JP2001294492A - Aluminum nitride sintered compact and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum nitride sintered compact excellent in mass- producibility, high in mechanical strength and reliability and further excellent in anti-plasma properties and to provide a method of producing the same. SOLUTION: The aluminum nitride sintered compact has alumina on its surface and the preferable aluminum nitride has θalumina layer having a thickness of 0.01 to 2.0 μm on its surface. The aluminum nitride sintered compact is obtained by heat-treating an aluminum nitride sintered compact having a relative density of >=97% at 800 to 1,000 deg.C under an oxygen atmosphere having a partial pressure of water vapor of <=1.0 kPa for 0.5 to 30 h.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an aluminum nitride sintered body having both high mechanical strength and excellent plasma resistance.

[0002]

2. Description of the Related Art Aluminum nitride is known as GTO (Gate Turbo).
n Off Thyristor) Thyristor and IGBT (Insulated G)
ate Bipolar Transistor) and other semiconductor devices have increased the amount of heat generated, and the range of use as a variety of heat-radiating and insulating materials, including semiconductor mounting substrates that utilize the property of high thermal conductivity, has increased. It is spreading more and more.

[0003] Of these, particularly in the application of a high-output semiconductor mounting substrate, a thin plate of copper or the like is bonded to an aluminum nitride sintered body to mount a semiconductor, or a further heat sink material (radiation fins) is used. Aluminum nitride itself is often used while various large stresses are applied to the aluminum nitride itself, for example, by bonding to a metal member. Recently, various halogen gases and halogen compound gases such as CF ₄ , ClF ₃ , NF ₃ , Cl ₂ , and HBr have been used as component materials used in semiconductor manufacturing apparatuses such as a plasma etching apparatus, a plasma ashing apparatus, and a plasma CVD apparatus. It came to be used under conditions.

[0004] Therefore, in such applications, in addition to the conventional high thermal conductivity, an aluminum nitride sintered body having higher mechanical strength and superior plasma resistance has been required.

In order to improve the plasma resistance of the aluminum nitride sintered body, for example, Japanese Patent Application Laid-Open No.
No. 409 and JP-A-11-214359,
As a method of providing a protective layer made of an alumina layer having a predetermined thickness on the surface of a sintered body, Japanese Patent Application Laid-Open No. H11-209182 discloses a method of controlling the surface roughness of the sintered body.

However, the above-mentioned Japanese Patent Application Laid-Open No. 9-232
In the method disclosed in Japanese Patent Application Laid-Open No. 409/409 and Japanese Patent Application Laid-Open No. H11-214359, cracks are likely to occur in the alumina layer due to the difference in thermal expansion between the alumina layer on the surface of the sintered body and the aluminum nitride sintered body due to repeated temperature rise and fall. Alternatively, the alumina layer tends to peel off easily, and there is room for improvement in the adhesion of the alumina layer. In addition, the method disclosed in Japanese Patent Application Laid-Open No. 11-209182 requires a polishing of the surface of the sintered body, and has a problem that the processing cost is high.

As a method for solving the above problem, for example, Japanese Patent Application Laid-Open No. 3-228874 discloses a method in which an aluminum nitride sintered body is heated at a temperature of 1050 to 1150 ° C. in an atmosphere having a water vapor partial pressure of 1.0 × 10 ⁻² atm or less. For 0.1 to 5 hours.

However, according to the method disclosed in JP-A-3-228874, the adhesion between the alumina layer and the underlying aluminum nitride crystal grains is insufficient, and the alumina layer peels off due to a temperature change in the halogen plasma treatment. There is room for improvement, and there is also room for improvement in mechanical strength with low bending strength.

On the other hand, in order to improve the mechanical strength of an aluminum nitride sintered body, for example, Japanese Patent Application Laid-Open No. 4-50171 discloses a method for controlling the linear shrinkage rate at the time of raising the firing temperature. JP-A-33531 discloses a method of forming an aluminum oxynitride layer near the surface of a sintered body to strengthen grain boundaries, and JP-A-7-172921 discloses a method of forming a silicon nitride layer.
A method of controlling the particle size distribution of a sintered body by adding a component such as Al ₂ O ₃ is disclosed.

