JP2009234803A - Method of manufacturing aluminum nitride-based material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming an aluminum oxide layer having high adhesive strength at high oxidation rate on the surface of an aluminum nitride-based sintered compact. <P>SOLUTION: The manufacturing method is provided with a heat treatment process for forming an aluminum oxide layer by heating aluminum nitride-based sintered compact at 1,000-1,500°C under a condition adjusted to an atmosphere of 0.0001-0.01 MPa oxygen partial pressure and ≥0.001 MPa water vapor partial pressure to oxidize the surface layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing an aluminum nitride-based substrate having an oxide film formed on the surface.

  An aluminum nitride-based substrate having high heat dissipation and high low thermal resistance can be used as a heat dissipation substrate for a semiconductor device such as a circuit board for mounting a light emitting diode (LED) or an in-vehicle electronic device substrate.

  When such an aluminum nitride-based substrate is used as it is, the aluminum nitride reacts with moisture in the air to generate ammonia and form aluminum hydroxide. The presence of such aluminum hydroxide causes the adhesion strength (peel strength) of the circuit formed on the circuit board to decrease, and causes electrical insulation and thermal conductivity to decrease.

  In order to suppress the contact between the aluminum nitride base material and moisture, a method of forming an oxide film on the surface layer of the aluminum nitride base material is known.

Specifically, Patent Document 1 below describes an aluminum nitride base material in which an aluminum oxide layer of 0.5 μm or more and 2 μm or less is formed by heat-treating an aluminum nitride sintered body in an oxidizing atmosphere. Further, in the examples, a sintered body obtained by holding aluminum nitride containing 5% by mass of yttrium oxide as a sintering aid in a non-oxidizing atmosphere at 1800 ° C. for 4 hours was obtained. It describes that a 0.5 to 2 μm aluminum oxide layer is formed on the surface by heat-treating the sintered body in an oxidizing atmosphere for a predetermined time.
Japanese Patent Application Laid-Open No. 2000-11190

  In the aluminum nitride base material as described in Patent Document 1, the weakness of the adhesion strength between the aluminum nitride sintered body and the aluminum oxide layer is not so problematic because the aluminum oxide layer is relatively thin. There wasn't.

  In recent years, laser processing is frequently used for circuit formation formed on the surface of an aluminum nitride substrate. In this case, when a relatively thick aluminum oxide layer that does not penetrate even by laser irradiation is formed, weak adhesion often becomes a problem. This is because as the film thickness of the aluminum oxide layer increases, the influence on the adhesion due to the difference in the thermal expansion coefficient between the aluminum nitride sintered body and the formed aluminum oxide layer, the mismatch of the lattice constant, etc. becomes more prominent. Because it becomes. And if adhesion strength becomes weak, water resistance and moisture resistance will become weak, and it will become easy to invite degradation of a sintered compact itself by seasonal change, moisture, etc.

  An object of this invention is to provide the method for forming the aluminum oxide layer which has higher adhesiveness on the surface of the aluminum nitride-type sintered compact which solves the above problems.

  As a method of forming an oxide film on the surface layer of an aluminum nitride sintered body, conventionally, it has been generally performed by heating in the air. In order to form an aluminum oxide layer having high adhesion strength on the surface layer portion of an aluminum nitride-based sintered body, the present inventors have applied an aluminum oxide layer to an aluminum nitride-based sintered body obtained under various conditions. As a result, it was found that an aluminum oxide layer having high adhesion strength was formed on a group of aluminum nitride-based substrates on which an aluminum oxide layer was formed. And when manufacturing conditions at that time were examined, it was found that the oxygen partial pressure was lower than about 0.02 MPa in the air under any conditions. However, when the oxygen partial pressure is low, the growth rate of the oxide film is lowered, so that this is not a practical method. Therefore, the present inventors have intensively studied a method for increasing the growth rate of the oxide film even when the oxygen partial pressure is low, and as a result, have arrived at the present invention as follows.

  That is, the method for producing an aluminum nitride-based substrate of the present invention is an aluminum nitride-based sintering under the conditions in which the oxygen partial pressure is adjusted to 0.0001 to 0.01 MPa and the water vapor partial pressure is adjusted to 0.001 MPa or more. The body is heat-treated in a temperature range of 1000 to 1500 ° C. to oxidize the surface layer to form an aluminum oxide layer. As a result of studying heat treatment conditions for an aluminum nitride-based sintered body that can maintain high adhesion even when a thick aluminum oxide layer is formed, the inventors have reduced the oxygen partial pressure as described above. I found out that it can be realized. However, such a method has a problem that the growth rate of the oxide film is low because the oxygen concentration is lowered. Furthermore, as a result of investigation, it was found that the growth rate of the oxide film is remarkably increased by using water as the oxidizing agent. That is, in an oxidizing atmosphere with a low oxygen concentration, an aluminum oxide layer having a high adhesion strength is formed in a relatively short time by containing moisture at a relatively high water vapor partial pressure. This effect is caused by oxidation with water vapor, and very fine pores are generated in the oxide film. Then, oxygen and moisture pass through the pores and oxidize, so that the growth rate of the oxide film becomes almost constant regardless of the oxide film thickness, so that the growth rate is considered to be maintained. On the other hand, since the oxide film without fine pores grows when the water vapor becomes dilute, the growth rate of the oxide film is governed by the diffusion rate of oxygen in the oxide film. It is considered that the growth rate is greatly reduced when the thickness exceeds the above value.

