JPH0524930A - Aln sintered compact and production thereof - Google Patents

Abstract

PURPOSE:To obtain the high-thermal conductivity AlN sintered compact having an excellent heat resistant fatigue characteristic, etc., by mixing AlN raw material powder, an oxygen content control agent and a sintering assistant of a Y system at regulated compounding ratios, oxygen content in the raw material, etc., then molding and sintering the mixture. CONSTITUTION:(A) The AlN raw material powder, (B) the oxygen content control agent (e.g.: alumina) and (C) the oxide and/or carbonate of Y are so mixed that the content of the component C attains 2 to 10wt.% in terms of Y2O3 by the total weight of the components A, B and C. Further, the the amt. of the component C to be added, designated as a wt.%, and the amt. of the carbon to be incorporated into the molding after degreasing, designated as c wt.%, are so adjusted that the b wt.% of the oxygen to be incorporated into the components B and A satisfies equation. The mixture is then molded and sintered. The AlN sintered compact which has 0.1 to 1.5mum average circumferential length of the grain boundary phase at the cut section of the sintered 0.5 to 1 ratio of the average min. diameter and the average max. diameter and <=0.5 ratio of the average grain size and the average grain size of the AlN particles and in which the grain boundary compsn. consists of 3Y2O3.5Al2O3 and Y2O3.Al2O3 is thereby obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high thermal conductivity AlN sintered body having excellent thermal fatigue resistance.

[0002]

2. Description of the Related Art In recent years, due to rapid technological innovation in the semiconductor industry, high integration and high output of large-scale integrated circuits such as ICs and LSIs have been remarkably achieved. However, the heat dissipation of the substrate material is becoming more important, and beryllia, which excels in thermal conductivity, is used as a substrate material instead of alumina. However, beryllia is highly toxic and has problems in handling. Therefore, AlN is attracting attention as a substrate material that replaces alumina and beryllia.

Sintered bodies such as auxiliary materials for AlN sintered bodies
There are various prior applications regarding the manufacturing method and its manufacturing method, and especially
Recently, the manufacturing method of high thermal conductivity AlN sintered body, the grain boundary of the sintered body
There are many applications regarding the composition and structure of phases (Japanese Patent Laid-Open No. 62-
52181, JP-A-62-171964, JP-A-2-3
8369). In addition, the effect on the thermal conductivity of the AlN sintered body
Various studies have also been conducted on the structure [24th Ceramic Industry
Proceedings of Basic Discussion P. 175 (1986), Nippon Cerami
Academic society journal97[12], 1478 (198
9)]. Also, the Ceramic Society of Japan93
[9], 41 (1985), Ca (N) as a sintering aid.
O₃)₂In the sintered body obtained by adding
The findings regarding that the grain boundary phase becomes spherical
ing.

[0004]

The AlN sintered body recently disclosed as described above has excellent thermal conductivity, but when the amount of heat generated by higher output and higher integration increases, heat cycle characteristics, etc. Thermal fatigue resistance becomes a problem, and cracks may occur in a thin plate such as a substrate, causing a problem in the circuit of the substrate. Therefore, it is necessary to improve the heat resistance cycle characteristics, and the present invention aims to improve the characteristics.

[0005]

Means for Solving the Problems As a result of various studies to solve the above-mentioned object, the present inventor has found that in an AlN sintered body containing a grain boundary phase, (a ) The average circumference is 0.1 to 15 μm, (b) the ratio of the average minimum diameter to the average maximum diameter is 0.5 to 1.0, and (c) the ratio of the average particle diameter to the average particle diameter of AlN particles. 0.5 or less and the composition of the grain boundary phase is 3Y ₂ O ₃ .5Al ₂ O ₃ and Y ₂ O ₃ .Al ₂ O ₃
Of AlN raw material powder, sintering aid and oxygen content adjusting agent as the total weight of YN oxide and / or carbonate as a method of making the sintered body. Is added to the oxide as an oxide Y ₂ O _{3 in} an amount of 2 wt% to 10 wt% as the addition amount of the sintering aid, and when the carbon amount contained in the molded body after degreasing is defined as cwt%, 0.3a + 1.3c + 2 The oxygen content adjusting agent and the oxygen content bwt% contained in the AlN raw material powder are adjusted so as to satisfy 3>b> 0.2a + 1.3c + 0.7, followed by mixing, molding and sintering. A method for manufacturing an AlN sintered body has been found.

[0006] Looking at the structure of the AlN sintered body using the sintering aid, "AlN (crystal) grains" are covered by the "grain boundary phase" which is a liquid phase in which the sintering aid is solidified as an oxide. However, the present inventors have found that the state of covering the grain boundary phase and the existence of the grain boundary phase are
It has been found that the thermal conductivity of the AlN sintered body is affected and that it is related to the thermal fatigue resistance such as the thermal cycle characteristics.