However, the above-mentioned Japanese Patent Application Laid-Open No. 4-501 is disclosed.
The method of controlling the linear shrinkage rate at the time of temperature increase described in Japanese Patent Publication No. 71 requires a special apparatus such as a baking furnace equipped with a thermal dilatometer and is applicable to an actual manufacturing apparatus. Comes with difficulties. In the grain boundary strengthening method described in JP-A-7-33531, the process of obtaining an aluminum oxynitride layer is complicated, and
In the method described in Japanese Patent Publication No.
strict control of the particle abundance per m
There was a problem that it was difficult to control it with a large sintered body or a mass production scale.

[0011]

Accordingly, there has been a demand for an aluminum nitride sintered body which is excellent in mass productivity, has high mechanical strength and high reliability, and has excellent plasma resistance.

[0012]

As a result of repeated studies by the present inventors, the alumina formed on the surface layer of the sintered body by the above-described method is α-alumina, and therefore, has poor plasma resistance and bending strength. It turned out to be enough.

As a result of intensive studies to solve the above-mentioned problems, the mechanical strength of the aluminum nitride sintered body is reduced by changing the alumina existing in the surface layer of the aluminum nitride sintered body to θ-alumina. The present inventors have found that they have remarkably improved and have excellent plasma resistance, and have proposed the present invention.

That is, the present invention is an aluminum nitride sintered body characterized in that alumina is present on the surface layer of the sintered body, and the alumina is substantially composed of θ-alumina.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum nitride sintered body of the present invention has alumina in the surface layer of the sintered body, and
It is necessary that the alumina is substantially composed of θ-alumina.

On the contrary, when the alumina present in the surface layer is composed of alumina such as α-alumina different from θ-alumina, the effects of the present invention cannot be obtained, which is not preferable.

In the present invention, the state substantially composed of θ-alumina means that 99% or more, preferably 99.9% or more of the alumina present in the surface layer is θ-alumina.
A state composed of alumina.

In the present invention, θ-alumina may be present on the surface layer of the sintered body in any form. However, considering the mechanical strength and plasma resistance of the sintered body, It is preferably present as a part of the sintered body, and is preferably in a state of covering the surface of the sintered body.

The amount of the θ-alumina present in the surface layer of the sintered body is not particularly limited, but considering mechanical strength and plasma resistance, it is 90% or more of the surface layer of the sintered body.
More preferably, it is 95% or more.

In the present invention, the thickness of the layer in which the above-mentioned θ-alumina exists is 0.01 to 2.0 μm in consideration of the mechanical strength and plasma resistance of the sintered body. Is preferred. If the thickness is less than 0.01 μm, the bending strength is not improved, and furthermore, the function as a plasma-resistant layer is poor, and the reaction with various types of plasma with aluminum nitride crystal particles and corrosion progress, which is not preferable. Also, 2.0μ
If it exceeds m, the flexural strength is reduced and the θ-alumina layer is easily peeled off, and as a result, the plasma resistance is undesirably reduced. Within the above range, the thickness of the layer in which the above-mentioned θ-alumina exists is 0.1 mm.
When the thickness is from 0.01 to 1.5 μm, the bending strength is significantly improved, which is preferable.

Incidentally, the θ-alumina in the present invention was identified by thin-film X-ray diffraction on the surface of the sintered body. Further, the thickness of the layer in which the above-mentioned θ-alumina is present is obtained by observing SEM at any five points in the vicinity of the surface of the fractured surface of the sintered body and obtaining the thickness of the layer from each SEM photograph. The average value was taken as the measured value.

The aluminum nitride sintered body of the present invention is not particularly limited as long as the alumina present on the surface is composed of θ-alumina. It is preferable to consider the strength and the plasma resistance.

That is, the relative density of the aluminum nitride sintered body of the present invention is preferably 97% or more in consideration of mechanical properties. Here, the relative density means the ratio of the measured density of the sintered body to the theoretical density of the sintered body calculated from the respective theoretical densities of aluminum nitride and various additives constituting the sintered body.

The average particle size of the aluminum nitride crystal particles of the aluminum nitride sintered body of the present invention is preferably 15 μm or less, more preferably 10 μm or less, in consideration of the bending strength of the sintered body.

Further, the bending strength of the aluminum nitride sintered body of the present invention is 400 MPa in consideration of the plasma resistance.
It is preferably at least a.