  The heat treatment step is performed in a closed furnace. After reducing the total pressure in the closed furnace to 100 Pa or less, the oxygen partial pressure in the closed furnace is 0.0001 to 0.001 MPa, water vapor It is preferable from the point that precise control of the oxidizing atmosphere is possible by adjusting the atmosphere in the closed furnace by supplying gas into the closed furnace so that the partial pressure becomes 0.001 MPa or more.

  The gas supplied into the closed furnace is obtained by bubbling in water a mixed gas containing oxygen and nitrogen adjusted so that the partial pressure ratio (oxygen / nitrogen) is 1/9 or less. It is preferable that the gas contains moisture because it is easy to control the partial pressure of water vapor in the oxidizing atmosphere.

  Moreover, it is preferable that the said heat processing process is performed within the furnace in which the predetermined amount of organic substance was accommodated. By containing an organic substance in the furnace, oxygen is consumed when the organic substance burns during heat treatment, and water is generated by the combustion. For this reason, the oxygen partial pressure and the water vapor partial pressure can be easily adjusted only by adjusting the kind and amount of the organic substance, without controlling strict atmospheric conditions.

  Moreover, when the surface roughness (Ra) of the aluminum nitride-based sintered body is in the range of 0.3 to 4 μm, it is preferable because adhesion can be further improved.

  Further, the aluminum oxide layer formed by the heat treatment step becomes an aluminum oxide layer having extremely high adhesion even if the thickness is 1 μm or more.

  According to the method for producing an aluminum nitride-based substrate of the present invention, an aluminum oxide layer having high adhesion strength can be formed at a high growth rate.

  The manufacturing method of the aluminum nitride-type base material which concerns on one Embodiment of this invention is demonstrated.

  The method for producing an aluminum nitride-based substrate of the present embodiment is performed under the condition that the aluminum nitride-based sintered body is adjusted to an atmosphere in which an oxygen partial pressure is 0.0001 to 0.01 MPa and a water vapor partial pressure is 0.001 MPa or more. In this embodiment, a heat treatment step is performed in which a surface layer of the aluminum nitride-based sintered body is oxidized to form an aluminum oxide layer by heat treatment in a temperature range of 1000 to 1500 ° C.

  The aluminum nitride-based sintered body used in the present embodiment is a conventionally known nitride obtained by sintering an aluminum nitride-based powder obtained by mixing a small amount of a sintering aid if necessary with an aluminum nitride powder. Any aluminum-based sintered body can be used without particular limitation.

  As the aluminum nitride powder, for example, a powder obtained by a direct nitridation method in which nitrogen or ammonia is directly reacted with aluminum or a reduction nitridation method in which nitrogen or ammonia is reacted with a mixture of alumina and carbon can be used without particular limitation. .

The sintering aid can be used without particular limitation as long as it is used as a sintering aid for the aluminum nitride sintered body. Specific examples thereof include, for example, yttrium, erbium, calcium, barium, strontium, or oxides thereof, such as yttrium oxide (Y ₂ O ₃ ), erbium oxide (Er ₂ O ₃ ), calcium oxide (CaO), Examples include barium oxide (BaO) and strontium oxide (SrO).

The blending ratio of the sintering aid is not particularly limited, but from the viewpoint of maintaining high thermal conductivity and insulating properties, for example, rare earth oxidation such as yttrium oxide (Y ₂ O ₃ ) or erbium oxide (Er ₂ O ₃ ). In the case of using a product, an alkali such as calcium oxide (CaO), barium oxide (BaO), strontium oxide (SrO) in the range of 0.5 to 3 mol%, further 0.6 to 1.5 mol% When an earth metal is used, it is preferably 0.1 mol% or less, more preferably 0.03 mol% or less.

  The aluminum nitride-based powder can be obtained by mixing aluminum nitride powder and a sintering aid blended as necessary. The mixing method is not particularly limited, and examples thereof include a method in which the above components are mixed with an organic solvent using a ball mill, and then the organic solvent is volatilized.

  The aluminum nitride powder is kneaded with a binder and formed into a preform with a predetermined shape. For kneading, a kneader, a single screw extruder, a twin screw extruder, a Banbury mixer, a roll or the like is used. As the binder, binders conventionally used in fields such as MIM (Metal Injection Molding) and CIM (Ceramic Injection Molding), specifically, for example, polyvinyl alcohol resin, acrylic resin, polystyrene, paraffin wax, Organic binders such as stearic acid, polyethylene, and polypropylene can be used.

  The molding method is not particularly limited, and various press molding methods such as compression molding, injection molding, transfer molding and the like are used.

  The obtained preform is preferably degreased (debindered) in advance by heating in the atmosphere at 400 to 450 ° C. for 24 to 72 hours.

  Further, as a forming method, a method of pressing and solidifying the aluminum nitride mixed powder by using a cold isostatic pressing method (CIP) without adding a binder may be used. According to CIP, molding can be performed without using a binder. Therefore, the degreasing process which usually requires about 1 to 3 days can be omitted. CIP is a method of forming a powder (the mixture) into various shapes by using a liquid such as water as a pressure medium and applying high pressure isotropic pressure to the powder (the mixture). can do.

