm or more is more preferable. Here, the average particle diameter of the aluminum nitride crystal particles in the aluminum nitride powder is measured by SEM (JSM-6510 manufactured by JEOL Ltd.).

(Sintering aid)
From the viewpoint of forming a high-quality sintered body, the raw material powder preferably further contains oxides, nitrides, fluorides, etc. of Group 2, 3 and 13 elements as sintering aids. . As the group 2 element, Mg, Ca, Sr and the like are preferably exemplified. Preferred examples of the Group 3 element include rare earth elements such as Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. A preferred example of the group 13 element is Al. In addition, the content of the sintering aid in the raw material powder is not particularly limited, but from the viewpoint of increasing the density of the sintered body and the purity of the main phase aluminum nitride by lowering the melting point during sintering, 1 mass% or more and 5 mass% or less are preferable, and 2 mass% or more and 3 mass% or less are more preferable.

(binder)
From the viewpoint of forming a high-quality sintered body, the raw material powder preferably further contains polyvinyl alcohol (PVA), polyvinyl butyral (PVB), acrylic, polyester, and the like as a binder. Further, the content of the binder in the raw material powder is not particularly limited, but from the viewpoint of improving the formability of the molded body and increasing the purity of aluminum nitride as the main phase of the sintered body, it is 15% by mass or more and 35% by mass or less. Is preferable, and 20 mass% or more and 30 mass% or less are more preferable.

(solvent)
Although there is no restriction | limiting in particular in a solvent, From a viewpoint of being easy to disperse | distribute raw material powder uniformly, an organic solvent is preferable. Preferred examples of the organic solvent include ethanol, methanol, hexane and the like.

(Distribution method)
The method for dispersing the raw material powder in the solvent is not particularly limited, but from the viewpoint of homogeneously dispersing the raw material powder in the solvent, preferable examples include dispersion by ball mill mixing and ultrasonic dispersion.

{Process for forming molded body}
In the manufacturing method of the aluminum nitride sintered body 11 of the present embodiment, next, after adjusting the pH of the raw slurry 9 to 1 or more and 6 or less, the main surface 10m is formed by slip casting in the magnetic field B. The process S20 which forms the molded object 10 which has is included. In this process, the magnetic field B is applied in a direction parallel to the one main surface 10 m of the molded body 10. By this process, the (11-20) plane of all the aluminum nitride crystal grains, or the (11-20) plane of a part of the aluminum nitride crystal grains and the (10-10) plane of the remaining aluminum nitride crystal grains are formed. A molded body 10 oriented parallel to one main surface 10m of the body 10 is obtained.

(Adjustment of pH of raw material slurry)
The pH of the raw material slurry 9 in which the raw material powder is dispersed in a solvent is adjusted to 1 or more and 6 or less. After the pH of the raw material slurry 9 is set to 1 or more and 6 or less, by applying a magnetic field B in a direction parallel to one main surface 10 m of the molded body 10, (11-20) plane of all aluminum nitride crystal particles, or The (11-20) plane of some of the aluminum nitride crystal grains and the (10-10) plane of the remaining aluminum nitride crystal grains are oriented parallel to one major surface 10m of the molded body 10 and From the viewpoint of increasing the density and increasing the thermal conductivity by reducing the remaining impurity oxygen, the pH of the raw slurry 9 is adjusted to 1 or more and 6 or less, preferably 2 or more and 5 or less. Adjustment of the pH of the raw material slurry 9 is not particularly limited, and is performed, for example, by adding an acidic substance such as hydrochloric acid.

When the pH of the raw material slurry 9 is strongly acidic below 1, it is due to formation of hydrated ions, and when the pH of the raw material slurry 9 is more than 6 neutral or alkaline, it is due to formation of hydroxides due to formation of these networks. Due to the steric hindrance, rotation of the aluminum nitride crystal particles by the magnetic field B is inhibited, and the orientation of the aluminum nitride crystal particles is inhibited. In addition, when the pH of the raw material slurry 9 is less than 1, the sintering aid contained in the raw material slurry 9 is preferentially eluted, so that the content of the sintering aid is reduced and formed during sintering. Since the liquid phase is reduced, it is difficult to increase the relative density of the sintered body. If the pH of the raw material slurry 9 is greater than 6, the viscosity of the raw material slurry 9 is increased by the hydrolysis reaction of the surface of the aluminum nitride crystal particles of the aluminum nitride powder contained in the raw material slurry 9, and the orientation of the aluminum nitride crystal particles is increased. In addition to being hindered, the thermal conductivity decreases due to impurity oxygen remaining after firing.

