JPH04275980A - Production of aluminum nitride sintered body - Google Patents

Abstract

PURPOSE:To obtain a high density AlN sintered body having high heat conductivity by firing AlN powder having <=0.8wt.% oxygen content. CONSTITUTION:The oxide of an alkaline earth metal or a rare earth metal is added to AlN powder having <=0.8wt.% oxygen content as starting material and an AlN sintered body is produced with the resulting powdery mixture having >=0.8wt.% total oxygen content.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing aluminum nitride sintered bodies.

0002

[Background Art] In recent years, due to rapid technological innovation in the semiconductor industry, large-scale integrated circuits such as ICs and LSIs have become more highly integrated and have higher output. The amount of heat generated has increased significantly. For this reason, a problem has begun to arise in which the normal operation of the silicon element is hindered by heat generation due to the energizing operation of the silicon element, and accordingly, an insulating substrate material with good thermal conductivity is required. Conventionally, alumina sintered bodies have generally been most commonly used as insulating substrate materials. However, recently, alumina substrates cannot be said to be satisfactory in terms of heat dissipation, and there has been a demand for the development of insulating substrate materials with even better heat dissipation properties (thermal conductivity). Such insulating substrate materials have characteristics such as good thermal conductivity (high thermal conductivity), electrical insulation, thermal expansion coefficient close to that of single crystal silicon, and high mechanical strength. required.

By the way, aluminum nitride, which is known to have good thermal conductivity, has a coefficient of thermal expansion of approximately 4.3×
10-6/℃ (average value from room temperature to 400℃), which is smaller than the approximately 7×10-6/℃ of alumina sintered body, and the coefficient of thermal expansion of silicon elements is 3.5 to 4.0×10- Close to 6/℃. It also has a mechanical strength of about 50 Kg/mm2 in terms of bending strength, which is a material with high strength and excellent electrical insulation, compared to the 20 to 30 Kg/mm2 of alumina sintered body. Conventionally,
Aluminum nitride (AlN) sintered bodies are obtained by molding and sintering aluminum nitride powder, but since aluminum nitride is a difficult-to-sinter substance, it is difficult to obtain dense sintered bodies. . Up to now, attempts have been made to obtain a dense aluminum nitride sintered body by adding a sintering aid and using pressureless sintering or hot pressing. For example, Showa 5
Page 301 of the 1999 Ceramics Association Annual Meeting Proceedings describes a method for producing aluminum nitride sintered bodies in which yttrium oxide (Y2O3) is added as a sintering agent, and according to this method, the thermal conductivity increases. An aluminum nitride sintered body of 100 W/m·K (room temperature) was obtained. In this case, the amount of oxygen contained in the aluminum nitride raw material powder was 1.0% by weight or more. However, with the recent development of integrated circuit technology, there is a demand for heat-dissipating substrate materials with even higher thermal conductivity.

0004

[Problems to be Solved by the Invention] The thermal conductivity of an aluminum nitride (hereinafter referred to as AlN) sintered body increases as the amount of oxygen remaining in the sintered body decreases. Conventionally, Al
Research on N sintered bodies has shown that the oxygen content in the AlN raw material is 1
．． Since the method was performed for 0% by weight or more, sintering of AlN raw material with an oxygen content of less than 1.0% by weight was performed.
Not much research has been done to increase the density and thermal conductivity of IN sintered bodies. Furthermore, when an AlN raw material with a small oxygen content is used, it is not possible to obtain a sintered body that has high thermal conductivity and densification at the same time, and the optimal conditions for achieving both cannot be obtained. was the reality. The present invention was made in order to solve the conventional problems as described above, and its purpose is to provide a method for manufacturing an aluminum nitride sintered body that can simultaneously satisfy high thermal conductivity and high density. do.