  An aluminum nitride-based sintered body is obtained by firing the preform thus obtained in a non-oxidizing atmosphere.

  The firing method is not particularly limited. Specifically, for example, a denitrated preform is placed on a boron nitride setter, and a boron nitride mortar is placed so as to cover the preform. Place. And the method etc. which heat the space enclosed by the setter and the mortar in non-oxidizing atmosphere are mentioned.

  Firing is performed in a temperature range of about 1750 to 1900 ° C. for a predetermined time, although it depends on the kind and blending amount of the firing aid.

  In this way, an aluminum nitride sintered body is obtained. The obtained aluminum nitride-based sintered body may be further consolidated by hot isostatic pressing (HIP) to increase the strength. HIP is a method in which a gas such as argon is used as a pressure medium and a high pressure isotropic pressure is applied to the entire surface of the molded body at a high temperature.

  Further, the surface roughness (arithmetic average roughness Ra) of the aluminum nitride sintered body is 0.3 μm or more, more preferably 0.6 μm or more, and preferably 4 μm or less, more preferably 3 μm or less. When the surface roughness of the aluminum nitride-based sintered body is in the above range, the adhesion of the formed aluminum oxide layer can be further increased. This is because the surface can be appropriately roughened to form a fine uneven shape on the surface, thereby allowing oxidation to proceed along the uneven shape from the surface layer of the sintered body. As a result, the interface between the sintered body and the aluminum oxide layer becomes wavy and the area of the interface increases, thereby increasing the adhesion. When Ra is too large, when a circuit is formed on the surface of the obtained aluminum nitride base material, the adhesion of the circuit tends to decrease or the adhesion to an element mounted on the surface tends to decrease. . The surface roughness can be appropriately adjusted by blasting the surface of the obtained sintered body.

  Next, the aluminum nitride-based sintered body is subjected to a temperature range of 1000 to 1500 ° C. in an oxidizing atmosphere condition in which an oxygen partial pressure is 0.0001 to 0.01 MPa and a water vapor partial pressure is adjusted to 0.001 MPa or more. Heat treatment.

  In the above oxidizing atmosphere conditions, the oxygen partial pressure is 0.0001 to 0.01 MPa, preferably 0.005 to 0.001 MPa. When the oxygen partial pressure is less than 0.0001 MPa, the growth rate of the aluminum oxide layer becomes low. On the other hand, when the oxygen partial pressure exceeds 0.01 MPa, the adhesion of the aluminum oxide layer is lowered.

  Moreover, in the said oxidation atmosphere conditions, water vapor partial pressure is 0.001 MPa or more, Preferably, it is 0.001-0.0025 MPa. When the water vapor partial pressure is less than 0.001 MPa, the growth rate of the aluminum oxide layer becomes low. On the other hand, when the water vapor partial pressure is too high, the oxidizing action by water becomes too high, and the growth rate of the aluminum oxide layer may become too high. In this case, the film thickness control becomes difficult.

  The adjustment of the oxidizing atmosphere condition is performed, for example, in a closed furnace for heat-treating an aluminum nitride-based sintered body, after reducing the total pressure in the closed furnace to 100 Pa or less, and then adjusting the oxygen content in the closed furnace. It is performed by supplying a gas from the outside so that the pressure is 0.0001 to 0.001 MPa and the water vapor partial pressure is 0.001 MPa or more.

  More specifically, after the aluminum nitride-based sintered body is stored in a closed furnace provided with a gas supply path and a gas discharge furnace, the closed furnace is sealed. Then, using a vacuum pump or the like, the pressure in the sealed furnace is reduced to a level of 100 Pa or less, and the air in the sealed furnace is discharged. And the gas adjusted so that oxygen partial pressure and water vapor partial pressure may become the said range is supplied from the gas supply path with which the closed furnace was equipped. After the oxidizing atmosphere is adjusted, heat treatment is performed by raising the temperature in the furnace. As the heat treatment proceeds, oxygen and water are consumed by the oxidation reaction. For this reason, during the heat treatment, it is preferable to maintain the oxidizing atmosphere condition by flowing a gas adjusted in the furnace at a predetermined flow rate.

  The total pressure in the closed furnace is preferably 0.08 to 0.12 MPa, more preferably 0.09 to 0.11 MPa, and particularly preferably near atmospheric pressure from the viewpoint of safety and durability of the closed furnace.

  As the gas to be supplied, for example, a gas containing moisture by bubbling a mixed gas containing oxygen and nitrogen in water with an oxygen / nitrogen partial pressure ratio of 1/9 or less is preferably used. At this time, by adjusting the water temperature to a temperature range of 5 to 20 ° C., a water-containing gas prepared to have an appropriate water vapor pressure is obtained. If the water temperature is too low, it becomes difficult to obtain a sufficient water vapor partial pressure, and if it is too high, the water vapor partial pressure becomes too high and the growth rate of the oxide film becomes too high, making it difficult to control the film thickness. Tend to be.

  In addition, as another method for adjusting the oxidizing atmosphere condition, there is a method of storing a predetermined amount of an organic substance together with an aluminum nitride sintered body to be processed in a furnace for heat treating the aluminum nitride sintered body. It is done. By containing an organic substance in the furnace, the organic substance burns during the heat treatment. At this time, due to the combustion of the organic matter, oxygen in the furnace combines with carbon in the hydrocarbon to become carbon dioxide, and combines with hydrogen in the hydrocarbon to generate water. That is, since oxygen is consumed by the combustion of organic matter, the oxygen partial pressure in the furnace decreases and the water vapor partial pressure increases. According to such a method, an oxidizing atmosphere as described above can be realized using a combustion furnace opened to the atmosphere without adjusting strict atmospheric conditions during heat treatment by adjusting the type and amount of organic matter. .

