JPS61209959A - Manufacture of aluminum nitride - 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] [Technical Field of the Invention] The present invention relates to an aluminum nitride sintered body and a method for manufacturing the same, and more particularly, to an aluminum nitride sintered body with high density and good thermal conductivity, and a method for manufacturing the same. It relates to a method that can be produced at low temperatures.

[Technical background of the invention and its problems] - Aluminum nitride (7□N) has high strength from room temperature to high temperature and has excellent chemical resistance, so it is used as a heat-resistant material, but its high thermal conductivity .

Due to its high electrical insulation properties, it is also seen as a promising material for heat sinks in semiconductor devices. Such &4N usually has no melting point and decomposes at high temperatures of 2200 C or higher, so it is used as a sintered body except for applications such as thin films.

For such people, eN sintered bodies are usually molded from A4N@ powder.

Obtained by sintering. However, when A, eN powder is used alone, the sinterability is not good, and it is difficult to obtain a dense, ie, high-density, sintered body except by the pot press method. Therefore, in the case of sintering under normal pressure, C2 is usually made into λbN powder for the purpose of increasing the density of the sintered body.
It is common practice to add rare earth oxides or alkaline earth metal oxides as sintering aids.

However, by adding the sintering aid in this way, the density of the sintered body was considerably increased.

On the other hand, the thermal conductivity of such AJN sintered bodies was currently lower than expected due to the presence of oxygen and other impurities and grain boundaries. That is, while the theoretical thermal conductivity of Alx is 32 ow/m-, that of the one-person AN sintered body is at most 20-6 ow/mIIk.

Furthermore, the temperature at which normal A-eN powder is sintered is usually 1
The temperature is extremely high, at 800 C or more, and this has hindered the reduction in manufacturing costs of A, 6N sintered bodies.

[Purpose of the invention]

The present invention solves the above-mentioned conventional problems, and aims to provide an AnN sintered body having high density and high thermal conductivity, and a method for producing the same by sintering at a relatively low temperature. .

[Summary of the invention]

The present inventors conducted various studies on the relationship between the sintering aid added to the human 2N powder and the density and thermal conductivity of the obtained sintered body, and as a result, the following findings were obtained.

That is, in the method of the present invention, at least one of a rare earth element and an alkaline earth element is added as a fluoride, and a rare earth compound and an alkaline earth compound are added simultaneously, thereby replacing the conventional addition of a rare earth element or an alkaline earth oxide alone. An A, gN sintered body with high density and high thermal conductivity can be obtained at a lower sintering temperature than in the case where the A, gN sintered body is used.

That is, the aluminum nitride sintered body of the present invention is characterized by being composed of aluminum nitride, a rare earth aluminum compound, and an alkaline earth aluminum compound, and the manufacturing method thereof includes adding (a) rare earth fluoride or oxide to aluminum nitride powder. at least one compound selected from the group consisting of compounds that become fluorides or oxides upon firing;

(b) Consists of at least one compound selected from the group consisting of alkaline earth fluorides or oxides and compounds that become these fluorides or oxides upon calcination, and both the alkaline earth and rare earth compounds are fluoride. oxides and compounds that become fluorides when fired, or some alkaline earth and rare earth compounds always contain fluorides and compounds that become fluorides when fired, and the total amount is calculated in terms of the weight of fluorides and oxides. So 0.01~20! After adding t%,
Molding.

When the constituent phases of the human AN sintered body of the present invention, which is characterized by sintering, are observed by X-ray diffraction, it contains, in addition to AAN, a rare earth aluminum oxide and a compound similar to but clearly different from the rare earth aluminum oxide. , and alkaline earth oxides and alkaline earth aluminum oxides and similar compounds have been produced. Or, in rare cases, A-13ON (oxynitride of human J) and polytype 27R of human 1N are mainly produced.For example, the rare earth element is yttrium [Y], and the oxide (Yt' s ), 3Y, Os・5A
A, 0. Or Y, O.

・Aβ203 and other rare earth aluminum oxides are produced, while in the case of fluoride (YF, ), 3
Y! o,・5 people! ! 0. Or Y, 03/A stone 0. Compounds similar to others but distinctly different are produced.

Next, when the alkaline earth element is calcium (Ca) and the oxide is 1:CaO:l, 6A-e,
O8 Sachi CaO or 2A4,0.・CaO and other alkaline earth aluminum oxides are produced, while fluoride (
CaF, ), then 6A-620, ·CaO or 2 people,! 3to, a compound similar to .CaO is produced. However, a compound consisting of a rare earth element and an alkaline earth element or a compound consisting of a rare earth element, an alkaline earth element, and aluminum is not produced. In such an AnN sintered body, the person 1
The composition ratio of N crystal grains is preferably 80 to 99.99% by weight of the total.

In the method for producing an A/N sintered body of the present invention, the oxygen content is 0.
．． It is particularly useful for applications where AfflN powder is between 0.001 and 7% by weight.