(Slip cast molding)
The slip cast molding is a process in which the raw material slurry 9 having a pH adjusted to 1 or more and 6 or less is poured into the porous mold 20 and the solvent in the raw material slurry 9 is absorbed into the porous mold 20 to dry the raw material slurry 9. A molding method for molding.

(Application of magnetic field)
The method for applying the magnetic field B is not particularly limited, but from the viewpoint of efficiently applying the magnetic field, a steady magnetic field method, a pulse magnetic field method, a gradient magnetic field method, and the like are preferable. The application direction of the magnetic field B is a direction parallel to one main surface 10 m of the molded body 10. By applying the magnetic field B in such a direction, the (11-20) face 10pa of all the aluminum nitride crystal particles 10p in the compact 10 or the (11-20) face 10pa of the aluminum nitride crystal particles 10p and the remaining part of the aluminum nitride crystal particles 10p. The (10-10) plane 10pm of the aluminum nitride crystal particles 10p is oriented parallel to the one main surface 10m of the molded body 10. The magnetic flux density of the applied magnetic field B is not particularly limited, but is preferably 1T (Tesla) or more and 15T or less, and more preferably 3T or more and 10T or less from the viewpoint of efficiently increasing the orientation of the aluminum nitride crystal particles.

(Molding equipment)
The molding apparatus 100 used in the step S20 for forming the molded body 10 is not particularly limited, but from the viewpoint of efficiently slip casting the raw material slurry 9 in a magnetic field, a porous mold having a space for containing the raw material slurry 9 is used. 20 and a magnetic field application unit 30 that applies a magnetic field B in a direction parallel to one main surface 10 m of the molded body 10 formed from the raw slurry 9. The porous mold 20 is not particularly limited as long as it is suitable for the slip casting of the raw material slurry 9, and suitable examples thereof include gypsum and a porous polymer. The magnetic field application unit 30 is not particularly limited as long as it can apply the magnetic field B in a direction parallel to the one main surface 10m of the molded body 10 formed from the raw slurry 9, and includes a high frequency coil unit, a superconducting magnet unit, and the like. Is mentioned.

{Process for forming aluminum nitride sintered body}
Next, the method for manufacturing the aluminum nitride sintered body 11 of the present embodiment includes the step S30 of forming the aluminum nitride sintered body 11 by sintering the formed body 10. In this step, the aluminum nitride sintered body 11 having the aluminum nitride crystal particles 11p in which the orientation of the aluminum nitride crystal particles 10p in the molded body 10 is maintained is obtained. That is, the molded body 10 in which the (11-20) plane 10pa of the aluminum nitride crystal particles 10p in the molded body 10 is oriented parallel to one main surface 10m of the molded body 10 is sintered, and the aluminum nitride sintered body 11 Thus, the aluminum nitride sintered body 11 in which the (11-20) plane 11pa of all the aluminum nitride crystal particles 11p is oriented parallel to the one main surface 11m of the aluminum nitride sintered body 11 is obtained. The (11-20) face 10pa of a part of the aluminum nitride crystal particles 10p and the (10-10) face 10pm of the remaining aluminum nitride crystal particles 10p in the compact 10 are the main parts of the compact 10. The compact 10 oriented parallel to the face 10m is sintered, and the (11-20) face 11pa of a part of the aluminum nitride crystal particles 11p in the aluminum nitride sintered body 11 and the remaining aluminum nitride crystal particles 11p ( 10-10) An aluminum nitride sintered body 11 is obtained in which the surface 11pm is oriented parallel to one principal surface 11m of the aluminum nitride sintered body 11.

The step S30 for forming the aluminum nitride sintered body 11 by sintering the molded body 10 is not particularly limited, but from the viewpoint of efficiently forming the high-quality aluminum nitride sintered body 11, a binder is included. It is preferable to include a sub-step S31 for debinding the formed body 10 and a sub-step S32 for sintering the de-bindered formed body 10.

(Sub-process for debinding the compact)
The sub-step S31 for removing the binder from the molded body 10 means a sub-step for removing the binder contained therein from the molded body 10. The method for removing the binder from the molded body 10 is not particularly limited, but is preferably heat-treated in a nitrogen gas atmosphere or an argon gas atmosphere at 700 ° C. to 900 ° C. for 1 hour to 3 hours.