  The organic material used in the above method is not particularly limited as long as it is an organic material having 5 or more carbon atoms that is liquid or solid at room temperature. Specifically, for example, saturated or unsaturated hydrocarbons having 5 or more carbon atoms, saturated or unsaturated fatty acids having 5 or more carbon atoms, alicyclic compounds, aromatic compounds, alcohols, and the like are used. Among these, various higher fatty acids (waxes) having 10 or more carbon atoms, specifically, paraffins are preferably used.

  The type and amount of organic matter stored in the furnace are appropriately adjusted according to the space volume of the furnace, the amount of the aluminum nitride-based sintered body to be processed, and the heat treatment time. Absent. However, as a guideline, for example, when paraffin is used as the organic substance, 0.01 to 0.1 g, further about 0.05 to 0.1 g can be stored with respect to 1 L of the space volume in the furnace. From the viewpoint of easy adjustment to the oxygen partial pressure and water vapor partial pressure.

  And heat processing is performed on the oxidizing atmosphere conditions adjusted in this way.

  The heat treatment temperature is preferably 1000 to 1500 ° C, more preferably 1050 to 1450 ° C, and particularly preferably 1100 to 1250 ° C. Note that the growth rate of the aluminum oxide layer is greatly influenced by the temperature, so that the growth rate is remarkably increased only by slightly raising the temperature. However, when heat treatment is performed at a temperature that is too high, large cracks or the like are generated in the aluminum oxide layer, and a rough film tends to be formed. According to this method, even when heat-treated at a relatively low temperature, an aluminum oxide layer having excellent adhesion can be formed at a relatively high growth rate. When the heat treatment temperature is lower than 1000 ° C., the growth rate of the aluminum oxide layer is significantly reduced. On the other hand, when the heat treatment temperature exceeds 1400 ° C., the growth rate of the aluminum oxide layer becomes too fast, making it difficult to control the film thickness and forming a rough aluminum oxide layer.

  The thickness of the aluminum oxide layer thus formed is preferably 1 to 20 μm, more preferably 2 to 5 μm. When the thickness of the formed aluminum oxide layer is too thin, when a conductive layer is formed on the surface of the aluminum oxide layer and a circuit is formed by laser processing, the laser penetrates the aluminum oxide layer, resulting in a short circuit. In addition, when it is too thick, there is a tendency that thermal conductivity is lowered or adhesion is lowered.

  According to the method for producing an aluminum nitride base material described above, an aluminum oxide layer having high adhesion is formed in a relatively short time on the surface layer of the aluminum nitride sintered body. When an electric circuit is formed on the surface of an aluminum nitride-based substrate obtained by such a manufacturing method, the occurrence of delamination at the interface between the aluminum oxide layer and the aluminum nitride-based sintered body is suppressed. A circuit pattern having adhesion can be formed. Since such an aluminum nitride-based substrate is difficult for water in the air to enter the aluminum nitride-based substrate and has excellent heat dissipation and electrical insulation properties, a three-dimensional structure in which a light emitting diode (LED) is mounted. It is preferably used for a three-dimensional circuit board that requires heat dissipation and insulation, such as a circuit board.

  Examples of the method for forming an electric circuit on the aluminum nitride-based substrate of the present invention include a method in which an electric circuit is formed through sputtering, laser etching, and a plating process.

  In such an electric circuit forming method, for example, a metal film is formed by sputtering on the surface of the aluminum nitride base material having a three-dimensional shape on which a circuit is formed. As the sputtering source (target), in the first stage, one kind of metal selected from the group consisting of chromium and titanium is used, and in the second stage, from copper, aluminum, aluminum alloy, gold and gold-tin alloy, etc. One metal selected from the group is used. And the circuit formation part used as an electric circuit is patterned with a laser from the formed metal film. And copper plating is given to the said circuit formation part by methods, such as electroplating. Then, by etching the portion where the copper plating is not formed, an electric circuit is formed and a three-dimensional circuit board is obtained. Here, the chromium film or the titanium film formed in the first stage is formed in order to improve the adhesion between the aluminum nitride base material and the electric circuit (copper foil circuit). Further, the patterning by laser is performed by removing the metal film at the contour portion of the circuit formation portion by high energy beam irradiation such as THG-YAG laser or SHG-YAG laser.

  The three-dimensional circuit board thus formed is preferably used as a three-dimensional circuit board on which light emitting diodes (LEDs), Peltier elements, and other various semiconductor elements are mounted, which require heat dissipation and insulation.

  The present invention will be described more specifically with reference to examples. The scope of the present invention is not limited by the examples.