In addition, the particle sizes of the 4N powder and sintering aid powder used are:
Both have an average particle size of 5 μm or less, preferably 4 μm
It is as follows.

Rare earth elements added as sintering aids include Y, L
a, Ce, am, Dy, Nd, Gd, Pr
, Ho, 'Br, Yb, etc., especially,
Y, La, and Ce are preferred. One or more of these rare earth elements are added to the AAN powder as a fluoride or an oxide, or a compound that becomes a fluoride or an oxide.

In addition, as alkaline earth metals, Mg, Ca, 8
r.

Examples include Ba, with Ca, 8r, and Ba being particularly preferred. As mentioned above, one or more of these alkaline earth metals are added to the 6N powder as a powder of a fluoride or oxide, or a compound that becomes a fluoride or oxide upon firing, respectively. .

The above-mentioned rare earth element compounds and alkaline earth metal compounds have a total of 0 when converted into oxide and fluoride states, respectively.
．． 01~203& amount is added. The total amount added is 0.
If it is less than 01wt%, the desired effect may not be obtained, while if it exceeds 20wt+jk%, not only the heat resistance and mechanical strength will be impaired, but also the thermal conductivity will decrease. There is. The total amount added is preferably 0.01 to 17% by weight.

The reasons why the thermal conductivity of the sintered body of the present invention increases and the sintering temperature decreases are largely unknown at present, but can be estimated as follows.

That is, one of the factors contributing to the high thermal conductivity is that in the sintered body of the present invention, A2 oxynitridation, ANON, and 1N 2N polytype (27R type) are difficult to form. According to the inventor's research results, it has been found that the sintered bodies produced by types A, #ON, and 27R all have low thermal conductivity. The production of AAON and 27R types is influenced by the purity of A, 4N powder, the atmosphere in the sintering furnace, the type and amount of sintering aid, etc., but the production of 1N by the same person
Comparing sintered bodies produced using powder under the same experimental conditions, it was found that the sintered bodies of the present invention had higher AAO
After applying N, the amount of 27R 凰 produced is clearly small or not produced at all.

On the other hand, the reason why the sintering temperature is lower than before is currently unknown, but compared to the conventional case where rare earth oxides or alkaline earth oxides are added alone, the sintering temperature is lower than before. It is thought that this causes the formation of a phase and promotes sintering.

Next, an example of the method for manufacturing the human-eN sintered body of the present invention will be described below.

First, a predetermined amount of powder made of the above-mentioned rare earth element compound and alkaline earth metal compound as a sintering aid is added to AJN powder, and then mixed using a ball mill or the like. For sintering, a pressureless sintering method, a hot press sintering method, etc. can be used. When using the pressureless sintering method, a binder is added to the mixed powder, and the powder is mixed, granulated, and sized, and then shaped.

As a molding method, a mold press, isostatic press, sheet molding, etc. can be applied. Subsequently, the molded body is heated with, for example, N,
After removing the binder by heating in a gas stream, it is sintered under normal pressure.

On the other hand, when using the hot press sintering method, the raw materials mixed in the ball mill or the like may be directly hot pressed.

In this process, the sintering temperature may be 1700C or less, and is practically 1550 to 1700C, whether the pressureless sintering method or the hot press sintering method is used.

The reason why sintering progresses at a lower temperature than in the past is not clear, but it is due to some kind of interaction between rare earth element fluorides and alkaline earth metal fluorides during the sintering process. It is assumed that

[Embodiments of the invention]

Example 1 Ca powder with an average particle size of 1.5 μm was added to human powder containing 3.6% by weight of oxygen as an impurity and with an average particle size of 2.2 μm.
A raw material was prepared by adding 4% by weight of a mixed powder of F2 and YF (weight ratio 1:3), pulverizing and mixing using a ball mill. Next, 7% by weight of paraffin is added to this raw material.
After adding it and granulating it, it was press-molded at a pressure of 3001 t/m to obtain a green compact of 30 x 30 x 8 m. This green compact was heated to 7,000 ℃ in three nitrogen gas surroundings to remove paraffin. Furthermore, it was placed in a carbon atmosphere and sintered under normal pressure at 1700C for 2 hours in a nitrogen gas atmosphere. The density of the obtained AAN sintered body was measured. Also, the diameter is 101m from the sintered body.

A disk with a thickness of 3.5 mm was ground and used as a test piece to measure thermal conductivity by a laser flash method.

The results are shown in Table 1.

Examples 2 to 10 AAN sintered bodies were manufactured in the same manner as in Example 1 above by changing the type of AAN powder and the type of sintering aid powder. The results were measured for each person's ff1N powder particle size, oxygen content,
The types, mixing ratios, particle sizes, and amounts of sintering aids are shown in Table 1.

Comparative Example 1 An A4N sintered body was produced in the same manner as in Example 1 from only the AAN powder used in Example 1.

Comparative Example 2 The average particle size of the 8N powder used in Example 1 was 2.4 μm.
CaC0, powder was converted to CaO and triple residue was added,
An AAN sintered body was produced in the same manner as in Example 1.