The method for producing the aluminum nitride sintered body of the present invention may be carried out by selecting appropriate conditions so as to have the properties specified in the present invention, and among them, the following method is employed to facilitate the production. Thus, an aluminum nitride sintered body having the properties defined in the present invention can be obtained.

That is, a non-oxidized aluminum nitride sintered body having a relative density of 97% or more (hereinafter, referred to as an untreated aluminum nitride sintered body) is treated under a specific condition to obtain a nitride layer existing on the surface layer. Oxidize aluminum to θ
-A method of forming alumina.

The untreated aluminum nitride sintered body used in the present invention is not particularly limited as long as the relative density is 97% or more, and a known untreated aluminum nitride sintered body can be employed. . By using the untreated aluminum nitride sintered body, it is sufficiently densified and no micropores remain in the sintered body structure, so that the mechanical strength is high and the formation of θ-alumina is facilitated.

The untreated aluminum nitride sintered body contains aluminum nitride alone or aluminum nitride as a main component, and various additives such as alkaline earth compounds such as CaO, MgO, and SrO, Y ₂ O ₃ , LaO ₃ , CeO ₃ , H
oO ₃ , Yb ₂ O ₃ , Gd ₂ O ₃ , Nb ₂ O ₃ , Sm ₂ O ₃ , D
sintering aids for rare earth compounds such as y ₂ O ₃ , SiC, Zr
It may contain O ₂ , TiO ₂ , Si ₃ N _{4 and the} like.

In the untreated aluminum nitride sintered body having a relative density of 97% or more, the concentration of a grain boundary phase generated by a sintering aid or the like is desirably 9.0% by weight or less. When the concentration of the grain boundary phase is 9.0% by weight or less, there is no generation of aggregates of the grain boundary phase crystal particles of the sintered body, and therefore, the bending strength is not reduced, and the grain boundary of the sintered body is not reduced. The phase crystal particles do not hinder the formation of θ-alumina.

The average particle size of the aluminum nitride crystal particles of the untreated aluminum nitride sintered body having the relative density of 97% or more is not particularly limited. However, taking the bending strength of the sintered body into consideration, the average particle diameter is 15 μm or less. Further, the thickness is preferably 10 μm or less.

Further, as a method for producing an untreated aluminum nitride sintered body, an aluminum nitride powder is granulated into granules and then molded by a dry press to obtain a pressed molded body.
Known methods such as a firing method, a hot press method, or a method of wet molding an aluminum nitride powder to obtain a green sheet, punching the green sheet into a predetermined shape, and firing the green sheet are widely adopted. After the firing, surface grinding or the like may be performed.

In order to suitably obtain the aluminum nitride sintered body of the present invention, the above-mentioned untreated aluminum nitride sintered body is placed in an oxygen atmosphere having a steam partial pressure of 1.0 kPa or less for 800 to 800 kPa.
It is important to treat at a temperature of 1000 ° C. for 0.5 to 30 hours.

The oxygen atmosphere is not particularly limited as long as it contains oxygen, and may be air. The water vapor partial pressure of the oxygen atmosphere is not particularly limited as long as it is 1.0 kPa or less, and may be appropriately set within the range. Usually, a range of 0.1 to 0.6 kPa is suitably adopted.
When the partial pressure of water vapor in the oxygen atmosphere is higher than 1.0 kPa, it is not preferable because it is impossible to obtain dense and highly adherent θ-alumina.

On the other hand, if the treatment temperature is lower than 800 ° C., θ-alumina is not formed, and the bending strength and plasma resistance are not improved, which is not preferable. If the temperature is higher than 1000 ° C., the formed θ-alumina is further transformed into α-alumina, so that the binding force of the surrounding aluminum nitride crystal particles is reduced, and the improvement in bending strength is reduced. It is not preferable because adhesion to aluminum crystal particles is deteriorated.

If the above treatment time is shorter than 0.5 hour, the formation of θ-alumina is insufficient, and the bending strength and the plasma resistance are not improved, which is not preferable. On the other hand, 30
If the time is longer than this, the layer in which the θ-alumina is present becomes too thick, and conversely, the binding force of the aluminum nitride crystal particles is reduced, so that the improvement in bending strength is reduced. Is not preferred because it becomes worse.

Among the above conditions, the partial pressure of water vapor in the oxygen atmosphere is 0.1 to 0.6 kPa, and the processing temperature is 830 to 9
It is more preferable that the treatment time is 70 ° C. and the treatment time is 1 to 20 hours in consideration of the mechanical strength and the reliability of the plasma resistance. The atmosphere of the above treatment is preferably air.