As a result of analyzing these, it was found that by limiting the shape, size and composition of the grain boundary phase, the thermal fatigue resistance can be improved while maintaining the high thermal conductivity of the AlN sintered body. It was That is, in the AlN sintered body, the grain boundary phase is small, spherical, and its composition is 3Y ₂ O ₃ ·.
5Al ₂ O ₃ (hereinafter abbreviated as YAG) and Y ₂ O ₃ · Al ₂ O ₃
(Hereinafter abbreviated as YAP).

To express it quantitatively, the average peripheral length of the grain boundary phase at the cut surface of the grain boundary phase of the AlN sintered body is 0.1 to 15 μm.
In m, the ratio of average minimum diameter to average maximum diameter is 0.5 to 1.0
And the ratio of the average particle size to the average particle size of AlN particles is 0.5 or less, and the composition thereof is YAG and YAP, the high thermal conductivity is maintained and the thermal fatigue resistance is excellent.
The present inventors have found that an AlN sintered body can be obtained.

If the average peripheral length of the grain boundary phase at the cut surface of the grain boundary phase of the AlN sintered body exceeds 15 μm, large cracks are easily generated in the grain boundary phase, and the thermal fatigue resistance of the sintered body deteriorates. 1μ
When it is less than m 3, the thermal conductivity is lowered, which is not preferable. Also, if the ratio of the average minimum diameter to the average maximum diameter is less than 0.5, or if the ratio of the average grain size of the grain boundary phase to the average grain size of AlN grains exceeds 0.5, the grain boundary phase has a large amount. Cracks easily occur and the thermal fatigue resistance of the AlN sintered body deteriorates. In the present invention, the grain boundary phase of the AlN sintered body exists spherically at the grain boundary or triple point of the AlN grain, and the size of the grain boundary phase and the contact area between the AlN grain and the grain boundary phase are very small.

Next, the method of manufacturing the sintered body of the present invention will be described in the order of steps. Except for the compounding ratio other than the mixing ratio of the addition amount of the sintering aid and the oxygen amount of the oxygen content adjusting agent, that is, AlN. The fine powder raw material, the binder and the like, the method of the raw material mixing method, the molding method, the degreasing and the sintering method and the conditions thereof have been conventionally used, and the method and the conditions can be used.

The AlN fine powder, which is the main raw material, has an average particle size of not less than 95% and a mean particle size of 20 μm or less, preferably 5 μm or less, and a metal impurity amount of 500 ppm or less, and an O ₂ content. Is preferably 4 wt% or less. As the sintering aid that plays an important role in the present invention, Y oxide and / or carbonate is used, but the amount of Y oxidation is larger than the total weight of AlN raw material powder, sintering aid and oxygen content adjuster. _{2 to} 10 wt% as a sintering aid addition amount awt% in terms of oxide Y ₂ O ₃ and carbon amount cwt% contained in the molded body after degreasing. The oxygen content adjusting agent and the oxygen content bwt% contained in the AlN raw material powder are adjusted so as to satisfy 0.3a + 1.3c + 2.3>b> 0.2a + 1.3c + 0.7. Mix the auxiliaries and oxygen content modifiers with the AlN raw powder. The "after degreasing" degreasing here will be described in detail later.

The addition amount of the sintering aid is calculated based on the oxide Y ₂ O ₃ .
2 to 10 wt% is added to the total weight of the AlN raw material powder, the sintering aid and the oxygen content adjusting agent, and the preferable range is 2 to 7 wt%. If it is less than 2 wt%, it takes a long time to obtain a dense sintered body, and if it exceeds 10 wt%, the thermal conductivity is lowered.

The oxygen content adjusting agent in the present invention is added to adjust the amount of oxygen related to the above formula, and alumina such as alumina Al ₂ O ₃ or oxynitride is used. If the above formula is satisfied and the oxygen in the AlN raw material fine powder is sufficient, it is not necessary to add an oxygen content modifier such as alumina.

If carbon is contained in the green body before sintering, it reacts with oxygen contained in the AlN raw material powder, so that the amount of the sintering aid added is reduced for the purpose of the present invention. Or
As a result, the added amount of the oxygen content modifier such as alumina is increased.

The AlN fine powder and the sintering aid are mixed by dry mixing or wet mixing using an organic solvent.
The latter wet mixing is preferable because it can mix well. Paraffin wax, polyvinyl butyral,
Add an organic binder such as ethyl cellulose to the mixed powder in an amount of 3 to 15 wt%, preferably 5 to 10 wt%,
It is formed into a predetermined shape by an appropriate forming means such as a dry pressing method, a rubber pressing method, an extrusion method, an injection method, and a doctor blade sheet forming method. Granulated powder is generally used in the mold forming method. In the case of an AlN sintered substrate, it is generally formed by the doctor blade method. In this case, use an organic solvent, a dispersant such as polyethylene glycol, a binder such as polyvinyl butyral, and a plasticizer such as butylphthalyl butyl glycolate.
It is general to make a thin plate (green sheet) by the doctor blade method by mixing with 1N raw material powder and a sintering aid.

After molding, 400, in vacuum, N ₂ , Ar or air
Degreasing treatment is performed at ˜700 ° C. for 0.1 to 24 hours. . In the present invention, "the amount of carbon contained in this molded body after degreasing" in the case where the amount of the sintering aid to be added is specified means that the degreased molded body is in a non-oxidizing atmosphere. Alternatively, the total amount of carbon contained in the molded body after being heated at 1300 ° C. for 2 hours in a vacuum atmosphere is represented in the present invention. The carbon content is preferably 2 wt% or less.

After degreasing, 0.1 to 1700 to 2000 ° C.
In 24 hours, it is -5 in vacuum or non-oxidizing gas such as N ₂ and Ar.
Sintering is performed under the conditions of 00 mmHg to 10 kg / cm ² . AlN (crystal) of the AlN sintered body of the present invention manufactured as described above
The grain boundary phase covering the grains is spherical at grain boundaries and triple points, and the size of the grain boundary phase and the contact area between AlN grains and the grain boundary phase are very small.

The grain boundary phase containing the sintering aid component of the AlN sintered body of the present invention is Y having a garnet type crystal structure.
It is composed of AG and YAP having a perovskite type crystal structure. These quantitative ratios were determined by powder X-ray diffraction (Cu Kα; 40
KV, 20mA; scan speed 1 deg / min) peak ratio, YAG phase, plane index (532) diffraction angle 2θ
= 46.6 ° diffraction peak height is I (YAG), YA
Assuming that the diffraction peak height of the P phase and the plane index (121) at the diffraction angle 2θ = 34.3 ° is I (YAP), the range of 0.1 ≦ I (YAG) / I (YAP) ≦ 10.0 is Preferably, in this case, the addition amount awt% of the above-mentioned sintering aid does not change from 2 to 10 wt%, but the oxygen amount bwt
The preferable range of% is 0.3a + 1.3c + 1.9 ≧ b ≧ 0.2a + 1.3c + 1.3, and the range of 0.1 ≦ I (YAG) / I (YAP) ≦ 2.0 is more preferable. In this case, awt% is 2-10
Although it does not change like wt%, the more preferable range of the oxygen amount b wt% is 0.3a + 1.3c + 1.6 ≧ b ≧ 0.2a + 1.3c + 1.3. In these formulas, a, b, and c have the same definitions as described above. The YAG phase and the YAP phase increase in the YAG phase when the amount of oxygen contained in the aluminum nitride raw material powder is large relative to the amount of the sintering aid such as yttrium oxide added.
The phases tend to decrease, and in the opposite case, the YAG phase tends to decrease and the YAP phase tends to increase.

[0019]

EXAMPLES The present invention will be described in detail below with reference to examples. Examples 1 to 16 AlN powder (average particle size 1.6 μm, BET specific surface area value 3.
8 cm ² / g, oxygen 2.4 wt%, Fe 60 ppm) Y ₂ O
₃ (purity 99.9%, average particle size 0.4 μm) powder sintering aid and oxygen content modifier Al ₂ O ₃ were mixed in the ratios shown in Table 1. However, only in Example 16, the oxygen content of the AlN raw material powder was 3.3 wt%. To 100 parts by weight of these mixed powders, 10 parts by weight of polyvinyl butyral as a molding binder, 2.5 parts by weight of butylphthalyl butyl glycolate as a plasticizer, 10 parts by weight of trichlorethylene as a solvent, and 20 parts by weight of tetrachloroethylene, respectively. , N
20 parts by weight of butyl alcohol were added. These were mixed for 48 hours in a nylon ball mill pot to form a slurry. The solid concentration of the slurry is 73.4.
It was wt%.

A green sheet having a thickness of 1.1 mm was prepared from this slurry by the doctor blade method. This green sheet was cut into 30 mm square and degreased at 600 ° C. for 2 hours in vacuum. The carbon content of this defatted body is 0.5
It was wt%. After degreasing, 1300 in vacuum atmosphere
The carbon content in the molded body after the heat treatment at 0 ° C. for 2 hours was 0.4 wt%. That is, the value of C in the formula defining the amount of the sintering additive to be added is 0.4 wt%.