[0005]

[Means for Solving the Problems] The present invention provides aluminum nitride raw material powder by adding an alkaline earth metal oxide or rare earth metal oxide to aluminum nitride raw material powder having an oxygen content of 0.8% by weight or less. The total amount of oxygen contained in the powder and the amount of oxygen contained in the additive is 0.8
This is a method for producing an aluminum nitride sintered body, which comprises molding and degreasing a mixed powder in an amount of at least % by weight, followed by firing.

The aluminum nitride raw material powder used in the present invention has an oxygen content of 0.8% by weight or less. If the oxygen content exceeds 0.8% by weight, a sintered body with high thermal conductivity cannot be obtained. In the present invention, additives include alkaline earth metal oxides, substances that become alkaline earth metal oxides through thermal decomposition, rare earth metal oxides, or substances that turn into rare earth metal oxides through thermal decomposition. is included. Specific examples of these compounds include CaC2, CaF2, C as alkaline earth metal compounds.
aCO3, BaC2, BaF2, BaCO3, SrC2
, SrF2, SrCO3, etc., and rare earth metal compounds such as Y2O3, YF3, Dy3O3, DyF
3, La2O3, LaF3, CeO2, Nd2O3, N
dF3, Sm2O3, SmF3, Gd2O3, GdF3
etc. The amount of oxygen contained in the mixed powder obtained by adding the above-mentioned additives to the AlN raw powder is required to be 0.8% by weight or more. If this amount is less than 0.8% by weight, a highly densified sintered body cannot be obtained. In order to produce an AlN sintered body, the above-mentioned AlN raw material powder and additives are mixed and homogenized, and then molded and sintered by a conventional method.

[0007]

[Effect] As a result of various studies on the relationship between the amount of oxygen contained in the Al raw material powder and the densification of the obtained sintered body, we found that the amount of oxygen contained in the AlN raw material powder and the relationship between the amount of oxygen contained in the additives (For example, CaCO3 decomposes during heating, and CaO
Since +CO2↑, the amount of oxygen is calculated as CaO. ) is 0.8% by weight or less, it has become clear that the AlN sintered body does not have a high density. That is,
When densifying an AlN sintered body, a certain amount of oxygen is required, and the amount of oxygen contained in the AlN raw material powder is 0.8
If it is less than % by weight, it is necessary to mix oxides as additives and add oxygen. This is because, for example, in the process of mixing these additives into the AlN raw material and sintering it to densify the AlN sintered body,
l2O3 or mY2O3・nAl2O3 (here m
, n indicates a positive integer. ), and a certain amount of calcium aluminate, yttrium aluminate, etc. is required for AlN to become completely densified. In addition, the mixture of AlN raw materials and additives is densified by firing, and at the same time, oxygen that is no longer needed in the firing process is polarized to the grain boundaries, and further passes through the grain boundaries to the outside of the AlN sintered body. evaporated and removed. This makes it possible to produce an AlN sintered body with high density and high thermal conductivity using AlN raw material powder containing less than 0.8% by weight of oxygen.

[0008]

[Example] Next, an example of the present invention will be described. Example 1 Average particle size is 0.5 μm, oxygen content is 0.4% by weight,
Additives as shown in Table 1 were added to three types of AlN raw material powders of 0.8% by weight and 1.0% by weight. This was mixed with a homogenizer for 5000 r. p. The mixture was mixed for 5 minutes at a rotational speed of m. After filtering and drying the slurry, a powder binder is added and molded using a uniaxial pressure molding machine at a pressure of 100 kg/cm2, and further pressurized at a pressure of 2000 kg/cm2 using a hydrostatic isostatic pressure molding machine to form a mold with a diameter of approximately φ40. It was molded into a disk of .0 x 5 mmt. Next, it is degreased in a degreasing furnace, and heated to 1900℃ in a firing furnace.
It was baked for 3 hours. The obtained sample was φ10×3.0mmt
The sintered density and thermal conductivity were measured and shown in Table 2. The theoretical density of the AlN sintered body is 3.2
It is 6g/cm3. Thermal conductivity was measured by the laser flash method.