(Sub-process for sintering the debindered compact)
In the sub-step S32 for sintering the debindered molded body 10, a method for sintering the debindered molded body 10 is not particularly limited, but is 700 ° C. or higher in a nitrogen gas atmosphere or an argon gas atmosphere. It is preferable to perform heat treatment at 900 ° C. or less under conditions of 1 hour or more and 3 hours or less.

{Process of mirror-finishing one main surface of aluminum nitride sintered body}
It is preferable that the manufacturing method of the aluminum nitride sintered body 11 of the present embodiment further includes a step S40 of mirror-finishing one main surface 11m of the aluminum nitride sintered body 11 by polishing. With this process, an aluminum nitride sintered body whose main surface is mirror-finished is obtained.

In the manufacturing method of the aluminum nitride sintered body 11 of the present embodiment, the arithmetic average roughness Ra specified in JIS B0601: 2013 on one main surface of the aluminum nitride sintered body 11 after the mirror finishing step S40 is 10 nm or less. In addition, the maximum height roughness Rz defined in JIS B0601: 2013 on one main surface is preferably 100 nm or less. Thereby, the aluminum nitride sintered compact 11 by which the main surface was mirror-finished is obtained. In the aluminum nitride sintered body 11 of the present embodiment, the arithmetic average roughness Ra of one principal surface 11m is preferably 10 nm or less, more preferably 5 nm or less, from the viewpoint that the one principal surface 11m is a flatter mirror surface. The following is more preferable. Further, the maximum height roughness Rz of one principal surface 11m is preferably 100 nm or less, more preferably 50 nm or less, and further preferably 30 nm or less. Here, the arithmetic average roughness Ra and the maximum height roughness Rz of one main surface 11m of the aluminum nitride sintered body 11 are measured by a three-dimensional optical profiler (Zygo New View 7300 manufactured by Canon Inc.).

The pH of the polishing slurry used for polishing is not particularly limited in the step of mirror-finishing the manufacturing method of the aluminum nitride sintered body 11 of the present embodiment, but the aluminum nitride crystal particles 11p in the sintered body at the time of polishing are not limited. 1 to 6 or less is preferable and 2 or more and 5 or less is more preferable from the viewpoint of suppressing the degranulation and maintaining the smoothness by suppressing the roughness of the surface state. When the pH of the polishing slurry when mirror-finishing the sintered body is less than 1, the sintering aid contained in the sintered body elutes preferentially, and aluminum nitride in the sintered body during polishing The degranulation of the crystal particles 11p is promoted, and the smoothness of one main surface of the sintered body is lowered. If the pH of the polishing slurry when the sintered body is mirror-finished is greater than 6, surface roughness is promoted by the hydrolysis reaction of the surface of the aluminum nitride crystal particles of the aluminum nitride powder contained in the sintered body. The smoothness of one main surface of the bonded body is lowered.

Example 1
1. Formation of Raw Material Slurry As raw material powder, aluminum nitride (AlN) powder, ytterbium oxide (Yb ₂ O ₃ ) powder, neodymium oxide (Nd ₂ O ₃ ) powder, aluminum oxide (Al ₂ O ₃ ) powder, and polyvinyl alcohol (PVA) ) A mixed powder having a ratio of 72.4% by mass, 0.8% by mass, 1.0% by mass, 0.7% by mass, and 25.1% by mass was prepared. Here, Yb ₂ O ₃ powder, Nd ₂ O ₃ powder and Al ₂ O ₃ powder were sintering aids, and PVA powder was a binder. 30.0% by mass of the raw material powder was uniformly dispersed in 70.0% by mass of ethanol as a solvent by ball mill mixing to form a raw material slurry.

2. Formation of Molded Body The pH of the raw material slurry was adjusted to 3 using hydrochloric acid. A compact was formed by slip casting in a magnetic field having a magnetic flux density of 3T. Here, the magnetic field was applied in a direction parallel to one main surface of the compact.

3. Formation of Aluminum Nitride Sintered Body The above molded body is first debindered by heat treatment at 800 ° C. for 1 hour in a nitrogen gas atmosphere, and then sintered by heat treatment at 1800 ° C. for 2 hours in a nitrogen gas atmosphere. Thus, an aluminum nitride (AlN) sintered body was formed. The relative density of the AlN sintered body was 99% as measured by the Archimedes method. The crystal phase in the AlN sintered body was analyzed and identified by the X-ray diffraction method, and was an AlN phase, an NdAlO ₃ phase, and a Yb ₂ O ₃ phase. When the AlN crystal particles in the AlN sintered body were analyzed by the X-ray diffraction method, the (11-20) plane of the AlN crystal particles was oriented parallel to one main surface of the AlN sintered body. The thermal conductivity of the AlN sintered body was 180 W · m ⁻¹ · K ^{−1 as} measured by a thermal diffusivity measuring device (TC-1200RH manufactured by Advance Riko Co., Ltd.).