Further, the weight increase of the aluminum nitride sintered body due to the above treatment is 0.005 to 0.080 mg / c.
The range of m ² is preferable because the thermal conductivity of the sintered body hardly decreases, the bending strength is improved, and effective plasma resistance can be imparted.

The above-mentioned treatment atmosphere, temperature and time may be within the above ranges depending on the surface condition such as the surface roughness of the untreated aluminum nitride sintered body to be treated as long as θ-alumina having a predetermined thickness is obtained. May be adjusted appropriately.

[0040]

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.

In the following Examples and Comparative Examples, various physical properties were measured by the following methods.

1) Relative Density of Sintered Body Using a “high-precision hydrometer DH” manufactured by Toyo Seiki, the relative density between the sintered body density and the theoretical sintered body density obtained by the Archimedes method was defined as the relative density. .

2) Bending strength According to JIS R1601, a crosshead speed of 0.5
The three-point bending strength was measured at a mm / min and a span of 30 mm. The test piece was prepared by cutting a sintered body in advance to 30 × 4 × 3 mm and grinding the surface under the respective heat treatment conditions. The bending strength was determined as an average value of five samples.

3) Thermal conductivity The thermal conductivity was measured by a laser flash method using a thermal constant measuring apparatus PS-7 manufactured by Rigaku Corporation. Thickness correction was performed using a calibration curve.

4) Identification of Alumina in Surface Layer of Sintered Body Using "RINT-1200" manufactured by Rigaku Corporation, the alumina in the surface layer was identified under the following conditions by thin-film X-ray diffraction. X-ray source: Cu-Kα 40 kV-50 mA 2θ scanning range: 30 ° to 140 ° 2θ scanning speed: 1 ° / min 2θ scanning step width: 0.05 ° θ fixed angle: 1 ° divergence slit: 0.2 mm height Limiting slit: 5 mm Light receiving slit: 5 mm Monochromator: Graphite (002) Monochromator light receiving slit: 0.8 mm Number of measurements: 2 times / sample.

5) Measurement of Surface Layer Thickness of Sintered Body Using “JSM-5400” manufactured by JEOL Co., Ltd., SEM observation was performed on any five locations of the fractured surface of the sintered body at a magnification of 10,000 times from SEM photograph. The thickness of the layer in which alumina was present was measured, and the average was taken as the measured thickness.

6) Measurement of Aluminum Nitride Crystal Particles in Sintered Body Aluminum nitride crystal particles were measured from the SEM photograph obtained by the above method, and the average value was defined as the average particle diameter.

7) Change in Weight of Sintered Body The weight of the sintered body before and after the heat treatment was measured with an electronic balance. The weight of the sintered body before the heat treatment was reduced from the weight of the sintered body after the heat treatment, and the difference in weight was gradually reduced by the surface area of the sintered body to determine the change in the weight of the sintered body per unit area.

8) Elemental analysis of sintered body surface after plasma treatment Elemental analysis of sintered body surface by X-ray microanalysis (EPMA) "JXA-8800M" manufactured by JEOL Ltd. X-ray intensity ratio of Al) was obtained.

Example 1 A ball made of alumina was placed in a nylon pot having an internal volume of 10 L, and then an average particle size of 1.5 μm and a specific surface area of 2.6.
100 parts by weight of aluminum nitride powder having m ² / g and an oxygen concentration of 0.80% by weight, 0.5 parts by weight of hexaglycerin monooleate as a surfactant, 3 parts by weight of n-butyl methacrylate, and 100 parts by weight of a toluene solvent were added. And 24
After ball milling for hours, a white slurry was obtained. Granulate the obtained slurry by spray dryer method,
Aluminum nitride granules having a size of φ70 to 100 μm were produced.

The granules were press-molded at a molding pressure of 1.0 t / cm ² to obtain a pressed body having a width of 40 mm and a thickness of 4 mm. Then, degreasing in air at 600 ° C. for 5 hours,
Put in a carbon crucible coated with boron nitride on the inner surface,
It was baked at 1850 ° C. for 8 hours in a nitrogen atmosphere to obtain an untreated sintered body. Thereafter, the unprocessed sintered body is □ 20 mm, thickness 3
mm, and ground. The relative density of the untreated sintered body is 99.0%, the bending strength is 380 MPa, and the thermal conductivity is 10
At 0 W / m · K, the surface roughness Ra was 0.40 μm. The average particle size of the aluminum nitride particles in the untreated sintered body was 8.8 μm.