FIG. 1 shows the relationship between the total amount of oxygen in the AlN mixed powder and the sintered density. It can be seen that the sintered density increases as the total amount of oxygen increases. Also, in Tables 1 and 2, No. Samples 1 to 5 and No. Sample 14 is a comparative example. No. For samples 1 to 5, even if additives are added, the total amount of oxygen contained in the AlN raw powder and the amount of oxygen contained in the additives does not reach 0.8% by weight. , is an example in which AlN is not densified, and No.
．． Sample No. 14 is an example in which, when the AlN raw powder contains 1.0% by weight of oxygen, the density can be increased without adding any additives, but the thermal conductivity is poor. No. 1
In the case of sample 4, oxygen is contained at 1.0% by weight, and this oxygen reacts with impurities contained in the AlN raw material powder, such as Ca and Ba, to form CaO and BaO, resulting in calcium aluminate and Produces barium aluminate, Al
It is thought that this is useful when increasing the density of N. Sample No.
．． In samples 6 to 13, the total amount of oxygen contained in the AlN raw powder and the amount of oxygen contained in the additive was 0.
．． This is an example of the present invention in which the content is 8% by weight or more, and densification,
This is an example of high thermal conductivity. Among these, sample No.
．． The sintered body of No. 6 had an oxygen content of 0.18%. As for other physical properties and characteristics, the coefficient of thermal expansion is approximately 4.3×1
0-6/°C, the specific resistance was about 3 x 1013 Ω·cm, the bending strength was about 40 Kg/mm2, and it also had translucency.

0010

[Table 1] ──────────────────────────
─────── In the raw materials
Total No. by additives and additives. Oxygen amount Added amount Added oxygen amount Oxygen amount
(Weight%) (Weight%)
(Weight%) (Weight%)────────
────────────────────────
1* 0.4 CaC
2 1.4 0.0
0.40 2* 0.4
CaF2 2.0 0.
0 0.40 3*
0.4 CaCO3 2.2
0.0 0.4
0────────────────────────
──────── 4* 0.4
CaF2 1.0 0.
21 0.61
Y2O3 1.0
────────────────────────
──────── 5* 0.4
CaF2 2.0 0.
38 0.78
Dy2O3 3.0
────────────────────────
──────── 6 0.4
Y2O3 3.0 0.
63 1.03 7
0.4 Y2O3 5.0
1.05 1.4
5 8 0.4Y
2O3 10.0 2.05
2.45 9 0.
4 Y2O3 15.0
3.15 3.5510
0.8 CaC2 1.4
0.0 0.
8011 0.8C
aF2 2.0 0.0
0.8012 0.8
Dy2O3 2.0 0
．． 26 1.0613
0.8 Sm2O3 2.0
0.27 1.0
7────────────────────────
────────14* 1.0
Additive-free 0.0
1.00────────────
────────────────────
* Mark: Comparative example.

[0011]

[Table 2]

0012

As explained above, the aluminum nitride sintered body produced by the production method of the present invention has high density and excellent thermal conductivity, and also has good thermal properties, mechanical properties, and optical properties. Therefore, in addition to being used as a heat dissipation material in the semiconductor industry, it is also possible to use it as a high-temperature material for crucibles, vapor deposition containers, heat-resistant jigs, and other high-temperature components.Furthermore, it can be used as a window that utilizes optical properties such as translucency. It has many industrial advantages, such as being able to be applied as an optical material.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the total amount of oxygen in the AlN mixed powder and the sintered density.

Claims (1)

[Claims] Claim 1: Alkaline earth metal oxides or rare earth metal oxides are added to aluminum nitride raw material powder containing 0.8% by weight or less of oxygen, and the oxygen contained in the aluminum nitride raw material powder is removed. of aluminum nitride sintered body, characterized in that it is formed by molding, degreasing, and then firing a mixed powder in which the total amount of oxygen and oxygen contained in additives is 0.8% by weight or more. Production method.