JPH11180774A - Silicon nitride-base heat radiating member and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable firing at <=1,800 deg.C under atmospheric pressure and to produce a low-cost silicon nitride-base heat radiating member having high heat conductivity. SOLUTION: A compact consisting of 70-95 mol.% silicon nitride (Si3 N4 ), 4-30 mol.% (expressed in terms of oxides), in total, of a rare earth metal (RE) and Mg in an RE2 O3 to MgO molar ratio of 0.1-15 and 0-1.0 mol.% (expressed in terms of oxide) Al is densified to >=90% relative density by firing at <=1,800 deg.C in a nonoxidizing atmosphere under atmospheric pressure to obtain the objective heat radiating member having >=30 W/m.K heat conductivity and >=600 MPa strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat dissipating member suitable for dissipating heat generated from a semiconductor element in a semiconductor element package and heat generated from various heating elements, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, heat generated from a semiconductor device has been increasing along with high integration of a semiconductor element. In order to eliminate malfunction of the semiconductor device, such heat is quickly released to the outside of the device. Substrate is required.

[0003] However, alumina materials used in the past, such as various insulating substrates and packages for housing semiconductor elements, have a low thermal conductivity of about 20 W / mK. Began to attract attention. However, it has been found that aluminum nitride cannot be applied to parts that have low strength and fracture toughness and are subject to high stress and fields that require high reliability. Accordingly, silicon nitride sintered bodies have recently been receiving attention as a material that meets demands for high thermal conductivity, high strength, and high reliability.

[0004] Conventionally, silicon nitride materials have been actively studied as high-temperature structural materials for gas turbines and the like, and some of them have reached practical use. Such a silicon nitride sintered body needs to be added with a rare earth oxide and fired at a very high temperature of 1800 to 2000 ° C. in order to enhance the strength characteristics from room temperature to a high temperature. In order to suppress the decomposition reaction at a high temperature, it is necessary to perform firing in a nitrogen atmosphere of several tens to 100 atm.

On the other hand, when characteristics at high temperatures are not required, they are manufactured by adding alumina or magnesia as a sintering aid and firing at a relatively low temperature of 1700 to 1800 ° C.

[0006]

However, while silicon nitride is predicted to have high thermal conductivity due to its constituent elements and crystal structure, much less research has been done on a heat dissipating member than on a structural material. Was. Recently, it has been found that a silicon nitride sintered body as a high-temperature structural material has a considerably high thermal conductivity, and studies on a heat dissipation member of this sintered body have begun.

[0007] From such circumstances, most of the research as a heat dissipating member is based on the premise of sintering at a high temperature.
Very little research has been done on the manufacturing technology of heat dissipating members under low temperature and pressure. For example, JP-A-6-13577
No. 1, Japanese Patent Application Laid-Open No. 7-149588 discloses a silicon nitride sinter having a thermal conductivity of 60 W / m · K or more by sintering nitrogen under pressure at 1800 to 2000 ° C. mainly containing a rare earth element oxide as an auxiliary agent. It is said that solidification is obtained. Also,
Japanese Patent Application Laid-Open No. 4-219731 discloses that by including 90% by weight or more of silicon nitride, making both Al and O 3.5% by weight or less and having a density of 3.15 g / cm ³ , a thermal conductivity of 40 W
It is described to obtain a silicon nitride sintered body of / mK or more.

As described above, firing at a high temperature requires a special firing method such as nitrogen pressure firing, which causes an increase in firing cost. In addition, it is difficult to completely suppress the decomposition of silicon nitride itself, and the burnt surface of the product becomes extremely rough, and processing such as surface polishing is required to actually use such a material. Therefore, it is troublesome and contributes to an increase in cost.

On the other hand, the firing of silicon nitride is performed at 1800
Normal pressure (atmospheric pressure) when performed at relatively low temperature below ℃
Can be fired in a non-oxidizing atmosphere, so that a product with less roughened surface can be obtained. However, the conventional silicon nitride sintered body produced by firing at a low temperature of 1800 ° C. or less has a thermal conductivity of 20 to 30 W / m · K.
And there was a problem that it was extremely reduced. Since this is mainly performed by using a rare earth oxide (RE ₂ O ₃ ) —Al ₂ O ₃ composite aid, nitriding is performed by solid solution of Al atoms in silicon nitride crystal particles and formation of sialon. This is probably because the thermal conductivity of the silicon crystal itself is reduced.

[0010] Accordingly, the present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a silicon nitride heat radiating member which can be fired under normal pressure of 1800 ° C. or less and has high thermal conductivity. It is an object of the present invention to provide a manufacturing method thereof.

[0011]

Means for Solving the Problems As a result of intensive studies on the above-mentioned problems, the present inventors have added a rare earth element compound and a magnesium compound together as sintering aids, It has been found that by controlling the amount of Al, it is possible to obtain a silicon nitride heat dissipation member that can be fired under normal pressure.