The above-mentioned degreased compact was placed in a sintering furnace and sintered in a nitrogen stream at an atmospheric pressure (flow rate 100 l / hr) at a sintering temperature shown in Table 1 for a total of 6 hours. . Next, in order to observe the structure and the like of the obtained sintered body, each sintered body was cut, the cut surface was polished, and the SEM and the image analyzer were used to measure the grain boundary phase of the sintered body. "Average circumference", "average minimum diameter to average maximum diameter", and "average grain size of grain boundary phase to average grain size of AlN grains" were obtained.

The sintered bodies were finely pulverized to form powder X-ray diffraction samples, I (YAG) / I (YAP).
The value was measured. The measuring device at this time is Geiger Flex RAD-2B manufactured by Rigaku Denki Co., Ltd., and the main measuring conditions are as follows. Target Cu Kα Voltage, current 40KV, 20mA Scan speed 1 deg / min Slit 1-0.3-1

Next, a thermal cycle test was conducted on each sintered body. The method etc. will be described below. In the thermal cycle test, first, the sintered body is 25 mm square and the thickness is 0.635.
It was processed into mm and used as an elementary sample.

[0024] Next Ti metal powder (d ₅₀ = 10μm) 2.0 parts by weight, Ag metal powder (d ₅₀ = 10μm) 71.0 parts by weight of Cu metal powder (d ₅₀ = 15μm) 27.0 parts by weight 10 parts by weight of ethyl cellulose and terpineol (commercially available from Wako Pure Chemical Industries, Ltd.) per 100 parts by weight of three kinds of metal powders
A paste was prepared by adding and mixing 0 parts by weight of each. Paste the paste into the shape and dimensions shown in Fig. 1 with thicknesses of 0.3 mm and 23 mm.
Apply to a square copper plate, and with the above AlN sintered body at 840 ℃ 1.
Bonding was carried out with pressure of 3 kg / cm ² . This bonded sample was used in each of Examples 1 to 16 shown in Table 1 for 10 times.
It was made one by one.

A thermal history was applied to these bonded samples by the thermal cycle shown in FIG. Thermal cycle test is -55 ° C → 1
After the thermal history of 1000 cycles with 50 ° C. → −55 ° C. as one cycle, it is observed with a stereoscopic microscope at 5 times to check for cracks. When even one of 10 sheets has cracks, x mark indicates, When none of them was observed, the evaluation was indicated by a circle, and the results are shown in Table 1.

Further, the open pores of the sintered body were boiled with water for 3 hours and determined from the saturated water weight thereof. The thermal conductivity of the sintered body used in the thermal cycle test was determined by the laser flash method and is also shown in Table 1.

Comparative Examples 1 to 5 Comparative Example 1 shown in Table 2 under the same conditions as in Examples 1 to 16
The raw material was mixed and slurried in a raw material mixing ratio of ˜5, and then formed into a sheet and sintered. The observation of the structure of the sintered body, the heat cycle test, the characteristics of the sintered body, and the like were performed under the same conditions as in Examples 1 to 16, and the results shown in Table 2 were obtained.

As a result, the high thermal conductivity as obtained in the examples and good results in the heat cycle test were not obtained in the comparative examples.

[0029]

[Table 1]

[0030]

[Table 2]

[0031]

According to the present invention, an unprecedented AlN sintered body, that is, an AlN sintered body which maintains high thermal conductivity and is excellent in heat cycle characteristics, was obtained.

[Brief description of drawings]

FIG. 1 is a plan view of a copper plate-clad AlN sintered body sample used in a thermal cycle test. (A) is the front surface and (b) is the back surface.

FIG. 2 is a cycle condition diagram of a heat cycle test.

[Explanation of symbols]

1 AlN sintered body 2 Copper plate

Claims (2)

[Claims] 1. An AlN sintered body containing a grain boundary phase,
The average peripheral length (a) of the grain boundary phase on the cut surface of the sintered body is 0.
1 to 15 μm, (b) the ratio of the average minimum diameter to the average maximum diameter is 0.5 to 1.0, and (c) the ratio of the average particle diameter to the average particle diameter of AlN particles is 0.5 or less, And the composition of the grain boundary phase is 3Y ₂
O ₃ · 5Al ₂ O ₃ and _{Y 2 O 3 · Al 2 O} 3 AlN sintered body, characterized in that it consists of. 2. The amount of sintering aid added in terms of oxide Y ₂ O ₃ awt% based on the total weight of AlN raw material powder, sintering aid and oxygen content modifier. As 2
Oxygen content was adjusted so as to satisfy 0.3a + 1.3c + 2.3>b> 0.2a + 1.3c + 0.7 when the amount of carbon contained in the molded body after degreasing is 10wt% and cwt%. A method for producing an AlN sintered body, which comprises adjusting the amount of oxygen bwt% contained in the agent and the AlN raw material powder, and mixing, shaping and sintering.