4). Mirror surface processing of aluminum nitride sintered body After grinding one main surface of an AlN sintered body with a surface grinding machine (SGE520 manufactured by Nagase Integrex Co., Ltd.), a polishing slurry having a pH of 3 and containing diamond abrasive grains having an average particle diameter of 50 nm Was polished with a polishing machine (EJW-6101 manufactured by Nippon Engis Co., Ltd.). Arithmetic mean roughness Ra and maximum height roughness Rz defined in JIS B0601: 2013 on one main surface after polishing of an AlN sintered body are measured by an optical measuring instrument (Zygo New View 7100 manufactured by Canon Inc.). , 3 nm and 28 nm, respectively. The results are summarized in Table 1.

(Example 2)
A raw material slurry, a molded body, and an AlN sintered body were formed in the same manner as in Example 1 except that hydrochloric acid was used to form a raw material slurry at the time of forming the molded body, and the pH of the raw material slurry was set to 1. One main surface was polished. The relative density of the AlN sintered body was 99%. The crystal phases in the AlN sintered body were an AlN phase, an NdAlO ₃ phase, and a Yb ₂ O ₃ phase. In the AlN crystal particles in the AlN sintered body, the (11-20) plane of the AlN crystal particles was oriented parallel to one main surface of the AlN sintered body. The thermal conductivity of the AlN sintered body was 175 W · m ⁻¹ · K ⁻¹ . The arithmetic average roughness Ra and the maximum height roughness Rz defined in JIS B0601: 2013 on one main surface after polishing of the AlN sintered body were 5 nm and 45 nm, respectively. The results are summarized in Table 1.

(Example 3)
A raw material slurry, a molded body, and an AlN sintered body were formed in the same manner as in Example 1 except that hydrochloric acid was used to form the molded body and the pH of the raw material slurry was set to 6. One main surface was polished. The relative density of the AlN sintered body was 99%. The crystal phases in the AlN sintered body were an AlN phase, an NdAlO ₃ phase, and a Yb ₂ O ₃ phase. In the AlN crystal particles in the AlN sintered body, the (11-20) plane of the AlN crystal particles was oriented parallel to one main surface of the AlN sintered body. The thermal conductivity of the AlN sintered body was 173 W · m ⁻¹ · K ⁻¹ . The arithmetic average roughness Ra and the maximum height roughness Rz defined in JIS B0601: 2013 on one main surface after polishing of the AlN sintered body were 8 nm and 78 nm, respectively. The results are summarized in Table 1.

Example 4
Except that the pH of the polishing slurry was set to 1 when polishing one main surface of the AlN sintered body, a raw material slurry, a molded body and an AlN sintered body were formed in the same manner as in Example 1, and the AlN sintered body was formed. One main surface of the body was polished. The relative density of the AlN sintered body was 99%. The crystal phases in the AlN sintered body were an AlN phase, an NdAlO ₃ phase, and a Yb ₂ O ₃ phase. In the AlN crystal particles in the AlN sintered body, the (11-20) plane of the AlN crystal particles was oriented parallel to one main surface of the AlN sintered body. The thermal conductivity of the AlN sintered body was 180 W · m ⁻¹ · K ⁻¹ . The arithmetic average roughness Ra and the maximum height roughness Rz defined in JIS B0601: 2013 on one main surface after polishing of the AlN sintered body were 4 nm and 32 nm, respectively. The results are summarized in Table 1.

(Example 5)
A raw material slurry, a molded body and an AlN sintered body are formed in the same manner as in Example 1 except that the pH of the polishing slurry is set to 6 when polishing one main surface of the AlN sintered body. One main surface of the body was polished. The relative density of the AlN sintered body was 99%. The crystal phases in the AlN sintered body were an AlN phase, an NdAlO ₃ phase, and a Yb ₂ O ₃ phase. In the AlN crystal particles in the AlN sintered body, the (11-20) plane of the AlN crystal particles was oriented parallel to one main surface of the AlN sintered body. The thermal conductivity of the AlN sintered body was 180 W · m ⁻¹ · K ⁻¹ . The arithmetic average roughness Ra and the maximum height roughness Rz defined in JIS B0601: 2013 on one main surface of the AlN sintered body after polishing were 9 nm and 93 nm, respectively. The results are summarized in Table 1.