That is, the silicon nitride heat radiating member of the present invention is characterized in that the silicon nitride is 70 to 95 mol%, and the rare earth metal (RE) and Mg are 4 to 30 mol% in total in terms of oxide; And the molar ratio (R
E ₂ O ₃ / MgO) is 0.1 to 15 and Al is 1.0 mol% or less in terms of oxide.
0% or more and a thermal conductivity of 30 W / m · K or more.

Further, as a method of manufacturing the same, silicon nitride (S
i ₃ N ₄ ) in an amount of 70 to 95 mol% and rare earth metal (RE)
And Mg in a total amount of 4 to 30 mol% in terms of oxide
And 0 to 1.0 mol% of Al in terms of oxide.
The molded body having a molar ratio (RE ₂ O ₃ / MgO) of 0.1 to 15 in terms of oxides of the rare earth metal and Mg, which is fired at a temperature of 1800 ° C. or less in a non-oxidizing atmosphere at normal pressure, is used. It is characterized by densification to a density of 90% or more.

[0014]

According to the silicon nitride heat dissipation member and the method of manufacturing the same of the present invention, the rare earth element compound and the Mg compound to be added as sintering aids are blended in the above-mentioned specific composition range, whereby the impurity oxygen in the silicon nitride raw material is mixed. And promotes sintering by producing a liquid phase. In addition, the presence of the rare earth element (RE) in the liquid phase promotes the crystallization of the grain boundary phase and reduces the low thermal conductivity glass phase remaining at the grain boundary, thereby improving the thermal conductivity of the sintered body. Let it. Further, the rare earth element (RE) has an effect of increasing the aspect ratio of the columnar crystal accompanying the α-β transition of silicon nitride and improving the fracture toughness of the obtained sintered body.

Al also reacts with other auxiliaries to help form a liquid phase at low temperatures. However, if it is present in a large amount, it forms a solid solution in silicon nitride grains or forms sialon to conduct heat. In order to reduce the rate, the Al content is set to 1.0 mol% or less, whereby low-temperature sinterability and high thermal conductivity can be simultaneously provided.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a silicon nitride heat radiation member and a method of manufacturing the same according to the present invention will be described in detail. First, as a silicon nitride raw material for producing the silicon nitride heat radiation member of the present invention, a material having an impurity oxygen amount of 0.5 to 3.0% by weight is preferable. If the amount of impurity oxygen is more than 3.0% by weight, the surface of the sintered body may be roughened and the strength may be deteriorated.
If the amount is less than 5% by weight, the sinterability is deteriorated.
Further, it is desirable that the average particle size is 0.1 to 1.5 μm and the α ratio is 90% or more.

The rare earth elements (RE) added to the silicon nitride raw material include Y, La, Ce, Pr, Nd, P
m, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
Any of m, Yb, and Lu can be suitably used. Among them, Y, Ce, Sm, Dy, Er, Y
b and Lu, particularly Y and Er, are desirable in terms of characteristics and cost.

The rare earth element (RE) is blended together with Mg. The rare earth element (RE) and Mg are compounded in the range of 4 to 30 mol%, particularly 5 to 25 mol% in terms of oxide. However, the rare earth element (R
E) and the molar ratio of Mg to oxide (RE ₂ O ₃ /
MgO) must be in the range of 0.1 to 15, especially 0.5 to 13.

If the total amount is less than 4 mol%, it is difficult to sufficiently densify the sintering at a temperature of 1800 ° C. or less. This is because the thermal conductivity decreases due to an increase in the absolute amount of Further, even if the ratio of RE ₂ O ₃ / MgO exceeds 15 or becomes smaller than 0.1, densification at a temperature of 1800 ° C. or less becomes insufficient, and the thermal conductivity decreases.

The compounding of an Al compound such as Al ₂ O ₃ greatly contributes to the improvement of the sinterability. However, the solid solution in the Si ₃ N ₄ crystal inhibits the diffusion of phonons. Is most preferably not present for high thermal conductivity. Specifically, Al is 1.0 mol% or less, preferably 0.5 mol% in terms of oxide.
Or less, more desirably 0.1 mol% or less, and more desirably 0.0 mol% or less.
The content is preferably set to 1 mol% or less.

The sintered body contains T as a coloring component.
Periodic tables 4a, 5a, 6 such as i, V, Nb, W, Mo
at least one of the group a metals is 0.05
To 1% by weight.

The silicon nitride heat radiation member of the present invention is composed of the above-mentioned respective component compositions. The relative density of the heat radiation member is preferably at least 90%, especially at least 95% in order to achieve high thermal conductivity. Importantly, if the relative density is lower than 90%, it is difficult to achieve a thermal conductivity of 30 W / m · K or more.