[Example 1]
5% by mass of yttrium oxide (Y ₂ O ₃ ) powder and 0.02% by mass of calcium oxide were blended with the aluminum nitride powder produced by the direct nitriding method, and mixed in an organic solvent by a ball mill for 6 hours. Thereafter, the organic solvent was sufficiently volatilized in the draft chamber to obtain an aluminum nitride-based powder. A polyvinyl alcohol (PVA) organic binder was blended into the obtained mixed powder and sufficiently kneaded. The obtained kneaded material was molded into a three-dimensional shape of 30 × 20 × 2 mm by a press molding method, and further kept pressed at 450 ° C. for 1 hour in the atmosphere. And the preformed body was obtained by degreasing by heat-processing at 450 degreeC for 72 hours. Next, the preform was placed on a setter and fired at 1825 ° C. for 3 hours in a nitrogen atmosphere to obtain an aluminum nitride sintered body. Ra on the surface of this sintered body was 1.2 μm.

  Next, the aluminum nitride sintered body was accommodated in a sealed furnace having a space volume of 60 L and sealed. And it degassed under reduced pressure to 50 Pa using the rotary pump and the mechanical booster pump through the gas exhaust port provided in the closed furnace. Then, a mixed gas having an oxygen fraction of 10% and a nitrogen fraction of 90% was bubbled in a water bath having a water temperature of 5 ° C., so that moisture was contained, and the moisture-containing gas was introduced at a flow rate of 10 L / min. For 24 hours. The total pressure in the furnace at this time was atmospheric pressure (0.1013 MPa), the oxygen partial pressure was 0.01 MPa, and the water vapor partial pressure was 0.0010 MPa. As a result, an aluminum oxide layer having a thickness of about 3 μm was formed on the surface of the aluminum nitride sintered body.

  Then, a chromium film was formed on the surface of the obtained aluminum nitride-based substrate by a sputtering method, and further a copper film was formed by a sputtering method, thereby forming a metal film. After forming a metal film by sputtering, the metal film was shaped into a 2 mm wide rectangle by laser patterning to produce a peel strength measurement site. Thereafter, electrolytic copper plating was performed to thicken the peel strength measurement site to a thickness of 15 μm. And peel strength of the conductor of JIS C5016 and the peel strength were measured by the following method according to Method A.

  The end part of the obtained site for measuring peel strength with a width of 2 mm was peeled off with a design cutter to produce a chucking part. This aluminum nitride-based substrate is fixed to a stage that can move freely in the width direction of the peel strength measurement part, the chucking part is chucked, and the load when pulling up is peeled off by the small desktop testing machine EZGraph (manufactured by Shimadzu Corporation) It was calculated with a measurement average value of 4 mm in the peeling test, and was calculated as an average value of N = 6 in this measurement. The peel strength obtained was 1.8 N / mm. At this time, peeling occurred at the interface between the aluminum oxide layer and the metal film. This indicates that the peel strength at the interface between the aluminum nitride sintered body and the aluminum oxide layer is 1.8 N / mm or more.

[Example 2]
Instead of blending 5% by mass of yttrium oxide (Y ₂ O ₃ ) powder and 0.02% by mass of calcium oxide, 7% by mass of erbium oxide (Er ₂ O ₃ ) powder and 0.001% by mass of calcium oxide were blended. Obtained a sintered body in the same manner as in Example 1. Ra on the surface of this sintered body was 1.5 μm.

  Next, the aluminum nitride sintered body was accommodated in a sealed furnace and sealed. And it degassed under reduced pressure to 50 Pa using the rotary pump and the mechanical booster pump through the gas exhaust port provided in the closed furnace. Then, a mixed gas having an oxygen fraction of 0.1% and a nitrogen fraction of 99.9% was bubbled in a water bath having a water temperature of 10 ° C., and the moisture-containing gas was introduced at a flow rate of 15 L / min. However, heat treatment was performed at 1300 ° C. for 15 hours. At this time, the total pressure in the furnace was 0.1013 MPa, the oxygen partial pressure was 0.0001 MPa, and the water vapor partial pressure was 0.0013 MPa. As a result, an aluminum oxide layer having a thickness of about 2 μm was formed on the surface of the aluminum nitride sintered body.

  Then, the peel strength was measured in the same manner as in Example 1. The peel strength obtained was 1.8 N / mm.

[Example 3]
Instead of blending 5% by weight of yttrium oxide (Y ₂ O ₃ ) powder and 0.02% by weight of calcium oxide, blending 5% by weight of yttrium oxide (Y ₂ O ₃ ) powder and 0.018% by weight of calcium oxide, A sintered body was obtained in the same manner as in Example 1 except that firing was performed at 1835 ° C. instead of firing at 1825 ° C. Ra on the surface of this sintered body was 2 μm.

  Next, the aluminum nitride sintered body was accommodated in a sealed furnace and sealed. And it degassed under reduced pressure to 50 Pa using the rotary pump and the mechanical booster pump through the gas exhaust port provided in the closed furnace. Then, a mixed gas having an oxygen fraction of 1% and a nitrogen fraction of 99% was bubbled in a water bath having a water temperature of 5 ° C., so that moisture was contained, and while introducing the moisture-containing gas at a flow rate of 10 L / min, 1450 ° C. For 15 minutes. At this time, the total pressure in the furnace was 0.1013 MPa, the oxygen partial pressure was 0.001 MPa, and the water vapor partial pressure was 0.0010 MPa. As a result, an aluminum oxide layer having a thickness of about 8 μm was formed on the surface of the aluminum nitride sintered body.

  Then, the peel strength was measured in the same manner as in Example 1. The peel strength obtained was 1.2 N / mm.

