JPS5832073A - sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sintered body having both high thermal conductivity and electrical insulation.

In recent years, the semiconductor industry has progressed rapidly, with insulating substrates used for large-scale integrated circuits having circuit components formed in high density.Furthermore, there has been a growing demand for miniaturization. , the amount of energy generated per unit area has increased significantly.On the other hand, it is desirable to develop an insulating substrate material with a coefficient of thermal expansion close to that of silicon, to which large silicon chips can be bonded. An alumina sintered body was used as the material. However, the alumina substrate has poor heat dissipation properties and a large coefficient of thermal expansion, so it reached its limit. There is a growing demand for the development of new insulating substrate materials whose coefficients are close to those of silicon.

The conditions that the insulating substrate material must meet are (1) high electrical insulation;

(2) High thermal conductivity.

(3) The coefficient of thermal expansion is close to that of silicon.

(4) High mechanical strength.

etc.

By the way, aluminum nitride has a coefficient of thermal expansion of approximately 5X.
Approximately 7 x 1 of that of the alumina sintered body at 10-'/°C
It is smaller than o = 7℃, and the thermal expansion coefficient of silicon is set 3.
．． Close to 3 x i 0-67 °C. It is also known that the mechanical strength is approximately 50 kg/cm2 in terms of bending strength, which is higher than the approximately 20 kg/cm2 of alumina sintered body. Furthermore, it is a material with excellent air insulation properties.

Conventionally known methods for producing aluminum nitride sintered bodies include a reaction sintering method, an atmospheric pressure sintering method, and a hot press sintering method.

Among these, the reactive sintering method is a method in which a molded body of metal aluminum is sintered while undergoing a nitriding reaction in a nitrogen gas atmosphere. In the reactive sintering method, the nitriding reaction is rate-limited by the diffusion of nitrogen gas, so if the product is thick, unreacted metal remains in the center, and the product is porous, so it cannot be used as an electrical insulator. In the pressureless sintering method, powders such as yttrium oxide, rare earth oxides, yttrium oxide, silicon dioxide, nickel, and calunium oxide are added to aluminum nitride powder and mixed, and then a molded body is formed.In the press sintering method, aluminum nitride, Add powders such as aluminum oxide, inotriuno oxide, and silicon dioxide to the powder and mix.7/
Thereafter, the molded body is formed and heated under pressure to obtain a sintered body. By using the conventional pressureless sintering method and hot press sintering method, it is possible to produce a sintered body made of densified aluminum nitride, which has high strength and electrical insulation +1. and low →
) (has an expansion coefficient. However, the thermal conductivity of the sintered body produced by the above method is small, and is usually 0.07 cm/1 l/C.
1'l! @S・℃ (room temperature), even the largest ones are 0.1 c, ;l 1! -7 (゛(口・S・℃) From these points, aluminum nitride sintered bodies will be used as insulating substrates for large-scale integrated circuits, etc., if those with high thermal conductivity paths are developed. Apart from that, it is extremely useful.

The object of the present invention is to provide a material having high thermal conductivity and suitable performance as an electrically insulating substrate, and a method for manufacturing the same.

The present invention resides in a sintered body of aluminum nitride which is doped with boron nitride in an Id ratio of 0.05 to 30. J to the sintered body
, the thermal conductivity at room temperature is 0.3 chz, 7c
m-s-'CI7. 1-, the electrical resistivity at room temperature is 10'2 ΩC1n or more, the average thermal expansion coefficient at 300°C from the chamber is 6×10-'/°C or less, and the density is 90 cm or more, which is the theoretical density of aluminum nitride.

In addition, the present invention provides aluminum nitride powder with an average particle size of 5 Q / (nl or less).
lt m or less boron nitride powder from 0.05 to 3 o@
The powder is mixed (7) into a compact and sintered under normal pressure at a temperature of 1,600 to 2,000°C in a non-oxidizing atmosphere, or 1.
Aluminum nitride sintered body with high thermal conductivity and excellent electrical insulation properties, which is hot-pressed under pressure of kg/cm2 or more and sintered for 7 minutes to obtain a density of 90 or more of the theoretical density of aluminum nitride Uno. It is in the manufacturing method.