Further, the above-mentioned untreated sintered body was heated at 950 ° C. for 15 minutes in air at a steam partial pressure of 0.61 kPa (dew point: 0 ° C.).
Heat treated for hours. The bending strength and thermal conductivity of the obtained sintered body were measured. The relative density of the sintered body after the treatment was 99.0%, and the average particle size of the aluminum nitride particles in the sintered body was 8.8 μm.

The surface layer of the sintered body after the treatment was identified by thin-film X-ray diffraction, and the thickness was measured by SEM observation of the fractured surface. 99.9% or more of the surface layer was alumina, and all of the alumina was composed of θ-alumina. Also,
The obtained sintered bodies were arranged on a susceptor, W was deposited at 475 ° C. using a W thermal CVD apparatus, and then W was removed for 12 minutes at 250 ° C. and a pressure of 20 Torr with ClF ₃ gas. . This CVD film formation and removal treatment was repeated 40 times, and the surface layer of the sintered body and the fluoride film (Al
The presence or absence of peeling of F ₃ ) and the relative intensity of F by EPMA (X-ray intensity ratio of F and Al) were examined. Table 1 shows the measurement results.

Example 2 An alumina ball was placed in a nylon pot having an internal volume of 10 L, and then an average particle size of 1.5 μm and a specific surface area of 2.6.
m ² / g, 100 parts by weight of aluminum nitride powder having an oxygen concentration of 0.80% by weight, 4 parts by weight of yttrium oxide as a sintering aid, 0.5 parts by weight of hexaglycerin monooleate as a surfactant, n-butyl methacrylate 3 After adding 100 parts by weight of a toluene solvent and 100 parts by weight of a toluene solvent and mixing with a ball mill for 24 hours, a white slurry was obtained. The obtained slurry is granulated by a spray dryer method,
Aluminum nitride granules having a size of 0 μm were prepared.

The granules were press-molded at a molding pressure of 1.0 t / cm ² to obtain a pressed body having a width of 40 mm and a thickness of 4 mm. Then, degreasing in air at 600 ° C. for 5 hours,
Put in a carbon crucible coated with boron nitride on the inner surface,
It was baked at 1820 ° C. for 5 hours in a nitrogen atmosphere to obtain an untreated sintered body. Thereafter, the unprocessed sintered body is □ 20 mm, thickness 3
mm, and ground. The relative density of the untreated sintered body is 99.5%, the bending strength is 440 MPa, and the thermal conductivity is 18
At 0 W / m · K, the surface roughness Ra was 0.40 μm. The average particle size of the aluminum nitride particles in the untreated sintered body was 3.4 μm.

Further, the above-mentioned untreated sintered body was heated at 950 ° C. for 15 minutes in an atmosphere of a steam partial pressure of 0.61 kPa (dew point: 0 ° C.).
Heat treated for hours. The bending strength and thermal conductivity of the obtained sintered body were measured. The relative density of the sintered body after the treatment was 99.5%, and the average particle size of the aluminum nitride particles in the sintered body was 3.4 μm.

The surface layer of the sintered body after the treatment was identified by thin film X-ray diffraction, and its thickness was measured by SEM observation of the fractured surface. 96% of the surface layer was alumina, and all of the alumina was composed of θ-alumina. Further, the obtained sintered body, arranged on the susceptor, thereby forming a W at 475 ° C. using a W thermal CVD device, then the ClF ₃ gas 250
A W removal treatment was performed for 12 minutes at a temperature of 20 ° C. and a pressure of 20 Torr. This CVD film formation and removal treatment was repeated 40 times, and the surface layer of the sintered body and the fluoride film (Al
The presence or absence of peeling of F ₃ ) and the relative intensity of F by EPMA (X-ray intensity ratio of F and Al) were examined. 96% of the surface layer was alumina, and all of the alumina was composed of θ-alumina. Table 1 shows the measurement results.