Comparative Example 3 Y! with an average particle size of 2.5 μm was added to the human AN powder used in Example 1. 3% by weight of O8 powder was added, and Aτ
A N sintered body was manufactured.

The density and thermal conductivity of each of the A4N sintered bodies obtained in Comparative Examples 1 to 3 were measured in the same manner as in Example 1. The results are also listed in Table 1.

(Left below) Example 11 To the AAN powder used in Example 1, 41 grams of a mixed powder of BaF2 with an average particle size of 1.5 μm and LaF with an average particle size of 2.5 μm (weight ratio 2:2) was added. A raw material was prepared by pulverizing and mixing using a ball mill.

Next, this raw material powder was press-molded at a pressure of 300 kg/l to obtain a compact having a diameter of 12 mm and a thickness of 10 mm. After that, this green compact was placed in a carbon mold and heated at 1700 C and 400'#/c! in a nitrogen gas atmosphere. Hot press burnout was carried out under a pressure of i for 1 hour. The density and thermal conductivity of the human 1 sintered body obtained in the same manner as in Example 1 were measured, and the results are shown in Table 2.

Comparative Example 4 A4N and J feed bodies were produced in the same manner as in Example 11 from only the A2N powder used in Example 1.

Comparative Example 5 A, g N sintered body was produced in the same manner as in Example 11 by adding 4% B a COs with an average particle size of 1.5 μm to the A-N powder used in Example 1. .

Comparative Example 6 The A-eN powder used in Example 1 had an average particle size of 2.5 μm.
A, eN sintered body was produced in the same manner as in Example 11 by adding 034% by weight of La.

The density and thermal conductivity of each of the human 2N sintered bodies obtained in Comparative Examples 4 to 6 were measured in the same manner as in Example 1, and the results are also listed in Table 2.

(Left below) Next, CaF* with an average particle size of 2.5 μm and CaF* with an average particle size of 0.8 μm were added to the human 1N powder containing 1.4% by weight of oxygen as an impurity and having an average particle size of 1.2 μm. By adding 2.8% by weight of mixed powder of YF (weight ratio 1:1), 1600C, 1650c,
17QOC11750C and 1800 r were sintered for 2 hours, and the density and thermal conductivity of the obtained AJeN sintered bodies were measured in the same manner as in Example 1, and the results are shown in curved lines in Figs. It was shown by

For comparison, the average particle size of 2N powder similar to the above was 2.
Raw material powder containing 0.5% by weight of CaC with a particle size of 5 μm and Y, 0.5 μm with an average particle size of 0.8 μm. Sintering was carried out at various temperatures in the same manner as above using raw material powder to which 2.3% by weight was added.
The density and thermal conductivity of the obtained sintered body were measured and the results are shown in curves B in Figures 1 and 2, respectively.

It is shown by curve C.

As is clear from FIGS. 1 and 2, A of the present invention
Since the NO-N sintered body can significantly lower the sintering temperature and has high density and high conductivity, it is different from conventional ll? It is possible to keep manufacturing costs low compared to N sintered bodies.

In the present invention (-), carbon, NiO, or the like may be added as a sintering aid in addition to those mentioned above.

〔Effect of the invention〕

As is clear from the above description, the human 2N sintered body of the present invention has high density and high thermal conductivity, and the manufacturing method thereof requires a sintering temperature of 1700 C or lower, which is higher than conventional sintered bodies. Since the temperature is relatively low, its industrial value is extremely large, and it is particularly useful as a heat sink material for semiconductor devices and the like.

[Brief explanation of drawings]

1 and 2 both show embodiments of the present invention. Figure 1 shows the relationship between the sintering temperature and the density of the obtained AAN sintered body, and Figure 2 shows the relationship between the sintering temperature and the thermal conductivity of the A, eN sintered body. FIG. Agent: Patent Attorney Noriyuki Chika (and 1 other person) / 4θ
D /7θθ lα Firing purity (°C) Figure 1

Claims (4)

[Claims] (1) Aluminum nitride contains (a) a rare earth fluoride or oxide and at least one compound that becomes a rare earth fluoride or oxide when fired, and (b) an alkaline earth fluoride or oxide and a compound that becomes a rare earth fluoride or oxide when fired. The additive auxiliary component contains at least one compound that becomes an alkaline earth fluoride or oxide, and contains at least one of the fluorides described in (a) and (b) above, with a total of 0.0
A method for producing an aluminum nitride sintered body, which comprises adding 1 to 20% by weight and sintering the aluminum nitride sintered body. (2) The method for producing an aluminum nitride sintered body according to claim 1, wherein the aluminum nitride contains 0.001 to 7% by weight of oxygen. (3) The method for producing an aluminum nitride sintered body according to claim 2, wherein the average particle size of the aluminum nitride powder is 5 μm or less. (4) The method for producing an aluminum nitride sintered body according to claim 2 or 3, wherein a pressureless sintering method is applied and the sintering temperature is 1700° C. or lower.