The reason why the amount of boron nitride added is set to 0.05 to 30% in the present invention is that if it is less than 0.05%, a dense sintered body cannot be obtained. It's 30 weight'1ft%
If the amount is more than 2, the coefficient of thermal expansion of the sintered body becomes large, and especially when used as an insulating substrate for a silicon-1 conductor element, the distance tα becomes 2.

In the present invention, the walled aluminum powder d: average particle size is 20 μm or less, 91 mm, and 1. Otr...Use a powder having the following particle size.

The firing conditions for the aluminum nitride powder compact containing boron nitride are also important. Firing is performed in a non-oxidizing atmosphere. Oxidizing 'r? If fired in an ambient atmosphere, the aluminum nitride will oxidize, making it impossible to form the desired sintered body.

The temperature during firing is 1600-2000℃, 1 is 1
A temperature of 700 to 1900°C is effective. Temperature is 1ri00℃
If the temperature is lower than that, a dense sintered body (4J Lesu, 2000
If it is higher than ℃, over-firing will occur. 14
No other effect can be obtained. The firing may be performed by normal pressure sintering or by hot pressing. If a sintered body is manufactured using a hot pressing method using -axis pressure, shrinkage will occur only in the axial direction of the press, making it possible to produce a sintered body with high dimensional accuracy and high strength. In this case, 1.0
It is necessary to apply a load of 0 kg/cm2 or more. Regarding the firing time (1) The optimum firing time is determined by the particle size of the raw material powder used, the addition of boron nitride ffl, 17171 degrees, and the presence or absence of load applied during firing and its size.In general, the particle size of the raw material powder When the temperature is small, the hot water temperature is high, and a load is applied during firing, the larger the applied load, the more dense the structure can be.

Next, an example will be shown and explained in JL format.

Example 1 Boron nitride powder having an average particle size of 17+m and having a crystalline form of the Oriental type was added to aluminum nitride powder with an average particle size of 2 μm11 in an amount of 0.03 to 50 μm and mixed.

Then, an IF force of QQO kg/cm2 was applied to the mixed powder at room temperature to form a compact. The molded body C2 is then placed in a firing furnace at a reduced pressure lXl0=~IX], 0-'! . Zeng: was completed in the vacuum of RL. Heating is about 11 degrees from room temperature to 1800℃.
The sample was heated to y1 at 1,800°C for 1.5 hours at 0.511, and then allowed to cool. Table 1 shows the properties of the aluminum nitride sintered body produced by the method described in Table 1.

Table 1 From the results, it can be seen that the amount of boron nitride added to the aluminum nitride lamb is 0.1 to 30% by weight, and the relative density of the sintered body is 90% or more for thermal conductivity at room temperature. The rate is Q, 2
ca, 4/cm, S, 'C or higher, lightning M resistivity is 101-2Q C1n or higher, thermal expansion coefficient is 6 x 1
It can be seen that the temperature is 0-7°C or less.

Example 2 The same aluminum nitride powder and boron nitride powder as those described in Example 1 were used, and the boron nitride addition [I-3] was used.
The mixture was mixed by weight to obtain a molded body. The molded body was made into a sintered body by changing the firing conditions in a vacuum.

Table 2 shows the manufacturing conditions of the sintered body and the phase 7 of the obtained sintered body.
It is a table showing the relationship between J density.

When the sintered body in Table 2 is densified to a relative density of 90% or more, the thermal conductivity at room temperature is 0.2 cr + l-7 cm *
s・℃ or more, electrical resistivity is to12ΩCIll or more 1-
1 had a coefficient of thermal expansion of 6xlO-67°C or less.

Example 3 An aluminum nitride molded body was prepared in the same manner as described in Example 2. Also. The sintered body was prepared in the same manner as described in Example 1. In Example 3, the atmosphere of the sintered body 117# was changed to argon gas, helium gas, or nitrogen gas. , hydrogen gas.

All of the obtained sintered bodies had characteristics similar to those of the sintered bodies described in Example 1, in which one amount of boron nitride was added by three weights.