(Example 6)
A raw material slurry, a molded body, and an AlN sintered body are formed in the same manner as in Example 1 except that the magnetic flux density of the magnetic field applied at the time of forming the molded body is 10 T. The surface was polished. The relative density of the AlN sintered body was 99%. The crystal phases in the AlN sintered body were an AlN phase, an NdAlO ₃ phase, and a Yb ₂ O ₃ phase. The AlN crystal particles in the AlN sintered body are oriented so that the (11-20) plane of some AlN crystal particles and the (10-10) plane of the remaining AlN crystal particles are parallel to one main surface of the AlN sintered body. Was. The thermal conductivity of the AlN sintered body was 177 W · m ⁻¹ · K ⁻¹ . The arithmetic average roughness Ra and the maximum height roughness Rz defined in JIS B0601: 2013 on one main surface after polishing of the AlN sintered body were 5 nm and 62 nm, respectively. The results are summarized in Table 1.

(Comparative Example 1)
In the same manner as in Example 1 except that the pH of the raw material slurry was set to 7 using hydrochloric acid and ammonia and no magnetic field was applied during the formation of the green body, the raw material slurry, the green body and the AlN sintered body were obtained. Then, one main surface of the AlN sintered body was polished. The relative density of the AlN sintered body was 92%. The crystal phases in the AlN sintered body were an AlN phase, an NdAlO ₃ phase, a Yb ₂ O ₃ phase, an Al ₂ O ₃ phase, and an AlON phase. In the AlN crystal particles in the AlN sintered body, there was no specific crystal plane of the AlN crystal particles oriented parallel to one main surface of the AlN sintered body. The thermal conductivity of the AlN sintered body was 22 W · m ⁻¹ · K ⁻¹ . The arithmetic average roughness Ra and the maximum height roughness Rz defined in JIS B0601: 2013 on one main surface after polishing of the AlN sintered body were 352 nm and 5300 nm, respectively. The results are summarized in Table 2.

(Comparative Example 2)
A raw material slurry, a molded body, and an AlN sintered body were formed in the same manner as in Example 1 except that hydrochloric acid was used to form the molded body and the pH of the raw material slurry was set to 0.5. One main surface of the body was polished. The relative density of the AlN sintered body was 83%. The crystal phases in the AlN sintered body were an AlN phase and an Al ₂ O ₃ phase. In the AlN crystal particles in the AlN sintered body, there was no specific crystal plane of the AlN crystal particles oriented parallel to one main surface of the AlN sintered body. The thermal conductivity of the AlN sintered body was 30 W · m ⁻¹ · K ⁻¹ . However, even if this AlN sintered body was polished, mirror finishing was difficult. The arithmetic average roughness Ra and the maximum height roughness Rz defined in JIS B0601: 2013 on one main surface after polishing of the AlN sintered body were too coarse to measure. The results are summarized in Table 2.

(Comparative Example 3)
The raw material slurry, the molded body, and the AlN sintered body were formed in the same manner as in Example 1 except that ammonia was used to adjust the pH of the raw material slurry to 12 when forming the formed body. One main surface was polished. The relative density of the AlN sintered body was 94%. The crystal phases in the AlN sintered body were an AlN phase, an AlON phase, an Al ₂ O ₃ phase, an NdAlO ₃ phase, and a Yb ₂ O ₃ phase. In the AlN crystal particles in the AlN sintered body, there was no specific crystal plane of the AlN crystal particles oriented parallel to one main surface of the AlN sintered body. The thermal conductivity of the AlN sintered body was 26 W · m ⁻¹ · K ⁻¹ . The arithmetic average roughness Ra and the maximum height roughness Rz defined in JIS B0601: 2013 on one main surface after polishing of the AlN sintered body were 155 nm and 1600 nm, respectively. The results are summarized in Table 2.