Examples 3 to 5 A sintered body was obtained and evaluated in the same manner as in Example 1 except that the heat treatment temperature and time were changed. The relative density of each of the sintered bodies after the treatment was 99.0%, and the average particle diameter of the aluminum nitride particles in each of the sintered bodies was 8.8 μm.
m. In Examples 3 and 4, 99% of the surface layer of the sintered body after the treatment was used. In Example 5, 9% of the surface layer of the sintered body after the treatment was used.
9.9% or more is alumina, and all of the alumina is θ
-Consisted of alumina. Table 1 shows the measurement results.

Example 6 A relative density of 9 was prepared by changing the firing temperature to 1830 ° C.
Example 1 except that a 7.5% untreated sintered body (bending strength: 350 MPa, thermal conductivity: 90 W / m · K, average particle diameter of aluminum nitride crystal in the sintered body: 7.6 μm) was used.
Heat treatment was performed in the same manner as described above to obtain a sintered body, which was evaluated. The relative density of the sintered body after the treatment is 97.599.0%,
The average particle size of the aluminum nitride particles in the sintered body is 7.6
μm. 99.9% of the surface layer of the sintered body after the treatment
The above was alumina, and all of the alumina was composed of θ-alumina. Table 1 shows the measurement results.

Comparative Example 1 A sintered body was obtained and evaluated in the same manner as in Example 1, except that the heat treatment temperature and time of the sintered body were changed to 1150 ° C. and 1 hour. Since the surface layer was composed of α-alumina, the adhesion was not sufficient, and the oxide film on the surface of the sintered body was peeled off when the film formation / removal treatment was repeated five times. Table 1 shows the measurement results.

Comparative Example 2 Except that the heat treatment time of the sintered body was changed to 90 hours,
A sintered body was obtained and evaluated in the same manner as in Example 1. The surface layer is a layer in which α-alumina and θ-alumina are mixed,
Since the alumina content was only 10%, the adhesion was not sufficient. Table 1 shows the measurement results.

Comparative Example 3 Example 1 was performed except that the heat treatment of the sintered body was not performed.
A sintered body was obtained in the same manner as described above (untreated sintered body) and evaluated. Table 1 shows the measurement results.

[0063]

[Table 1]

[0064]

The aluminum nitride sintered body according to the present invention in which the alumina present in the surface layer of the sintered body is composed of θ-alumina,
It has excellent mechanical properties and plasma-resistant properties, and has a very simple means of heat-treating a densified aluminum nitride sintered body in an oxygen atmosphere with a specific partial pressure of water vapor. It is possible to easily produce an aluminum nitride sintered body having excellent plasma characteristics.

Although it is not clear how the effects of the present invention are exhibited, the present inventors presume as follows. Usually, θ-alumina is an intermediate alumina having high crystallinity, and is transformed into α-alumina when treated at a higher temperature. In the method of the present invention, (10)
It is considered that the 0) plane is selectively oxidized to form θ-alumina. That is, by the treatment according to the method of the present invention, oxygen atoms penetrating from the (100) plane of the aluminum nitride crystal on the surface layer of the sintered body cut the Al—N bond to form a θ-alumina nucleus. It is believed that the volume expansion of the aluminum nitride is constrained by the surrounding aluminum nitride crystal particles, so that it remains as a compressive stress during cooling, and the mechanical strength is improved. In addition, according to the method of the present invention, the aluminum nitride crystal (1) having a high possibility of being corroded by water, various acids, alkali solutions, various plasma gases, and the like.
Since oxygen is selectively taken into the (00) plane to form [theta] -alumina, it is considered to have both corrosion resistance and adhesion.

Therefore, according to the present invention, in addition to high thermal conductivity, high mechanical strength and excellent plasma resistance are imparted, so that the use of aluminum nitride as an industrial material is further expanded, The value is great.

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Claims (3)

[Claims] (1) alumina is present on a surface layer of a sintered body,
In addition, the aluminum nitride sintered body, wherein the alumina is substantially composed of θ-alumina. 2. A method according to claim 1, wherein the thickness of the layer in which alumina is present is 0.0
The aluminum nitride sintered body according to claim 1, which has a thickness of 1 to 2.0 m. 3. A method for treating an aluminum nitride sintered body having a relative density of 97% or more at a temperature of 800 to 1000 ° C. for 0.5 to 30 hours in an oxygen atmosphere having a water vapor partial pressure of 1.0 kPa or less. The method for producing an aluminum nitride sintered body according to claim 1 or 2, wherein: