JP2742600B2 - Aluminum nitride sintered body and method for producing the same - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an aluminum nitride sintered body and a method for producing the same, and more particularly, to an electronic component material such as a substrate having high thermal conductivity and heat dissipation. The present invention relates to a low-temperature sinterable aluminum nitride sintered body and a method for producing the same.

(Prior art) In recent years, as information processing devices have become higher in performance and higher in speed, the density of semiconductor integrated circuits constituting the information processing devices has also been rapidly increasing, and thus the power consumption of semiconductor integrated circuit devices has been increasing. Therefore, the amount of heat generated by the element is remarkably increased. In order to operate the semiconductor integrated circuit element normally and stably, it is an issue how to efficiently remove the generated heat.

Therefore, conventional semiconductor packages based on alumina have low thermal conductivity and insufficient heat dissipation.
A beryllium oxide sintered body has been proposed as a ceramic material having a high thermal conductivity, but has a problem in use due to its toxicity.

Therefore, it has high mechanical strength from room temperature to high temperature, has high electrical insulation, has high thermal conductivity, and has a thermal expansion coefficient higher than that of alumina. Attention has been paid to aluminum nitride-based sintered bodies having excellent properties such as those close to.

However, aluminum nitride is inherently difficult to sinter, and it was difficult to obtain a high-density sintered body having high thermal conductivity simply. Therefore, as a sintering aid for aluminum nitride raw material powder, group IIa element or II
A sintered body is obtained by adding a compound of an Ia group element, for example, an alkaline earth metal such as calcium, strontium and barium, or a compound of yttrium and a rare earth element.

(Problems to be Solved by the Invention) However, in the conventional method, firing at a high temperature of 1700 ° C. or more was required to obtain an aluminum nitride sintered body. When the co-firing with a metal conductor is performed at such a high sintering temperature, the cost of the firing furnace and the cost of firing are increased, and the bonding strength of the conductor is reduced due to the grain growth of the metal conductor. There was a point.

In order to further reduce the firing temperature, Y, L
a, Ce, Nd, Sm, a method of simultaneously adding an oxide of an alkaline earth metal compound with an oxide of Dy is described in JP-A-61-117160, but the thermal conductivity is as low as 110 W / mk at most. Was something. A method of lowering the sintering temperature by adding a rare earth metal fluoride is described in Japanese Patent Application Laid-Open No. 61-209959, but the use of fluoride significantly increases the raw material cost. It is not suitable for production, such as corrosion of a furnace due to generation of oxides.

(Object of the Invention) The present invention has a main object to solve the above-mentioned problems, and specifically, a nitride having a high thermal conductivity and a high density of uniform quality and capable of being fired at a low temperature of 1700 ° C or less. Another object of the present invention is to provide an aluminum-based sintered body, and to provide a method for easily and stably producing the sintered body.

(Means for Solving the Problems) The present inventors have conducted research on the above problems, and as a result,
It has been found that the heavy rare earth metal compound and the alkaline earth metal compound may be added simultaneously. That is, the present invention relates to an AlN powder of 83 to 97% by weight and Yb ₂ O ₃ as a heavy rare earth metal compound.
3-15% by weight of powder, Ca as alkaline earth metal compound
After molding a mixture containing O powder at a rate of 0.01 to 2% by weight, the mixture is fired at a temperature of 1700 ° C. or less in a non-oxidizing atmosphere containing 1 Torr or more of nitrogen gas, and Yb metal is contained in the sintered body. Alternatively, the metal compound is converted to metal at 0.5% by weight or more, and the Ca metal or the metal compound is converted to metal at 0.1% by weight.
By leaving 005% by weight or more, the bulk density is 3.2 to 3.
It is characterized by obtaining an aluminum nitride sintered body having a thermal conductivity of 6 g / cm ³ and a thermal conductivity of 120 W / m · K or more.

 Hereinafter, the present invention will be described in detail.

A major feature of the present invention is that a heavy rare earth metal or its metal compound and an alkaline earth metal or its metal compound are used simultaneously as a sintering aid. The heavy rare earth metal compound includes Yb ₂ O ₃ , and the alkaline earth metal compound includes CaO.

On the other hand, the aluminum nitride powder used in the present invention is manufactured by a known method such as a direct nitriding method or an alumina reduction method, and has an oxygen content of 1.5% by weight or less and a carbon content of 0.1% or less.
5% by weight or less, cationic impurity content excluding aluminum 0.1% by weight or less, especially when both Si content and Fe content are 1
It is a powder having an average particle size of not more than 00 ppm and not more than 2 μm.

The aluminum nitride powder and the sintering aid are mixed in such an amount that the sintering aid can sufficiently form a liquid phase in firing, and the aluminum nitride powder is 83 to 97% by weight, and the Yb ₂ O ₃ powder is _{3 to} 15%. % Of Cao powder and 0.01 to 2% by weight.

The compounded powder is mixed in an organic solvent, if desired. At this time, the amount of water contained in the organic solvent is set to 0.4% by weight or less. As a result, the dispersibility of the AlN powder is improved, and the reaction with water in the solvent
Oxidation of the AlN particle surface can be prevented.

The obtained mixed powder is formed into a desired shape by known molding means, for example, press molding using a mold or hydrostatic pressure, sheet molding, extrusion molding, and the like, and then is transferred to firing.

The firing is performed at a firing temperature of 1500 to 1700 ° C. in a non-oxidizing atmosphere containing nitrogen gas at 1 Torr or more, particularly 760 Torr or more. Examples of the firing means include normal pressure firing and nitrogen gas pressure firing. Further, the rare earth metal or metal compound in the sintered body obtained by firing is 0.5% by weight or more in terms of metal, and alkaline earth Densification can be promoted by hot isostatic firing of a sintered body containing 0.005% by weight or more of metal or metal compound in terms of metal.

According to the present invention, in the firing step, the rate of temperature increase from 1200 ° C. to the firing temperature is set to an average of 40 ° C./min or less, and the sintering aid and the nitriding It is desirable to uniformly generate aluminate as a liquid phase component by reaction with oxygen on the surface of the aluminum powder, and if the rate of temperature rise exceeds an average of 40 ° C./min, aluminate that is a liquid phase component is not sufficiently generated As it reaches the firing temperature,
The sintering aid volatilizes, so that sufficient sintering does not proceed, and a high-density sintered body cannot be obtained.

In order to keep the liquid phase component until sintering progresses sufficiently with aluminate sufficiently generated, for example, the same auxiliary powder as the sintering aid in the compact is installed in a firing furnace. By doing so, the surroundings of the molded body are made substantially the same as the vapor pressure of the auxiliary, and after the sintering has sufficiently proceeded, the gas in the firing furnace is forcibly replaced, and the surroundings of the molded body of the auxiliary are By keeping the pressure lower than the vapor pressure, the volatilization of the auxiliary can be promoted.

In the firing step, the amount of the sintering aid is finally adjusted to 0.5% by weight or more in terms of Yb metal and 0.005% by weight or more in terms of Ca metal.

After sintering, average from sintering temperature to 1200 ° C at 40 ° C
It is desirable that the temperature be lowered at a rate of not more than / min, thereby eliminating any non-uniform layer on the surface of the sintered body and achieving uniformity.

By such a manufacturing method, in the final sintered body,
A density of 3.2 to 3.6 g / cm ³ and a thermal conductivity of 120 W / m · K or more are achieved.

Incidentally, the amount of the auxiliary agent remaining in the sintered body is calculated as 0.
The reason for limiting the amount to 005% by weight or more is that if the amount of the remaining auxiliary agent is less than 0.5% by weight in terms of Yb metal, and if it is less than 0.005% by weight in terms of Ca metal, sintering is insufficient and a thermal conductivity of 120 W / m · K is achieved. This is because the sintered body is not uniform. Also,
Those with a bulk density of less than 3.2 g / cm ³ have many pores and 3.6 g / c
A value larger than m ³ means that there are many auxiliary components which have not reacted with oxygen in the aluminum nitride.

Furthermore, the amount of sintering aid Yb ₂ O ₃ powder 3 to 15 wt%, was limiting the CaO powder 0.01 to 2.0 wt%, Yb ₂ O ₃
If the amount is less than 3% by weight, sufficient densification of the sintered body will not be achieved even if the amount of CaO is increased, and if it exceeds 15% by weight, a large amount of oxygen and unreacted auxiliary in aluminum nitride will remain. , The thermal conductivity decreases and the sintered body becomes non-uniform.
If the powder content is less than 0.01% by weight, the thermal conductivity is lower than 120 W / m · K, and if it exceeds 2% by weight, no improvement in the thermal conductivity is observed.

 Hereinafter, the present invention will be described with reference to the following examples.

When adding the sintering aid, in addition to Yb ₂ O ₃ and CaO, they may be added in the form of carbonates, nitrates or composite oxides thereof which can be converted to these oxides by firing. .

(Example) First, the oxygen content is 1.5% by weight or less, the carbon content is 0.15% by weight or less, and the cationic impurity content excluding aluminum is 0.1%.
1% by weight or less of a commercially available aluminum nitride raw material powder and Yb ₂
O ₃ and CaCO ₃ were mixed in different amounts. Next, a pressure of 1000 kg / cm ² was applied to the mixed powder at room temperature to obtain a molded body. The molded body was placed under a nitrogen gas atmosphere containing carbon for 16 hours.
Sintering was performed at 00 ° C. for 5 hours under normal pressure. In the firing, the temperature was raised from 1200 ° C. to each firing temperature at a rate of 20 ° C./min.

At this heating rate, it was confirmed that a reaction product (aluminate) with Al ₂ O ₃ was generated in each sample. After reaching the firing temperature, the firing was always performed with the nitrogen gas replaced. In addition, the rate of cooling down to 1200 ° C is 20 ° C / m
set to in.

Table 1 shows the results obtained by measuring the density of the aluminum nitride sintered body thus obtained by the Archimedes method and measuring the thermal conductivity by the laser flash method.

In addition, the amount of the assistant (metal equivalent) in the sintered body was measured by ICP emission spectroscopy.

As is clear from the results in Table 1, No. 18, 1 using Y ₂ O ₃
In all of the samples, the density was low and no sintering was performed.

In the sample of No. 1 in which the addition amount of Yb ₂ O ₃ was less than 3% by weight, sintering was insufficient, and high thermal conductivity was not achieved. In addition, in the sample of No. 7 in which the addition amount exceeded 15% by weight, the remaining amount of the auxiliary agent was large, and color unevenness and spotting occurred.

No. 8 and 9 samples in which the amount of CaO added was less than 0.01% by weight did not achieve high thermal conductivity. The addition amount is 2% by weight
No improvement in thermal conductivity was observed in the sample of No. 17 exceeding

On the other hand, Sample Nos. 2 to 6 and 10 to 16 of the present invention all had an apparent density of 3.2 to 3.6 g / cm ³ and a thermal conductivity of 120 W / m · K or more.

FIG. 1 shows a change in bulk density of a sample having the same composition as Sample No. 4 depending on the firing temperature, and FIG. 2 shows a change in thermal conductivity.

〔The invention's effect〕

As described in detail above, the aluminum nitride sintered body of the present invention has high density, excellent thermal conductivity, good thermal, electrical, and mechanical properties, low raw material costs, and low-temperature firing. It is possible to manufacture easily and stably without unevenness of properties in the material, so that when manufacturing electronic component materials such as insulating substrates on which electronic components are mounted, simultaneous firing with a metal conductor becomes possible. Has many advantages.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the firing temperature and the bulk density in the composition of Sample No. 4, and FIG. 2 is a diagram showing the relationship between the firing temperature and the thermal conductivity.

Claims (2)

(57) [Claims] 1. A sintering aid containing yttrium (Yb) metal or a metal compound thereof and calcium (Ca) metal or a metal compound thereof as a sintering aid.
The bulk density of the metal or its metal compound is 0.5% by weight or more in terms of metal, and the bulk density of the Ca metal or its metal compound is 0.005% by weight or more in terms of metal.
Aluminum nitride sintered body with 3.6 g / cm ³ and thermal conductivity of 120 W / m · K or more. 2. An AlN powder of 83 to 97% by weight and a Yb ₂ O ₃ powder of 3
After molding a mixture containing -15% by weight and 0.01-2% by weight of CaO powder, the mixture is sintered at a temperature of 1700 ° C or less in a non-oxidizing atmosphere containing 1 Torr or more of nitrogen gas, and sintered. Converting Yb metal or its metal compound to metal in the body
A method for producing an aluminum nitride sintered body, wherein 0.5% by weight or more of Ca metal or a metal compound thereof is left in an amount of 0.005% by weight or more in terms of metal.