[Example 4]
Instead of blending 5% by weight of yttrium oxide (Y ₂ O ₃ ) powder and 0.02% by weight of calcium oxide, blending 5% by weight of yttrium oxide (Y ₂ O ₃ ) powder and 0.022% by weight of calcium oxide, A sintered body was obtained in the same manner as in Example 1 except that firing was performed at 1815 ° C. instead of firing at 1825 ° C. Ra on the surface of the sintered body was 1 μm.

  Next, the aluminum nitride sintered body was accommodated in a sealed furnace and sealed. And it degassed under reduced pressure to 50 Pa using the rotary pump and the mechanical booster pump through the gas exhaust port provided in the closed furnace. Then, a mixed gas having an oxygen fraction of 10% and a nitrogen fraction of 90% was bubbled in a water bath having a water temperature of 20 ° C., so that moisture was contained, and the gas containing moisture was introduced at a flow rate of 10 L / min. For 24 hours. At this time, the total pressure in the furnace was 0.1013 MPa, the oxygen partial pressure was 0.01 MPa, and the water vapor partial pressure was 0.023 MPa. As a result, an aluminum oxide layer having a thickness of about 2 μm was formed on the surface of the aluminum nitride sintered body.

  Then, the peel strength was measured in the same manner as in Example 1. The peel strength obtained was 1.5 N / mm.

[Example 5]
Instead of blending 5% by weight of yttrium oxide (Y ₂ O ₃ ) powder and 0.02% by weight of calcium oxide, blending 5% by weight of yttrium oxide (Y ₂ O ₃ ) powder and 0.015% by weight of calcium oxide, Further, a sintered body was obtained in the same manner as in Example 1 except that firing was performed at 1800 ° C. instead of firing at 1825 ° C. Ra on the surface of the sintered body was 0.6 μm.

  Next, the aluminum nitride sintered body was accommodated in a sealed furnace and sealed. And it degassed under reduced pressure to 50 Pa using the rotary pump and the mechanical booster pump through the gas exhaust port provided in the closed furnace. Then, a mixed gas having an oxygen fraction of 5% and a nitrogen fraction of 95% was bubbled in a water bath having a water temperature of 10 ° C. so as to contain moisture, and while introducing the moisture-containing gas at a flow rate of 10 L / min, 1200 ° C. For 10 hours. At this time, the total pressure in the furnace was 0.1013 MPa, the oxygen partial pressure was 0.005 MPa, and the water vapor partial pressure was 0.013 MPa. As a result, an aluminum oxide layer having a thickness of about 4 μm was formed on the surface of the aluminum nitride sintered body.

  Then, the peel strength was measured in the same manner as in Example 1. The peel strength obtained was 1.3 N / mm.

[Example 6]
Instead of blending 5% by mass of yttrium oxide (Y ₂ O ₃ ) powder and 0.02% by mass of calcium oxide, 5% by mass of yttrium oxide (Y ₂ O ₃ ) powder and 0.001% by mass of calcium oxide were blended. Obtained a sintered body in the same manner as in Example 1. The surface of this sintered body was blasted with alumina abrasive grains having an average particle diameter of 250 μm. The Ra of the surface of the blasted sintered body was 4 μm.

  Next, the aluminum nitride sintered body was accommodated in a sealed furnace and sealed. And it degassed under reduced pressure to 50 Pa using the rotary pump and the mechanical booster pump through the gas exhaust port provided in the closed furnace. Then, a mixed gas having an oxygen fraction of 5% and a nitrogen fraction of 95% was bubbled in a water bath having a water temperature of 10 ° C. so as to contain moisture, and while introducing the moisture-containing gas at a flow rate of 10 L / min, 1200 ° C. For 5 hours. At this time, the total pressure in the furnace was 0.1013 MPa, the oxygen partial pressure was 0.005 MPa, and the water vapor partial pressure was 0.0013 MPa. As a result, an aluminum oxide layer having a thickness of about 2 μm was formed on the surface of the aluminum nitride sintered body.

  Then, the peel strength was measured in the same manner as in Example 1. The peel strength obtained was 2.0 N / mm.

[Example 7]
The surface of the sintered body obtained in the same manner as in Example 1 was blasted with alumina abrasive grains having an average particle diameter of 10 μm. Ra of the surface of the blasted sintered body was 0.3 μm.

  Next, the aluminum nitride sintered body was accommodated in a sealed furnace and sealed. And it degassed under reduced pressure to 50 Pa using the rotary pump and the mechanical booster pump through the gas exhaust port provided in the closed furnace. Then, a mixed gas having an oxygen fraction of 1% and a nitrogen fraction of 99% was bubbled in a water bath having a water temperature of 5 ° C., so that water was included, and while introducing the gas containing moisture at a flow rate of 10 L / min, 1200 ° C. For 24 hours. At this time, the total pressure in the furnace was 0.1013 MPa, the oxygen partial pressure was 0.001 MPa, and the water vapor partial pressure was 0.0010 MPa. As a result, an aluminum oxide layer having a thickness of about 4 μm was formed on the surface of the aluminum nitride sintered body.

  Then, the peel strength was measured in the same manner as in Example 1. The peel strength obtained was 1.1 N / mm.