(Example 7)
A raw material slurry, a molded body and an AlN sintered body were formed in the same manner as in Example 1 except that the polishing slurry had a pH of 0.5 when polishing one main surface of the AlN sintered body. One main surface of the sintered body was polished. The relative density of the AlN sintered body was 99%. The crystal phases in the AlN sintered body were an AlN phase, an NdAlO ₃ phase, and a Yb ₂ O ₃ phase. In the AlN crystal particles in the AlN sintered body, the (11-20) plane of the AlN crystal particles was oriented parallel to one main surface of the AlN sintered body. The thermal conductivity of the AlN sintered body was 180 W · m ⁻¹ · K ⁻¹ . The arithmetic average roughness Ra and the maximum height roughness Rz defined in JIS B0601: 2013 on one main surface after polishing of the AlN sintered body were 339 nm and 3500 nm, respectively. The results are summarized in Table 2.

(Example 8)
A raw material slurry, a molded body and an AlN sintered body were formed in the same manner as in Example 1 except that the polishing slurry had a pH of 12 when polishing one main surface of the AlN sintered body. One main surface of the body was polished. The relative density of the AlN sintered body was 99%. The crystal phases in the AlN sintered body were an AlN phase, an NdAlO ₃ phase, and a Yb ₂ O ₃ phase. In the AlN crystal particles in the AlN sintered body, the (11-20) plane of the AlN crystal particles was oriented parallel to one main surface of the AlN sintered body. The thermal conductivity of the AlN sintered body was 180 W · m ⁻¹ · K ⁻¹ . The arithmetic average roughness Ra and the maximum height roughness Rz defined in JIS B0601: 2013 on one main surface after polishing of the AlN sintered body were 134 nm and 1500 nm, respectively. The results are summarized in Table 2.

As shown in Table 1 and Table 2, it has one main surface and includes a plurality of aluminum nitride crystal particles, and the aluminum nitride crystal particles are (11-20) planes of all the aluminum nitride crystal particles, or a part of The aluminum nitride sintered body in which the (11-20) plane of the aluminum nitride crystal grains and the (10-10) plane of the remaining aluminum nitride crystal grains are oriented parallel to the principal plane is obtained by polishing. Can be easily mirror-finished, and by polishing with a polishing slurry having a pH of 1 or more and 6 or less, the arithmetic average roughness Ra and maximum height roughness specified in JIS B0601: 2013 on one main surface thereof Mirror surfaces having Rz of 10 nm or less and 100 nm or less were obtained.

It should be considered that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

9 Raw material slurry, 10 molded body, 10m, 11m one main surface, 10p, 11p aluminum nitride crystal particles, 10pa, 11pa (11-20) surface, 10pm, 11pm (10-10) surface, 11 aluminum nitride sintered body, 20 porous mold, 30 magnetic field applying unit, 100 forming apparatus, B magnetic field, S10 forming raw material slurry, S20 forming green body, S30 forming aluminum nitride sintered body, S31 forming body debinding A sub-process of S32, a sub-process of sintering the debindered compact, and a step of mirror-finishing the S40 aluminum nitride sintered body.

Claims (6)

1. A plurality of aluminum nitride crystal grains having a major surface,
   The aluminum nitride crystal particles are all (11-20) planes of the aluminum nitride crystal particles, or (10-20) planes of a part of the aluminum nitride crystal particles and (10 -10) An aluminum nitride sintered body having a plane oriented parallel to the one principal surface.
2. The arithmetic average roughness Ra defined in JIS B0601: 2013 of the one principal surface is 10 nm or less, and the maximum height roughness Rz defined in JIS B0601: 2013 of the one principal surface is 100 nm or less. 2. The aluminum nitride sintered body according to 1.
3. Forming a raw material slurry by dispersing a raw material powder containing aluminum nitride powder in a solvent;
   A step of forming the molded body having one principal surface by adjusting the pH of the raw material slurry to 1 to 6 and then slip casting in a magnetic field;
   Forming an aluminum nitride sintered body by sintering the molded body;
   Including
   In the step of forming the formed body, the magnetic field is applied in a direction parallel to the one main surface of the formed body.
4. The method for producing an aluminum nitride sintered body according to claim 3, further comprising a step of mirror-finishing one main surface of the aluminum nitride sintered body.
5. Regarding the aluminum nitride sintered body after the mirror-finishing step, the arithmetic average roughness Ra defined in JIS B0601: 2013 of the one main surface is 10 nm or less, and the JIS B0601: 2013 of the one main surface The method for producing an aluminum nitride sintered body according to claim 4, wherein the maximum height roughness Rz to be defined is 100 nm or less.
6. 6. The method for producing an aluminum nitride sintered body according to claim 4, wherein the polishing slurry used for the polishing has a pH of 1 or more and 6 or less in the mirror finishing step.

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