The silicon nitride heat radiation member of the present invention is obtained by mixing a silicon nitride powder, a rare earth element compound, a Mg compound and, in some cases, an Al compound in the above ratio, and adding an organic binder and a solvent to the mixed powder. Using the prepared molding raw material, a molded body is produced by any one of molding methods such as a press molding method, a CIP molding method, a tape molding method, an extrusion molding method, and an injection molding method. Thereafter, the molded body is subjected to a binder removal treatment at a predetermined temperature in a weakly oxidizing atmosphere, and then, in a non-oxidizing atmosphere such as nitrogen, at 1800 ° C. or less, particularly
It is manufactured by firing at a temperature of not more than ° C. to densify to a relative density of 90% or more.

The compound as a sintering aid in the raw material is preferably a compound capable of forming an oxide by firing, such as an oxide, a carbonate or an acetate.

The silicon nitride heat radiation member of the present invention can be used, for example, as a heat sink member in a package on which a semiconductor element is mounted, and also as an insulating substrate of a wiring board on which the semiconductor element is mounted.
In that case, a wiring layer may be formed on the surface or inside of the insulating substrate. In such a case, Cu, W, Mo-Mn, Mo, Pd-Ag
Before baking with a heat radiating member, or by printing and applying a conductive paste made of a refractory metal such as W or Mo on the surface of the molded body, and then simultaneously baking in a non-oxidizing atmosphere. Can be made.

[0026]

EXAMPLES average particle size of 1.2 [mu] m, the amount of oxygen 1.0% by weight, the silicon nitride raw material powder prepared by the α of 93% of the direct nitriding method, rare earth oxide, MgCO _3, Al ₂ O ₃ Each of the sintering aids is added and mixed in a composition as shown in Tables 1 and 2, paraffin wax is added as a forming binder to the mixed powder using isopropyl alcohol as a solvent, kneaded and dried, and then formed through a sieve. A granule for use was obtained, and the granule was formed into a disk having a diameter of 12 mm and a thickness of 5 mm by a mold press at a molding pressure of 1 ton / cm ² .

After debinding the thus obtained molded body at a predetermined temperature, the molded body is removed under a normal pressure (atmospheric pressure) and nitrogen atmosphere.
It was fired at a temperature of 00 to 1800 ° C. for 3 hours to produce a silicon nitride-based sintered body, which was used as a sample for evaluation.

Using the evaluation sample, first, the density of the silicon nitride sintered body was measured by the Archimedes method, and the ratio (%) to the theoretical density was calculated. Next, the thermal conductivity was measured by a laser flash method. Furthermore, JISR16
According to No. 01, the three-point bending strength of the burnt skin surface at room temperature was measured. The results are shown in Tables 1 and 2.

[0029]

[Table 1]

[0030]

[Table 2]

According to the results of Tables 1 and 2, the samples No. 1 to No. 1
As can be seen from FIG. 9, when the amount of Si ₃ N _{4 and the} amount of RE ₂ O ₃ + MgO deviated from the range of the present invention, the relative density was lowered or the thermal conductivity was lowered, and the desired characteristics could not be obtained.
Further, the sample Nanba10～20, Sample No.10,19 RE ₂ O ₃ / MgO molar ratio is outside the 0.1 to 15, are difficult to densify, this Al ₂ O ₃ In the samples Nos. 11 and 20 in which sintering was added, the sinterability was improved, but the effect of improving the thermal conductivity was not obtained. Sample Nos. 21 and 2
In Sample No. 5, the content of Al exceeded 1 mol%.
In the case of No. 25, although it was dense, thermal conductivity fell. From Samples Nos. 26 to 33, similar sintering behavior and high thermal conductivity were also exhibited in various other rare earth elements in place of Y as the rare earth element.

[0032]

As described above in detail, according to the silicon nitride heat radiation member and the method of manufacturing the same of the present invention, it can be fired at a temperature of 1800 ° C. or less and has a thermal conductivity of 30 W / m ·
Since high strength of K or more and strength of 600 MPa or more can be achieved, it can be applied to a wide range of fields as various heat dissipating members with low cost.

Claims (2)

[Claims] 1. An amount of silicon nitride of 70 to 95 mol% and rare earth metal (RE) and Mg of 4 to 3 in terms of oxide.
0 mol%, the molar ratio of the rare earth metal and Mg in terms of oxide (RE ₂ O ₃ / MgO) is 0.1 to 15, and Al is 1.0 mol% or less in terms of oxide. A silicon nitride based heat radiation member having a relative density of 90% or more and a thermal conductivity of 30 W / m · K or more. 2. A silicon nitride (Si ₃ N ₄ ) content of 70 to 95 mol%, a rare earth metal (RE) and Mg in a total content of 4 to 30 mol% in terms of oxide, and an Al content of 0 to 0 in terms of oxide. ~
1.0 mol%, and the molar ratio (RE ₂ O ₃ / MgO) of the rare earth metal and Mg in terms of oxide was 0.1 mol%.
1 to 15 in a non-oxidizing atmosphere at normal pressure,
A method for producing a silicon nitride-based heat radiating member, wherein the member is baked at a temperature of 00 ° C. or less to densify to a relative density of 90% or more.