[Example 8]
Instead of blending 5% by mass of yttrium oxide (Y ₂ O ₃ ) powder and 0.02% by mass of calcium oxide, 7% by mass of erbium oxide (Er ₂ O ₃ ) powder and 0.001% by mass of calcium oxide were blended. Obtained an aluminum nitride-based powder in the same manner as in Example 1. The obtained aluminum nitride-based powder was CIM-molded to obtain a three-dimensional preform having a plurality of projection shapes at predetermined positions at 30 × 40 × 1 mm. Then, the preform was placed on a setter and fired at 1825 ° C. for 3 hours in a nitrogen atmosphere to obtain an aluminum nitride-based sintered body. Ra on the surface of this sintered body was 1.5 μm.

  Next, the aluminum nitride sintered body was accommodated in a sealed furnace and sealed. And it degassed under reduced pressure to 50 Pa using the rotary pump and the mechanical booster pump through the gas exhaust port provided in the closed furnace. Then, a mixed gas having an oxygen fraction of 5% and a nitrogen fraction of 95% was bubbled in a water bath having a water temperature of 10 ° C. so as to contain moisture, and while introducing the moisture-containing gas at a flow rate of 15 L / min, 1200 ° C. For 10 hours. At this time, the total pressure in the furnace was 0.1013 MPa, the oxygen partial pressure was 0.005 MPa, and the water vapor partial pressure was 0.0013 MPa. As a result, an aluminum oxide layer having a thickness of about 3 μm was formed on the surface of the aluminum nitride sintered body.

  Then, the peel strength was measured in the same manner as in Example 1. The peel strength obtained was 2.0 N / mm.

[Example 9]
Instead of blending 5% by mass of yttrium oxide (Y ₂ O ₃ ) powder and 0.02% by mass of calcium oxide, 5% by mass of yttrium oxide (Y ₂ O ₃ ) powder and 0.001% by mass of calcium oxide were blended. Obtained a sintered body in the same manner as in Example 1. Ra on the surface of the sintered body was 1.8 μm.

  Next, 5.0 g of paraffin as an organic substance was stored in an open-type heating furnace having a space volume of 125 L. At this time, the total volume of the setter on which the aluminum nitride-based sintered body and the aluminum nitride-based sintered body were placed was 15 L, so the space in the furnace was about 110 L.

  And it heat-processed at 1100 degreeC for 15 hours. Under an environment where the temperature is 25 ° C. and the humidity is 50%, the total pressure in the furnace at this time is 0.1013 MPa, the oxygen partial pressure is about 0.0090 to 0.0095 MPa, and the water vapor partial pressure is 0.0016 MPa. It was. As a result, an aluminum oxide layer having a thickness of about 3 μm was formed on the surface of the aluminum nitride sintered body.

  Then, the peel strength was measured in the same manner as in Example 1. The peel strength obtained was 1.8 N / mm.

[Example 10]
Instead of blending 5% by mass of yttrium oxide (Y ₂ O ₃ ) powder and 0.02% by mass of calcium oxide, 5% by mass of yttrium oxide (Y ₂ O ₃ ) powder and 0.022% by mass of calcium oxide were blended. Obtained a sintered body in the same manner as in Example 1. Ra on the surface of the sintered body was 1.8 μm.

  Next, 8.5 g of paraffin as an organic nitride was stored in an open-type heating furnace having a space volume of 125 L. At this time, since the total volume of the setter on which the aluminum nitride-based sintered body and the aluminum nitride-based sintered body were placed was 25 L, the space in the furnace was about 100 L.

  And it heat-processed at 1350 degreeC for 10 hours. In an environment where the temperature is 25 ° C. and the humidity is 50%, the total pressure in the furnace at this time is 0.1013 MPa, the oxygen partial pressure is about 0.0015 to 0.0020 MPa, and the water vapor partial pressure is in the range of 0.0015 MPa. Met. As a result, an aluminum oxide layer of about 2 μm was formed on the surface of the aluminum nitride sintered body.

  Then, the peel strength was measured in the same manner as in Example 1. The peel strength obtained was 2.2 N / mm.

[Comparative Example 1]
In the same manner as in Example 1, the aluminum nitride sintered body was housed in a closed furnace and sealed. And it degassed under reduced pressure to 50 Pa using the rotary pump and the mechanical booster pump through the gas exhaust port provided in the closed furnace. Then, air (oxygen fraction of about 21%) was bubbled in a water bath with a water temperature of 5 ° C. so as to contain moisture, and heat-treated at 1100 ° C. for 15 hours while introducing air containing moisture at a flow rate of 10 L / min. . At this time, the total pressure in the furnace was 0.1013 MPa, the oxygen partial pressure was 0.021 MPa, and the water vapor partial pressure was 0.0010 MPa. As a result, an aluminum oxide layer having a thickness of about 2 μm was formed on the surface of the aluminum nitride sintered body.

  Then, the peel strength was measured in the same manner as in Example 1. The peel strength obtained was 0.5 N / mm.

[Comparative Example 2]
In the same manner as in Example 1, the aluminum nitride sintered body was housed in a closed furnace and sealed. And it degassed under reduced pressure to 50 Pa using the rotary pump and the mechanical booster pump through the gas exhaust port provided in the closed furnace. Then, a mixed gas having an oxygen fraction of 0.05% and a nitrogen fraction of 99.95% was bubbled in a water bath having a water temperature of 5 ° C., so that the moisture-containing gas was introduced at a flow rate of 10 L / min. However, heat treatment was performed at 1100 ° C. for 144 hours. At this time, the total pressure in the furnace was 0.1013 MPa, the oxygen partial pressure was 0.00005 MPa, and the water vapor partial pressure was 0.0010 MPa. As a result, an aluminum oxide layer having a thickness of about 2 μm was formed on the surface of the aluminum nitride sintered body.