Example 4 In the same manner as in Example 1, boron nitride powder having a cubic crystal form with an average particle size of 11 tm was added to aluminum nitride to form a compact. Prepare the sintered body in the same manner as above. When the sintered body has the same amount of boron nitride added, the value of thermal conductivity (10) is higher when cubic □ system boron nitride powder is used than that described in Example 1. Other characteristics were similar.

Example 5 A sintered body was obtained in the same manner as in Example 1 except that 3% by weight of orthogonal boron nitride was added to aluminum nitride powders having different average particle sizes. Table 3 shows the relative density of the obtained sintered body, and when the average grain size of aluminum nitride is 20 μm or less, a sintered body with a relative density of 90% or more can be obtained.

Table 3 These sintered bodies had almost the same characteristics as those described in Example 1 when the amount of boron nitride (11) added was 3 years.

Example 6 As a specific example of the electrically insulating substrate of the present invention, the alumina nitride substrate and sintered body obtained in Example 1 with an added amount of boron nitride of 3% by weight was used as the insulating substrate. This will be explained using a semiconductor power module.

FIG. 1 is an assembled sectional view of a conventional structure. The conductor 4 and the heat sink 6 and the heat sink 6 and the metal support plate 8 are insulated by the organic insulator 5 and the alumina substrate 7 to alleviate strain caused by the difference in thermal expansion coefficient between the silicon element 1 and the heat sink 6. A molybdenum spacer 3 was interposed therein. FIG. 2 is an assembled sectional view of a module using an insulating substrate according to the present invention. The insulating substrate 15 is directly brazed to the silicon element 11, and has an extremely simple structure.

The semiconductor device was held at −60° C. for 30 minutes, then held at room temperature for 5 minutes, and then subjected to a heat cycle in which the temperature was raised to 125° C. and held for 30 minutes. The semiconductor device (FIG. 1) using the conventional method (12) suffered from peeling at the soldered area after 20 heat cycles. No abnormality was observed in the semiconductor device according to the present invention (FIG. 2) even after 150 heat cycles.

Comparative Example 10 parts by weight of yttrium oxide was added to aluminum nitride powder having an average particle size of 11 tm and mixed to form a compact. The compact was hot-pressed in a vacuum of I x 10-" orr at a temperature of 1800°C, a load of 300 kg 7 cm2, and a time of 0.5 h to form a sintered body. The sintered body was densified to a relative density of 99. Other properties of the sintered body include thermal conductivity of 0107Cat/Cm-5°C (room temperature);
Electrical resistivity is 10”Ωcm (room temperature), thermal expansion coefficient is 5
x 10-''7°C (room temperature to 300°C).

The aluminum nitride sintered body of the present invention is dense and has the characteristics of high thermal conductivity, high electrical resistance, and low coefficient of thermal expansion. Therefore, as mentioned above, it is not only useful as an electrically insulating substrate material, but also a member that requires heat resistance, oxidation resistance, and chemical resistance (13), and surface heat impact resistance. It is also a suitable material for parts that require high strength at high temperatures.

[Brief explanation of drawings]

FIG. 1 is an assembly diagram of a silicon semiconductor device according to a conventional method, and FIG. 2 is an assembly diagram of a silicon semiconductor device using a substrate according to the present invention. 1.11...Silicon element, 2.12...Lead wire, 3...Molybdenum baser, 4., -14...
・Conductor, 5...Organic insulator, 6...Heat//ri,
7... Alumina substrate, 8... Support plate, 9, 10.1
3...Solder, 15 (14)

Claims (1)

[Claims] 1. Boron nitride is added from 0.1 to aluminum nitride.
A sintered body characterized by adding 30% by weight of ffr. 2 90% or more of the theoretical density of aluminum nitride
The sintered body according to claim m1, which has a density of . 3. Thermal conductivity at room temperature is 0.2 Cat/CmaS
- The sintered body according to claim 1, characterized in that the temperature is at least ℃. 4. The sintered body according to claim 1, which has an electrical resistivity of 10<13 >[Omega]Cm or more at room temperature. 5. The sintered body according to claim 1, wherein the boron nitride is cubic boron nitride or solid boron nitride.