  Then, the peel strength was measured in the same manner as in Example 1. The peel strength obtained was 1.5 N / mm.

[Comparative Example 3]
In the same manner as in Example 1, the aluminum nitride sintered body was housed in a closed furnace and sealed. And it degassed under reduced pressure to 50 Pa using the rotary pump and the mechanical booster pump through the gas exhaust port provided in the closed furnace. Then, a mixed gas having an oxygen fraction of 10% and a nitrogen fraction of 90% was bubbled in a water bath having a water temperature of 3 ° C. so as to contain moisture, and while introducing the moisture-containing gas at a flow rate of 10 L / min, 1100 ° C. For 120 hours. At this time, the total pressure in the furnace was 0.1013 MPa, the oxygen partial pressure was 0.01 MPa, and the water vapor partial pressure was 0.0008 MPa. As a result, an aluminum oxide layer having a thickness of about 3 μm was formed on the surface of the aluminum nitride sintered body.

  Then, the peel strength was measured in the same manner as in Example 1. The peel strength obtained was 1.3 N / mm.

[Comparative Example 4]
An aluminum nitride base material on which an aluminum oxide layer was formed was obtained in the same manner as in Example 9 except that paraffin was not stored as an organic substance during the heat treatment of the aluminum nitride sintered body. In addition, the heat processing at this time was performed at 1100 degreeC for 10 hours. The total pressure in the furnace during the heat treatment was 0.1013 MPa, the oxygen partial pressure was in the range of about 0.02 to 0.021 MPa, and the water vapor partial pressure was in the range of 0.0016 MPa. As a result, an aluminum oxide layer having a thickness of about 3 μm was formed on the surface of the aluminum nitride sintered body. Then, the peel strength was measured in the same manner as in Example 1. The peel strength obtained was 0.5 N / mm.

  The above results are summarized in Table 1.

  From the results of Table 1, the aluminum nitride-based substrates of Examples 1 to 10 according to the present invention have a peel strength of 1.1 to 2.2 N / mm, and all have high adhesion of the aluminum oxide layer. It was. Moreover, in Example 1 heat-processed at 1100 degreeC, the oxidation rate was as high as 0.125 micrometer / hour.

  On the other hand, in Comparative Example 1 where the oxygen partial pressure was the same partial pressure as the atmosphere, the peel strength was low. Further, in Comparative Example 2 in which the oxygen partial pressure was lower than the range in the present invention, the oxygen partial pressure was too low, and when the heat treatment was performed at 1100 ° C., the oxygen partial pressure was extremely low, 0.014 μm / hour.

  Furthermore, also in Comparative Example 3 where the water vapor partial pressure was lower than the range in the present invention, the oxidation rate when heat-treated at 1100 ° C. was remarkably low at 0.025 μm / hour.

  Further, Comparative Example 4 is an example performed in the same manner as Example 9 except that the organic substance was not stored in the furnace during the heat treatment of the aluminum oxide sintered body. From this result, in Example 9 in which the organic matter was stored in the furnace, the partial pressure of oxygen and the partial pressure of water vapor were maintained within the scope of the present invention by the combustion of the organic matter, whereby the peel strength was as high as 1.8 N / mm. However, in the case of the comparative example 4 which did not store organic substance, it turns out that peel strength was as low as 0.5 N / mm on the same temperature conditions.

Claims (6)

  By heat-treating the aluminum nitride-based sintered body in a temperature range of 1000 to 1500 ° C. under conditions adjusted to an oxygen partial pressure of 0.0001 to 0.01 MPa and a water vapor partial pressure of 0.001 MPa or more. A method for producing an aluminum nitride base material, comprising a heat treatment step of oxidizing a surface layer of the aluminum nitride based sintered body to form an aluminum oxide layer.   The heat treatment step is performed in a closed furnace, and after reducing the total pressure in the closed furnace to 100 Pa or less, the oxygen partial pressure is 0.0001 to 0.01 MPa and the water vapor partial pressure is 0.001 MPa or more. The method for producing an aluminum nitride-based substrate according to claim 1, wherein the method is carried out while adjusting the atmosphere in the closed furnace by supplying a gas into the closed furnace.   Moisture obtained by bubbling in water a mixed gas containing oxygen and nitrogen adjusted so that the partial pressure ratio (oxygen / nitrogen) is 1/9 or less as the gas supplied into the closed furnace The method for producing an aluminum nitride-based substrate according to claim 2, wherein the gas contains gas.   The manufacturing method of the aluminum nitride-type base material of Claim 1 with which the said heat processing process is performed within the furnace in which the predetermined amount of organic substance was accommodated.   The method for producing an aluminum nitride-based substrate according to any one of claims 1 to 4, wherein a surface roughness (Ra) of the aluminum nitride-based sintered body is in a range of 0.3 to 4 µm.   The method for producing an aluminum nitride-based substrate according to any one of claims 1 to 5, wherein a thickness of the aluminum oxide layer formed by the heat treatment step is 1 µm or more.